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Sample records for superconducting properties depend

  1. Stoichiometry and thickness dependence of superconducting properties of niobium nitride thin films

    Energy Technology Data Exchange (ETDEWEB)

    Beebe, Melissa R., E-mail: mrbeebe@email.wm.edu; Beringer, Douglas B.; Burton, Matthew C.; Yang, Kaida; Lukaszew, R. Alejandra [Department of Physics, The College of William & Mary, Small Hall, 300 Ukrop Way, Williamsburg, Virginia 23185 (United States)

    2016-03-15

    The current technology used in linear particle accelerators is based on superconducting radio frequency (SRF) cavities fabricated from bulk niobium (Nb), which have smaller surface resistance and therefore dissipate less energy than traditional nonsuperconducting copper cavities. Using bulk Nb for the cavities has several advantages, which are discussed elsewhere; however, such SRF cavities have a material-dependent accelerating gradient limit. In order to overcome this fundamental limit, a multilayered coating has been proposed using layers of insulating and superconducting material applied to the interior surface of the cavity. The key to this multilayered model is to use superconducting thin films to exploit the potential field enhancement when these films are thinner than their London penetration depth. Such field enhancement has been demonstrated in MgB{sub 2} thin films; here, the authors consider films of another type-II superconductor, niobium nitride (NbN). The authors present their work correlating stoichiometry and superconducting properties in NbN thin films and discuss the thickness dependence of their superconducting properties, which is important for their potential use in the proposed multilayer structure. While there are some previous studies on the relationship between stoichiometry and critical temperature T{sub C}, the authors are the first to report on the correlation between stoichiometry and the lower critical field H{sub C1}.

  2. Annealing condition dependence of the superconducting property and the pseudo-gap in the protect-annealed electron-doped cuprates

    Energy Technology Data Exchange (ETDEWEB)

    Jung, Woo Been; Cho, Su Hyun; Kim, Chang Young [Center for Correlated Electron Systems, Institute for Basic Science, Seoul (Korea, Republic of); Song, Dong Joon [National Institute of Advanced Industrial Science and Technology, Tsukuba (Japan); Park, Seung Ryong [Dept. of Physics, Research Institute of Basic Sciences, Incheon National University, Incheon (Korea, Republic of)

    2016-06-15

    Annealing as-grown electron-doped cuprates under a low oxygen-partial-pressure condition is a necessary step to achieve superconductivity. It has been recently found that the so-called protect annealing results in much better superconducting properties in terms of the superconducting transition temperature and volume fraction. In this article, we report on angle-resolved photoemission spectroscopy studies of a protect-annealed electron-doped cuprate Pr0.9La1.0Ce0.1CuO4 on annealing condition dependent superconducting and pseudo-gap properties. Remarkably, we found that the one showing a better superconducting property possesses almost no pseudo-gap while others have strong pseudo-gap feature due to an anti-ferromagnetic order.

  3. Sintering time dependence of iron diffusion in MgB2 and its effect on superconducting properties

    Science.gov (United States)

    Ulgen, Asaf Tolga; Belenli, Ibrahim

    2017-02-01

    We have investigated the effects of the iron diffusion on the crystal structure and superconducting properties of pelletised magnesium diboride (MgB2) bulk samples employing X-ray diffraction (XRD), critical transition temperature, and room temperature resistivity measurements. The Fe diffusion into MgB2 bulk pellets upon sintering at 900°C has been studied for sintering time durations of 15 minutes, 30 minutes, 1 hour, 2 hours, and 4 hours. We have carried out XRD and room temperature resistivity determinations along the depth starting from iron coated surface by successive removal of thin layers from the surface mechanically. Sintering time dependence of the Fe diffusion coefficients has been calculated from depth profiles of lattice parameter c and room temperature resistivity values. It has been found that the Fe diffusion coefficient decreases with increasing sintering time.

  4. Dependences on RE of superconducting properties of transition metal co-doped (Ca, RE)FeAs2 with RE = La-Gd

    Science.gov (United States)

    Yakita, H.; Ogino, H.; Sala, A.; Okada, T.; Yamamoto, A.; Kishio, K.; Iyo, A.; Eisaki, H.; Shimoyama, J.

    2015-11-01

    Dependence of superconducting properties of (Ca, RE)(Fe, TM)As2 [(Ca, RE)112, TM: Co, Ni)] on RE elements (RE = La-Gd) was systematically investigated. Improvement of superconducting properties by Co or Ni co-doping was observed for all (Ca, RE)112, which is similar to Co-co-doped (Ca, La)112 or (Ca, Pr)112. Tc of Co-co-doped samples decreased from 38 K for RE = La to 29 K for RE = Gd with decreasing ionic radii of RE3+. However, Co-co-doped (Ca, Eu)112 showed exceptionally low Tc = 21 K probably due to the co-existence of Eu3+ and Eu2+ suggested by longer interlayer distance dFe-Fe of (Ca, Eu)112 than other (Ca, RE)112.

  5. Strain dependence of critical superconducting properties of Nb3Sn with different intrinsic strains based on a semi-phenomenological approach

    Science.gov (United States)

    Zhang, Rui; Gao, Peifeng; Wang, Xingzhe

    2017-09-01

    A semi-phenomenological approach, which combined the microscopic properties calculated by first-principles and macroscopic critical characteristics determined from empirical relations, is suggested to investigate the superconducting critical properties of the low temperature superconductor Nb3Sn with different intrinsic strain modes like uniaxial tension, shear and torsion deformations. Firstly, the microscopic properties of the electronic structure and density of state for Nb3Sn are numerically obtained by first-principles calculations using density-functional theory in the generalized gradient approximation. These are further incorporate with the macroscopic empirical relation of the unified scaling law for predicting critical parameters of the strained Nb3Sn superconductor. The superconducting critical profiles of critical temperature, magnetic field and current, in such a way, are achieved for Nb3Sn under different strains. The predictions on the critical parameters of the superconductor bulk in uniaxial tension/compression state exhibit obvious degradations and bell-shaped curves with maximum critical values at zero strain and a slight asymmetry between the tensile and compressive strains, which show quite good agreements with the experimental data. As for Nb3Sn under shear and torsion deformations, the similar degradations on critical parameters also are presented which are monotonously decreased with the applied strains. The first-principles calculations and results in this work are based on an assumption which the superconducting critical properties from the strain-induced variations in the electronic density of states. Furthermore, the modified critical surfaces of Nb3Sn, determined by the critical temperature, current and magnetic field dependence upon the applied different strains are depicted. The present study will be helpful to identify the scaling relation for the critical parameters and understanding the origin of strain sensitivity in Nb3Sn

  6. Coherence properties in superconducting flux qubits

    Energy Technology Data Exchange (ETDEWEB)

    Spilla, Samuele

    2015-02-16

    The research work discussed in this thesis deals with the study of superconducting Josephson qubits. Superconducting qubits are solid-state artificial atoms which are based on lithographically defined Josephson tunnel junctions properties. When sufficiently cooled, these superconducting devices exhibit quantized states of charge, flux or junction phase depending on their design parameters. This allows to observe coherent evolutions of their states. The results presented can be divided into two parts. In a first part we investigate operations of superconducting qubits based on the quantum coherence in superconducting quantum interference devices (SQUID). We explain experimental data which has been observed in a SQUID subjected to fast, large-amplitude modifications of its effective potential shape. The motivations for this work come from the fact that in the past few years there have been attempts to interpret the supposed quantum behavior of physical systems, such as Josephson devices, within a classical framework. Moreover, we analyze the possibility of generating GHZ states, namely maximally entangled states, in a quantum system made out of three Josephson qubits. In particular, we investigate the possible limitations of the GHZ state generation due to coupling to bosonic baths. In the second part of the thesis we address a particular cause of decoherence of flux qubits which has been disregarded until now: thermal gradients, which can arise due to accidental non equilibrium quasiparticle distributions. The reason for these detrimental effects is that heat currents flowing through Josephson tunnel junctions in response to a temperature gradient are periodic functions of the phase difference between the electrodes. The phase dependence of the heat current comes from Andreev reflection, namely an interplay between the quasiparticles which carry heat and the superconducting condensate which is sensitive to the superconducting phase difference. Generally speaking

  7. Vortex properties of mesoscopic superconducting samples

    Energy Technology Data Exchange (ETDEWEB)

    Cabral, Leonardo R.E. [Laboratorio de Supercondutividade e Materiais Avancados, Departamento de Fisica, Universidade Federal de Pernambuco, Recife 50670-901 (Brazil); Barba-Ortega, J. [Grupo de Fi' sica de Nuevos Materiales, Departamento de Fisica, Universidad Nacional de Colombia, Bogota (Colombia); Souza Silva, C.C. de [Laboratorio de Supercondutividade e Materiais Avancados, Departamento de Fisica, Universidade Federal de Pernambuco, Recife 50670-901 (Brazil); Albino Aguiar, J., E-mail: albino@df.ufpe.b [Laboratorio de Supercondutividade e Materiais Avancados, Departamento de Fisica, Universidade Federal de Pernambuco, Recife 50670-901 (Brazil)

    2010-10-01

    In this work we investigated theoretically the vortex properties of mesoscopic samples of different geometries, submitted to an external magnetic field. We use both London and Ginzburg-Landau theories and also solve the non-linear Time Dependent Ginzburg-Landau equations to obtain vortex configurations, equilibrium states and the spatial distribution of the superconducting electron density in a mesoscopic superconducting triangle and long prisms with square cross-section. For a mesoscopic triangle with the magnetic field applied perpendicularly to sample plane the vortex configurations were obtained by using Langevin dynamics simulations. In most of the configurations the vortices sit close to the corners, presenting twofold or three-fold symmetry. A study of different meta-stable configurations with same number of vortices is also presented. Next, by taking into account de Gennes boundary conditions via the extrapolation length, b, we study the properties of a mesoscopic superconducting square surrounded by different metallic materials and in the presence of an external magnetic field applied perpendicularly to the square surface. It is determined the b-limit for the occurrence of a single vortex in a mesoscopic square of area d{sup 2}, for 4{xi}(0){<=}d{<=}10{xi}(0).

  8. RF and Surface Properties of Superconducting Samples

    CERN Document Server

    Junginger, T; Weingarten, W; Welsch, C

    2011-01-01

    At CERN a compact Quadrupole Resonator has been developed for the RF characterization of superconducting samples at different frequencies. In this paper, results from measurements on bulk niobium and niobium filmon copper substrate samples are presented. We show how different contributions to the surface resistance depend on temperature, applied RF magnetic field and frequency. Furthermore, measurements of the maximum RF magnetic field as a function of temperature and frequency in pulsed and CW operation are presented. The study is accompanied by measurements of the surface properties of the samples by various techniques.

  9. Superconductivity

    CERN Document Server

    Poole, Charles P; Farach, Horacio A

    1995-01-01

    Superconductivity covers the nature of the phenomenon of superconductivity. The book discusses the fundamental principles of superconductivity; the essential features of the superconducting state-the phenomena of zero resistance and perfect diamagnetism; and the properties of the various classes of superconductors, including the organics, the buckministerfullerenes, and the precursors to the cuprates. The text also describes superconductivity from the viewpoint of thermodynamics and provides expressions for the free energy; the Ginzburg-Landau and BCS theories; and the structures of the high

  10. Tunneling properties of electromagnetic wave in slab superconducting material

    Institute of Scientific and Technical Information of China (English)

    Khem B. Thapa; Sanjay Srivastava; Alka Vishwakarma; S. P. Ojha

    2011-01-01

    When the electromagnetic wave propagates through a slab superconducting material in microwave ranges, tunneling properties of the electromagnetic wave at critical temperature are investigated theoretically. The transmittance and the reflectance of the slab superconducting material vary with the thickness of material as well as the refractive index of substrates.The high transmittance is found for thin superconductor at low wavelength region.However, optical properties are strongly dependent upon temperature and incidence wavelength. The electromagnetic wave is totally transmitted without loss for incidence wavelength (λ = 5000 nm) due to the zero refractive index and infinite penetration depth of the superconductor at the critical temperature.

  11. Properties of superconducting Bi-Sr-Ca-Cu-O system remelted under higher gravity conditions

    Science.gov (United States)

    Volkov, M. P.; Melekh, B. T.; Parfeniev, R. V.; Kartenko, N. F.; Regel, L. L.; Turchaninov, A. M.

    1992-04-01

    The structure and magnetic properties of high Tc superconductor Bi-Sr-Ca-Cu-O samples remelted under 1 g0, 8 g0 and 12 g0 gravity levels have been investigated. Superconducting properties make a change along the ingots. The dependence of structural and superconducting properties on the gravity level and their time degradation have been observed.

  12. Superconductivity

    CERN Document Server

    Thomas, D B

    1974-01-01

    A short general review is presented of the progress made in applied superconductivity as a result of work performed in connection with the high-energy physics program in Europe. The phenomenon of superconductivity and properties of superconductors of Types I and II are outlined. The main body of the paper deals with the development of niobium-titanium superconducting magnets and of radio-frequency superconducting cavities and accelerating structures. Examples of applications in and for high-energy physics experiments are given, including the large superconducting magnet for the Big European Bubble Chamber, prototype synchrotron magnets for the Super Proton Synchrotron, superconducting d.c. beam line magnets, and superconducting RF cavities for use in various laboratories. (0 refs).

  13. Tuning the Superconducting Properties of Magnesium Diboride

    Energy Technology Data Exchange (ETDEWEB)

    Theoderich Wilke, Rudeger Heinrich [Iowa State Univ., Ames, IA (United States)

    2005-01-01

    This work is presented in the following order: A review of the relevant physics and discussion of theoretical predictions for a two gap superconducting compound is given in chapter 2. Chapter 3 provides a review of the basic properties of MgB2. Details of sample synthesis and characterization are given in chapter 4. Chapter 5 presents normal state and superconducting properties of Mg(B1-xCx)2 wires. Attempts to increase critical current densities in filaments via titanium additions are discussed in chapter 6. In chapters 7 and 8 alternative methods for synthesizing doped MgB2 powders are explored. In chapter 7 we synthesize Mg(B1-xCx)2 up to x=0.069 using a mixture of Mg, B, and the binary compound B4C. Chapter 8 explores an alternative method, plasma spray synthesis, to produce nanometer sized doped boron powders for powder-in-tube applications. The effects of neutron irradiation on pure MgB2 wires is discussed in chapter 9. This is followed by a study of the effects of neutron irradiation on Mg(B.962C.038)2 wires, presented in chapter 10. I will summarize the results of all of these studies in chapter 11 and discuss future directions for research in understanding the physics behind this novel material as well as its development for practical applications. In this thesis I have presented the results of investigations into the changes in the superconducting properties of MgB2 as a function of carbon doping and neutron irradiation. The goal has been to understand the physics underlying this unique two-gap superconductor as different types of perturbations are made to the system. Such knowledge not only contributes to our understanding of two-gap superconductivity, but could potentially lead to the development of superconducting MgB2 wires for the use in power applications near 20 K.

  14. Properties of superconducting Bi-Sr-Ca-Cu-O system remelted under higher gravity conditions

    Energy Technology Data Exchange (ETDEWEB)

    Volkov, M.P.; Melekh, B.T.; Parfeniev, R.V.; Kartenko, N.F. (A.F. Ioffe Physical Technical Inst., Academy of Sciences, Moscow (Russia)); Regel, L.L.; Turchaninov, A.M. (Space Research Inst., Academy of Sciences, Moscow (Russia))

    1992-04-01

    The structure and magnetic properties of high Tc superconductor Bi-Sr-Ca-Cu-O samples remelted under 1g{sub 0}, 8g{sub 0} and 12g{sub 0} gravity levels have been investigated. Superconducting properties make a change along the ingots. The dependence of structural and superconducting properties on the gravity level and their time degradation have been observed. (orig.).

  15. Superconductivity

    CERN Document Server

    Poole, Charles P; Creswick, Richard J; Prozorov, Ruslan

    2014-01-01

    Superconductivity, Third Edition is an encyclopedic treatment of all aspects of the subject, from classic materials to fullerenes. Emphasis is on balanced coverage, with a comprehensive reference list and significant graphics from all areas of the published literature. Widely used theoretical approaches are explained in detail. Topics of special interest include high temperature superconductors, spectroscopy, critical states, transport properties, and tunneling. This book covers the whole field of superconductivity from both the theoretical and the experimental point of view. This third edition features extensive revisions throughout, and new chapters on second critical field and iron based superconductors.

  16. Superconducting properties in tantalum decorated three-dimensional graphene and carbon structures

    Energy Technology Data Exchange (ETDEWEB)

    Cobaleda, Cayetano S. F., E-mail: ccobaleda@usal.es, E-mail: wpan@sandia.gov [Sandia National Laboratories, P.O. Box 5800, MS 1086, Albuquerque, New Mexico 87185 (United States); Laboratorio de Bajas Temperaturas, Universidad de Salamanca, E-37008 Salamanca (Spain); Xiao, Xiaoyin; Burckel, D. Bruce; Polsky, Ronen; Pan, W., E-mail: ccobaleda@usal.es, E-mail: wpan@sandia.gov [Sandia National Laboratories, P.O. Box 5800, MS 1086, Albuquerque, New Mexico 87185 (United States); Huang, Duanni [Sandia National Laboratories, P.O. Box 5800, MS 1086, Albuquerque, New Mexico 87185 (United States); Department of Electrical and Computer Engineering, University of California, Santa Barbara, California 93106 (United States); Diez, Enrique [Laboratorio de Bajas Temperaturas, Universidad de Salamanca, E-37008 Salamanca (Spain)

    2014-08-04

    We present here the results on superconducting properties in tantalum thin films (100 nm thick) deposited on three-dimensional graphene (3DG) and carbon structures. A superconducting transition is observed in both composite thin films with a superconducting transition temperature of 1.2 K and 1.0 K, respectively. We have further measured the magnetoresistance at various temperatures and differential resistance dV/dI at different magnetic fields in these two composite thin films. In both samples, a much large critical magnetic field (∼2 T) is observed and this critical magnetic field shows linear temperature dependence. Finally, an anomalously large cooling effect was observed in the differential resistance measurements in our 3DG-tantalum device when the sample turns superconducting. Our results may have important implications in flexible superconducting electronic device applications.

  17. 1D-transport properties of single superconducting lead nanowires

    DEFF Research Database (Denmark)

    Michotte, S.; Mátéfi-Tempfli, Stefan; Piraux, L.

    2003-01-01

    We report on the transport properties of single superconducting lead nanowires grown by an electrodeposition technique, embedded in a nanoporous track-etched polymer membrane. The nanowires are granular, have uniform diameter of ̃40 nm and a very large aspect ratio (̃500). The diameter of the nan......We report on the transport properties of single superconducting lead nanowires grown by an electrodeposition technique, embedded in a nanoporous track-etched polymer membrane. The nanowires are granular, have uniform diameter of ̃40 nm and a very large aspect ratio (̃500). The diameter...... of the nanowire is small enough to ensure a 1D superconducting regime in a wide temperature range below T. The non-zero resistance in the superconducting state and its variation caused by fluctuations of the superconducting order parameter were measured versus temperature, magnetic field, and applied DC current...

  18. Investigation of Properties of Motion of Superconductive Electrons in Superconductors by Nonlinear Quantum Mechanical Theory

    Institute of Scientific and Technical Information of China (English)

    Xiao-Feng Pang

    2008-01-01

    The properties and rules of motion of superconductive electrons in steady and time-dependent non-equilibrium states of superconductors are studied by using the Ginzberg-Landau (GL) equations and nonlinear quantum theory. In the absence of external fields, the superconductive electrons move in the solitons with certain energy and velocity in a uniform system, The superconductive electron is still a soliton under action of an electromagnetic field, but its amplitude, phase and shape are changed. Thus we conclude that super- conductivity is a result of motion of soliton of superconductive electrons. Since soliton has the feature of motion for retaining its energy and form, thus a permanent current occurs in superconductor. From these solutions of GL equations under action of an electromagnetic field, we gain the structure of vortex lines-magnetic flux lines observed experimentally in type-II superconductors. In the time-dependent non- equilibrium states of superconductor, the motions of superconductive electrons exhibit still the soliton features, but the shape and amplitude have changed. In an invariant electric-field, it moves in a constant acceleration. In the medium with dissipation, the superconductive electron behaves still like a soliton, although its form, amplitude, and velocity are altered. Thus we have to convince that the superconductive electron is essentially a soliton in both non-equilibrium and equilibrium superconductors.

  19. Superconducting and normal-state properties of novel materials

    Energy Technology Data Exchange (ETDEWEB)

    Crespi, Vincent Henry [Univ. of California, Berkeley, CA (United States)

    1994-09-01

    Interest in solid state physics naturally gravitates towards novel systems such as the copper oxide superconductors or the alkali-doped fullerenes. This paper tackles high temperature superconductivity by extension of the BCS theory for ordinary superconductors, in particular, incorporation of anharmonicity in phonon dynamics and anisotropy in electron-phonon coupling. These refinements can account for many anomalous properties of the cuprates. Phonon anharmonicity is consistent with a small isotope effect at optimal doping and a larger isotope effect in suboptimal systems. Anisotropy in the interaction, a plausible consequence of certain anharmonic models, can circumvent objections to electron-phonon coupling based on transport measurements. Such anisotropy is consistent with gap anisotropy and strong temperature dependence of Hall coefficient. In contrast to cuprates, the doped fullerenes appear understandable within the standard model of single electron band theory and BCS theory. Microscopic parameters derivable from transport and critical field measurements yield a self-consistent picture of a disordered Type-2 BCS superconductor. Isotope effects imply that superconductivity is mediated by carbon phonons opposed to alkali atom vibrations. The novel properties of the fullerenes are generally traceable to their microscopic heterogeneity, being a collection of tightly bound but weakly overlapping molecules. Separation of electronic regimes into weak intermolecular overlap and strong carbon-carbon on-ball bonds yields a superconductor with both a large density of states and a high phonon frequency, properties consistent with a relatively high {Tc}. Disordered nature of intermolecular overlap produces a large residual resistivity and a universal dependence to the Hall coefficient. This disorder is also consistent with the anomalously large carbon isotope effect for heterogeneous isotopic substitution.

  20. Some unique superconductive Properties of Cuprates

    Science.gov (United States)

    Müller, K. A.

    2013-04-01

    Copper oxides are the only materials that show transition temperatures, Tc, above the boiling point of liquid nitrogen, with a maximum Tmc of 162 K under pressure. Their structure is layered, with one to several CuO2 planes, and upon hole doping, their transition temperature follows a dome-shaped curve with a maximum at Tmc. In the underdoped regime, i.e., below Tmc, a pseudogap T* is found, with T* always being larger than Tc, a property unique to the copper oxides [1]. In the superconducting state, Cooper pairs (two holes with antiparallel spins) are formed that exhibit coherence lengths on the order of a lattice distance in the CuO2 plane and one order of magnitude less perpendicular to it. Their macroscopic wave function is parallel to the CuO2 plane near 100% d at their surface, but only 75% d and 25 % s in the bulk, and near 100% s perpendicular to the plane in YBCO. There are two gaps with the same Tc [2]. As function of doping, the oxygen isotope effect is novel and can be quantitatively accounted for by a two-band vibronic theory [3] near Tmc, and underdoped below it till Tc = 0 with by a formula valid for (bi)polarons [4]. These cuprates are intrinsically heterogeneous in a dynamic way. In terms of quasiparticles, Jahn-Teller bipolarons are present at low doping, and aggregate upon cooling [1], so that probably ramified clusters and/or stripes are formed, leading over to a more Fermi-liquid-type behavior at large carrier concentrations above Tmc.

  1. Superconductivity and magnetism: Materials properties and developments

    Energy Technology Data Exchange (ETDEWEB)

    Andersen, N.H.; Bay, N.; Grivel, J.C. (eds.) [and others

    2003-07-01

    The 24th Risoe International Symposium on Materials Science focuses on development of new materials, devices and applications, as well as experimental and theoretical studies of novel and unexplained phenomena in superconductivity and magnetism, e.g. within high.T{sub c} superconductivity, magnetic superconductors, MgB{sub 2}, CMR materials, nanomagnetism and spin-tronics. The aim is to stimulate exchange of ideas and establish new collaborations between leading Danish and international scientists. The topics are addressed by presentations from 24 invited speakers and by 41 contributed papers. (ln)

  2. Stress dependent oxidation of sputtered niobium and effects on superconductivity

    Science.gov (United States)

    David Henry, M.; Wolfley, Steve; Monson, Todd; Clark, Blythe G.; Shaner, Eric; Jarecki, Robert

    2014-02-01

    We report on the suppression of room temperature oxidation of DC sputtered niobium films and the effects upon the superconductive transition temperature, Tc. Niobium was sputter-deposited on silicon dioxide coated 150 mm wafers and permitted to oxidize at room temperature and pressure for up to two years. Resistivity and stress measurements indicate that tensile films greater than 400 MPa resist bulk oxidation with measurements using transmission electron microscope, electron dispersive X-ray spectroscopy, x-ray photoelectric spectroscopy, and secondary ion mass spectrometry confirming this result. Although a surface oxide, Nb2O5, consumed the top 6-10 nm, we measure less than 1 at. % oxygen and nitrogen in the bulk of the films after the oxidation period. Tc measurements using a SQUID magnetometer indicate that the tensile films maintained a Tc approaching the dirty superconductive limit of 8.4 K after two years of oxidation while maintaining room temperature sheet resistance. This work demonstrates that control over niobium film stress during deposition can prevent bulk oxidation by limiting the vertical grain boundaries ability to oxidize, prolonging the superconductive properties of sputtered niobium when exposed to atmosphere.

  3. Investigation of superconducting properties of nanowires prepared by template synthesis

    DEFF Research Database (Denmark)

    Michotte, S.; Mátéfi-Tempfli, Stefan; Piraux, L.

    2003-01-01

    We report on the transport properties of single superconducting lead nanowires grown by an electrodeposition technique, embedded in a nanoporous track-etched polymer membrane. The nanowires are granular, have a uniform diameter of ∼40 nm and a very large aspect ratio (∼500). The diameter of the n......We report on the transport properties of single superconducting lead nanowires grown by an electrodeposition technique, embedded in a nanoporous track-etched polymer membrane. The nanowires are granular, have a uniform diameter of ∼40 nm and a very large aspect ratio (∼500). The diameter...

  4. Superconducting properties of long TiN wires

    Science.gov (United States)

    Mironov, A. Yu.; Postolova, S. V.; Nasimov, D. A.

    2016-12-01

    The low-temperature transport properties of titanium nitride wires with the width comparable with or much larger than the superconducting coherence length are studied experimentally. It is shown that the reduction of the width of wires does not affect the transport properties at the temperatures above the superconducting transition temperature and electron transport in this temperature range is determined by quantum contributions to the conductivity from weak localization and electron-electron interaction. It is established that the reduction of the width of wires does not change the superconducting transition temperature but completely suppresses the topological Berezinskii-Kosterlitz-Thouless transition. It is found that the threshold magnetic field increases with a decrease in the width of wires.

  5. Vortex Properties of Nanosized Superconducting Strips with One Central Weak Link Under an Applied Current Drive

    Science.gov (United States)

    Peng, Lin; Cai, Chuanbing

    2016-06-01

    The static and dynamic properties of vortices in a nanosized superconducting strip with one central weak link (weakly superconducting region or normal metal) are investigated in the presence of external magnetic and electric fields. The time-dependent Ginzburg-Landau equations are used to describe the electronic transport and have been solved numerically by a finite element analysis. Anisotropy is included through the spatially dependent anisotropy coefficient ζ in different layers of the sample. Our results show that the energy barrier for vortices to enter a weak link is smaller than that for vortices to enter the superconducting layers. The magnetization shows periodic oscillations. With the introduction of the weak link, the period of oscillations decreases.

  6. Superconducting properties of MgB2 from first principles.

    Science.gov (United States)

    Floris, A; Profeta, G; Lathiotakis, N N; Lüders, M; Marques, M A L; Franchini, C; Gross, E K U; Continenza, A; Massidda, S

    2005-01-28

    Solid MgB(2) has rather interesting and technologically important properties, such as a very high superconducting transition temperature. Focusing on this compound, we report the first nontrivial application of a novel density-functional-type theory for superconductors, recently proposed by the authors. Without invoking any adjustable parameters, we obtain the transition temperature, the gaps, and the specific heat of MgB(2) in very good agreement with experiment. Moreover, our calculations show how the Coulomb interaction acts differently on sigma and pi states, thereby stabilizing the observed superconducting phase.

  7. Proximity Induced Superconducting Properties in One and Two Dimensional Semiconductors

    DEFF Research Database (Denmark)

    Kjærgaard, Morten

    that a superconducting 1D nanowire can harbor Majorana bound states in the absence of spin–orbit coupling. We fabricate and measure micrometer–sized mesoscopic devices demonstrating the inheritance of superconducting properties in the 2D electron gas. By placing a quantum point contact proximal to the interface between...... the 2D electron gas and the aluminum, we are able to demonstrate quantization of conductance in units of 4e2/h indicative of perfect Andreev reflection at the interface. We show that the quantum point contact can be operated as a tunnel probe to locally measure the density of states in the electron gas...... with a superconducting pairing potential, Majorana bound states can exist in the absence of spin–orbit coupling. Our proposal dispenses with spin–orbit coupling at the expense of a locally varying magnetic field. The presence of the topological state is demonstrated analytically by mapping our model onto...

  8. Robust superconductivity and transport properties in (Li1- x Fe x )OHFeSe single crystals

    Science.gov (United States)

    Lin, Hai; Xing, Jie; Zhu, XiYu; Yang, Huan; Wen, Hai-Hu

    2016-05-01

    The recently discovered (Li1- x Fe x )OHFeSe superconductor with T c about 40 K provides a good platform for investigating the magnetization and electrical transport properties of FeSe-based superconductors. By using a hydrothermal ion-exchange method, we have successfully grown crystals of (Li1- x Fe x )OHFeSe. X-ray diffraction on the sample shows the single crystalline PbO-type structure with the c-axis preferential orientation. Magnetic susceptibility and resistive measurements show an onset superconducting transition at around T c =38.3 K. Using the magnetization hysteresis loops and Bean critical state model, a large critical current J s is observed in low temperature region. The critical current density is suppressed exponentially with increasing magnetic field. Temperature dependencies of resistivity under various currents and fields are measured, revealing a robust superconducting current density and bulk superconductivity.

  9. Hamiltonian Dynamics and Adiabatic Invariants for Time-Dependent Superconducting Qubit-Oscillators and Resonators in Quantum Computing Systems

    Directory of Open Access Journals (Sweden)

    Jeong Ryeol Choi

    2015-01-01

    Full Text Available An adiabatic invariant, which is a conserved quantity, is useful for studying quantum and classical properties of dynamical systems. Adiabatic invariants for time-dependent superconducting qubit-oscillator systems and resonators are investigated using the Liouville-von Neumann equation. At first, we derive an invariant for a simple superconducting qubit-oscillator through the introduction of its reduced Hamiltonian. Afterwards, an adiabatic invariant for a nanomechanical resonator linearly interfaced with a superconducting circuit, via a coupling with a time-dependent strength, is evaluated using the technique of unitary transformation. The accuracy of conservation for such invariant quantities is represented in detail. Based on the results of our developments in this paper, perturbation theory is applicable to the research of quantum characteristics of more complicated qubit systems that are described by a time-dependent Hamiltonian involving nonlinear terms.

  10. Superconductivity

    Science.gov (United States)

    1989-07-01

    SUPERCONDUCTIVITY HIGH-POWER APPLICATIONS Electric power generation/transmission Energy storage Acoustic projectors Weapon launchers Catapult Ship propulsion • • • Stabilized...temperature superconductive shields could be substantially enhanced by use of high-Tc materials. 27 28 NRAC SUPERCONDUCTIVITY SHIP PROPULSION APPLICATIONS...motor shown in the photograph. As a next step in the evolution of electric-drive ship propulsion technology, DTRC has proposed to scale up the design

  11. Measurement of improved pressure dependence of superconducting transition temperature

    Science.gov (United States)

    Karmakar, S.

    2013-06-01

    We describe a technique for making electrical transport measurements in a diamond anvil cell at liquid helium temperature having in situ pressure measurement option, permitting accurate pressure determination at any low temperature during the resistance measurement scan. In general, for four-probe resistivity measurements on a polycrystalline sample, four fine gold wires are kept in contact with the sample with the help of the compression from the soft solid (usually alkali halides such as NaCl, KCl, etc.) acting as a pressure-transmitting medium. The actual pressure on the sample is underestimated if not measured from a ruby sphere placed adjacent to the sample and at that very low temperature. Here, we demonstrate the technique with a quasi-four-probe resistance measurement on an Fe-based superconductor in the temperature range 1.2-300 K and pressures up to 8 GPa to find an improved pressure dependence of the superconducting transition temperature.

  12. Proximity Induced Superconducting Properties in One and Two Dimensional Semiconductors

    DEFF Research Database (Denmark)

    Kjærgaard, Morten

    a voltage is passed through the Josephson junction, we observe multiple Andreev reflections and preliminary results point to a highly transmissive interface between the 2D electron gas and the superconductor. In the theoretical section we demonstrate analytically and numerically, that in a 1D nanowire......This report is concerned with the properties of one and two dimensional semiconducting materials when brought into contact with a superconductor. Experimentally we study the 2D electron gas in an InGaAs/InAs heterostructure with aluminum grown in situ on the surface, and theoretically we show...... that a superconducting 1D nanowire can harbor Majorana bound states in the absence of spin–orbit coupling. We fabricate and measure micrometer–sized mesoscopic devices demonstrating the inheritance of superconducting properties in the 2D electron gas. By placing a quantum point contact proximal to the interface between...

  13. Physical properties of the superconducting spin-valve Fe/Cu/Fe/In heterostructure

    Science.gov (United States)

    Leksin, P. V.; Garif'yanov, N. N.; Garifullin, I. A.; Schumann, J.; Kataev, V.; Schmidt, O. G.; Büchner, B.

    2012-01-01

    We report on structural, magnetic, and superconducting properties of the spin-valve multilayer system CoOx/Fe1/Cu/Fe2/In. For most of the thicknesses of the second iron layer dFe2 up to 2 nm, we have observed a full spin-valve effect for the superconducting current, i.e., a complete transition from the normal to the superconducting state by changing the mutual orientation of the magnetizations of the Fe1 and Fe2 layers. For dFe2<1 nm, the superconducting transition temperature TcP for the parallel orientation of magnetizations of the Fe1 and Fe2 layers is smaller than that for the antiparallel orientation TcAP, which corresponds to the direct spin-valve effect. For dFe2⩾1 nm, we have found the inverse spin-valve effect with ΔTc=TcAP-TcP<0. Further, in samples with a fixed thickness of the In layer, we have observed an oscillating dependence of its superconducting transition temperature Tc on dFe2. The analysis of the Tc(dFe2) dependence using the theory of the superconducting-ferromagnetic proximity effect has enabled determination of all microscopic parameters of the studied system. With these parameters, a satisfactory description of the sign-changing oscillating behavior of the spin-valve effect ΔTc(dFe2) has been obtained using a recent theory by Fominov [Ya. V. Fominov , Pis'ma Zh. Eksp. Teor. Fiz. 91, 329 (2010) [JETP Lett.JTPLA20021-364010.1134/S002136401006010X 91, 308 (2010)

  14. Superconductivity

    CERN Document Server

    Ketterson, John B

    2008-01-01

    Conceived as the definitive reference in a classic and important field of modern physics, this extensive and comprehensive handbook systematically reviews the basic physics, theory and recent advances in the field of superconductivity. Leading researchers, including Nobel laureates, describe the state-of-the-art in conventional and unconventional superconductors at a particularly opportune time, as new experimental techniques and field-theoretical methods have emerged. In addition to full-coverage of novel materials and underlying mechanisms, the handbook reflects continued intense research into electron-phone based superconductivity. Considerable attention is devoted to high-Tc superconductivity, novel superconductivity, including triplet pairing in the ruthenates, novel superconductors, such as heavy-Fermion metals and organic materials, and also granular superconductors. What’s more, several contributions address superconductors with impurities and nanostructured superconductors. Important new results on...

  15. The Properties of Normal Conducting Cathodes in FZD Superconducting Gun

    CERN Document Server

    Xiang, R; Buettig, H; Janssen, D; Justus, M; Lehnert, U; Michel, P; Murcek, P; Schamlott, A; Schneider, Ch; Schurig, R; Staufenbiel, F; Teichert, J

    2009-01-01

    The superconducting radio frequency photoinjector (SRF photoinjector) is one of the latest applications of SC technology in the accelerator field. Since superconducting cathodes with high QE are not available up to now, normal conducting cathode material is the main choice for the SRF photoinjectors. However, the compatibility between the cathode and the cavity is one of the challenges for this concept. The SRF gun with Cs2Te cathode has been successfully operated under the collaboration of BESSY, DESY, FZD, and MBI. In this paper, some experience gained in the gun commissioning will be concluded. The results of the properties of Cs2Te photocathode in the cavity will be presented, such as the Q.E., the life time, the dark current and the thermal emittance.

  16. The crystal structure and superconducting properties of monatomic bromine.

    Science.gov (United States)

    Duan, Defang; Meng, Xing; Tian, Fubo; Chen, Changbo; Wang, Liancheng; Ma, Yanming; Cui, Tian; Liu, Bingbing; He, Zhi; Zou, Guangtian

    2010-01-13

    The crystal structure and superconducting properties of monatomic bromine under high pressure have been studied by first-principles calculations. We have found the following phase transition sequence with increasing pressure: from body-centered orthorhombic (bco, phase II) to body-centered tetragonal structure (bct, phase III) at 126 GPa, then to face-centered cubic structure (fcc, phase IV) at 157 GPa, which is stable at least up to 300 GPa. The calculated superconducting critical temperature T(c) = 1.46 K at 100 GPa is consistent with the experimental value of 1.5 K. In addition, our results of T(c) decrease with increasing pressure in all the monatomic phases of bromine, similar to monatomic iodine. Further calculations show that the decrease of λ with pressure in phase IV is mainly attributed to the weakening of the 'soft' vibrational mode caused by pressure.

  17. Superconducting properties of combustion synthesized MgB{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Takano, Yoshihiko; Oguro, Nobutaka; Kaieda, Yoshinari; Togano, Kazumasa

    2004-10-01

    We have successfully prepared the MgB{sub 2} superconducting bulk and powdered materials by the method of combustion synthesis. The starting materials used in this study were powders of Mg and B. X-ray powder diffraction pattern was well assigned to the P6/mmm MgB{sub 2} phase. The temperature dependence of magnetization shows sharp superconducting transition around 38 K. The critical current density can be estimated from the hysteresis of the magnetization curvature using the Bean's model. The powdered sample shows a high critical current density of 2 x 10{sup 6} A/cm{sup 2} at 5 K under the magnetic field of 1 T.

  18. Microwave dependence of subharmonic gap structure in superconducting junctions

    DEFF Research Database (Denmark)

    Sørensen, O. Hoffman; Kofoed, Bent; Pedersen, Niels Falsig

    1974-01-01

    with the superconducting energy gap itself. The location in voltage of all these structures is given by eV=(2Δ±nh ν) / m, where 2Δ is the superconducting energy gap, ν is the applied frequency, h is Planck's constant, e is the magnitude of the electronic charge, V is the dc voltage drop across the junction, and m and n...

  19. Thermomechanical properties of the coil of the superconducting magnets for the Large Hadron Collider

    CERN Document Server

    Couturier, K; Scandale, Walter; Todesco, Ezio; Tommasini, D

    2002-01-01

    The correct definition and measurement of the thermomechanical properties of the superconducting cable used in high-field magnets is crucial to study and model the behavior of the magnet coil from assembly to the operational conditions. In this paper, the authors analyze the superconducting coil of the main dipoles for the Large Hadron Collider. They describe an experimental setup for measuring the elastic modulus at room and at liquid nitrogen temperature and for evaluating the thermal contraction coefficient. The coils exhibit strong nonlinear stress-strain behavior characterized by hysteresis phenomena, which decreases from warm to cold temperature, and a thermal contraction coefficient, which depends on the stress applied to the cable during cooldown. (35 refs).

  20. Evaluating Superconducting YBCO Film Properties Using X-Ray Photoelectron Spectroscopy (Postprint)

    Science.gov (United States)

    2012-02-01

    AFRL-RZ-WP-TP-2012-0093 EVALUATING SUPERCONDUCTING YBCO FILM PROPERTIES USING X-RAY PHOTOELECTRON SPECTROSCOPY (POSTPRINT) Paul N. Barnes...2012 Conference Paper Postprint 01 January 2002 – 01 January 2004 4. TITLE AND SUBTITLE EVALUATING SUPERCONDUCTING YBCO FILM PROPERTIES USING X-RAY

  1. Superconducting properties of lithium-decorated bilayer graphene

    Science.gov (United States)

    Szczȩśniak, Dominik

    2015-07-01

    The present study provides a comprehensive theoretical analysis of the superconducting phase in selected lithium-decorated bilayer graphene nanostructures. The numerical calculations, conducted within the Eliashberg formalism, give quantitative estimations of the most important thermodynamic properties such as the critical temperature, specific heat, critical field and others. It is shown that discussed lithium-graphene systems present enhancement of their thermodynamic properties comparing to the monolayer case, e.g., the critical temperature can be raised to ∼15 \\text{K} . Furthermore, estimated characteristic thermodynamic ratios exceed predictions of the Bardeen-Cooper-Schrieffer theory suggesting that the considered lithium-graphene systems can be properly analyzed only within the strong-coupling regime.

  2. Bias dependence of the response of superconducting tunnel junctions used as photon detectors

    CERN Document Server

    Poelaert, A; Peacock, A; Kozorezov, A; Wigmore, J K

    2000-01-01

    In the last decade, several research groups have developed superconducting tunnel junctions (STJ) for photon detection in astronomy. Despite extensive studies, the behavior of multi-layered devices, subject to the superconducting proximity effect (proximized devices), has remained difficult to model. Recently, a new model has been presented, leading to a more realistic approach for the photon detection within an STJ. This model is based on the existence of local traps in the superconducting electrodes of the STJ. In this paper, we show that the new model is successful in predicting the bias dependence of the response of an STJ. The bias dependence also demonstrates that the quasiparticles, i.e. the charge carriers created as a result of the photon absorption process, cannot relax down to the superconducting energy gap. This result is important, since most theoretical developments to date (implicitly) assume that quasiparticle relax to the gap energy. crystal-structure; energy-levels; tantalum-; traps cooper-p...

  3. Screening-Dependent Study of Superconductivity in 3d-Transition Metals Binary Alloys Superconductors

    Institute of Scientific and Technical Information of China (English)

    Aditya M. Vora

    2009-01-01

    In the present article, we report the screening-dependent study of the superconducting state parameters (SSPs), viz. electron-phonon coupling strength A, Coulomb pseudopotential μ*, transition temperature Tc, isotope effect exponent a, and effective interaction strength NoV of 3d-band transition metals binary alloys superconductors have been made extensively in the present work using a model potential formalism and employing the pseudo-alloy-atom (PAA) model for the first time. Five local field correction functions proposed by Hartree (H), Taylor (T), Ichimaxu-Utsumi (IU), Farid et al. (F) and Sarkar et al. (S) are used in the present investigation to study the screening influence on the aforesaid properties. The present results of the SSPs obtained from H-screening are found in qualitative agreement with the available experimental data wherever exist.

  4. Magnetic field dependence of the superconducting proximity effect in a two atomic layer thin metallic film

    Energy Technology Data Exchange (ETDEWEB)

    Caminale, Michael; Leon Vanegas, Augusto A.; Stepniak, Agnieszka; Oka, Hirofumi; Fischer, Jeison A.; Sander, Dirk; Kirschner, Juergen [Max-Planck-Institut fuer Mikrostrukturphysik, Halle (Germany)

    2015-07-01

    The intriguing possibility to induce superconductivity in a metal, in direct contact with a superconductor, is under renewed interest for applications and for fundamental aspects. The underlying phenomenon is commonly known as proximity effect. In this work we exploit the high spatial resolution of scanning tunneling spectroscopy at sub-K temperatures and in magnetic fields. We probe the differential conductance along a line from a superconducting 9 ML high Pb nanoisland into the surrounding two layer thin Pb/Ag wetting layer on a Si(111) substrate. A gap in the differential conductance indicates superconductivity of the Pb island. We observe an induced gap in the wetting layer, which decays with increasing distance from the Pb island. This proximity length is 21 nm at 0.38 K and 0 T. We find a non-trivial dependence of the proximity length on magnetic field. Surprisingly, we find that the magnetic field does not affect the induced superconductivity up to 0.3 T. However, larger fields of 0.6 T suppress superconductivity in the wetting layer, where the Pb island still remains superconducting. We discuss the unexpected robustness of induced superconductivity in view of the high electronic diffusivity in the metallic wetting layer.

  5. Microstructural and Superconducting Properties of V-Doped MgB2 Bulk and Wires

    Science.gov (United States)

    Castillo, O. E.; Sastry, P. V. P. S. S.; Trociewitz, B.; Trociewitz, U. P.; Schwartz, J.

    2004-06-01

    Studies of the effects of doping MgB2 bulk and Fe-clad wires with V are presented. Samples of composition Mg1-xVxB2 (x = 0.0, 0.05, 0.10, 0.15) have been investigated to understand the role of V doping on the phase formation, microstructure and superconducting properties. Fe-clad wires were fabricated by groove rolling and cold drawing. The superconducting transition temperature remained constant at about 39 K for all the compositions studied. Energy dispersive x-ray (EDX) analysis confirmed the presence of V in the superconducting phase. Enhancement of magnetization hysteresis loop widths indicates an improvement in flux pinning for V-doped samples. Studies on the variation of maximum reaction temperatures suggest that the optimum reaction temperature varies with V content. The optimum reaction temperature also depended on the wire diameter with the larger wires requiring higher reaction temperature. The transport critical current densities measured for groove-rolled wires were in the range of 1.0 - 1.4 × 105 A/cm2.

  6. Superconducting properties of La{sub 2-x}Ba{sub 2}CuO{sub 4} under pressure

    Energy Technology Data Exchange (ETDEWEB)

    Schottenhamel, Wolf; Wolter-Giraud, Anja; Buechner, Bernd [Leibniz Institute for Solid State and Materials Research Dresden, IFW Dresden (Germany); Huecker, Markus [Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, NY (United States)

    2016-07-01

    La{sub 2-x}Ba{sub 2}CuO{sub 4} displays an anomalous doping dependence associated with a deep suppression of superconductivity at the hole concentration x=1/8. The so-called 1/8-anomaly is accompanied by a structural transition in the average rotational symmetry of the CuO{sub 2} planes coinciding with the onset of a charge stripe order. It has been claimed that static stripe order destroys the superconducting phase coherence, while dynamic stripe correlations may promote superconductivity. In order to achieve more information about the relationship between superconductivity, stripe order and crystal structure we performed magnetization measurements under pressure up to 3 GPa on the single crystalline La{sub 2-x}Ba{sub 2}CuO{sub 4} with 0.095 ≤ x ≤ 0.125. Moreover, we relate the magnetization data to pressure dependent X-Ray diffraction studies. This way, we show that the specific superconducting properties as function of pressure are clearly correlated to structural changes.

  7. Size effects of nano-scale pinning centers on the superconducting properties of YBCO single grains

    Science.gov (United States)

    Moutalbi, Nahed; Noudem, Jacques G.; M'chirgui, Ali

    2014-08-01

    High pinning superconductors are the most promising materials for power engineering. Their superconducting properties are governed by the microstructure quality and the vortex pinning behavior. We report on a study of the vortex pinning in YBa2Cu3O7-x (YBCO) single grain with defects induced through the addition of insulating nano-particles. In order to improve the critical current density, YBCO textured bulk superconductors were elaborated using the Top Seeded Melt Texture and Growth process with different addition amounts of Al2O3 nano-particles. Serving as strong pinning centers, 0.05% excess of Al2O3 causes a significant enhancement of the critical current density Jc under self field and in magnetic fields at 77 K. The enhanced flux pinning achieved with the low level of alumina nano-particles endorses the effectiveness of insulating nano-inclusions to induce effectives pinning sites within the superconducting matrix. On the other side, we focused on the effect of the size of pinning centers on the critical current density. This work was carried out using two batches of alumina nano-particles characterized by two different particle size distributions with mean diameters PSD1 = 20 nm and PSD2 = 2.27 μm. The matching effects of the observed pinning force density have been compared. The obtained results have shown that the flux pinning is closely dependent on the size of the artificial pinning centers. Our results suggest that the optimization of the size of the artificial pinning centers is crucial to a much better understanding of the pinning mechanisms and therefore to insure high superconducting performance for the practical application of superconducting materials.

  8. Intercalated Nanocomposites Based on High-Temperature Superconducting Ceramics and Their Properties

    Directory of Open Access Journals (Sweden)

    Sevan Davtyan

    2009-12-01

    Full Text Available High temperature superconducting (SC nanocomposites based on SC ceramics and various polymeric binders were prepared. Regardless of the size of the ceramics’ grains, the increase of their amount leads to an increase of resistance to rupture and modulus and a decrease in limiting deformation, whereas an increase in the average ceramic grain size worsens resistance properties. The SC, thermo-chemical, mechanical and dynamic-mechanical properties of the samples were investigated. Superconducting properties of the polymer ceramic nanocomposites are explained by intercalation of macromolecule fragments into the interstitial layer of the ceramics’ grains. This phenomenon leads to a change in the morphological structure of the superconducting nanocomposites.

  9. Dependence of superconductivity in CuxBi2Se3 on quenching conditions

    Science.gov (United States)

    Schneeloch, J. A.; Zhong, R. D.; Xu, Z. J.; Gu, G. D.; Tranquada, J. M.

    2015-04-01

    Topological superconductivity, implying gapless protected surface states, has recently been proposed to exist in the compound CuxBi2Se3 . Unfortunately, low diamagnetic shielding fractions and considerable inhomogeneity have been reported in this compound. In an attempt to understand and improve on the finite superconducting volume fractions, we have investigated the effects of various growth and postannealing conditions. With a melt-growth (MG) method, diamagnetic shielding fractions of up to 56% in Cu0.3Bi2Se3 have been obtained, the highest value reported for this method. We investigate the efficacy of various quenching and annealing conditions, finding that quenching from temperatures above 560∘C is essential for superconductivity, whereas quenching from lower temperatures or not quenching at all is detrimental. A modified floating zone (FZ) method yielded large single crystals but little superconductivity. Even after annealing and quenching, FZ-grown samples had much less chance of being superconducting than MG-grown samples. From the low shielding fractions in FZ-grown samples and the quenching dependence, we suggest that a metastable secondary phase having a small volume fraction in most of the samples may be responsible for the superconductivity.

  10. Critical current characteristics and history dependence in superconducting SmFeAsOF bulk

    Energy Technology Data Exchange (ETDEWEB)

    Ni, B; Ge, J [Department of Life, Environment and Materials Science, Fukuoka Institute of Technology, Fukuoka 811-0295 (Japan); Kiuchi, M; Otabe, E S [Faculty of Computer Science and Systems Engineering, Kyushu Institute of Technology, Iizuka 820-8502 (Japan); Gao, Z; Wang, L; Qi, Y; Zhang, X; Ma, Y, E-mail: nee@fit.ac.j [Key Laboratory of Applied Superconductivity, Institute of Electrical Engineering, Chinese Academy of Sciences, PO Box 2703, Beijing 100190 (China)

    2010-06-01

    The superconducting SmFeAsO{sub 1-x}F{sub x} (x=0.2) polycrystalline bulks were prepared by the powder-in-tube (PIT) method. The magnetic field and temperature dependences of critical current densities in the samples were investigated by resistive and ac inductive (Campbell's) methods. It was found that a fairly large shielding current density over 10{sup 9} A/m{sup 2}, which is considered to correspond to the local critical current density, flows locally with the perimeter size similar to the average grain size of the bulk samples, while an extremely low transport current density of about 10{sup 5} A/m{sup 2} corresponding to the global critical current density flows through the whole sample. Furthermore, a unique history dependence of global critical current density was observed, i.e., it shows a smaller value in the increasing-field process than that in the decreasing-field process. The history dependence of global critical current characteristic in our case can be ascribed to the existence of the weak-link property between the grains in SmFeAsO{sub 1-x}F{sub x} bulk.

  11. Critical current characteristics and history dependence in superconducting SmFeAsOF bulk

    Science.gov (United States)

    Ni, B.; Ge, J.; Kiuchi, M.; Otabe, E. S.; Gao, Z.; Wang, L.; Qi, Y.; Zhang, X.; Ma, Y.

    2010-06-01

    The superconducting SmFeAsO1-xFx (x=0.2) polycrystalline bulks were prepared by the powder-in-tube (PIT) method. The magnetic field and temperature dependences of critical current densities in the samples were investigated by resistive and ac inductive (Campbell's) methods. It was found that a fairly large shielding current density over 109 A/m2, which is considered to correspond to the local critical current density, flows locally with the perimeter size similar to the average grain size of the bulk samples, while an extremely low transport current density of about 105 A/m2 corresponding to the global critical current density flows through the whole sample. Furthermore, a unique history dependence of global critical current density was observed, i.e., it shows a smaller value in the increasing-field process than that in the decreasing-field process. The history dependence of global critical current characteristic in our case can be ascribed to the existence of the weak-link property between the grains in SmFeAsO1-xFx bulk.

  12. Size dependence of phase transition temperatures of ferromagnetic ,ferroelectric and superconductive nanocrystals

    Institute of Scientific and Technical Information of China (English)

    LANG Xing-you; JIANG Qing

    2007-01-01

    With the miniaturization of devices,size and interface effects become increasingly important for the properties and performances of nanomaterials.Here,we present a thermodynamic approach to the mechanism behind size-induced unusual behavior in the phase stabilities of ferromagnetic(FM),antiferromagnetic(AFM),ferroelectric (FE),and superconductive(SC)nanocrystals,which are different dramatically from their bulk counterparts.This method is based on the Lindemann criterion for melting,Mott's expression for the vibrational melting entropy,and the Shi model for the size-dependent melting temperature.Simple and unified functions,without any adjustable parameter,are established for the size and interface dependences of thermal and phase stabilities of FM,AFM,FE and SC nanocrystals.According to these analytic functions,as the size of nanocrystals is reduced,the thermal and phasestabilities may strengthen or weaken,depending on the confluence of the.surface/volume ratio of nanocrystals and the FM(AFM,FE or SC)/substrate interface situations.The validity of this model is confirmed by a large number of experimental results.This theory will be significant for the choice of materials and the design of devices for practicalapplication.

  13. Electromechanical properties of superconducting MgB{sub 2} wire

    Energy Technology Data Exchange (ETDEWEB)

    Salama, K; Zhou, Y X; Hanna, M; Alessandrini, M; Putman, P T; Fang, H [Mechanical Engineering Department and Texas Center for Superconductivity, University of Houston, Houston, TX (United States)

    2005-12-15

    The current-carrying capability of superconducting wires is degraded by stress. Therefore electromechanical properties are one of the key feedback parameters needed for progress in conductor applications. In this work, uniaxial tensile stresses and bending stresses were applied to Fe /MgB{sub 2} wires at room temperature, followed by measurement of critical current using a transport method at 4.2 K. Basic mechanical properties were calculated from the measured stress-strain characteristics. The irreversible tensile strain at which the critical current density of MgB{sub 2} wire starts to degrade was found to be 0.5%. In addition, the degradation of I{sub c} with decreasing bending diameters was found to be very rapid for wires that were deformed after the heat treatment that forms the MgB{sub 2} compound, while not much degradation of I{sub c} was found for wires that were bent before being annealed. SEM observations confirmed that cracks could be healed by post-annealing.

  14. Effects of phosphorous doping on the superconducting properties of SmFeAs(O,F)

    Energy Technology Data Exchange (ETDEWEB)

    Singh, Shiv Jee, E-mail: shivjees@gmail.com; Shimoyama, Jun-ichi; Yamamoto, Akiyasu; Ogino, Hiraku; Kishio, Kohji

    2014-09-15

    Highlights: • Doping effects of P on the superconducting properties of Sm1111 is studied. • P doping induces chemical pressure and strongly deteriorate the superconductivity. • These isovalent doping effects are compared with Mn and Ni doping in FeAs layers. • Electron type charge carrier dominates in the transport properties. • Doping without disrupting FeAs layer is a best way for high T{sub c} superconductivity. - Abstract: The systematic doping effect induced by the isovalent substitution of P for As on the superconducting properties of F-doped SmFeAsO{sub 0.88}F{sub 0.12} (Sm1111) has been studied by physical and magnetic measurements. The cell volume (V) decreases with P doping and the anisotropic chemical pressure might be induced. However, the superconducting transition temperature (T{sub c}) and the upper critical field (H{sub c2}) are suppressed. Thermoelectric power (S) indicates the majority of electron type charge carriers in support of Hall measurements and its magnitude does not change very much for different P concentrations. The present investigation depicts that isovalent substitutions in the FeAs layer strongly deteriorate the superconducting properties of Sm1111 as a result of increase in chemical pressure. These isovalent substitution effects are comparatively discussed with hole (Mn) and electron (Ni) type substitutions in the superconducting layer of Sm1111.

  15. Microstructure and superconducting properties of MgB{sub 2} films prepared by solid state reaction of multilayer precursors of the elements

    Energy Technology Data Exchange (ETDEWEB)

    Kugler, B. [Max Planck Institute for Intelligent Systems, Heisenbergstr, 3, D-70569 Stuttgart (Germany); Aalen University, Beethovenstr, 1, D-73430 Aalen (Germany); Stahl, C.; Treiber, S. [Max Planck Institute for Intelligent Systems, Heisenbergstr, 3, D-70569 Stuttgart (Germany); Soltan, S. [Max Planck Institute for Solid State Research, Heisenbergstr, 1, D-70569 Stuttgart (Germany); Physics Department, Faculty of Science, Helwan University,11792-Cairo (Egypt); Haug, S.; Schuetz, G. [Max Planck Institute for Intelligent Systems, Heisenbergstr, 3, D-70569 Stuttgart (Germany); Albrecht, J., E-mail: ja@mf.mpg.de [Aalen University, Beethovenstr, 1, D-73430 Aalen (Germany)

    2012-09-30

    Surface morphology and superconducting properties of MgB{sub 2} superconducting thin films prepared by ex-situ annealing of multilayer Mg/B precursors in Mg vapor are studied. Depending on the precursor structure different physical and microstructural properties of the superconductor evolve. Structure and composition of the films are analyzed by scanning electron microscopy and wavelength dispersive x-ray spectroscopy. It is found that certain precursor structures can lead to high quality superconducting films, however, in specific precursor structures mechanical stress leads to the formation of wrinkles strongly affecting the superconducting homogeneity of the films. A correlation between microstructure and superconducting properties, such as pinning or critical current density, can be provided via magneto-optical Faraday microscopy. - Highlights: Black-Right-Pointing-Pointer Correlation of microstructure and properties of MgB2 films Black-Right-Pointing-Pointer Electron and ion based analysis of microstructure Black-Right-Pointing-Pointer Superconducting properties by magneto-optical imaging Black-Right-Pointing-Pointer Enhanced magnetic field stability by a particular microstructure.

  16. Temperature dependence of the superconducting proximity effect quantified by scanning tunneling spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Stępniak, A.; Caminale, M.; Leon Vanegas, A. A.; Oka, H.; Sander, D., E-mail: sander@mpi-halle.mpg.de [Max-Planck-Institut für Mikrostrukturphysik, Weinberg 2, 06120 Halle (Saale) (Germany); Kirschner, J. [Max-Planck-Institut für Mikrostrukturphysik, Weinberg 2, 06120 Halle (Saale) (Germany); Institut für Physik, Martin-Luther-Universität Halle-Wittenberg, 06120 Halle (Saale) (Germany)

    2015-01-15

    Here, we present the first systematic study on the temperature dependence of the extension of the superconducting proximity effect in a 1–2 atomic layer thin metallic film, surrounding a superconducting Pb island. Scanning tunneling microscopy/spectroscopy (STM/STS) measurements reveal the spatial variation of the local density of state on the film from 0.38 up to 1.8 K. In this temperature range the superconductivity of the island is almost unaffected and shows a constant gap of a 1.20 ± 0.03 meV. Using a superconducting Nb-tip a constant value of the proximity length of 17 ± 3 nm at 0.38 and 1.8 K is found. In contrast, experiments with a normal conductive W-tip indicate an apparent decrease of the proximity length with increasing temperature. This result is ascribed to the thermal broadening of the occupation of states of the tip, and it does not reflect an intrinsic temperature dependence of the proximity length. Our tunneling spectroscopy experiments shed fresh light on the fundamental issue of the temperature dependence of the proximity effect for atomic monolayers, where the intrinsic temperature dependence of the proximity effect is comparably weak.

  17. Temperature dependence of the superconducting proximity effect quantified by scanning tunneling spectroscopy

    Directory of Open Access Journals (Sweden)

    A. Stępniak

    2015-01-01

    Full Text Available Here, we present the first systematic study on the temperature dependence of the extension of the superconducting proximity effect in a 1–2 atomic layer thin metallic film, surrounding a superconducting Pb island. Scanning tunneling microscopy/spectroscopy (STM/STS measurements reveal the spatial variation of the local density of state on the film from 0.38 up to 1.8 K. In this temperature range the superconductivity of the island is almost unaffected and shows a constant gap of a 1.20 ± 0.03 meV. Using a superconducting Nb-tip a constant value of the proximity length of 17 ± 3 nm at 0.38 and 1.8 K is found. In contrast, experiments with a normal conductive W-tip indicate an apparent decrease of the proximity length with increasing temperature. This result is ascribed to the thermal broadening of the occupation of states of the tip, and it does not reflect an intrinsic temperature dependence of the proximity length. Our tunneling spectroscopy experiments shed fresh light on the fundamental issue of the temperature dependence of the proximity effect for atomic monolayers, where the intrinsic temperature dependence of the proximity effect is comparably weak.

  18. Superconductivity and physical properties of CaPd2Ge2 single crystals.

    Science.gov (United States)

    Anand, V K; Kim, H; Tanatar, M A; Prozorov, R; Johnston, D C

    2014-10-08

    We present the superconducting and normal state properties of CaPd(2)Ge(2) single crystals investigated by magnetic susceptibility χ, isothermal magnetization M, heat capacity Cp, in-plane electrical resistivity ρ and London penetration depth λ versus temperature T and magnetic field H measurements. Bulk superconductivity is inferred from the ρ(T) and Cp(T) data. The ρ(T) data exhibit metallic behavior and a superconducting transition with T(c onset) = 1.98 K and zero resistivity at T(c 0) = 1.67 K. The χ(T) reveals the onset of superconductivity at 2.0 K. For T > 2.0 K, the χ(T) and M(H) are weakly anisotropic paramagnetic with χ(ab) > χ(c). The Cp(T) data confirm the bulk superconductivity below T(c) = 1.69(3) K. The superconducting state electronic heat capacity is analyzed within the framework of a single-band α-model of BCS superconductivity and various normal and superconducting state parameters are estimated. Within the α-model, the Cp(T) data and the ab plane λ(T) data consistently indicate a moderately anisotropic s-wave gap with Δ(0)/k(B)T(c) ≈ 1.6, somewhat smaller than the BCS value of 1.764. The relationship of the heat capacity jump at Tc and the penetration depth measurement to the anisotropy in the s-wave gap is discussed.

  19. Effects of phosphorous doping on the superconducting properties of SmFeAs(O,F)

    Science.gov (United States)

    Singh, Shiv Jee; Shimoyama, Jun-ichi; Yamamoto, Akiyasu; Ogino, Hiraku; Kishio, Kohji

    2014-09-01

    The systematic doping effect induced by the isovalent substitution of P for As on the superconducting properties of F-doped SmFeAsO0.88F0.12 (Sm1111) has been studied by physical and magnetic measurements. The cell volume (V) decreases with P doping and the anisotropic chemical pressure might be induced. However, the superconducting transition temperature (Tc) and the upper critical field (Hc2) are suppressed. Thermoelectric power (S) indicates the majority of electron type charge carriers in support of Hall measurements and its magnitude does not change very much for different P concentrations. The present investigation depicts that isovalent substitutions in the FeAs layer strongly deteriorate the superconducting properties of Sm1111 as a result of increase in chemical pressure. These isovalent substitution effects are comparatively discussed with hole (Mn) and electron (Ni) type substitutions in the superconducting layer of Sm1111.

  20. Analysis of the local superconducting properties in YBCO coated conductors with striations

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Mu Yong; Park, Sang Kook; Park, Hee Yeon; Ri, Hyeong Cheol [Dept. of Physics, Kyungpook National University, Daegu (Korea, Republic of)

    2015-06-15

    In order to realize economical applications, it is important to reduce the ac loss of 2G high-temperature superconductor coated conductors. It seems to be reasonable that a multi-filamentary wire can decrease the magnetization loss. In this study, we prepared two samples of YBCO coated conductors with striations. We measured local superconducting properties of both samples by using Low Temperature Scanning Laser and Hall Probe Microscopy (LTSLHPM). The distribution of the local critical temperature of samples was analyzed from experimental results of Low Temperature Scanning Laser Microscopy (LTSLM) near the superconducting transition temperature. According to LTSLM results, spatial distributions of the local critical temperature of both samples are homogeneous. The local current density and the local magnetization in samples were explored from measuring stray fields by using Scanning Hall Probe Microscopy (SHPM). From SHPM results, the remanent field pattern of the one bridge sample in an external magnetic field confirms the Bean's critical state model and the three bridge sample has similar remanent field pattern of the one bridge sample. The local magnetization curve in the three bridge sample was measured from external fields from -500 Oe to 500 Oe. We visualized that the distribution of local hysteresis loss are related in the distribution of the remanent field of the three bridge sample. Although the field dependence of the critical current density must be taken into account, the relation of the local hysteresis loss and the remanent field from Bean's model was useful.

  1. Microwave properties of YBa2Cu3O(7-delta) high-transition-temperature superconducting thin films measured by the power transmission method

    Science.gov (United States)

    Miranda, F. A.; Gordon, W. L.; Bhasin, K. B.; Heinen, V. O.; Warner, J. D.

    1991-01-01

    The microwave response of YBa2Cu3O(7-delta) superconducting thin films deposited on LaAlO3, MgO, YSZ, and LaGaO3 substrates are studied. It is found that the microwave transmission properties are very weakly dependent on temperature in the normal state but change drastically upon transition to the superconducting state. In particular, the transmission decreases and there is a negative phase shift with respect to the phase at room temperature when the sample is cooled through its transition temperature. The magnetic penetration depth for all the films was determined from the surface reactance of the films. The microwave complex conductivity is determined in both the normal and the superconducting state. It is observed that both sigma1 and sigma2 increase in transition to the superconducting state. The surface resistivity is calculated for all the films.

  2. Superconductivity and Properties of FeTeOx Films

    Energy Technology Data Exchange (ETDEWEB)

    D Telesca; j Budnick; B Sinkovic; R Ramprasad; B Wells

    2011-12-31

    Films of the parent compound FeTe can be made superconducting via the addition of interstitial oxygen. The process is reversible. We have characterized the new superconductors with a variety of experiments. X-ray diffraction shows that the superconductor has the same overall structure but a small lattice constant change compared to pure FeTe. X-ray absorption shows that superconducting FeTeO{sub x} has a nominal valence of 3+. DFT calculations show the most likely position for interstitial oxygen and confirm that such oxygen incorporation does not produce a large change in structure.

  3. Physical Properties of Niobium and Specifications for Fabrication of Superconducting Cavities

    Energy Technology Data Exchange (ETDEWEB)

    Antoine, C.; Foley, M.; Dhanaraj, N.; /Fermilab

    2011-07-01

    It is important to distinguish among the properties of niobium, the ones that are related to the cavity's SRF performances, the formability of the material, and the mechanical behavior of the formed cavity. In general, the properties that dictate each of the above mentioned characteristics have a detrimental effect on one another and in order to preserve the superconducting properties without subduing the mechanical behavior, a balance has to be established. Depending on the applications, some parameters become less important and an understanding of the physical origin of the requirements might help in this optimization. SRF applications require high purity niobium (high RRR), but pure niobium is very soft from fabrication viewpoint. Moreover conventional fabrication techniques tend to override the effects of any metallurgical process meant to strengthen it. As those treatments dramatically affect the forming of the material they should be avoided. These unfavorable mechanical properties have to be accounted for in the design of the cavities rather than in the material specification. The aim of this paper is to review the significance of the important mechanical properties used to characterize niobium and to present the optimal range of values. Most of the following information deals with the specification of sheets for cell forming unless otherwise noted.

  4. Randomly distributed spin induced suppression of superconducting properties in Gd-123

    Science.gov (United States)

    Biswas, B.; Haldar, S.; Mukherjee, I.; Kumar Ghosh, Ajay

    2017-02-01

    Suppression of superconducting property in presence of inhomogeneous spin distribution in GdBa2Cu3-xCoxO6.9 has been studied. A superconducting sample without Co exhibits superconducting transition at 56.1 K. The current-voltage (I-V) characteristics exhibit nonlinear to linear transformation above a certain temperature. Two other samples (i) with Co and (ii) without Cu are found to be nonsuperconducting with very high resistive in nature at lower temperature. Localization length decreases with the increase in Co substitution. Suppression of the superconducting transition has been attributed to the change in the magnetic fluctuations induced by the randomness in spin substitution. An exponent has been extracted to understand the current-voltage behaviour. Kosterlitz-Thouless (KT) transition may be affected strongly by the shifting of magnetic fluctuations.

  5. Structural properties of superconducting Bi-2223/Ag tapes

    Energy Technology Data Exchange (ETDEWEB)

    Gottschalck Andersen, L.

    2001-05-01

    The structural properties of silver clad high-T{sub c} superconducting ceramic tapes of (Bi,Pb){sub 2}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub x} (Bi-2223) have been investigated by means of synchrotron X-ray diffraction (including the 3DXRD microscope setup), transmission electron microscopy (TEM) and scanning electron microscopy (SEM) with energy dispersive X-ray analysis (EDS). By synchrotron X-ray diffraction in situ studies of the phase development during the transformation of (Bi,Pb){sub 2}Sr{sub 2}Ca{sub 1}Cu{sub 2}O{sub x} (Bi-2212) into Bi-2223, the stoichiometry changes and the texture have been performed during annealing in 8% O{sub 2} and in air. Furthermore, an annealing with two high temperature cycles has been performed to study the equilibrium phenomena. During heating (Ca,Sr){sub 2}PbO{sub 4} decomposes at temperatures between 700 deg. C and 840 deg.C. Simultaneously, the Bi-2212 lattice contracts, indicating an incorporation of Pb. Moreover, the grain mis-alignment decreases significantly. In air we have observed that Bi-2212 partly dissociates into (Ca,Sr){sub 2}CuO{sub 3} and a liquid at temperatures above 812 deg. C. At the annealing temperature Bi-2212 and (Ca,Sr){sub 2}CuO{sub 3} react with the liquid to form Bi-2223. The transformation mechanism is discussed. During cooling below {approx}750 deg.C (Ca,Sr){sub 2}CuO{sub 3} and the liquid mainly transform into Bi-2201. Below {approx}780 deg. C Bi-2223 decomposes to 3221. In addition, a two-step cooling experiment and a decomposition study have been performed in 8% O{sub 2}. By TEM the grain and colony size in the c-axis direction, the angles of c-axis tilt grain boundaries and the intergrowth content are investigated. A fully processed tape has on average 50% thicker grains than a tape after the 1st annealing. The angles of c-axis tilt grain boundaries are on average 14 deg. and 26 deg. for the fully processed tape and the tape after the 1st annealing, respectively. The intergrowth content (15%) and

  6. Superconducting MgB2 flowers: growth mechanism and their superconducting properties

    Science.gov (United States)

    Seong, Won Kyung; Ranot, Mahipal; Lee, Ji Yeong; Yang, Cheol-Woong; Lee, Jae Hak; Oh, Young Hoon; Ahn, Jae-Pyoung; Kang, Won Nam

    2016-04-01

    We report for the first time the growth and the systematic study of the growth mechanism for flower-like MgB2 structures fabricated on the substrates for solid-state electronics by the hybrid physical-chemical vapor deposition (HPCVD) technique. The MgB2 flower has a width of 30 μm and a height of 10 μm. The superconductivity of MgB2 flowers was confirmed by a magnetization measurement, and the transition temperature is 39 K, which is comparable with high-quality bulk samples. The excellent current-carrying capability was demonstrated by MgB2 flowers. To understand the nucleation and growth mechanism of MgB2 flowers a very systematic study was performed by a high-resolution transmission electron microscope (HRTEM) and atom probe (AP) microscopy. The HRTEM revealed that the seed grain of a MgB2 flower has a [101¯0] direction, and the flower is composed of micro-columnar MgB2 grains having pyramidal tips and which are grown along the (0001) plane. A clear understanding of the growth mechanism for MgB2 flowers could lead to the growth of other low-dimensional MgB2 structures for superconducting electronic devices.

  7. Effect of the time-dependent coupling on a superconducting qubit-field system under decoherence: Entanglement and Wehrl entropy

    Energy Technology Data Exchange (ETDEWEB)

    Abdel-Khalek, S., E-mail: sayedquantum@yahoo.co.uk [Mathematics Department, Faculty of Science, Sohag University, 82524 Sohag (Egypt); The Abdus Salam International Centre for Theoretical Physics, Strada Costiera 11, Miramare-Trieste (Italy); Berrada, K. [The Abdus Salam International Centre for Theoretical Physics, Strada Costiera 11, Miramare-Trieste (Italy); Al Imam Mohammad Ibn Saud Islamic University (IMSIU), College of Science, Department of Physics, Riyadh (Saudi Arabia); Eleuch, H. [Department of Physics, McGill University, 3600 rue University, Montreal, QC, H3A 2T8 (Canada); Department of Physics, Université de Montréal, 2900 boul. douard-Montpetit, Montreal, QC, H3T 1J4 (Canada)

    2015-10-15

    The dynamics of a superconducting (SC) qubit interacting with a field under decoherence with and without time-dependent coupling effect is analyzed. Quantum features like the collapse–revivals for the dynamics of population inversion, sudden birth and sudden death of entanglement, and statistical properties are investigated under the phase damping effect. Analytic results for certain parametric conditions are obtained. We analyze the influence of decoherence on the negativity and Wehrl entropy for different values of the physical parameters. We also explore an interesting relation between the SC-field entanglement and Wehrl entropy behavior during the time evolution. We show that the amount of SC-field entanglement can be enhanced as the field tends to be more classical. The studied model of SC-field system with the time-dependent coupling has high practical importance due to their experimental accessibility which may open new perspectives in different tasks of quantum formation processing.

  8. Nonequilibrium interpretation of DC properties of NbN superconducting hot electron bolometers

    CERN Document Server

    Shcherbatenko, M; Lobanov, Yu; Maslennikov, S N; Kaurova, N; Finkel, M; Voronov, B; Goltsman, G; Klapwijk, T M

    2016-01-01

    We present a physically consistent interpretation of the dc electrical properties of niobiumnitride (NbN)-based superconducting hot-electron bolometer (HEB-) mixers, using concepts of nonequilibrium superconductivity. Through this we clarify what physical information can be extracted from the resistive transition and the dc current-voltage characteristics, measured at suitably chosen temperatures, and relevant for device characterization and optimization. We point out that the intrinsic spatial variation of the electronic properties of disordered superconductors, such as NbN, leads to a variation from device to device.

  9. Nonequilibrium Properties of Variable-Thickness Superconducting Micro-bridges.

    Science.gov (United States)

    1978-01-01

    shor t is always lef t near the leads to prevent acci- dental burnout. This short is only removed once the leads are soldered (with an unplugged and...interest here, by overlaying a superconduct- ing film with a normal metal,14 by optical, phonon or quasi— 15 16particle injection, by ion implantation or...which might not be justified in the regimes of interest. Experimentall y, further work is requir ed in order to understand the low voltage I—V

  10. Orbital-dependent two-band superconductivity in MgB sub 2

    CERN Document Server

    Yanagisawa, T

    2003-01-01

    We show that a two-band model with k-dependent superconducting gaps well describes the transmission and optical conductivity measured for MgB sub 2 thin films. It is also shown that the two-band anisotropic modelconsistently describes the specific-heat jump and thermodynamic critical magnetic field H sub c. A single-gap anisotropic model is shown to be insufficient to understand consistently optical and thermodynamic behaviors. In our model, the pairing symmetry in each band has an anisotropic characteristic which is determined almost uniquely; the superconducting gap in the sigma-band has anisotropy in the ab-plane and the gap in the pi-band has a prolate form exhibiting anisotropy in the c-direction. (author)

  11. Anisotropic superconducting property studies of single crystal PbTaSe2

    Science.gov (United States)

    Sankar, Raman; Narsinga Rao, G.; Panneer Muthuselvam, I.; Chang, Tay-Rong; Jeng, H. T.; Senthil Murugan, G.; Lee, Wei-Li; Chou, F. C.

    2017-03-01

    The anisotropic superconducting properties of PbTaSe2 single crystal is reported. Superconductivity with T c  =  3.83  ±  0.02 K has been characterized fully with electrical resistivity ρ(T), magnetic susceptibility χ(T), and specific heat C p (T) measurements using single crystal samples. The superconductivity is type-II with lower critical field H c1 and upper critical field H c2 of 65 and 450 Oe (H⊥  to the ab-plane), 140 and 1500 Oe (H|| to the ab-plane), respectively. These results indicate that the superconductivity of PbTaSe2 is anisotropic. The superconducting anisotropy, electron-phonon coupling λ ep, superconducting energy gap Δ0, and the specific heat jump ΔC/γT c at T c confirms that PbTaSe2 can be categorized as a bulk superconductor.

  12. Anisotropic superconducting property studies of single crystal PbTaSe2.

    Science.gov (United States)

    Sankar, Raman; Rao, G Narsinga; Muthuselvam, I Panneer; Chang, Tay-Rong; Jeng, H T; Murugan, G Senthil; Lee, Wei-Li; Chou, F C

    2017-03-08

    The anisotropic superconducting properties of PbTaSe2 single crystal is reported. Superconductivity with T c  =  3.83  ±  0.02 K has been characterized fully with electrical resistivity ρ(T), magnetic susceptibility χ(T), and specific heat C p (T) measurements using single crystal samples. The superconductivity is type-II with lower critical field H c1 and upper critical field H c2 of 65 and 450 Oe (H⊥  to the ab-plane), 140 and 1500 Oe (H|| to the ab-plane), respectively. These results indicate that the superconductivity of PbTaSe2 is anisotropic. The superconducting anisotropy, electron-phonon coupling λ ep, superconducting energy gap Δ0, and the specific heat jump ΔC/γT c at T c confirms that PbTaSe2 can be categorized as a bulk superconductor.

  13. Higher Order Mode Properties of Superconducting Two-Spoke Cavities

    Energy Technology Data Exchange (ETDEWEB)

    Hopper, C. S.; Delayen, J. R.; Olave, R. G.

    2011-07-01

    Multi-Spoke cavities lack the cylindrical symmetry that many other cavity types have, which leads to a more complex Higher Order Mode (HOM) spectrum. In addition, spoke cavities offer a large velocity acceptance which means we must perform a detailed analysis of the particle velocity dependence for each mode's R/Q. We present here a study of the HOM properties of two-spoke cavities designed for high-velocity applications. Frequencies, R/Q and field profiles of HOMs have been calculated and are reported.

  14. Thermal properties of a large-bore cryocooled 10 T superconducting magnet for a hybrid magnet

    Energy Technology Data Exchange (ETDEWEB)

    Ishizuka, M., E-mail: Mas_Ishizuka@shi.co.j [Graduate School of Engineering, Tohoku University, 6-6 Aramaki Aza Aoba, Aoba-ku, Sendai 980-8579 (Japan); Research and Development Center, Sumitomo Heavy Industries, Ltd., 19 Natsushima-chou, Yokosuka, Kanagawa 237-8555 (Japan); Hamajima, T. [Graduate School of Engineering, Tohoku University, 6-6 Aramaki Aza Aoba, Aoba-ku, Sendai 980-8579 (Japan); Itou, T. [Ehime Works, Sumitomo Heavy Industries, Ltd., 5-2 Soubiraki-cho, Niihama, Ehime 792-8588 (Japan); Sakuraba, J. [Research and Development Center, Sumitomo Heavy Industries, Ltd., 19 Natsushima-chou, Yokosuka, Kanagawa 237-8555 (Japan); Nishijima, G.; Awaji, S.; Watanabe, K. [Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577 (Japan)

    2010-11-01

    A cryocooled 10 T superconducting magnet with a 360 mm room temperature bore has been developed for a hybrid magnet. The superconducting magnet cooled by four Gifford-McMahon cryocoolers has been designed to generate a magnetic field of 10 T. Since superconducting wires composed of coils were subjected to large hoop stress over 150 MPa and Nb{sub 3}Sn superconducting wires particularly showed a low mechanical strength due to those brittle property, Nb{sub 3}Sn wires strengthened by NbTi-filaments were developed for the cryocooled superconducting magnet. We have already reported that the hybrid magnet could generate the resultant magnetic field of 27.5 T by adding 8.5 T from the superconducting magnet and 19 T from a water-cooled Bitter resistive magnet, after the water-cooled resistive magnet was inserted into the 360 mm room temperature bore of the cryocooled superconducting magnet. When the hybrid magnet generated the field of 27.5 T, it achieved the high magnetic-force field (B x {partial_derivative}Bz/{partial_derivative}z) of 4500 T{sup 2}/m, which was useful for magneto-science in high fields such as materials levitation research. In this paper, we particularly focus on the cause that the cryocooled superconducting magnet was limited to generate the designed magnetic field of 10 T in the hybrid magnet operation. As a result, it was found that there existed mainly two causes as the limitation of the magnetic field generation. One was a decrease of thermal conductive passes due to exfoliation from the coil bobbin of the cooling flange. The other was large AC loss due to both a thick Nb{sub 3}Sn layer and its large diameter formed on Nb-barrier component in Nb{sub 3}Sn wires.

  15. Effect of Pressure on Magneto-Transport Properties in the Superconducting and Normal Phases of the Metallic Double Chain Compound Pr2Ba4Cu7O15-δ

    Science.gov (United States)

    Kuwabara, Masayoshi; Matsukawa, Michiaki; Sugawara, Keisuke; Taniguchi, Haruka; Matsushita, Akiyuki; Hagiwara, Makoto; Sano, Kazuhiro; Ōno, Yoshiaki; Sasaki, Takahiko

    2016-12-01

    To examine the electronic phase diagram of superconducting CuO double chains, we report the effect of external pressure on the magneto-transport properties in superconducting and non-superconducting polycrystalline samples of Pr2Ba4Cu7O15-δ at low temperatures (1.8-40 K) under various magnetic fields (up to 14 T). In the as-sintered non-superconducting sample, the magneto-resistance (MR) follows a power law of H3/2 at low temperatures, which is in no agreement with the H2 dependence of MR in the PrBa2Cu4O8 system. The negative pressure dependence of the superconducting phase is qualitatively consistent with a theoretical prediction on the basis of the Tomonaga-Luttinger liquid theory. The 48-h-reduced superconducting sample at ambient pressure exhibits no clear increase in MR for T > Tc,on = 26.5 K. In contrast, with the application of pressure to the superconducting sample, the MR effects reappear and are also well fitted by H3/2. The model of slightly warped Fermi surfaces explains not only the MR effect of the non-superconducting sample, but is also related to the reasons for the pressure-induced MR phenomena of the superconducting sample.

  16. Magnetic field and temperature dependence of the critical vortex velocity in type-II superconducting films.

    Science.gov (United States)

    Grimaldi, G; Leo, A; Cirillo, C; Attanasio, C; Nigro, A; Pace, S

    2009-06-24

    We study the vortex dynamics in the instability regime induced by high dissipative states well above the critical current in Nb superconducting strips. The magnetic field and temperature behavior of the critical vortex velocity corresponding to the observed dynamic instability is ascribed to intrinsic non-equilibrium phenomena. The Larkin-Ovchinnikov (LO) theory of electronic instability in high velocity vortex motion has been applied to interpret the temperature dependence of the critical vortex velocity. The magnetic field dependence of the vortex critical velocity shows new features in the low-field regime not predicted by LO.

  17. Magnetic field and temperature dependence of the critical vortex velocity in type-II superconducting films

    Energy Technology Data Exchange (ETDEWEB)

    Grimaldi, G; Leo, A; Cirillo, C; Attanasio, C; Nigro, A; Pace, S [CNR-INFM Laboratorio Regionale SuperMat, Via Salvador Allende, I-84081 Baronissi (Italy)], E-mail: grimaldi@sa.infn.it

    2009-06-24

    We study the vortex dynamics in the instability regime induced by high dissipative states well above the critical current in Nb superconducting strips. The magnetic field and temperature behavior of the critical vortex velocity corresponding to the observed dynamic instability is ascribed to intrinsic non-equilibrium phenomena. The Larkin-Ovchinnikov (LO) theory of electronic instability in high velocity vortex motion has been applied to interpret the temperature dependence of the critical vortex velocity. The magnetic field dependence of the vortex critical velocity shows new features in the low-field regime not predicted by LO.

  18. Characterization of superconducting properties of BSCCO powder prepared by attrition milling

    Energy Technology Data Exchange (ETDEWEB)

    Patel, R H [Brockhouse Institute for Materials Research, McMaster University, 1280 Main Street West, Hamilton, ON, L8S 4M1 (Canada); Nabialek, A [Brockhouse Institute for Materials Research, McMaster University, 1280 Main Street West, Hamilton, ON, L8S 4M1 (Canada); Niewczas, M [Brockhouse Institute for Materials Research, McMaster University, 1280 Main Street West, Hamilton, ON, L8S 4M1 (Canada)

    2005-03-01

    The nonconventional technique of attrition milling has been used to produce superconducting BSCCO powder from the starting powders of oxides and carbonates of Bi, Sr, Ca and Cu. This process shows a drastic reduction in processing time by 80% from the conventional solid-state reaction. The completion of the reaction was determined by x-ray diffraction of the milled powder. The superconducting property characterization was done for the critical transition temperature and the critical current density of the processed powder by magnetic methods. The attrition milled powder shows a T{sub c} of about 87 K after two high temperature treatments for 60 h and J{sub c} of the order of 10{sup 6} A cm{sup -2} at 4 K. The superconducting properties of the processed powder are discussed in the framework of the Bean model.

  19. International round robin test for mechanical properties of REBCO superconductive tapes at room temperature

    NARCIS (Netherlands)

    Osamura, K.; Shin, H.S.; Weiss, K.; Nyilas, A.; Nijhuis, A.; Yamamoto, K.; Machiya, S.; Nishijima, G.

    2014-01-01

    An international round robin test was promoted to establish a test method for room temperature mechanical properties of commercial REBCO superconductive tapes. Seven laboratories practiced a tensile test under the direction of guideline REBCO13 for four different kinds of REBCO tape. From the stress

  20. International round robin test for mechanical properties of REBCO superconductive tapes at room temperature

    NARCIS (Netherlands)

    Osamura, K.; Shin, H.S.; Weiss, K.; Nyilas, A.; Nijhuis, Arend; Yamamoto, K.; Machiya, S.; Nishijima, G.

    2014-01-01

    An international round robin test was promoted to establish a test method for room temperature mechanical properties of commercial REBCO superconductive tapes. Seven laboratories practiced a tensile test under the direction of guideline REBCO13 for four different kinds of REBCO tape. From the stress

  1. Magnetic response and critical current properties of mesoscopic-size YBCO superconducting samples

    Energy Technology Data Exchange (ETDEWEB)

    Lisboa-Filho, P N [UNESP - Universidade Estadual Paulista, Grupo de Materiais Avancados, Departamento de Fisica, Bauru (Brazil); Deimling, C V; Ortiz, W A, E-mail: plisboa@fc.unesp.b [Grupo de Supercondutividade e Magnetismo, Departamento de Fisica, Universidade Federal de Sao Carlos, Sao Carlos (Brazil)

    2010-01-15

    In this contribution superconducting specimens of YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} were synthesized by a modified polymeric precursor method, yielding a ceramic powder with particles of mesoscopic-size. Samples of this powder were then pressed into pellets and sintered under different conditions. The critical current density was analyzed by isothermal AC-susceptibility measurements as a function of the excitation field, as well as with isothermal DC-magnetization runs at different values of the applied field. Relevant features of the magnetic response could be associated to the microstructure of the specimens and, in particular, to the superconducting intra- and intergranular critical current properties.

  2. Laser patterning: A new approach to measure local magneto-transport properties in multifilamentary superconducting tapes

    Energy Technology Data Exchange (ETDEWEB)

    Sanchez Valdes, C.F. [Superconductivity Laboratory, Magnetism Laboratory, IMRE-Physics Faculty, University of Havana, 10400 Havana (Cuba); Perez-Penichet, C. [Superconductivity Laboratory, Magnetism Laboratory, IMRE-Physics Faculty, University of Havana, 10400 Havana (Cuba); Noda, C. [Superconductivity Laboratory, Magnetism Laboratory, IMRE-Physics Faculty, University of Havana, 10400 Havana (Cuba); Arronte, M. [Laser Technology Laboratory, CICATA-IPN, ALTAMIRA, Altamira 89600, TAMPS (Mexico); Batista-Leyva, A.J. [Department of General Physics and Mathematics, InSTEC, 10400 Havana (Cuba); Haugen, O. [Department of Physics, University of Oslo, Blindern, N-0316 Oslo (Norway); Johansen, T.H. [Department of Physics, University of Oslo, Blindern, N-0316 Oslo (Norway); Han, Z. [Applied Superconductivity Research Center, Department of Physics, Tsinghua University, Beijing 100084 (China); Altshuler, E. [Superconductivity Laboratory, Magnetism Laboratory, IMRE-Physics Faculty, University of Havana, 10400 Havana (Cuba)]. E-mail: ea@infomed.sld.cu

    2007-09-15

    The determination of inter- and intra-filament characteristics in superconducting composites such as BSCCO-Ag tapes is of great importance for material evaluation towards applications. Most attempts to separate the two contributions have relied on indirect methods based on magnetic measurements such as SQUID or magneto-optic imaging techniques. Here we show that laser patterning of superconducting BSCCO-Ag tapes constitutes a simple approach to measure local transport properties in a direct way, even able to separate inter- and intra-filament contributions to the overall transport behavior of the sample.

  3. Homogeneous lattice disorder and superconducting properties of YBa2Cu3O6.9 films.

    Science.gov (United States)

    Pavuna, Davor; Gauzzi, Andrea

    We discuss the striking changes of the superconducting properties of YBa2Cu3O6.9 films to the homogeneous lattice disorder, induced by varying growth temperatures: Tc decreases with increasing disorder, while the width of the resistive transition and the normal state resistivity increase. We estimate the length scale of such dis- order from the broadening DJ of the lt; 005 > X-ray diffraction rocking curves. The suppression of superconductivity and normal conductivity scales as DJ and appears for in-plane lattice coherence lengths rc ≫ 1/DJ smaller than about 10 nm.

  4. Superconductivity without dependence on valence electron density in Zn doped YBCO systems

    Institute of Scientific and Technical Information of China (English)

    Li Ping-Lin; Wang Yong-Yong; Tian Yong-Tao; Wang Jing; Niu Xiao-Li; Wang Jun-Xi; Wang Dan-Dan; Wang Xiao-Xia

    2008-01-01

    This paper reports that the YBa2Cu3-xZnxO7-δ(x=0-0.4)samples are researched by means of x-ray diffraction,calculations of binding energy,the positron experiments and variations of oxygen content.The results of simulated calculations,positron experiments and variations of oxygen content support the existence of cluster effect.Moreover,it is concluded that the cluster effect is an important factor on suppression of high-Tc cuprate superconductivity and the Tc does not depend on the density of valence electron directly.

  5. The focusing properties of both normal and superconducting low energy CW proton Linacs

    CERN Document Server

    Zhihui, Li

    2016-01-01

    The continue wave (CW) high current proton linac has wide applications as the front end of the high power proton machines. The low energy part is the most difficult one and there is no widely accepted solution yet. Both normal conducting and superconducting acceleration structures are thought to be the possible solutions. Although the characteristics of normal conducting structures and superconducting ones are quite different, such as acceleration voltage, maximum electric field and so on, we found the focusing properties of the lattice composed by these two acceleration structures are quite similar for different reasons. The advantages and disadvantages of lattices composed of both the normal conducting and superconducting structures are analysed from the beam dynamics point of view, and their constraints on beam main parameters are discussed.

  6. High-Pressure Structures of Disilane and Their Superconducting Properties

    Science.gov (United States)

    Flores-Livas, José A.; Amsler, Maximilian; Lenosky, Thomas J.; Lehtovaara, Lauri; Botti, Silvana; Marques, Miguel A. L.; Goedecker, Stefan

    2012-03-01

    A systematic ab initio search for low-enthalpy phases of disilane (Si2H6) at high pressures was performed based on the minima hopping method. We found a novel metallic phase of disilane with Cmcm symmetry, which is enthalpically more favorable than the recently proposed structures of disilane up to 280 GPa, but revealing compositional instability below 190 GPa. The Cmcm phase has a moderate electron-phonon coupling yielding a superconducting transition temperature Tc of around 20 K at 100 GPa, decreasing to 13 K at 220 GPa. These values are significantly smaller than previously predicted Tc’s for disilane at equivalent pressure. This shows that similar but different crystalline structures of a material can result in dramatically different Tc’s and stresses the need for a systematic search for a crystalline ground state.

  7. Size Dependence of Oxygen-Annealing Effects on Superconductivity of Fe1+yTe1-xSx

    Science.gov (United States)

    Yamazaki, Teruo; Sakurai, Tatsuya; Yaguchi, Hiroshi

    2016-11-01

    For the Fe-based superconductor Fe1+yTe1-xSx, superconductivity is induced by annealing treatment in oxygen atmosphere, whereas as-grown samples do not show superconductivity. We investigated the sample-size dependence of O2-annealing effects in Fe1.01Te0.91S0.09. The annealing conditions were fixed to 1 atm, 200 °C, and 2 h. We carried out magnetic susceptibility and specific heat measurements in order to evaluate the superconducting volume fraction. We found that Fe1+yTe1-xSx has an optimal size for the induction of bulk superconductivity by O2 annealing. Our results indicate that O2 annealing is probably effective near the surface of samples over a length of a few tens of micro meters.

  8. Anisotropy of normal state and superconducting properties of oxypnictides

    Energy Technology Data Exchange (ETDEWEB)

    Haindl, Silvia; Kidszun, Martin; Kauffmann, Alexander; Kozlova, Nadja; Iida, Kazumasa; Vakaliuk, Oleksii; Panarina, Nadezda; Hess, Christian; Buechner, Bernd [IFW Dresden (Germany); Thersleff, Thomas [IFW Dresden (Germany); The Angstroem Laboratory, Department of Engineering Sciences, Division of Applied Materials Science, Uppsala University (Sweden); Kawaguchi, Takahiko; Ikuta, Hiroshi [Department of Crystalline Materials Science, Nagoya University (Japan); Kampert, Erik; Wosnitza, Joachim [Hochfeld-Magnetlabor Dresden (HLD), Helmholtz-Zentrum Dresden-Rossendorf, Dresden (Germany)

    2013-07-01

    The very large upper critical fields of the oxypnictides complicate the experimental determination of their anisotropy, γ{sub Hc2}, especially at low temperatures. We have applied the anisotropic Ginzburg-Landau scaling on angular-dependent critical-current densities measured for an epitaxially grown La(O{sub 1-x}F{sub x})FeAs thin film. The obtained scaling parameter matches γ{sub H{sub c{sub 2}}} as can be demonstrated by recent magnetotransport measurements in pulsed magnetic fields up to 70 T and down to 2 K. Using the method of critical current scaling H{sub c2}{sup ab} for Nd(O{sub 1-x}F{sub x})FeAs is extrapolated. In addition we discuss normal state electrical transport properties of La(O{sub 1-x}F{sub x})FeAs and Nd(O{sub 1-x}F{sub x})FeAs thin films.

  9. Effect of layer thickness on the superconducting properties in ultrathin Pb films

    Science.gov (United States)

    Durajski, A. P.

    2015-09-01

    Recently, superconductivity was found in one atomic layer of Pb film, promising a new field of research where superconductors can be studied on the atomic level. In the presented paper, we report a theoretical study of the superconductivity in ultrathin Pb films consisting of five to ten monolayers. Using the strong coupling Eliashberg formalism we reproduced the experimental values of critical temperature (TC) and we estimated the superconducting energy gap (Δ (0)), thermodynamic critical field (HC) and the specific heat jump at critical temperature (Δ C≤ft({T}{{C}}\\right)\\equiv {C}{{S}}≤ft({T}{{C}}\\right)-{C}{{N}}≤ft({T}{{C}}\\right)) for a wide range of film thicknesses. In these systems, we found an oscillatory behaviour of the above thermodynamic properties modulated by quantum size effects. Moreover, the large values of 2Δ (0){/k}{{B}}{T}{{C}} and Δ C≤ft({T}{{C}}\\right)/{C}{{N}}≤ft({T}{{C}}\\right), and the small values of {T}{{C}}{C}{{N}}≤ft({T}{{C}}\\right)/{H}{{C}}2(0) prove that the thermodynamic properties of Pb films cannot be correctly described using the Bardeen-Cooper-Schrieffer (BCS) theory of superconductivity due to the strong coupling and retardation effects.

  10. Point contact tunneling spectroscopy apparatus for large scale mapping of surface superconducting properties

    Energy Technology Data Exchange (ETDEWEB)

    Groll, Nickolas; Pellin, Michael J. [Materials Science Division, Argonne National Laboratory, Lemont, Illinois 60439 (United States); Zasadzinksi, John F. [Illinois Institute of Technology, Chicago, Illinois 60616 (United States); Proslier, Thomas, E-mail: prolier@anl.gov [Materials Science Division, Argonne National Laboratory, Lemont, Illinois 60439 (United States); High Energy Physics Division, Argonne National Laboratory, Lemont, Illinois 60439 (United States)

    2015-09-15

    We describe the design and testing of a point contact tunneling spectroscopy device that can measure material surface superconducting properties (i.e., the superconducting gap Δ and the critical temperature T{sub C}) and density of states over large surface areas with size up to mm{sup 2}. The tip lateral (X,Y) motion, mounted on a (X,Y,Z) piezo-stage, was calibrated on a patterned substrate consisting of Nb lines sputtered on a gold film using both normal (Al) and superconducting (PbSn) tips at 1.5 K. The tip vertical (Z) motion control enables some adjustment of the tip-sample junction resistance that can be measured over 7 orders of magnitudes from a quasi-ohmic regime (few hundred Ω) to the tunnel regime (from tens of kΩ up to few GΩ). The low noise electronic and LabVIEW program interface are also presented. The point contact regime and the large-scale motion capabilities are of particular interest for mapping and testing the superconducting properties of macroscopic scale superconductor-based devices.

  11. Spin-dependent boundary conditions for isotropic superconducting Green’s functions

    NARCIS (Netherlands)

    Cottet, A.; Huertas-Hernando, D.; Belzig, W.; Nazarov, Y.V.

    2009-01-01

    The quasiclassical theory of superconductivity provides the most successful description of diffusive heterostructures comprising superconducting elements, namely, the Usadel equations for isotropic Green’s functions. Since the quasiclassical and isotropic approximations break down close to interface

  12. Velocity dependence of rotational loss in Evershed-type superconducting bearings

    Science.gov (United States)

    Hull, John R.; Mulcahy, Thomas M.; Labataille, Joseph F.

    1997-02-01

    Results of free spin down in vacuum are reported for an Evershed-type superconducting bearing in which a permanent magnet (PM) ring is levitated over an array of high-temperature superconductors (HTSs) and under a similar PM ring in magnetic attraction. The velocity dependence of the rotational loss strongly suggests that the observed velocity-dependent losses are primarily due to eddy currents induced in the PM by inhomogeneity of the field produced by the magnetized HTS array. The results show that the Evershed-type bearing is capable of reducing these eddy-current losses to an extremely low level, so that at a maximum magnet rim velocity of 28 m/s, the fractional kinetic-energy loss per hour was 2.4×10-4. Significant levitation heights are also possible, and at a 23 mm height, we measured a low-speed coefficient of friction of 3×10-8.

  13. Angular Dependence of Lateral and Levitation Forces in Asymmetric Small Magnet/Superconducting Systems

    Institute of Scientific and Technical Information of China (English)

    H. M. Al-Khateeb; M. K. Alqadi; F. Y. Alzoubi; N. Y. Ayoub

    2007-01-01

    The dipole-dipole interaction model is used to calculate the angular dependence of lateral and levitation forces on a small permanent magnet and a cylindrical superconductor in the Meissner state lying laterally offthe symmetric axis of the cylinder. Under the assumption that the lateral displacement of the magnet is small compared with the physical dimensions of the system, we obtain analytical expressions for the lateral and levitation forces as functions of geometrical parameters of the superconductor as well as the height, the lateral displacement and the orientation of magnetic moment of the magnet. The effect of thickness and radius of the superconductor on the levitation force is similar to that for a symmetric magnet/superconducting cylinder system, but within the range of lateral displacement. The splitting in the levitation force increases with the increasing angle of orientation of the magnetic moment of the magnet. For a given lateral displacement of the magnet, the lateral force vanishes when the magnetic moment is perpendicular to the surface of the superconductor and has a maximum value when the moment is parallel to the surface. For a given orientation of the magnetic moment, the lateral force has a linear relationship with the lateral displacement. The stability of the magnet above the superconducting cylinder is discussed in detail.

  14. Fracture behaviors of thin superconducting films with field-dependent critical current density

    Energy Technology Data Exchange (ETDEWEB)

    He, An; Xue, Cun; Yong, Huadong; Zhou, Youhe, E-mail: zhouyh@lzu.edu.cn

    2013-09-15

    Highlights: • The fracture behaviors of superconducting films for the Kim model are studied. • The profile of stress intensity factor is generally the same as magnetostriction. • The crack problem of two collinear cracks is also researched for the Kim model. -- Abstract: The fracture behaviors under electromagnetic force with field-dependent critical current density in thin superconducting film are investigated. Applying finite element method, the energy release rates and stress intensity factors of one central crack versus applied field and crack length are obtained for the Bean model and Kim model. It is interesting that the profile of the stress intensity factor is generally the same as the magnetostrictive behavior during one full cycle applied field. Furthermore, the crack problem of two collinear cracks with respect to crack length and distance is also researched for the Kim model. The results show that the energy release rates and stress intensity factors of the two collinear cracks at left tip and right tip are remarkably different for relatively small crack distance and long crack length. This work can offer good estimations and provide a basis for interpretation of cracking and mechanical failure of HTS thin films in numerous real situations.

  15. Tensile properties and probability of filament fracture in Bi-2223 superconducting tapes

    Energy Technology Data Exchange (ETDEWEB)

    Rabara, Michal [School of Engineering, The University of Tokyo, Tokai-mura, Naka-gun, Ibaraki 319-1106 (Japan). E-mail: rabara at tokai.t.u-tokyo.ac.jp; Sekimura, Naoto [School of Engineering, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 117-0033 (Japan); Kitaguchi, Hidetoshi [National Research Institute for Metals, 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047 (Japan); Kovac, Pavol [Institute of Electrical Engineering, Slovak Academy of Sciences, Dubravskacesta 9, 842 39 Bratislava (Slovakia); Demachi, Kazuyuki; Miya, Kenzo [School of Engineering, The University of Tokyo, Tokai-mura, Naka-gun, Ibaraki 319-1106 (Japan)

    1999-07-01

    Investigation of the mechanical properties of Bi-2223 superconducting tapes was performed by tensile tests. The results show rapid degradation of the critical current after exceeding 0.4% strain. The shape of the I{sub c}=f({epsilon}) curves and the so-called irreversible strain remain identical for various magnetic fields (0-8 T) and temperatures (4.2, 20, 77 K), demonstrating independence of the mechanical properties from these parameters. The superconducting tapes were treated as a composite consisting of a plastic matrix with brittle ceramic fibres. Under uniform tensile load, the probability of the filament fracture follows a Weibull distribution. Its inverse function, the probability of the number of unbroken filaments, is compared with the relative degradation of the critical current obtained from experiment. (author)

  16. Influence of hydrostatic pressure on superconducting properties of niobium thin film

    Energy Technology Data Exchange (ETDEWEB)

    Pristáš, Gabriel; Gabáni, Slavomír; Gažo, Emil [Centre of Low Temperature Physics, Institute of Experimental Physics, Slovak Academy of Sciences, Watsonova 47, 040 01 Košice (Slovakia); Komanický, Vladimír; Orendáč, Matúš [Centre of Low Temperature Physics, Faculty of Science, P. J. Šafárik University, Park Angelinum 9, SK-04154 Košice (Slovakia); You, Hoydoo [Materials Science Division, Argonne National Laboratory, Argonne, IL 60439 (United States)

    2014-04-01

    We have studied superconducting properties of niobium thin films under hydrostatic pressures up to 3 GPa. The films with thickness of 100 nm were prepared in the high vacuum DC magnetron sputtering system (with critical temperature TC = 8.95 K at ambient pressure). The produced high quality films have been characterized using electrical resistivity and magnetization measurements, X-ray diffraction, and atomic force microscope imaging. We have observed increase of TC with increasing value of applied pressure (dTC/dp = 73 mK/GPa) up to 3 GPa. This observation is different to pressure effect observed on bulk sample of Nb. In this paper we are discussing the origin of this discrepancy. - Highlights: • We have studied superconducting properties of niobium thin films under pressure. • The 100 nm thick films were prepared in DC magnetron sputtering system. • We have observed different behavior of T{sub C} for thin film and for bulk sample.

  17. Superconducting Properties of the K$_{{x}}$WO$_{3}$ Tetragonal Tungsten Bronze and the Superconducting Phase Diagram of the Tungsten Bronze Family

    OpenAIRE

    Haldolaarachchige, Neel; Gibson, Quinn; Krizan, Jason; Cava, R. J.

    2014-01-01

    We report the superconducting properties of the K$_{x}$WO$_{3}$ tetragonal tungsten bronze. The highest superconducting transition temperature ($T_{c}=2.1$K) was obtained for K$_{0.38}$WO$_{3}$. $T_{c}$ decreases linearly with increasing K content. Using the measured values for the upper critical field $H_{c2}$, and the specific heat $C$, we estimate the orbital critical field $H_{c2}$(0), coherence length $\\xi$(0), Debye temperature $\\Theta _{D}$ and coupling constant $\\lambda _{ep}$. The ma...

  18. Effect of the laser sputtering parameters on the orientation of a cerium oxide buffer layer on sapphire and the properties of a YBa2Cu3Ox superconducting film

    DEFF Research Database (Denmark)

    Mozhaev, P. B.; Ovsyannikov, G. A.; Skov, Johannes

    1999-01-01

    The effect of the laser sputtering parameters on the crystal properties of CeO2 buffer layers grown on a (1 (1) under bar 02) sapphire substrate and on the properties of superconducting YBa2Cu3Ox thin films are investigated. It is shown that (100) and (111) CeO2 growth is observed, depending...

  19. Role of kinetic inductance in transport properties of shunted superconducting nanowires.

    Science.gov (United States)

    Lin, Shi-Zeng; Roy, Dibyendu

    2013-08-14

    Recently, transport measurements have been carried out in resistively shunted long superconducting nanowires (Brenner et al 2012 Phys. Rev. B 85 224507). The measured voltage-current (V-I) characteristics were explained by the appearance of the phase slip centers in the shunted wire, and the whole wire was modeled as a single Josephson junction. The kinetic inductance of the long nanowires used in experiments is generally large. Here we argue that the shunted superconducting nanowire acts as a Josephson junction in series with an inductor. The inductance depends on the length and the cross section of the wire. The inclusion of inductance in our analysis modifies the V-I curves, and increases the rate of switching from the superconducting state to the resistive state. The quantitative differences can be quite large in some practical parameter sets, and might be important to properly understand the experimental results. Our proposed model can be verified experimentally by studying the shunted superconducting nanowires of different lengths and cross sections.

  20. Effect of the Ni site substitution on superconducting properties of YNi 2B 2C

    Science.gov (United States)

    Bud'ko, S. L.; Elmassalami, M.; Fontes, M. B.; Mondragon, J.; Vanoni, W.; Giordanengo, B.; Baggio-Saitovitch, E. M.

    1995-02-01

    Structural and superconducting properties of Y(Ni 1- xM x) 2B 2C compounds with MCo, Fe and Ru have been studied. A fast decrease of Tc with the concentration of the dopants was found. This effect can be attributed to the shift of the Fermi level induced by the dopant concentration with the additional contributions from the chemical-pressure effects and from the decrease of the electronic mean free path.

  1. Titania doping effect on superconducting properties of MgB2 bulk samples

    Science.gov (United States)

    Serrano, G.; Bridoux, G.; Serquis, A.

    2009-05-01

    In this work we study the microstructural and superconducting properties of doped and undoped bulk MgB2 samples prepared by solid-state reaction, with 0 and 2.5 %at. nominal TiO2 nanotubes contents, annealed at different temperatures in the 750-900°C range. We discuss the Tc, Jc and Hc2 performance and their correlation with the different synthesis parameters.

  2. Structural, electronic, superconducting and mechanical properties of ReC and TcC

    Energy Technology Data Exchange (ETDEWEB)

    Kavitha, M.; Priyanga, G. Sudha; Rajeswarapalanichamy, R., E-mail: rajeswarapalanichamy@gmail.com; Santhosh, M. [Department of Physics, N.M.S.S.V.N College, Madurai, Tamilnadu-625019 (India)

    2015-06-24

    The structural, electronic, superconducting and mechanical properties of ReC and TcC are investigated using density functional theory calculations. The lattice constants, bulk modulus, and the density of states are obtained. The calculated lattice parameters are in good agreement with the available results. The density of states reveals that ReC and TcC exhibit metallic behavior at ambient condition. A pressure-induced structural phase transition is observed in both materials.

  3. Superconducting Properties of MgB2 Prepared by High and Ambient Pressures

    Institute of Scientific and Technical Information of China (English)

    REN Zhi-An; CHE Guang-Can; ZHAO Zhong-Xian; CHEN Hong; DONG Cheng; NI Yong-Ming; JIA Shun-Lian; WEN Hai-Hu

    2001-01-01

    The new superconductor MgB2 has been prepared in two ways, by high pressure and ambient pressure synthesis.The superconducting properties were measured and compared. It is found that the sample prepared by highpressure is much denser than that prepared under ambient pressure. Accordingly the high pressure sample has avery narrow transition width and a much higher bulk critical current densityC

  4. Structural, electronic, superconducting and mechanical properties of ReC and TcC

    Science.gov (United States)

    Kavitha, M.; Priyanga, G. Sudha; Rajeswarapalanichamy, R.; Santhosh, M.

    2015-06-01

    The structural, electronic, superconducting and mechanical properties of ReC and TcC are investigated using density functional theory calculations. The lattice constants, bulk modulus, and the density of states are obtained. The calculated lattice parameters are in good agreement with the available results. The density of states reveals that ReC and TcC exhibit metallic behavior at ambient condition. A pressure-induced structural phase transition is observed in both materials.

  5. Titania doping effect on superconducting properties of MgB{sub 2} bulk samples

    Energy Technology Data Exchange (ETDEWEB)

    Serrano, G; Serquis, A [Institute Balseiro - Centra Atomico Bariloche and CONICET, (8400) S. C. de Bariloche, Rio Negro (Argentina); Bridoux, G, E-mail: serranog@ib.cnea.gov.a [Institute Balseiro - Centra Atomico Bariloche, (8400) S. C. de Bariloche, Rio Negro (Argentina)

    2009-05-01

    In this work we study the microstructural and superconducting properties of doped and undoped bulk MgB{sub 2} samples prepared by solid-state reaction, with 0 and 2.5 %at. nominal TiO{sub 2} nanotubes contents, annealed at different temperatures in the 750-900 deg. C range. We discuss the T{sub c}, J{sub c} and H{sub c2} performance and their correlation with the different synthesis parameters.

  6. Superconducting properties of Tl-Ba-Ca-Cu-O films on silver substrates

    Energy Technology Data Exchange (ETDEWEB)

    Dye, R.C.; Arendt, P.N.; Martin, J.A.; Hubbard, K.M.; Elliott, N.; Reeves, G. (Los Alamos National Lab., NM (United States))

    1991-03-01

    Films of Ba-Ca-Cu-O have been rf magnetron sputtered onto Consil 995 substrates. A post deposition anneal in an over pressure of Tl produces the superconducting 1212 and 2212 phases. Varying the annealing procedures changes the electrical properties of the final films dramatically. Dynamic impedance, an approach to the electrical characterization of these films on a conductive substrate is discussed and compared in this paper, with SEM, XRD and RBS measurements as a function of differing annealing protocols.

  7. Superconducting properties of Tl-Ba-Ca-Cu-O films on silver substrates

    Energy Technology Data Exchange (ETDEWEB)

    Dye, R.C.; Arendt, P.N.; Martin, J.A.; Hubbard, K.M.; Elliott, N.; Reeves, G.

    1990-01-01

    Films of Ba-Ca-Cu-O have been rf magnetron sputtered onto Consil 995 substrates. A post deposition anneal in an over pressure of Tl produces the superconducting 1212 and 2212 phases. Varying the annealing procedures changes the electrical properties of the final films dramatically. Dynamic impedance, a novel approach to the electrical characterization of these films on a conductive substrate is discussed and compared with SEM, XRD and RBS measurements as a function of differing annealing protocols. 3 refs., 9 figs.

  8. Superconducting properties of the KxWO3 tetragonal tungsten bronze and the superconducting phase diagram of the tungsten bronze family

    Science.gov (United States)

    Haldolaarachchige, Neel; Gibson, Quinn; Krizan, Jason; Cava, R. J.

    2014-03-01

    We report on the superconducting properties of the KxWO3 tetragonal tungsten bronze. The highest superconducting transition temperature (Tc=2.1 K) was obtained for K0.38WO3. Tc decreases linearly with increasing K content. Using the measured values for the upper critical field Hc2 and the specific heat C, we estimate the orbital critical field Hc2(0), coherence length ξ(0), Debye temperature ΘD, and coupling constant λe-p. The magnitude of the specific-heat jump at Tc suggests that the KxWO3 tetragonal tungsten bronze is a weakly coupled superconductor. The superconducting phase diagram of the doped tungsten bronze family is presented.

  9. Detection of second harmonic of phase dependence of superconducting current in Nb/Au/YBCO heterojunctions

    CERN Document Server

    Komissinskij, F V; Ilichev, E V; Ivanov, Z G

    2001-01-01

    The results of the experimental study on the current phase dependence (CPD) of the heterotransitions, consisting of the niobium and the YBa sub 2 Cu sub 3 O sub x (YBCO) film with an additional interlayer from gold (Nb/Au/YBCO) are presented. The CPD measurement is carried out through the radiofrequency superconducting quantum interferometer. The CPD second harmonic is determined in the Nb/Au/YBCO heterotransitions. Possible causes of its appearance are discussed within the frames of the d +- s combined symmetry of the YBCO order parameter. One of the causes of the CPD second harmonic appearance is the twinning of the YBCO films (001). The second cause of existing the anomalously high critical current consists in the availability of the Nb/Au boundary with the transparence of approx 10 sup - sup 1 in the Nb/Au/YBCO

  10. Fracture behaviors of thin superconducting films with field-dependent critical current density

    Science.gov (United States)

    He, An; Xue, Cun; Yong, Huadong; Zhou, Youhe

    2013-09-01

    The fracture behaviors under electromagnetic force with field-dependent critical current density in thin superconducting film are investigated. Applying finite element method, the energy release rates and stress intensity factors of one central crack versus applied field and crack length are obtained for the Bean model and Kim model. It is interesting that the profile of the stress intensity factor is generally the same as the magnetostrictive behavior during one full cycle applied field. Furthermore, the crack problem of two collinear cracks with respect to crack length and distance is also researched for the Kim model. The results show that the energy release rates and stress intensity factors of the two collinear cracks at left tip and right tip are remarkably different for relatively small crack distance and long crack length. This work can offer good estimations and provide a basis for interpretation of cracking and mechanical failure of HTS thin films in numerous real situations.

  11. The Solution to the BCS Gap Equation for Superconductivity and Its Temperature Dependence

    Directory of Open Access Journals (Sweden)

    Shuji Watanabe

    2013-01-01

    Full Text Available From the viewpoint of operator theory, we deal with the temperature dependence of the solution to the BCS gap equation for superconductivity. When the potential is a positive constant, the BCS gap equation reduces to the simple gap equation. We first show that there is a unique nonnegative solution to the simple gap equation, that it is continuous and strictly decreasing, and that it is of class with respect to the temperature. We next deal with the case where the potential is not a constant but a function. When the potential is not a constant, we give another proof of the existence and uniqueness of the solution to the BCS gap equation, and show how the solution varies with the temperature. We finally show that the solution to the BCS gap equation is indeed continuous with respect to both the temperature and the energy under a certain condition when the potential is not a constant.

  12. High temperature interfacial superconductivity

    Science.gov (United States)

    Bozovic, Ivan [Mount Sinai, NY; Logvenov, Gennady [Port Jefferson Station, NY; Gozar, Adrian Mihai [Port Jefferson, NY

    2012-06-19

    High-temperature superconductivity confined to nanometer-scale interfaces has been a long standing goal because of potential applications in electronic devices. The spontaneous formation of a superconducting interface in bilayers consisting of an insulator (La.sub.2CuO.sub.4) and a metal (La.sub.1-xSr.sub.xCuO.sub.4), neither of which is superconducting per se, is described. Depending upon the layering sequence of the bilayers, T.sub.c may be either .about.15 K or .about.30 K. This highly robust phenomenon is confined to within 2-3 nm around the interface. After exposing the bilayer to ozone, T.sub.c exceeds 50 K and this enhanced superconductivity is also shown to originate from a 1 to 2 unit cell thick interfacial layer. The results demonstrate that engineering artificial heterostructures provides a novel, unconventional way to fabricate stable, quasi two-dimensional high T.sub.c phases and to significantly enhance superconducting properties in other superconductors. The superconducting interface may be implemented, for example, in SIS tunnel junctions or a SuFET.

  13. Dynamic studies on the influence of strain on superconducting properties using piezoelectric substrates

    Energy Technology Data Exchange (ETDEWEB)

    Trommler, Sascha; Huehne, Ruben; Iida, Kazumasa; Haindl, Silvia; Haenisch, Jens; Pahlke, Patrick; Thersleff, Thomas; Schultz, Ludwig; Holzapfel, Bernhard [IFW Dresden (Germany)

    2011-07-01

    The interplay between structural parameters and superconducting properties attracts high interest in particular regarding the iron based superconductors. In contrast to the cuprate family, superconductivity of the latter can be induced using either pressure or chemical substitution. Nevertheless little is known about this relationship when biaxial strain is applied. The generation of biaxial strain by the preparation of thin films on substrates with different lattice mismatch is well established for cuprates. However, high quality films are necessary to correlate structural changes with electronic properties. In this work an alternative approach is used. Single crystalline piezoelectric substrates offer the unique opportunity to tune the lattice parameters continuously using the inverse piezoelectric effect. We prepared thin epitaxial La{sub 1-x}Sr{sub x}CuO{sub 4} and BaFe{sub 2-x}Co{sub x}As{sub 2} films on piezoelectric (001) Pb(Mg{sub 1/3}Nb{sub 2/3}){sub 0.72}Ti{sub 0.28}O{sub 3} (PMN-PT) substrates. A reversible shift of the superconducting transition has been achieved with a value of 0.44 K for La{sub 1.85}Sr{sub 0.15}CuO{sub 4} and 0.2 K for BaFe{sub 1.8}Co{sub 0.2}As{sub 2} for a biaxial strain of 0.022% and 0.017%, respectively.

  14. Superconducting and normal-state properties of the noncentrosymmetric superconductor Re6Zr

    Science.gov (United States)

    Mayoh, D. A.; Barker, J. A. T.; Singh, R. P.; Balakrishnan, G.; Paul, D. McK.; Lees, M. R.

    2017-08-01

    We systematically investigate the normal and superconducting properties of noncentrosymmetric Re6Zr using magnetization, heat capacity, and electrical resistivity measurements. Resistivity measurements indicate Re6Zr has poor metallic behavior and is dominated by disorder. Re6Zr undergoes a superconducting transition at Tc=(" close=")10.3 ±0.1 )">6.75 ±0.05 K. Magnetization measurements give a lower critical field, μ0Hc 1=(11.2 ±0.2 )T , which is close to the Pauli limiting field of 12.35 T and which could indicate singlet-triplet mixing. However, low-temperature specific-heat data suggest that Re6Zr is an isotropic, fully gapped s -wave superconductor with enhanced electron-phonon coupling. Unusual flux pinning resulting in a peak effect is observed in the magnetization data, indicating an unconventional vortex state.

  15. Calculated Changes in the Elastic Properties of MgCNi3 at the Superconducting Transition

    Directory of Open Access Journals (Sweden)

    R. Abd-Shukor

    2013-01-01

    Full Text Available We calculated the elastic properties of MgCNi3 at the superconducting transition ( using various thermodynamic and acoustic data. From the calculations, a step discontinuity of 8 ppm in the bulk modulus, 7 ppm in the Young’s modulus, and 3 ppm in the longitudinal sound velocity ( is expected at . The step discontinuities at the transition temperature indicated the importance of lattice changes to the superconducting mechanism of MgCNi3. The Debye temperature was calculated to be 460 K. The electron-phonon coupling constants calculated in the weak and strong coupling limits of the BCS theory and the van Hove scenario showed that MgCNi3 is a moderately strong coupled superconductor.

  16. Modifications of Superconducting Properties of Niobium Caused by Nitrogen Doping Recipes for High Q Cavities

    Energy Technology Data Exchange (ETDEWEB)

    Vostrikov, Alexander [Fermilab; Checchin, Mattia [Fermilab; Grassellino, Anna [Fermilab; Kim, Young-Kee [U. Chicago (main); Romanenko, Alexander [Fermilab

    2015-06-01

    A study is presented on the superconducting properties of niobium used for the fabrication of the SRF cavities after treating by recently discovered nitrogen doping methods. Cylindrical niobium samples have been subjected to the standard surface treatments applied to the cavities (electro-polishing, l 20°C bake) and compared with samples treated by additional nitrogen doping recipes routinely used to reach ultra-high quality factor values (>3· 1010 at 2 K, 16 MV/m). The DC magnetization curves and the complex magnetic AC susceptibility have been measured. Evidence for the lowered field of first flux penetration after nitrogen doping is found suggesting a correlation with the lowered quench fields. Superconducting critical temperatures Tc = 9.25 K are found to be in agreement with previous measurements, and no strong effect on the critical surface field (Bd) from nitrogen doping was found.

  17. Current dependence of heat leak on the terminals in the superconducting DC transmission and distribution system of CASER-2

    Science.gov (United States)

    Kawahara, Toshio; Watanabe, Hirofumi; Emoto, Masahiko; Hamabe, Makoto; Yamaguchi, Sataro; Hikichi, Yasuo; Minowa, Masahiro

    2012-12-01

    Superconductivity can solve the energy problems in the world as energy saving technologies. In particular, superconducting direct current (DC) transmission and distribution (T&D) systems is promising, as it can be easily extended to large scale energy transmission systems for energy sharing. We are developing criogenic systems for effective cooling of superconducting T&D systems. In the cooling experiments with the 200 m-class superconducting DC T&D system at Chubu University (CASER-2), we have estimated the performance of the system. For example, our superconducting cable is connected to the outside at the terminals using Peltier current leads (PCLs). The PCL is composed of a thermoelectric material and a copper lead. Small thermal conductivity and large thermopower of the thermoelectric modules can effectively insulate the heat leak to the low temperature end. We measured the temperature along the current leads and the heat leak at the terminals. As current leads have an optimal shape factor, the optimum operation current exists. The current dependence of the system performance is discussed.

  18. Temperature Dependence of the Superconducting Gap Anistropy in Bi_2 Sr_2CaCu_2O8+x

    Science.gov (United States)

    Ma, Jian; Quitmann, C.; Kelley, R. J.; Berger, H.; Margaritondo, G.; Onellion, M.

    1995-02-01

    Detailed data on the momentum-resolved temperature dependence of the superconducting gap of Bi_2Sr_2CaCu_2O8+x are presented, complemented by similar data on the intensity of the photoemission superconducting condensate spectral area. The gap anisotropy between the Gamma-overline{M} and Gamma-X directions increases markedly with increasing temperature, contrary to what happens for conventional anisotropic-gap superconductors, such as lead. Specifically, the size of the superconducting gap along the Gamma-X direction decreases to values indistinguishable from zero at temperatures for which the gap retains virtually full value along the Gamma-overline{M} direction. These data rule out the simplest type of d-wave order parameter.

  19. Superconducting correlations and thermodynamic properties in 2D square and triangular t-J model

    Science.gov (United States)

    Ogata, Masao

    2006-03-01

    Equal-time superconducting correlation functions of the two-dimensional t-J model on the square lattice are studied using high-temperature expansion method.[1] The sum of the pairing correlation, its spatial dependence and correlation length are obtained down to T ˜0.2t. By comparison of single-particle contributions in the correlation functions, we find effective attractive interactions between quasi-particles in dx^2-y^2-wave channel. It is shown that d-wave correlation grows rapidly at low temperatures for the doping 0.1 0 with hole doping, a rapid growth of effective d-wave paring interaction is found that indicates the resonating-valence-bond superconductivity. In contrast, when tJ. Phys. Soc. Japan 74, 1390 (2005). [2] T. Koretsune and M. Ogata, Phys. Rev. Lett. 89, 116401 (2002), and Phys. Rev. B72, 134513 (2005).

  20. Transport properties of a superconducting single-electron transistor coupled to a nanomechanical oscillator

    Science.gov (United States)

    Koerting, V.; Schmidt, T. L.; Doiron, C. B.; Trauzettel, B.; Bruder, C.

    2009-04-01

    We investigate a superconducting single-electron transistor capacitively coupled to a nanomechanical oscillator and focus on the double Josephson quasiparticle resonance. The existence of two coherent Cooper-pair tunneling events is shown to lead to pronounced back action effects. Measuring the current and the shot noise provides a direct way of gaining information on the state of the oscillator. In addition to an analytical discussion of the linear-response regime, we discuss and compare results of higher-order approximation schemes and a fully numerical solution. We find that cooling of the mechanical resonator is possible and that there are driven and bistable oscillator states at low couplings. Finally, we also discuss the frequency dependence of the charge noise and the current noise of the superconducting single electron transistor.

  1. Superconducting and normal state properties of the systems La1 -xMxPt4Ge12 (M = Ce ,Th )

    Science.gov (United States)

    Huang, K.; Yazici, D.; White, B. D.; Jeon, I.; Breindel, A. J.; Pouse, N.; Maple, M. B.

    2016-09-01

    Electrical resistivity, magnetization, and specific heat measurements were performed on polycrystalline samples of the filled-skutterudite systems La1 -xMxPt4Ge12(M =Ce and Th ) . Superconductivity in LaPt4Ge12 was quickly suppressed with Ce substitution and no evidence for superconductivity was found down to 1.1 K for x >0.2 . Temperature-dependent specific heat data at low temperatures for La1 -xCexPt4Ge12 show a change from power-law to exponential behavior, which may be an indication for multiband superconductivity in LaPt4Ge12 . A similar crossover was observed in the Pr1 -xCexPt4Ge12 system. However, the suppression rates of the superconducting transition temperatures Tc(x ) in the two systems are quite disparate, indicating a difference in the nature of superconductivity, which is conventional in LaPt4Ge12 and unconventional in PrPt4Ge12 . In comparison, a nearly linear and smooth evolution of Tc with increasing Th was observed in the La1 -xThxPt4Ge12 system, with no change of the superconducting energy gap in the temperature dependence of the specific heat, suggesting similar types of superconductivity in both the LaPt4Ge12 and ThPt4Ge12 compounds.

  2. Superconductivity and superconductive electronics

    Science.gov (United States)

    Beasley, M. R.

    1990-12-01

    The Stanford Center for Research on Superconductivity and Superconductive Electronics is currently focused on developing techniques for producing increasingly improved films and multilayers of the high-temperature superconductors, studying their physical properties and using these films and multilayers in device physics studies. In general the thin film synthesis work leads the way. Once a given film or multilayer structure can be made reasonably routinely, the emphasis shifts to studying the physical properties and device physics of these structures and on to the next level of film quality or multilayer complexity. The most advanced thin films synthesis work in the past year has involved developing techniques to deposit a-axis and c-axis YBCO/PBCO superlattices and related structures. The in-situ feature is desirable because no solid state reactions with accompanying changes in volume, morphology, etc., that degrade the quality of the film involved.

  3. Thermoelectric Property Dependence on Performance of Peltier Current Leads Under Overcurrent Conditions

    Science.gov (United States)

    Kawahara, Toshio; Emoto, Masahiko; Hamabe, Makoto; Watanabe, Hirofumi; Ivanov, Yury; Sun, Jian; Yamaguchi, Satarou

    2012-06-01

    Superconductivity can potentially provide a solution to the world's energy needs because superconducting transmission and distribution (T&D) systems can decrease losses and are also capable of integrating renewables into the power grid. At Chubu University we have built a 200-m-class superconducting direct-current T&D system (CASER-2). To minimize heat leakage from the current leads, we investigated thermoelectric materials. The Peltier current lead (PCL) is one of the key technologies that will enhance the performance of superconducting systems: as direct current (DC) flows through the current lead, thermoelectric elements on opposite terminations of the superconducting line can be used to decrease the heat ingress to the cryogenic environment ( n-type on one end, p-type on the opposite end). The heat leakage to the cryogenic environment depends on the properties of the thermoelectric materials. In this paper, we estimate the performance of PCLs in cryogenic operations, including the potential for overcurrent operation, through both modeling and experiments at CASER-2.

  4. Grain-size dependence of superconductivity in dc sputtered Nb films

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    The superconducting transition temperature and grain size of dc sputtered Nb films are systematically investigated. The results show that the superconductivity is closely related to the grain size, rather than to the scattering strength of electrons or the surface layer proximity effect of the films.

  5. Atomically flat superconducting nanofilms: multiband properties and mean-field theory

    Science.gov (United States)

    Shanenko, A. A.; Aguiar, J. Albino; Vagov, A.; Croitoru, M. D.; Milošević, M. V.

    2015-05-01

    Recent progress in materials synthesis enabled fabrication of superconducting atomically flat single-crystalline metallic nanofilms with thicknesses down to a few monolayers. Interest in such nano-thin systems is attracted by the dimensional 3D-2D crossover in their coherent properties which occurs with decreasing the film thickness. The first fundamental aspect of this crossover is dictated by the Mermin-Wagner-Hohenberg theorem and concerns frustration of the long-range order due to superconductive fluctuations and the possibility to track its impact with an unprecedented level of control. The second important aspect is related to the Fabri-Pérot modes of the electronic motion strongly bound in the direction perpendicular to the nanofilm. The formation of such modes results in a pronounced multiband structure that changes with the nanofilm thickness and affects both the mean-field behavior and superconductive fluctuations. Though the subject is very rich in physics, it is scarcely investigated to date. The main obstacle is that there are no manageable models to study a complex magnetic response in this case. Full microscopic consideration is rather time consuming, if practicable at all, while the standard Ginzburg-Landau theory is not applicable. In the present work we review the main achievements in the subject to date, and construct and justify an efficient multiband mean-field formalism which allows for numerical and even analytical treatment of nano-thin superconductors in applied magnetic fields.

  6. Magnetization of a Current-Carrying Superconducting Disk with B-Dependent Critical Current Density

    Science.gov (United States)

    Sohrabi, Mahdi; Babaei-Brojeny, Ali A.

    2010-11-01

    In the frame work of the critical state model (CSM), the magnetic response of a thin type-II superconducting disk that carries a radial transport current and is subjected to an applied magnetic field have been studied. To this end, we have studied the process of the magnetic flux-penetration. For a disk initially containing no magnetic flux but carrying a radial current, when a perpendicular magnetic field is applied, magnetic flux-penetration occurs in three stages: (1) the magnetic flux gradually penetrates from the edges of the disk until an instability occurs, (2) there is a rapid inflow of magnetic flux into the disk’s central region, which becomes resistive, and (3) magnetic flux continues to enter the disk, while persistent azimuthal currents flow in an outer annular region where the net current density is equal to J c . Also the behavior of a current-carrying disk subjected to an AC magnetic field is calculated. The magnetic flux, the current profiles and the magnetization hysteresis loops are calculated for several commonly used J c ( B) dependences. Finally, the results of the applications of the local field-dependent of the critical current density J c ( B) are compared with those obtained from the Bean model.

  7. Thermodynamic and transport properties of superconducting Mg10B2.

    Science.gov (United States)

    Finnemore, D K; Ostenson, J E; Bud'ko, S L; Lapertot, G; Canfield, P C

    2001-03-12

    Transport and thermodynamic properties of a sintered pellet of the newly discovered MgB2 superconductor have been measured to determine the characteristic critical magnetic fields and critical current densities. Both resistive transition and magnetization data give similar values of the upper critical field, Hc2, with magnetization data giving dHc2/dT = 0.44 T/K at the transition temperature of Tc = 40.2 K. Close to the transition temperature, magnetization curves are thermodynamically reversible, but at low temperatures the trapped flux can be on the order of 1 T. The value of dHc/dT at Tc is estimated to be about 12 mT/K, a value similar to classical superconductors like Sn. Hence, the Ginzburg-Landau parameter kappa approximately 26. Estimates of the critical supercurrent density, Jc, using hysteresis loops and the Bean model, give critical current densities on the order of 10(5) A/cm2. Hence the supercurrent coupling through the grain boundaries is comparable to intermetallics like Nb3Sn.

  8. Effect of nanowires SiO2 on superconducting properties of YBa2Cu3O7-d bulks

    Science.gov (United States)

    Salem, M. K. Ben; Hannachi, E.; Slimani, Y.; Hamrita, A.; Bessais, L.; Azzouz, F. Ben; Salem, M. Ben

    2013-12-01

    The effects of SiO2 nanowires on the superconducting properties of YBa2Cu3O7-d (YBCO) compound were studied. Samples were synthesized in air using a standard solid state reaction technique by adding nanowires SiO2 up to 1wt.%. Phase analysis by X-ray diffraction (XRD), microstructure investigation by scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectroscopy (EDXS), critical current density dependence on applied magnetic field Jc(H) and electrical resistivity as a function of temperature ρ(T) were carried out to evaluate the relative performance of samples. We find that Tco does not change much (90.8-90.2 K) with the low concentration of SiO2 (≤ 0.1 wt.%) and Jc(H) is enhanced.

  9. Superconducting correlations above Tc in the pseudogap state of Bi2Sr2CaCu2O8 +δ cuprates revealed by angular-dependent magnetotunneling

    Science.gov (United States)

    Jacobs, Th.; Katterwe, S. O.; Krasnov, V. M.

    2016-12-01

    We present an angular-dependent magnetotunneling technique, which facilitates unambiguous separation of superconducting (supporting circulating screening currents) and nonsuperconducting (not supporting screening currents) contributions to the pseudogap phenomenon in layered Bi2Sr2CaCu2O8 +δ cuprates. Our data indicate persistence of superconducting correlations at temperatures up to 1.5 Tc in a form of both phase and amplitude fluctuations of the superconducting order parameter. However, despite a profound fluctuations region, only a small fraction of the pseudogap spectrum is caused by superconducting correlations, while the dominating part comes from a competing nonsuperconducting order, which does not support circulating orbital currents.

  10. Unconventional superconductivity in cuprates, cobaltates and graphene. What is universal and what is material-dependent in strongly versus weakly correlated materials?

    Energy Technology Data Exchange (ETDEWEB)

    Kiesel, Maximilian Ludwig

    2013-02-08

    A general theory for all classes of unconventional superconductors is still one of the unsolved key issues in condensed-matter physics. Actually, it is not yet fully settled if there is a common underlying pairing mechanism. Instead, it might be possible that several distinct sources for unconventional (not phonon-mediated) superconductivity have to be considered, or an electron-phonon interaction is not negligible. The focus of this thesis is on the most probable mechanism for the formation of Cooper pairs in unconventional superconductors, namely a strictly electronic one where spin fluctuations are the mediators. Studying different superconductors in this thesis, the emphasis is put on material-independent features of the pairing mechanism. In addition, the investigation of the phase diagrams enables a view on the vicinity of superconductivity. Thus, it is possible to clarify which competing quantum fluctuations enhance or weaken the propensity for a superconducting state. The broad range of superconducting materials requires the use of more than one numerical technique to study an appropriate microscopic description. This is not a problem but a big advantage because this facilitates the approach-independent description of common underlying physics. For this evaluation, the strongly correlated cuprates are simulated with the variational cluster approach. Especially the question of a pairing glue is taken into consideration. Furthermore, it is possible to distinguish between retarded and non-retarded contributions to the gap function. The cuprates are confronted with the cobaltate Na{sub x}CoO{sub 2} and graphene. These weakly correlated materials are investigated with the functional renormalization group (fRG) and reveal a comprehensive phase diagram, including a d+id-wave superconductivity, which breaks time-reversal symmetry. The corresponding gap function is nodeless, but for NaCoO, it features a doping-dependent anisotropy. In addition, some general

  11. Electrical and structural properties of the YBCO superconducting-semiconducting interface

    Energy Technology Data Exchange (ETDEWEB)

    Sobolewski, R. (Dept. of Electrical Engineering and Lab. for Laser Energetics, Univ. of Rochester, NY (United States) Inst. of Physics, Polish Academy of Sciences, Warszawa (Poland)); Xiong, W. (Dept. of Electrical Engineering and Lab. for Laser Energetics, Univ. of Rochester, NY (United States)); Kula, W. (Dept. of Electrical Engineering and Lab. for Laser Energetics, Univ. of Rochester, NY (United States) Inst. of Physics, Polish Academy of Sciences, Warszawa (Poland)); McIntyre, B. (Inst. of Optics, Univ. of Rochester, NY (United States))

    1994-02-01

    We report our studies on electrical and structural properties of an interface between the oxygen-poor (semiconducting) and oxygen-rich (superconducting, T[sub c] = 89.5 K) YBa[sub 2]Cu[sub 3]O[sub y]. Our thin-film test structures were fully monolithic and prepared by a laser-writing patterning technique. Scanning electron and optical microscopy measurements revealed that the interface was very sharp (<1 [mu]m wide) and did not smear over the period of several months. Electrical measurements of the interface showed completely linear current-voltage characteristics in the tested temperature range between 77 and 300 K. (orig.)

  12. Analysis of HOM Properties of Superconducting Parallel-Bar Deflecting/Crabbing Cavities

    Energy Technology Data Exchange (ETDEWEB)

    S.U. De Silva, J.R. Delayen

    2011-07-01

    The superconducting parallel-bar cavity is currently being considered for a number of deflecting and crabbing applications due to improved properties and compact design geometries. The 499 MHz deflecting cavity proposed for the Jefferson Lab 12 GeV upgrade and the 400 MHz crab cavity for the proposed LHC luminosity upgrade are two of the major applications. For high current applications the higher order modes must be damped to acceptable levels to eliminate any beam instabilities. The frequencies and R/Q of the HOMs and mode separation are evaluated and compared for different parallel-bar cavity designs.

  13. Mechanical, electronic, optical, thermodynamic properties and superconductivity of ScGa3

    Science.gov (United States)

    Parvin, F.; Hossain, M. A.; Ali, M. S.; Islam, A. K. M. A.

    2015-01-01

    The rare occurrence of type-I superconductivity in binary system ScGa3 has experimentally been shown recently. In the present paper we study the electronic, optical, thermodynamic properties and some aspects of superconductivity of this compound using first-principles calculations. The mechanical properties like elastic constants, bulk modulus, shear modulus, Pugh's ductility index, Young's modulus, Poisson's ratio, elastic anisotropy factor, Peierls stress are calculated for the first time. The material is anisotropic and brittle. Electronic band structure, density of states, Fermi surfaces and bonding nature have also been studied. The optical functions are estimated and discussed for the first time. The high reflectivity is found in the ultraviolet regions up to ~13 eV and thus ScGa3 can serve as a possible shielding material for ultraviolet radiation. Thermal effects on some macroscopic properties of ScGa3 are predicted using the quasi-harmonic Debye model and phonon approximation in the temperature and hydrostatic pressure in the ranges of 0-1000 K and 0-40 GPa, respectively. The calculated electron-phonon coupling constant λ=0.52 yields Tc=2.6 K, which is in very good agreement with the experimentally observed value. The value of the coupling constant and the Ginzburg-Landau parameter (κ=0.09) indicate that the compound is a weak-coupled type-I rare binary BCS superconductor.

  14. Properties of superconductivity on a density wave background with small ungapped Fermi surface parts

    Science.gov (United States)

    Grigoriev, P. D.

    2008-06-01

    We investigate the properties and the microscopic structure of superconductivity (SC) coexisting and sharing the common conducting band with density wave (DW). Such coexistence may take place when the nesting of the Fermi surface (FS) is not perfect, and in the DW state some quasiparticle states remain on the Fermi level and lead to the Cooper instability. The dispersion of such quasiparticle states strongly differs from that without DW, and so do the properties of SC on the DW background. The upper critical field Hc2 in such a SC state increases as the system approaches the critical pressure, where the ungapped quasiparticles and superconductivity just appear, and it may considerably exceed the usual Hc2 value without DW. The spin-density wave (SDW) background strongly suppresses the singlet SC pairing, while it does not affect so much the triplet SC transition temperature. The results obtained explain the experimental observations in layered organic metals (TMTSF)2PF6 and α-(BEDT-TTF)2KHg(SCN)4 , where SC appears in the DW states under pressure and shows many unusual properties.

  15. Mechanical, electronic, optical, thermodynamic properties and superconductivity of ScGa{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Parvin, F. [Department of Physics, Rajshahi University, Rajshahi (Bangladesh); Hossain, M.A. [Department of Physics, Mawlana Bhashani Science and Technology University, Santosh, Tangail 1902 (Bangladesh); Ali, M.S. [Department of Physics, Rajshahi University, Rajshahi (Bangladesh); Islam, A.K.M.A., E-mail: azi46@ru.ac.bd [International Islamic University Chittagong, 154/A College Road, Chittagong 4203 (Bangladesh)

    2015-01-15

    The rare occurrence of type-I superconductivity in binary system ScGa{sub 3} has experimentally been shown recently. In the present paper we study the electronic, optical, thermodynamic properties and some aspects of superconductivity of this compound using first-principles calculations. The mechanical properties like elastic constants, bulk modulus, shear modulus, Pugh's ductility index, Young's modulus, Poisson's ratio, elastic anisotropy factor, Peierls stress are calculated for the first time. The material is anisotropic and brittle. Electronic band structure, density of states, Fermi surfaces and bonding nature have also been studied. The optical functions are estimated and discussed for the first time. The high reflectivity is found in the ultraviolet regions up to ∼13 eV and thus ScGa{sub 3} can serve as a possible shielding material for ultraviolet radiation. Thermal effects on some macroscopic properties of ScGa{sub 3} are predicted using the quasi-harmonic Debye model and phonon approximation in the temperature and hydrostatic pressure in the ranges of 0–1000 K and 0–40 GPa, respectively. The calculated electron–phonon coupling constant λ=0.52 yields T{sub c}=2.6 K, which is in very good agreement with the experimentally observed value. The value of the coupling constant and the Ginzburg–Landau parameter (κ=0.09) indicate that the compound is a weak-coupled type-I rare binary BCS superconductor.

  16. Anisotropic Field Dependence of the Superconducting Transition in the Magnetic Molecular Superconductor κ-(BETS)2FeBr4

    Science.gov (United States)

    Fukuoka, Shuhei; Yamashita, Satoshi; Nakazawa, Yasuhiro; Yamamoto, Takashi; Fujiwara, Hideki

    2017-01-01

    Angle-resolved heat capacity measurements of a π-d interacting system of κ-(BETS)2FeBr4 [BETS = bis(ethylenedithio)tetraselenafulvalene] with in-plane magnetic fields are performed. We observed a thermal anomaly in association with the superconducting transition of the π electrons in the π-d compound for the first time. By pursuing a systematic change in the thermal anomaly, we found that the thermodynamic feature of the superconducting state shows large anisotropy against in-plane magnetic fields. When the field is applied parallel to the c-axis, the thermal anomaly remains up to 2.6 T with a distinct peak structure. On the other hand, it is suppressed in synchrony with the decrease of the antiferromagnetic transition temperature, when the field is applied parallel to the a-axis. Our thermodynamic results indicate that the effect of the π-d interaction appears even when the π electrons are itinerant and that the anisotropic field-direction dependence of the superconducting transition originates from the correlation between superconductivity and magnetism.

  17. Doping dependence of spin excitations and its correlations with high-temperature superconductivity in iron pnictides.

    Science.gov (United States)

    Wang, Meng; Zhang, Chenglin; Lu, Xingye; Tan, Guotai; Luo, Huiqian; Song, Yu; Wang, Miaoyin; Zhang, Xiaotian; Goremychkin, E A; Perring, T G; Maier, T A; Yin, Zhiping; Haule, Kristjan; Kotliar, Gabriel; Dai, Pengcheng

    2013-01-01

    High-temperature superconductivity in iron pnictides occurs when electrons and holes are doped into their antiferromagnetic parent compounds. Since spin excitations may be responsible for electron pairing and superconductivity, it is important to determine their electron/hole-doping evolution and connection with superconductivity. Here we use inelastic neutron scattering to show that while electron doping to the antiferromagnetic BaFe₂As₂ parent compound modifies the low-energy spin excitations and their correlation with superconductivity (100 meV), hole-doping suppresses the high-energy spin excitations and shifts the magnetic spectral weight to low-energies. In addition, our absolute spin susceptibility measurements for the optimally hole-doped iron pnictide reveal that the change in magnetic exchange energy below and above T(c) can account for the superconducting condensation energy. These results suggest that high-T(c) superconductivity in iron pnictides is associated with both the presence of high-energy spin excitations and a coupling between low-energy spin excitations and itinerant electrons.

  18. Influence of preparation conditions on superconducting properties of Bi-2223 thin films

    Indian Academy of Sciences (India)

    N T Mua; A Sundaresan; N K Man; D D Dung

    2014-02-01

    We report electrical transport properties of Bi2Sr2Ca2Cu3O10+ (Bi-2223) superconducting thin films fabricated by pulsed-laser deposition on SrTiO3 substrate. The aim of the study was to investigate the influence of preparation conditions such as deposition temperature (S), annealing time (A) and deposition rate (). A critical temperature (c) as high as 110 K and critical current density (c) of 6.2 × 106 A/cm2 at 20 K were obtained for S = 760° C, A = 4h and = 1.5 Å/s. We also investigated the effect of Li doping on Bi-2223 thin films. Li intercalation results in high resistive onset transition temperature and the resistivity shows broadening in magnetic field that increases with field. The large broadening of resistivity curve in magnetic field suggests that this phenomenon is directly related to the intrinsic superconducting properties of the copper oxide superconductors. The sudden drop in c at relatively low magnetic field ( < 0.5 tesla) is due to the effect of Josephson weak-links at the grain boundaries.

  19. Heat treatment effects on the superconducting properties of Ag-doped SrKFeAs compounds

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    The superconducting properties of polycrystalline Sr0.6K0.4Fe2As2 were strongly influenced by Ag doping(Supercond.Sci.Technol.23(2010) 025027).Ag addition is mainly dominated by silver diffusing,so the annealing process is one of the essential factors to achieve high quality Ag doped Sr0.6K0.4Fe2As2.In this paper,the optimal annealing conditions were studied for Ag doped Sr0.6K0.4Fe2As2 bulks prepared by a one-step solid reaction method.It is found that the annealing temperature has a strong influence on the superconducting properties,especially on the critical current density Jc.As a result,higher heat treatment temperature(~900℃) is helpful in diffusing Ag and reducing the impurity phase gathered together to improve the grain connectivity.In contrast,low-temperature sintering is counterproductive for Ag doped samples.These results clearly suggest that annealing at ~900℃ is necessary for obtaining high Jc Ag-doped samples.

  20. Elastic properties of superconducting bulk metallic glasses; Elastische Eigenschaften von supraleitenden massiven metallischen Glaesern

    Energy Technology Data Exchange (ETDEWEB)

    Hempel, Marius

    2015-07-01

    Within the framework of this thesis the elastic properties of a superconducting bulk metallic glass between 10 mK and 300 K were first investigated. In order to measure the entire temperature range, in particular the low temperature part, new experimental techniques were developed. Using an inductive readout scheme for a double paddle oscillator it was possible to determine the internal friction and the relative change of sound velocity of bulk metallic glasses with high precision. This allowed for a detailed comparison of the data with different models. The analysis focuses on the low temperature regime where the properties of glassy materials are governed by atomic tunneling systems as described by the tunneling model. The influence of conduction electrons in the normal conducting state and quasiparticles in the superconducting state of the glass were accounted for in the theoretical description, resulting in a good agreement over a large temperature range between measured data and prediction of the tunneling model. This allowed for a direct determination of the coupling constant between electrons and tunneling systems. In the vicinity of the transition temperature Tc the data can only be described if a modified distribution function of the tunneling parameters is applied.

  1. The effects of disorder on the normal state and superconducting properties of Nb3Sn

    Science.gov (United States)

    Mentink, M. G. T.; Dhalle, M. M. J.; Dietderich, D. R.; Godeke, A.; Hellman, F.; ten Kate, H. H. J.

    2017-02-01

    The effect of disorder on the normal state resistivity and the superconducting properties of Nb{}3Sn is explored in a combination of ab initio calculations and microscopic theory. The crystal symmetry is calculated to be preferentially tetragonal at a normal state resistivity below 27.0 ± 1.4 μ {{Ω }}{cm}, and preferentially cubic above this value, which is shown to be consistent with the experimentally observed transition point. The phonon density of states, the Eliashberg spectrum {α }2(ω )F(ω ), the electron-phonon coupling constant, the characteristic frequency, the critical temperature T c, and the upper critical magnetic field at 0 K {H}{{c}2}(0) are calculated over a large normal state resistivity range and shown to be consistent with experimental observations. The high degree of consistency between the calculation results and experimental observations is a strong indication that the calculation approach utilized here, a combination of ab initio calculations and microscopic theory, is a useful tool for understanding the superconducting and normal state properties of Nb{}3Sn.

  2. Superconductivity in doped Dirac semimetals

    Science.gov (United States)

    Hashimoto, Tatsuki; Kobayashi, Shingo; Tanaka, Yukio; Sato, Masatoshi

    2016-07-01

    We theoretically study intrinsic superconductivity in doped Dirac semimetals. Dirac semimetals host bulk Dirac points, which are formed by doubly degenerate bands, so the Hamiltonian is described by a 4 ×4 matrix and six types of k -independent pair potentials are allowed by the Fermi-Dirac statistics. We show that the unique spin-orbit coupling leads to characteristic superconducting gap structures and d vectors on the Fermi surface and the electron-electron interaction between intra and interorbitals gives a novel phase diagram of superconductivity. It is found that when the interorbital attraction is dominant, an unconventional superconducting state with point nodes appears. To verify the experimental signature of possible superconducting states, we calculate the temperature dependence of bulk physical properties such as electronic specific heat and spin susceptibility and surface state. In the unconventional superconducting phase, either dispersive or flat Andreev bound states appear between point nodes, which leads to double peaks or a single peak in the surface density of states, respectively. As a result, possible superconducting states can be distinguished by combining bulk and surface measurements.

  3. Control of the superconducting properties of Sr{sub 2−x}Ca{sub x}VO{sub 3}FeAs through isovalent substitution

    Energy Technology Data Exchange (ETDEWEB)

    Corkett, Alex J.; Free, David G. [Department of Chemistry, University of Oxford, Inorganic Chemistry Laboratory, South Parks Road, Oxford, OX1 3QR (United Kingdom); Cassidy, Simon J. [Department of Chemistry, University of Oxford, Inorganic Chemistry Laboratory, South Parks Road, Oxford, OX1 3QR (United Kingdom); Diamond Light Source Limited, Harwell Science and Innovation Campus, Didcot, OX11 0DE (United Kingdom); Ramos, Silvia [Diamond Light Source Limited, Harwell Science and Innovation Campus, Didcot, OX11 0DE (United Kingdom); Clarke, Simon J., E-mail: simon.clarke@chem.ox.ac.uk [Department of Chemistry, University of Oxford, Inorganic Chemistry Laboratory, South Parks Road, Oxford, OX1 3QR (United Kingdom)

    2014-08-15

    The effect of the isovalent substitution of Sr{sup 2+} by Ca{sup 2+} on the structure and superconducting properties of Sr{sub 2−x}Ca{sub x}VO{sub 3}FeAs is described in the compositional range 0≤x≤0.5. SQUID magnetometry measurements reveal that after an initial increase in T{sub c}, which is maximised at 29.5 K in Sr{sub 1.95}Ca{sub 0.05}VO{sub 3}FeAs, a rapid suppression of superconductivity is observed with increasing x. XANES spectra of Sr{sub 2−x}Ca{sub x}VO{sub 3}FeAs collected on the Fe and V absorption K-edges show that the position of both edges are invariant with composition within the experimental uncertainty. A combination of synchrotron X-ray powder diffraction and neutron powder diffraction techniques is used to rationalise the observed changes in T{sub c} with x, in terms of changes to the structure of the FeAs layer upon partial Ca substitution. These findings demonstrate that superconductivity in the Fe-based superconductors is extremely sensitive to the crystal structure with T{sub c} maximised in samples with regular FeAs{sub 4}-tetrahedra. - Graphical abstract: Superconducting transition temperature is controlled by structural parameters in Sr{sub 2−x}Ca{sub x}VO{sub 3}FeAs. - Highlights: • Substitution of Sr by Ca in the superconductor Sr{sub 2}VO{sub 3}FeAs is isovalent. • Relationship between superconducting T{sub c} and structural parameters is demonstrated. • Linear dependence of T{sub c} on structural parameters rather than composition.

  4. A visualization instrument to investigate the mechanical-electro properties of high temperature superconducting tapes under multi-fields

    Science.gov (United States)

    Liu, Wei; Zhang, Xingyi; Liu, Cong; Zhang, Wentao; Zhou, Jun; Zhou, YouHe

    2016-07-01

    We construct a visible instrument to study the mechanical-electro behaviors of high temperature superconducting tape as a function of magnetic field, strain, and temperature. This apparatus is directly cooled by a commercial Gifford-McMahon cryocooler. The minimum temperature of sample can be 8.75 K. A proportion integration differentiation temperature control is used, which is capable of producing continuous variation of specimen temperature from 8.75 K to 300 K with an optional temperature sweep rate. We use an external loading device to stretch the superconducting tape quasi-statically with the maximum tension strain of 20%. A superconducting magnet manufactured by the NbTi strand is applied to provide magnetic field up to 5 T with a homogeneous range of 110 mm. The maximum fluctuation of the magnetic field is less than 1%. We design a kind of superconducting lead composed of YBa2Cu3O7-x coated conductor and beryllium copper alloy (BeCu) to transfer DC to the superconducting sample with the maximum value of 600 A. Most notably, this apparatus allows in situ observation of the electromagnetic property of superconducting tape using the classical magnetic-optical imaging.

  5. Superconducting properties of “111” type LiFeAs iron arsenide single crystals

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    LiFeAs single crystal has been grown with superconducting transition temperature Tc comparable to that of polycrystals.A magnetic transition is found at about 160 K,which suggests the correlation of superconductivity with spin wave density.

  6. Peak effect and superconducting properties of SmFeAsO{sub 0.8}F{sub 0.2} wires

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Y L; Cui, Y J; Yang, Y; Zhang, Y; Wang, L; Zhao, Y [Key Laboratory of Magnetic Levitation Technologies and Maglev Trains, Ministry of Education of China, and Superconductivity R and D Center (SRDC), Southwest Jiaotong University, Chengdu, Sichuan 610031 (China); Cheng, C H; Sorrell, C [School of Materials Science and Engineering, University of New South Wales, Sydney, NSW 2052 (Australia)], E-mail: yzhao@swjtu.edu.cn

    2008-11-15

    Ta-sheathed SmFeAsO{sub 0.8}F{sub 0.2} superconducting wires with T{sub c} = 52.5 K have been fabricated using the powder-in-tube (PIT) method and the superconducting properties of the wires have been investigated. The wires exhibit a very large intragrain critical current density at a temperature below 30 K. A peak effect with maximal J{sub c} = 0.6 MA cm{sup -2} at 10 K under 6 T field was observed. The peak field H{sub pear} is strongly temperature-dependent. A severe weak-link effect depresses the development of global supercurrent owing to a very short coherence length. The wires also show a power law temperature dependence for the irreversibility line with H{sub irr}{approx_equal}(1-T/T{sub c}){sup 1.5}. The H-T phase diagram was found to be similar to that of other superconducting cuprates.

  7. Influence of filament diameter on superconducting properties of MgB2 multi-core wires

    Science.gov (United States)

    Reissner, M.; Bulla, L.; Husek, I.; Melišek, T.; Kováč, P.

    2013-06-01

    Magnetic behaviour of a series of MgB2 wires, in each case with 19 filaments of superconductor, surrounded by Ti as barrier and reinforced by stainless steel, prepared in the same way but mechanically deformed to different filament diameters ϕ between 58.5 and 17.7 µm, was investigated. Whereas no influence of ϕ on superconducting transition temperature is found, the width of the transition increases with ϕ. Critical current density, irreversibility line and mean effective activation energy U decrease systematically with decreasing ϕ. From a comparison of the field dependence of the pinning force and the temperature dependence of U, it is concluded, that pinning is dominated at low fields by grain boundary pinning and at higher fields by point defect pinning, with a rather broad distribution of pinning energies.

  8. Field-dependent critical state of high-Tc superconducting strip simultaneously exposed to transport current and perpendicular magnetic field

    Science.gov (United States)

    Xue, Cun; He, An; Yong, Huadong; Zhou, Youhe

    2013-12-01

    We present an exact analytical approach for arbitrary field-dependent critical state of high-Tc superconducting strip with transport current. The sheet current and flux-density profiles are derived by solving the integral equations, which agree with experiments quite well. For small transport current, the approximate explicit expressions of sheet current, flux-density and penetration depth for the Kim model are derived based on the mean value theorem for integration. We also extend the results to the field-dependent critical state of superconducting strip in the simultaneous presence of applied field and transport current. The sheet current distributions calculated by the Kim model agree with experiments better than that by the Bean model. Moreover, the lines in the Ia-Ba plane for the Kim model are not monotonic, which is quite different from that the Bean model. The results reveal that the maximum transport current in thin superconducting strip will decrease with increasing applied field which vanishes for the Bean model. The results of this paper are useful to calculate ac susceptibility and ac loss.

  9. Field-dependent critical state of high-Tc superconducting strip simultaneously exposed to transport current and perpendicular magnetic field

    Directory of Open Access Journals (Sweden)

    Cun Xue

    2013-12-01

    Full Text Available We present an exact analytical approach for arbitrary field-dependent critical state of high-Tc superconducting strip with transport current. The sheet current and flux-density profiles are derived by solving the integral equations, which agree with experiments quite well. For small transport current, the approximate explicit expressions of sheet current, flux-density and penetration depth for the Kim model are derived based on the mean value theorem for integration. We also extend the results to the field-dependent critical state of superconducting strip in the simultaneous presence of applied field and transport current. The sheet current distributions calculated by the Kim model agree with experiments better than that by the Bean model. Moreover, the lines in the Ia-Ba plane for the Kim model are not monotonic, which is quite different from that the Bean model. The results reveal that the maximum transport current in thin superconducting strip will decrease with increasing applied field which vanishes for the Bean model. The results of this paper are useful to calculate ac susceptibility and ac loss.

  10. Field-dependent critical state of high-Tc superconducting strip simultaneously exposed to transport current and perpendicular magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Xue, Cun; He, An; Yong, Huadong; Zhou, Youhe, E-mail: zhouyh@lzu.edu.cn [Key Laboratory of Mechanics on Disaster and Environment in Western China attached to the Ministry of Education of China, and Department of Mechanics and Engineering Sciences, College of Civil Engineering and Mechanics, Lanzhou University, Lanzhou, Gansu 730000 (China)

    2013-12-15

    We present an exact analytical approach for arbitrary field-dependent critical state of high-T{sub c} superconducting strip with transport current. The sheet current and flux-density profiles are derived by solving the integral equations, which agree with experiments quite well. For small transport current, the approximate explicit expressions of sheet current, flux-density and penetration depth for the Kim model are derived based on the mean value theorem for integration. We also extend the results to the field-dependent critical state of superconducting strip in the simultaneous presence of applied field and transport current. The sheet current distributions calculated by the Kim model agree with experiments better than that by the Bean model. Moreover, the lines in the I{sub a}-B{sub a} plane for the Kim model are not monotonic, which is quite different from that the Bean model. The results reveal that the maximum transport current in thin superconducting strip will decrease with increasing applied field which vanishes for the Bean model. The results of this paper are useful to calculate ac susceptibility and ac loss.

  11. Correlation of normal and superconducting properties and unified approach to the description of high Tc oxides

    Science.gov (United States)

    Kresin, V. Z.; Wolf, S. A.

    1991-01-01

    We present a unified approach based on the Fermi liquid picture which allows us to describe the normal as well as the superconducting properties of the doped cuprates. The theory that is presented is for the doped compounds which are metallic. One can distinguish two interrelated, but nevertheless, different directions in the physics of high T(sub c): one involving the problem of carrier doping and the transition to the metallic state, and the second being the description of the metallic state. It is important that this metallic phase undergoes the transition into the superconducting state; as a result, our analysis is directly related to the origin of high T(sub c). We are using a quasi-2D Fermi liquid model to estimate the fundamental parameters of these very interesting materials. We find that this description is able to describe these materials and also that phonons and plasmons play a major role in the mechanism of high T(sub c).

  12. Improving superconducting properties of YBCO high temperature superconductor by Graphene Oxide doping

    Energy Technology Data Exchange (ETDEWEB)

    Dadras, S., E-mail: dadras@alzahra.ac.ir; Dehghani, S.; Davoudiniya, M.; Falahati, S.

    2017-06-01

    In this research, we report the synthesis and characterization of YBa{sub 2}Cu{sub 3}O{sub 7-δ} (YBCO) high temperature superconductor prepared by sol-gel method and doped with Graphene Oxide (GO) in different weight percentages, 0, 0.1, 0.7 and 1 % wt. The x-ray diffraction (XRD) analysis confirms the formation of orthorhombic phase of superconductivity for all the prepared samples. We found that GO doping reduces the crystalline size of the samples. We evaluated the effects of GO doping on the normal state resistivity (ρ), superconducting transition temperature (T{sub c}) and critical current density (J{sub c}). The results show that the GO doping has a positive effect on these properties. Also, the highest J{sub c} is obtained for the 0.7 %wt GO doped YBCO compound that its critical current density is about 15 times more than the J{sub c} of pure one in 0.4 T magnetic field. The scanning electron microscope (SEM) analysis shows that there are better connections between the grains of GO doped samples. - Highlights: • Graphene Oxide doping increased the YBCO critical current density. • Graphene Oxide creates a better connection between the YBCO grains. • The normal resistivity of samples were decreased by GO doping to YBCO compounds. • Graphene Oxide doping has a positive effect on the critical transition temperature.

  13. Isospin dependent properties of asymmetric nuclear matter

    CERN Document Server

    Chowdhury, P Roy; Samanta, C

    2009-01-01

    The density dependence of nuclear symmetry energy is determined from a systematic study of the isospin dependent bulk properties of asymmetric nuclear matter using the isoscalar and the isovector components of density dependent M3Y interaction. The incompressibility $K_\\infty$ for the symmetric nuclear matter, the isospin dependent part $K_{asy}$ of the isobaric incompressibility and the slope $L$ are all in excellent agreement with the constraints recently extracted from measured isotopic dependence of the giant monopole resonances in even-A Sn isotopes, from the neutron skin thickness of nuclei and from analyses of experimental data on isospin diffusion and isotopic scaling in intermediate energy heavy-ion collisions. This work provides a fundamental basis for the understanding of nuclear matter under extreme conditions, and validates the important empirical constraints obtained from recent experimental data.

  14. Microstructural and transport properties of superconducting FeTe0.65Se0.35 crystals

    Science.gov (United States)

    Sivakov, A. G.; Bondarenko, S. I.; Prokhvatilov, A. I.; Timofeev, V. P.; Pokhila, A. S.; Koverya, V. P.; Dudar, I. S.; Link, S. I.; Legchenkova, I. V.; Bludov, A. N.; Monarkha, V. Yu; Gawryluk, D. J.; Pietosa, J.; Berkowski, M.; Diduszko, R.; Puzniak, R.; Wisniewski, A.

    2017-01-01

    The issue concerning the nature and the role of microstructural inhomogeneities in iron chalcogenide superconducting crystals of FeTe0.65Se0.35 and their correlation with transport properties of this system was addressed. The presented data demonstrate that chemical disorder originating from the kinetics of the crystal growth process significantly influences the superconducting properties of an Fe-Te-Se system. Transport measurements of the transition temperature and critical current density performed for microscopic bridges allow us to deduce the local properties of a superconductor with microstructural inhomogeneities, and significant differences were noted. The variances observed in the local properties were explained as a consequence of weak superconducting links existing in the studied crystals. The results confirm that the inhomogeneous spatial distribution of ions and small hexagonal symmetry nanoscale regions with nanoscale phase separation also seem to enhance the superconductivity in this system with respect to the values of the critical current density. Magnetic measurements performed in order to determine, in an alternative way, the values of the critical current density, as well as to find the relaxation rate and to check the scaling of the pinning force, confirm the conclusions drawn from the transport measurements.

  15. Thermoelectric Property Dependence and Geometry Optimization of Peltier Current Leads Using Highly Electrically Conductive Thermoelectric Materials

    Science.gov (United States)

    Fujii, Tomohiro; Fukuda, Shinji; Emoto, Masahiko; Osada, Koudai; Kawahara, Toshio; Hamabe, Makoto; Watanabe, Hirofumi; Ivanov, Yury; Sun, Jian; Yamaguchi, Satarou

    2011-05-01

    Thermoelectric materials are promising candidates for use in energy-saving devices in many fields. They are also useful in superconducting applications such as those using Peltier current leads (PCLs) to reduce system heat loss. In the case of PCLs, consideration must be given to Joule heating. Furthermore, the performance of PCLs is intricately dependent on their thermoelectric properties. In addition to the figure of merit Z, consideration of the electrical conductivity is also important for the design of high-performance PCLs. In this paper, we discuss the resistivity dependence of the performance of PCLs using model parameters obtained from real devices.

  16. Crystal structure, superconductivity and magnetic properties of the superconducting ferromagnets Gd{sub 1.4-x}Dy{sub x}Ce{sub 0.6}Sr{sub 2}RuCu{sub 2}O{sub 10} (x=0-0.6)

    Energy Technology Data Exchange (ETDEWEB)

    Kalavathi, S.; Janaki, J.; Reddy, G.V.R.; Rao, G.V.N.; Sankara Sastry, V.; Hariharan, Y

    2003-07-15

    The structural, electrical and magnetic properties of the superconducting ferromagnets, Gd{sub 1.4-x}Dy{sub x}Ce{sub 0.6}Sr{sub 2}RuCu{sub 2}O{sub 10} (x=0-0.6) are systematically investigated as a function of Dy doping and temperature. These compounds are characterized by high temperature superconductivity (T{sub c} ranging from 20 to 40 K depending upon the Dy content) co-existing with weak ferromagnetism with two magnetic transitions (T{sub M2} ranging from 95 to 106 K and T{sub M1} around 120 K). Doping with Dy gives no significant structural changes except for a minor change in the c/a ratio. However the superconducting transition temperature is significantly suppressed and magnetic ordering temperature enhanced on Dy doping. These effects are described and discussed.

  17. Neutron irradiation damage effect on superconducting and normal state properties of the YBa 2Cu 3O 7 system

    Science.gov (United States)

    Przysłupski, P.; Wiśniewski, A.; Koleśnik, S.; Dobrowolski, W.; Pajączkowska, A.; Pytel, K.; Pytel, B.

    1988-06-01

    Effect of irradiation by fast neutrons on superconducting and normal state properties of the YBa 2Cu 3O 7 samples is presented. Transport measurements showed a degradation of all superconducting parameters, especially the transport critical current density. Critical current densities obtained from magnetization data exhibited a substantial increase / about 15 times at 77 K and H = 10 kOe/ after the irradiation with the fluence in the range 2.4·10 17 ÷ 8.7 · 10 17 n/cm 2. Such an anomalous bahavior is explained in terms of neutron created defects at intergrain regions and improved intragrain pinning.

  18. Electronic structure, magnetic and superconducting properties of co-doped iron-arsenide superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Rosner, Helge; Schnelle, Walter; Nicklas, Michael; Leithe-Jasper, Andreas [MPI CPfS Dresden (Germany); Weikert, Franziska [Los Alamos National Laboratory, New Mexico (United States); HLD Dresden Rossendorf (Germany); Wosnitza, Joachim [HLD Dresden Rossendorf (Germany)

    2013-07-01

    We present a joint experimental and theoretical study of co-doped iron-arsenide superconductors of the 122 family A{sub 1-x}K{sub x}Fe{sub 2-y}T{sub y}As{sub 2} (A = Ba,Sr,Eu; T = Co,Ru,Rh). In these systems, the co-doping enables the separation of different parameters - like electron count, disorder or the specific geometry of the FeAs layer - with respect to the position of the respective compounds in the general 122 phase diagram. For a series of compounds, we investigate the relevance of the different parameters for the magnetic, thermodynamic and superconducting properties. Our experimental investigations are supported by density functional electronic structure calculations applying different approximations for doping and disorder.

  19. Rheological behavior and cryogenic properties of cyanate ester/epoxy insulation material for fusion superconducting magnet

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Z. X.; Huang, C. J. [Key Laboratory of Cryogenics, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190, PR (China); Li, L. F. [Key Laboratory of Cryogenics, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190, PR China and State Key Laboratory of Technologies in Space Cryogenic Propellants, Technical Institute of Physics and Chemistry, C (China); Li, J. W. [Key Laboratory of Cryogenics, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190, PR China and University of Chinese Academy of Sciences, Beijing 100049, PR (China); Tan, R.; Tu, Y. P. [North China Electric Power University, Beijing 102206, PR (China)

    2014-01-27

    In a Tokamak fusion reactor device like ITER, insulation materials for superconducting magnets are usually fabricated by a vacuum pressure impregnation (VPI) process. Thus these insulation materials must exhibit low viscosity, long working life as well as good radiation resistance. Previous studies have indicated that cyanate ester (CE) blended with epoxy has an excellent resistance against neutron irradiation which is expected to be a candidate insulation material for a fusion magnet. In this work, the rheological behavior of a CE/epoxy (CE/EP) blend containing 40% CE was investigated with non-isothermal and isothermal viscosity experiments. Furthermore, the cryogenic mechanical and electrical properties of the composite were evaluated in terms of interlaminar shear strength and electrical breakdown strength. The results showed that CE/epoxy blend had a very low viscosity and an exceptionally long processing life of about 4 days at 60 °C.

  20. An AFM study of the morphology and local mechanical properties of superconducting YBCO thin films

    Energy Technology Data Exchange (ETDEWEB)

    Soifer, Ya.M.; Verdyan, A.; Azoulay, J.; Kazakevich, M.; Rabkin, E

    2004-02-01

    The morphology of thin superconducting YBCO films deposited on sapphire and on SrTiO{sub 3} was studied with the help of atomic force and scanning electron microscopies. The intrinsic mechanical properties in the flat, particles-free and chemically homogeneous regions of the films were determined with the aid of nanoindenting atomic force microscope. Also the microscopy studies revealed the difference in topography of the films, the nanohardness and Young's modulus of two films were very close to each other. For the indents shallower than 0.2 of the film thickness the Young's modulus and hardness of the films on two different substrates converged to the values of 210 and 8.5 GPa, respectively. The possible deformation mechanisms determining the localized deformation of intrinsically brittle ceramic films are discussed.

  1. An AFM study of the morphology and local mechanical properties of superconducting YBCO thin films

    Science.gov (United States)

    Soifer, Ya. M.; Verdyan, A.; Azoulay, J.; Kazakevich, M.; Rabkin, E.

    2004-02-01

    The morphology of thin superconducting YBCO films deposited on sapphire and on SrTiO 3 was studied with the help of atomic force and scanning electron microscopies. The intrinsic mechanical properties in the flat, particles-free and chemically homogeneous regions of the films were determined with the aid of nanoindenting atomic force microscope. Also the microscopy studies revealed the difference in topography of the films, the nanohardness and Young’s modulus of two films were very close to each other. For the indents shallower than 0.2 of the film thickness the Young’s modulus and hardness of the films on two different substrates converged to the values of 210 and 8.5 GPa, respectively. The possible deformation mechanisms determining the localized deformation of intrinsically brittle ceramic films are discussed.

  2. Magnetic and mechanical properties of a finite-thickness superconducting strip with a cavity in oblique magnetic fields

    Science.gov (United States)

    Huang, Chen-Guang; Liu, Jun

    2017-01-01

    This paper presents an investigation of the mechanical response of a finite-thickness superconducting strip containing an elliptical cavity in oblique magnetic fields. After the Bean critical state model and the minimum magnetic energy variation procedure are employed, the dependency of the magnetic and mechanical properties on the aspect ratio of the strip and the tilt angles of the applied field and elliptical cavity is discussed. The results show that for a strip in an oblique magnetic field, the current front penetrates non-monotonically from the surface inwards in the initial stage. The magnetization of the strip and the applied field are not collinear, and the angle between them becomes smaller with increasing field. Simultaneously, the strip suffers from a torque produced by the electromagnetic force and then has a tendency to rotate. Compared with the defect-free case, the appearance of the elliptical cavity affects the magnetic property of the strip and further causes significant stress concentration. If the tilt angle of the elliptical cavity is small, a position of stable mechanical equilibrium will exist for the strip. It is interesting that due to the elliptical cavity effect, an oblique magnetization and a non-zero torque are generated even if the applied field is perpendicular or parallel to the strip.

  3. Effect of Er doping on the superconducting properties of porous MgB2

    Indian Academy of Sciences (India)

    O Erdem; E Yanmaz

    2015-02-01

    MgB2 bulk sample with porous structure was produced by using the in-situ solid-state reaction method under argon (Ar) atmosphere of 10 bar. Elemental Er in powder form was doped into MgB2 with different compositions (Mg1−Er)B2, where = 0.00, 0.03 and 0.05, in order to investigate the effect of rare-earth (RE) element Er on the structural and electromagnetic properties of porous MgB2. The Er-doped samples result in small grain size structure compared to the undoped one. The lattice constants and of the doped samples, determined from X-ray diffraction (XRD) analysis, increase with the increasing Er content, and consequently the superconducting transition temperature ($T^{\\text{onset}}_{c}$) of MgB2, determined from resistivity measurements, is slightly suppressed. Also, the upper critical field ($B_{c2}$), the irreversibility field ($B_{\\text{irr}}$) and the critical current density ($J_{c}$) values are significantly enhanced in the doped samples. For the best sample ( = 0.03), at 15 K under a magnetic field of 4 T, the $J_{c}$ value reaches 2.4×104 A cm-2, which is higher than that of the porous sample by an order of 103, and the $B_{\\text{irr}}$ value at 20 K reaches 9.7 T. These results imply that the RE element Er fills the pores, enhances the density and the grain connectivity. Hence, the superconducting properties of the porous MgB2 sample improve by Er doping.

  4. Characterization of the critical current and physical properties of superconducting epitaxial NbTiN sub-micron structures

    Energy Technology Data Exchange (ETDEWEB)

    Klimov, A., E-mail: aklimov@ite.waw.pl [Institute of Electron Technology, Al. Lotników 32/46, 02-668 Warsaw (Poland); Słysz, W.; Guziewicz, M. [Institute of Electron Technology, Al. Lotników 32/46, 02-668 Warsaw (Poland); Kolkovsky, V.; Zaytseva, I.; Malinowski, A. [Institute of Physics Polish Academy of Science, Al. Lotników 32/46, 02-668 Warsaw (Poland)

    2017-05-15

    Highlights: • This manuscript presents investigation of the critical current dependence of Nb(Ti)N nanostructured superconducting single photon detectors (SNSPD) in function of temperature and applied magnetic field. • Presented results are complimentary and compared with the same data received for submicron-wide single bridge Nb(Ti)N structures. • Our data demonstrate significant influence of local constrictions on physical properties of our SNSPD detectors. - Abstract: Measurements of critical current in NbTiN as a function of applied magnetic field and temperature are reported for two samples: 700-nm-wide bridge and 100-nm-wide meander. In 700-nm-wide NbTiN bridge we pinpointed the limiting factors for the critical current density to be current-driven vortex de-pinning at low temperatures and thermally activated flux flow closer to the transition temperature. In 100-nm-wide NbTiN meander we found phase slips activation, accompanied by hotspots formation at all measured temperatures. These two types of structures demonstrate different dependence of the critical current on the applied magnetic field. Although our NbTiN meander structures has high de-pairing critical current densities ∼10{sup 7} A/cm{sup 2} at low temperatures, the real critical currents are smaller due to the presence of the local constrictions.

  5. Normal and superconducting properties in the Ca 1-xCd xLaBaCu 3O y system

    Science.gov (United States)

    Zhang, X.-J.; Wang, J.-S.; Xu, Z.-A.; Jiao, Z.-K.; Zhang, Q. R.

    1994-11-01

    The superconducting behavior of the superconductor CaLaBaCu 3O y (CLBCO) has been studied as a function of substitution of Cd for Ca. Electrical resistivity measurements show that the superconducting critical temperature ( Tc) decreases monotonously with increasing substituent Cd concentration x. Within the composition range O⩽ x⩽1, the samples remain in single phase. Thermogravimetry (TG) studies of the samples show that the oxygen content greatly influences the normal and superconducting properties of the Ca 1- xCd xLaBaCu 3O y system. The substitution of Cd for Ca leads to deficiencies of oxygen in Cu-O chain. As the substituent Cd concentration x increases, the oxygen content decreases monotonously. It is concluded that the reason why Cd leads to the suppression of Tc is the reduction of oxygen content caused by substitution of Cd for Ca.

  6. Synthesis of fullerene nanowhiskers using the liquid-liquid interfacial precipitation method and their mechanical, electrical and superconducting properties

    Science.gov (United States)

    Miyazawa, Kun'ichi

    2015-02-01

    Fullerene nanowhiskers (FNWs) are thin crystalline fibers composed of fullerene molecules, including C60, C70, endohedral, or functionalized fullerenes. FNWs display n-type semiconducting behavior and are used in a diverse range of applications, including field-effect transistors, solar cells, chemical sensors, and photocatalysts. Alkali metal-doped C60 (fullerene) nanowhiskers (C60NWs) exhibit superconducting behavior. Potassium-doped C60NWs have realized the highest superconducting volume fraction of the alkali metal-doped C60 crystals and display a high critical current density (Jc) under a high magnetic field of 50 kOe. The growth control of FNWs is important for their success in practical applications. This paper reviews recent FNWs research focusing on their mechanical, electrical and superconducting properties and growth mechanisms in the liquid-liquid interfacial precipitation method.

  7. Optical properties of c-axis oriented superconducting MgB2 films.

    Science.gov (United States)

    Tu, J J; Carr, G L; Perebeinos, V; Homes, C C; Strongin, M; Allen, P B; Kang, W N; Choi, E M; Kim, H J; Lee, S I

    2001-12-31

    Temperature dependent optical conductivities and dc resistivity of c-axis oriented superconducting (T(c) = 39.6 K) MgB2 films (approximately 450 nm) have been measured. The normal state ab-plane optical conductivities can be described by the Drude model with a temperature independent Drude plasma frequency of omega(p,D) = 13 600+/-100 cm(-1) or 1.68+/-0.01 eV. The normal state resistivity is fitted by the Bloch-Grüneisen formula with an electron-phonon coupling constant lambda(tr) = 0.13+/-0.02. The optical conductivity spectra below T(c) of these films suggest that MgB2 is a multigap superconductor.

  8. Microstructure and superconducting properties of nanocarbon-doped internal Mg diffusion-processed MgB2 wires fabricated using different boron powders

    Science.gov (United States)

    Xu, Da; Wang, Dongliang; Li, Chen; Yuan, Pusheng; Zhang, Xianping; Yao, Chao; Dong, Chiheng; Huang, He; Ma, Yanwei; Oguro, Hidetoshi; Awaji, Satoshi; Watanabe, Kazuo

    2016-04-01

    MgB2/Nb/Monel monofilament wires were fabricated using four different boron powders by an internal Mg diffusion (IMD) process. The microstructure, morphology and the critical current density (J c) of the used boron powders and the formative MgB2 layers were analyzed and compared. It was found that the purity and particle size of the boron powder influence the superconducting properties of MgB2 wires; further that the optimized heat-treatment condition also depends on the quality of the boron powder. The highest J c was obtained in the MgB2 layer made using amorphous boron (AB) powder, although a certain amount of voids existed in the superconducting layer. The IMD-processed MgB2 layer fabricated using high-purity boron (HB) powder had also a high J c compared with the powder-in-tube (PIT) process and a few unreacted boron particles remained in it. MgB2 wire fabricated using low-purity boron (LB) powder had a high cost-performance ratio compared with the others, which is expected to allow the fabrication of large-scale and low-cost superconducting wires for practical application. However, the enhancement of the J c was not found in the MgB2 layer manufactured using the ball-milled LB (MLB) powder as expected due to the increased percentage of impurity.

  9. Competing effects of surface phonon softening and quantum size effects on the superconducting properties of nanostructured Pb

    Energy Technology Data Exchange (ETDEWEB)

    Bose, Sangita; Galande, Charudatta; Chockalingam, S P; Raychaudhuri, Pratap; Ayyub, Pushan [Department of Condensed Matter Physics and Material Science, Tata Institute of Fundamental Research, Mumbai 400005 (India); Banerjee, Rajarshi [Department of Materials Science and Engineering, University of North Texas, Denton, TX 76203-5310 (United States)], E-mail: Sangita.Bose@fkf.mpg.de, E-mail: pratap@tifr.res.in, E-mail: pushan@tifr.res.in

    2009-05-20

    The superconducting transition temperature (T{sub C}) in nanostructured Pb decreases from 7.24 to 6.4 K as the particle size is reduced from 65 to 7 nm, below which superconductivity is lost rather abruptly. In contrast, there is a large enhancement in the upper critical field (H{sub C2}) in the same size regime. We explore the origin of the unusual robustness of T{sub C} over such a large particle size range in nanostructured Pb by measuring the temperature dependence of the superconducting energy gap in planar tunnel junctions of Al/Al{sub 2}O{sub 3}/nano-Pb. We show that below 22 nm, the electron-phonon coupling strength increases monotonically with decreasing particle size, and almost exactly compensates for the quantum size effect, which is expected to suppress T{sub C}.

  10. Controlled creation of structural defects in the heavy fermion superconductor UPt{sub 3} and its influence on the superconducting properties

    Energy Technology Data Exchange (ETDEWEB)

    Suderow, H. [CEA, Grenoble (France). Dept. de Recherche Fondamentale sur la Mateiere Condensee]|[CNRS, Grenoble (France). Centre des Recherches sur les Tres Basses Temperatures]|[Univ. Autonoma de Madrid (Spain). Lab. de Bajas Temperaturas; Kambe, S.; Huxley, A.; Flouquet, J. [CEA, Grenoble (France). Dept. de Recherche Fondamentale sur la Mateiere Condensee; Brison, J.P. [CNRS, Grenoble (France). Centre des Recherches sur les Tres Basses Temperatures; Rullier-Albenque, F. [Ecole Polytechnique, Palaiseau (France). Lab. des Solides Irradies

    1999-09-01

    The superconducting properties of the heavy fermion UPt{sub 3} have been changed by irradiation with high energy electrons which creates point defects in a reproducible and controlled way. Measurements of the residual resistivity, critical temperature, upper critical field and thermal conductivity have been realized on these irradiated samples. The strong suppression of superconductivity with increasing defect concentration is in agreement with the theory of unconventional superconductivity. However, the thermal conductivity data contradicts the simple predictions derived from the most popular models (E{sub 1g} and E{sub 2u}) of the superconducting order parameter in UPt{sub 3}.

  11. Large-scale modulation in the superconducting properties of thin films due to domains in the SrTi O3 substrate

    Science.gov (United States)

    Wissberg, Shai; Kalisky, Beena

    2017-04-01

    Scanning superconducting quantum interference device measurements reveal large-scale modulations of the superfluid density and the critical temperature in superconducting Nb, NbN, and underdoped YB a2C u3O7 -δ films deposited on SrTi O3 (STO). We show that these modulations are a result of the STO domains and domain walls, forming below the 105 K structural phase transition of STO. We found that the flow of normal current, measured above the superconducting transition, is also modulated over the same domain structure, suggesting a modified carrier density. In clean STO, domain walls remain mobile down to low temperatures. Modulated superconductivity over mobile channels offers the opportunity to locally control superconducting properties and better understand the relations between superconductivity and the local structure.

  12. Superconducting and ferromagnetic properties of NbN/NiCu and NbTiN/NiCu bilayer nanostructures for photon detection

    Science.gov (United States)

    Klimov, A.; Puźniak, R.; Aichner, B.; Lang, W.; Joon, E.; Stern, R.; Słysz, W.; Guziewicz, M.; Juchniewicz, M.; Borysiewicz, M. A.; Kruszka, R.; Wegrzecki, M.; Łaszcz, A.; Czerwinski, A.; Sobolewski, Roman

    2015-05-01

    Performance of superconducting single-photon detectors based on resistive hotspot formation in nanostripes upon optical photon absorption depends strongly on the critical current density JC of the fabricated nanostructure. Utilization of an ultrathin, weak-ferromagnet cap layer on the top of a superconducting film enhances of the structure's JC due to an extra flux pinning. We have fabricated a number of both NbN/NiCu and NbTiN/NiCu superconductor/ferromagnet (S/F) ultrathin bilayers and microbridges. NbN and NbTiN underlayers with thicknesses varying from 4 to 7 nm were grown using dc-magnetron sputtering on chemically cleaned sapphire single-crystal substrates. After rapid thermal annealing at high temperatures, the S films were coated with Ni0.54Cu0.46 overlayers with thicknesses of about 6 nm, using cosputtering. Compositions of the deposited films were confirmed by EDX spectroscopy analysis, while TEM studies demonstrated excellent epitaxial quality of our S layers with ~2-nm-thick F/S transition layer and atomically-sharp S/substrate interface. Magnetic properties of bilayers were studied using both the SQUID and Vibrating Sample Magnetometer techniques in low and high magnetic fields. Low-temperature tests confirmed that in all cases NiCu films were ferromagnetic with the Curie temperature of above 30 K. Below the bilayer critical temperature of approx. 12-13 K, the structures were fully proximitized with the strong superconducting signal. For superconducting transport properties characterization, we used bilayers patterned into 40-μm-long microbridges with the width varying from 0.4 μm to 2 μm. The same S/F nanostructures were also used to study their superconducting fluctuations. The temperature dependence of magnetoresistance demonstrated highly 2-dimensional character with an unusual negative region that extended almost to room temperature. In the S/F sample, the fluctuations were observed to be substantially below theoretical expectations.

  13. Magneto-elastic behaviour of thin type-II superconducting strip with field-dependent critical current

    Science.gov (United States)

    Xue, Cun; He, An; Yong, Huadong; Zhou, Youhe

    2013-01-01

    The magneto-elastic behavior of thin superconducting strip in perpendicular magnetic field with field-dependent critical current is studied. We calculate numerically the body force, strain, displacement, and thickness changes in the strip for the Bean model and Kim model during the field ascent and descent. The differences in magnetostriction between the Bean model and the Kim model are analyzed. The magnetostriction during one full cycle of the applied field for both models is presented. The results show that magnetostriction loops are different in these models, and at low temperatures Kim model is in better agreement with experiment than Bean model.

  14. Experimental studies on the thermal properties of fast pulsed superconducting accelerator magnets; Experimentelle Untersuchungen thermischer Eigenschaften schnell gepulster supraleitender Beschleunigermagnete

    Energy Technology Data Exchange (ETDEWEB)

    Bleile, Alexander

    2016-01-06

    The new Facility for Antiproton and Ion Research FAIR is being constructed at the GSI research center in Darmstadt (Germany). This wordwide unique accelerator facility will provide beams of ions and antiprotons at high intensities and high energies for the fundamental research in nuclear, atomic and plasma physics as well as for applied science. The superconducting synchrotron SIS100 with a magnetic rigidity of 100 T/m, the core component of the FAIR facility will provide primary ion beams of all types from hydrogen up to uranium. One of the key technical systems of a new synchrotron are fast ramped electromagnets for the generation of fast ramped magnetic fields for deflecting and focusing of the ion beams. To reduce the energy consumption and to keep the operating costs of the synchrotron as low as possible superconducting magnet technology is applied in the SIS100. Superconducting magnets have been developed at GSI within the scope of the FAIR project. Although the superconducting magnet technology promises high cost saving, the power consumption of the fast ramped superconducting magnets can't be completely neglected. The pulsed operation generates dynamic losses in the iron yokes as well as in the superconducting coils of the magnets. A forced two-phase helium flow provides effective cooling for supercounducting magnets exposed to a continous relative high heat flow. The subject of this PhD thesis is experimental investigations and analysis of the dynamic power losses in fast ramped superconducting magnets and their dependencies on the operation cycles of the synchrotron. This research was conducted on the the first series SIS100 dipole magnet. Based on the experimentally defined dynamic heat loads and helium mass flow rates in the dipole magnet the heat loads and helium consumption for all other types of superconducting magnet modules of the SIS100 have been estimated. These results are essential for the development of the cooling system for the the

  15. Superconducting properties of the s ±-wave state: Fe-based superconductors

    Science.gov (United States)

    Bang, Yunkyu; Stewart, G. R.

    2017-03-01

    Although the pairing mechanism of Fe-based superconductors (FeSCs) has not yet been settled with consensus with regard to the pairing symmetry and the superconducting (SC) gap function, the vast majority of experiments support the existence of spin-singlet sign-changing s-wave SC gaps on multi-bands ({{s}+/- } -wave state). This multi-band {{s}+/- } -wave state is a very unique gap state per se and displays numerous unexpected novel SC properties, such as a strong reduction of the coherence peak, non-trivial impurity effects, nodal-gap-like nuclear magnetic resonance signals, various Volovik effects in the specific heat (SH) and thermal conductivity, and anomalous scaling behaviors with a SH jump and condensation energy versus T c, etc. In particular, many of these non-trivial SC properties can easily be mistaken as evidence for a nodal-gap state such as a d-wave gap. In this review, we provide detailed explanations of the theoretical principles for the various non-trivial SC properties of the {{s}+/- } -wave pairing state, and then critically compare the theoretical predictions with experiments on FeSCs. This will provide a pedagogical overview of to what extent we can coherently understand the wide range of different experiments on FeSCs within the {{s}+/- } -wave gap model.

  16. History dependence of magnetomechanical properties of steel

    Science.gov (United States)

    Melquiond, F.; Mouroux, A.; Jouglar, J.; Vuillermoz, P. L.; Weinstock, H.

    1996-05-01

    Magnetomechanical measurements using a superconducting SQUID magnetic gradiometer and a tensile-testing machine have been performed on a variety of steel specimens to determine the change in magnetization due to applied stress and the possible application of the observed behavior as a new form of nondestructive evaluation in steel. This study builds on earlier related measurements.

  17. Doping dependence of the vortex dynamics in single-crystal superconducting NaFe{}_{1-x}Co x As

    Science.gov (United States)

    Ahmad, D.; Choi, W. J.; Seo, Y. I.; Jung, S.-G.; Kim, Y. C.; Salem-Sugui, S., Jr.; Park, T.; Kwon, Y. S.

    2017-10-01

    We investigate the doping dependence of flux pinning in superconducting NaFe{}1-xCo x As (x = 0.01, 0.03, 0.05 and 0.07) single crystals grown by the Bridgman method. The electronic specific heat displays a pronounced anomaly in a sample series at superconducting transition temperature, which hardly shows any residual part at low temperature. We found that Co doping plays an important role in signifying the secondary peak in the magnetic hysteresis of optimally doped (x = 0.03) and heavily doped (x = 0.05, 0.07) crystals. Furthermore, the dependence of the relaxation rate S = ∣d ln M/d ln t∣ on magnetic field and temperature exhibits a decreasing trend within a certain range corresponding to the secondary peak effect in the optimally and heavily doped samples. The magnetic relaxation rate combined with the Maley analysis of the current-dependent creep energy shows a single-vortex pinning in the lightly doped sample dominant at low applied fields, and plastic pinning at high applied fields, without showing a secondary peak. However, in the optimally and heavily doped samples, the magnetic relaxation rate and U(J) isothermal analysis show that the collective pinning that dominates below H peak crosses over to plastic pinning for fields above H peak.

  18. On the Field Dependent Surface Resistance Observed in Superconducting Niobium Cavities

    CERN Document Server

    Weingarten, W

    2009-01-01

    A quantitative description is presented of the non-linear current-voltage response in superconducting niobium cavities for accelerator application. It is based on a fit for a large sample of data from cavity tests of different kind. Trial functions for the surface resistance describing this non-linear relation are established by a least square data fit. Those trial functions yielding the best fit are quantitatively explained by basic physics.

  19. Relationships between oxygen content, modulation period and superconducting property of Bi-based superconducting oxides. Bi kei sankabtsu chodendotai ni okeru sanso ganryo, hencho kozo oyobi chodendo tokusei no sokan

    Energy Technology Data Exchange (ETDEWEB)

    Deshimaru, Y.; Shimizu, Y.; Miura, N.; Yamazoe, N. (Kyushu Univ., Fukuoka (Japan). Graduate School of Engineering Sciences); Hiroi, Z.; Bando, Y. (Kyoto Univ., Kyoto (Japan). Inst. for Chemical Research)

    1992-09-10

    Two (2223 and 2212) of three superconducting phases in the Pb-doped Bi-Sr-Ca-Cu-O (BSCCO) oxide superconductor were examined for their changes of crystal structures and superconducting properties with changing oxygen content. Their oxygen sorption behavior examined by the temperature-programmed-desorption method showed that both samples desorb trace amounts of oxygen in a temperature range of 350-600 centigrade and the behavior examined by the temperature-programmed oxidation method showed that they absorb (absorb) reversibly oxygen desorbed above in a range of 100-350 centigrade. The critical temperature to bear diamagnetism (Tc) of the 2223 sample fell from 111 K to 96 K as oxygen was desorbed up to 600 centigrade. However, Tc recovers reversibly to the initial value when oxygen was re-absorbed. Contrary to the 2223, the 2212 sample showed the opposite Tc change. Both samples increased in their c-axes lengths and their modulation periods and the changes were reversible respectively. It was pointed out that the Tc behaviors of both sample systems were dependent on the concentration of holes on the CuO2 surfaces. 33 refs., 9 figs.

  20. Structural and superconducting properties of ion beam sputtered Nb thin films and Nb/Cu bilayers

    Science.gov (United States)

    Nath, S. K.; Dhawan, R.; Rai, S.; Lodha, G. S.; Sokhey, K. J. S.

    2012-01-01

    We present the results of a study of structural and superconducting properties of polycrystalline Nb thin films (200 Å, 300 Å, 400 Å, 700 Å and 1000 Å) and Nb/Cu bilayers (300 Å/300 Å and 400 Å/300 Å) prepared on Si substrates by ion beam sputtering at room temperature. The thicknesses, roughnesses at the surfaces and interfaces were determined by X-ray reflectivity whereas the grain sizes were determined from grazing incidence X-ray diffraction and transmission electron microscopic studies. The superconducting transition temperature ( T C) of Nb thin films are smaller than T C of bulk Nb. The Nb-200 Å sample does not show T C down to 2.3 K. The average size of the grains varies from 42 Å for Nb-200 Å sample to 69 Å for Nb-1000 Å sample. Our results show that the T C in these polycrystalline films is not only limited by its thickness but also by the size of the grains. The Nb films deposited in situ on the Cu layer (Nb/Cu) show a marginal increase in average sizes of the grains as compare to their respective values in Nb films of same thicknesses. As a result a marginal increase in T C of these films is also observed. The maximum decrease in T C due to oxygen intake during deposition should be about 0.5 K from its bulk value (9.28 K). We have attributed the large decrease in T C in our case on the basis of decrease in the Debye temperature and density of states at the Fermi level for Nb thin films as compared to their respective values for bulk Nb.

  1. Improvement of superconducting properties of (Bi, Pb)-2223phase by TlF{sub 3} doping

    Energy Technology Data Exchange (ETDEWEB)

    Saoudel, A., E-mail: dca.saoudel@yahoo.fr [LEND, Faculty of Science and Technology, Med Seddik Benyahia University, 18000 Jijel (Algeria); Amira, A.; Mahamdioua, N.; Boudjadja, Y. [LEND, Faculty of Science and Technology, Med Seddik Benyahia University, 18000 Jijel (Algeria); Varilci, A.; Altintas, S.P.; Terzioglu, C. [Department of Physics, Faculty of Arts and Sciences, Abant Izzet Baysal University, 14280 Bolu (Turkey)

    2016-11-15

    In this work, the superconducting properties of thallium fluoride (TlF{sub 3})doped Bi{sub 1.8−x}Tl{sub x}Pb{sub 0.35}Sr{sub 2}Ca{sub 2Cu3}O{sub y}F{sub 3x}(x=0–0.15)compounds are presented. The X-ray diffraction analysis shows that the proportion of (Bi, Pb)-2223phase is higher than the secondary (Bi, Pb)-2212one in all samples and its highest value is about 82.74%for x=0.05. From the resistivity curves, the highest values of the onset critical transition temperature (T{sub c.on}), the offset critical transition temperature (T{sub c.off}) are seen for x=0.10. The calculation of activation energy (U{sub 0}) in the TAFF (thermally activation flux flow) region proves the positive effect of TlF{sub 3} doping on the dissipative behavior of energy near T{sub c.off}. Flux pinning strength is enhanced by increasing TlF{sub 3}content up to x=0.10, and decreased by the application of a magnetic field. The other superconducting parameters like T(H{sub c2}), T(H{sub irr}), ξ(0) and μ{sub 0}H{sub c2}(0) are also improved significantly by doping. The obtained results of Ac susceptibility measurements show that the onset temperature of diamagnetism is improved by TlF{sub 3} doping, in accordance with the resistivity results.

  2. Pressure dependence of structural phase transition and superconducting transition in CsI

    CERN Document Server

    Nirmala-Louis, C

    2003-01-01

    The self-consistent band structure calculation for CsI performed both in CsCl and HCP structures using the TB-LMTO method is reported. The equilibrium lattice constant, bulk modulus and the phase-transition pressure at which the compound undergoes structural phase transition from CsCl to HCP are predicted from the total-energy calculations. The band structure, density of states (DOS), electronic charge distributions, metallization and superconducting transition temperature (T sub c) of CsI are obtained as a function of pressure for both the CsCl and HCP structures. It is found that the charge transfer from s and p states to d state causes metallization and superconductivity in CsI. The highest T sub c estimated is 2.11 K and the corresponding pressure is 1.8 Mbar. This value is in agreement with the recent experimental observation. The experimental trend - ''metallization and superconductivity is rather insensitive to the crystal structure of CsI'' - is also confirmed in our work. (Abstract Copyright [2003], ...

  3. Thermo-mechanical properties of epoxy GFRPs used in superconducting magnet winding

    Science.gov (United States)

    Usami, S.; Suzuki, T.; Ejima, H.; Asano, K.

    A tightly constructed rigid structure of a conductor winding and GFRP spacers in a coil case is an essential element for a superconducting magnet, that is to operate at a cryogenic temperature and sustain large magnetic forces. However, the contact pressures on the conductor, the spacers and the coil case, which are imposed in fabrication process, may be greatly reduced by relaxation at room temperature and by thermal contraction in the GFRP spacers during cool-down process. We therefore studied 61 kinds of commercial and test GFRPs and established a basis for suitable GFRP spacer material to be used in superconducting magnet windings. Glass transition temperature, Tg, of the impregnating resin plays an important role in transverse creep deformation of GFRPs. GFRP spacers with Tg above 423 K can maintain 80% of the initial pressure in a winding for two years at room temperature. This result was obtained by utilizing the transverse creep moduli of GFRPs at different temperatures and the time-temperature superposition principle. Transverse thermal contraction from 293 to 4 K decreases uniformly in all GFRPs as the resin weight content, Rc, decreases. Also, contraction is smaller than that of the 304 stainless steel used for the coil case when Rc is less than 15%. As a result, pressure decrease in the winding can be prevented during cool-down. The elastic modulus in the transverse direction of a GFRP is calculated by dividing the elastic modulus of the impregnating resin by Rc. Fractures of the GFRPs at low temperatures are primarily in shear mode under four-point bending, in-plane compression, transverse compression, or interlaminar shear loading. Moreover, the transverse-compressive fatigue limit of plain-woven GFRP at low temperature depends on the maximum compressive stress of the cyclic loading under high mean-compressive stress and the stress range under low mean-compressive stress.

  4. Study of the superconducting properties of the new intermetallic compound {{Zr}}_{1-x}{{Nb}}_{x}{B}_{2}

    Science.gov (United States)

    Marques, M. D. R.; Portela, F. S.; Corredor, L. T.; Zhang, G.; Vanacken, J.; Moshchalkov, V. V.; Correa, L. E.; Renosto, S. T.; Cigarroa, O.; Machado, A. J. S.; Aguiar, J. Albino

    2016-09-01

    In this paper we report on the synthesis and the structural, electrical, magnetic and thermal analysis for the new material {{{Zr}}}1-x{{{Nb}}}x{{{B}}}2 (0.01 ≤slant x ≤slant 0.05). A superconducting transition was observed for all x values studied, despite the non-superconducting matrix ZrB2, which indicates that the superconducting state is induced by the presence of Nb. The results show that the critical temperature increases with Nb content, reaching its maximum (T c = 8.1 K) for x = 0.04. From the specific heat data we find a Sommerfeld constant of γ = 1.6 mJ molK-2 and a Debye temperature of {θ }D = 615.5 K. Unconventional behaviors are observed in specific heat dependence with temperature and in {H}{{c}1}(T) diagram. These behaviors are investigated in {C}{{e}}/T versus T curve, where an upturn appears for T\\lt 2.3 K, and in {ln}({C}{{e}}/γ {T}{{c}}) versus {T}{{c}}/T dependence, which shows a clear deviation from BCS theory for low temperatures. Also, contrary to the conventional theories we found a positive curvature for temperatures near T c in the lower critical field, besides an upturn around 2.3 K. We suggest that these behaviors possibly arise from multiband superconductivity in {{Zr}}0.96{{Nb}}0.04{{{B}}}2.

  5. Experimental study on the ac loss properties of two-strand parallel conductors composed of superconducting multifilamentary strands

    CERN Document Server

    Iwakuma, M; Funaki, K

    2002-01-01

    The ac loss properties of two-strand superconducting parallel conductors were experimentally investigated by using NbTi multifilamentary strands with a rectangular cross section. We prepared the simple situation that was supposed in the previous theoretical study (M Iwakuma et al 2002 Supercond. Sci. Technol. 15 1525-36). The two insulated strands were sparsely co-wound into one-layer solenoidal coils. They were transposed only once and soldered at both ends. The ac losses in the sample coils were measured by a pick-up-coil method by applying uniform ac magnetic field parallel to the coil axis and comparing it with the theoretical results. The validity of the theoretical expressions derived in the previous paper was verified by the quantitative agreement with experiment in all the aspects, i.e. the dependencies on frequency, field amplitude and the deviation length in transposition in both the non-saturation and saturation cases and also the threshold condition between them. The results obtained support the t...

  6. Statistical correlations for thermophysical properties of Supercritical Argon (SCAR) used in cooling of futuristic High Temperature Superconducting (HTS) cables

    Science.gov (United States)

    Kalsia, Mohit; Dondapati, Raja Sekhar; Usurumarti, Preeti Rao

    2017-05-01

    High Temperature Superconducting (HTS) cables are emerging as an alternative to conventional cables in efficient power transmission. However, these HTS cables require cooling below the critical temperature of superconductors used to transmit larger currents. With the invention of high temperature superconductors whose critical temperatures are up to 134 K (Hg based), it is a great challenge to identify a suitable coolant which can carry away the heating load on the superconductors. In order to accomplish such challenge, an attempt has been made in the present work to propose supercritical Argon (SCAR) as the alternative to cool the HTS cables. Further, a statistical correlation has been developed for the thermophysical properties such as density, viscosity, specific heat and thermal conductivity of SCAR. In addition, the accuracy of developed correlations is established with the help of few statistical parameters and validated with standard database available in the literature. These temperature dependent accurate correlations are useful in predicting the pressure drop and heat transfer behaviour in HTS cables using numerical or computational techniques. In recent times, with the sophistication of computer technology, solving of various complex transport equations along with the turbulence models became popular and hence the developed correlations would benefit the technological community. It is observed that, a decrease in pressure, density and viscosity are found to be decreasing whereas the thermal conductivity and specific heat increase significantly. It can be concluded that higher heat transfer rate and lower pumping power can be achieved with SCAR as coolant in the HTS cables.

  7. Structural properties of strained YBa2Cu3O6+x superconducting films grown by pulsed laser deposition

    Science.gov (United States)

    Ariosa, Daniel; Abrecht, M.; Pavuna, Davor; Onellion, Marshall

    2000-09-01

    In YBa2Cu3O6+x compound the tetragonal to orthorhombic transition occurs around x equals 0.3, followed by a continuum variation of lattice parameters. Hence both, the structural and superconducting properties, depend upon the oxygen content in CuO chains. Conversely, the epitaxial stress, exerted by the substrate on YBCO films, modified the lattice parameters influencing the oxygen stability in the chains. The understanding of this mechanism is essential when growing epitaxial films for in- situ photoemission studies as well as for tunneling experiments, since the oxygen stability up to the top surface unit-cell is a central issue. We have studied this effect on c-axis oriented YBCO films grown by laser ablation on (001) STO single crystals. Accurate x-ray diffraction analysis of thick films (t GRT 500 angstrom) indicates the presence of two distinct layers, one strained and the other relaxed. Detailed analysis shows that the relaxed layer is as well oxidized as bulk samples, while the strained one is oxygen deficient. Furthermore, despite an oxygen content of about x equals 0.65, the strained layer is in the tetragonal phase (in bulk, the tetragonal phase exists for x < 0.3). We discuss these results in terms of competition between the chemical pressure induced by oxygen inclusion in the chains, and the uniaxial stress within the film.

  8. Tailoring of the flip effect in the orientation of a magnet levitating over a superconducting torus: Geometrical dependencies

    Energy Technology Data Exchange (ETDEWEB)

    Diez-Jimenez, Efren, E-mail: ediez@ing.uc3m.e [Departamento de Ingenieria Mecanica, Universidad Carlos III de Madrid, Butarque, 15, E28911 Leganes (Spain); Sander, Berit; Timm, Lauri; Perez-Diaz, Jose-Luis [Departamento de Ingenieria Mecanica, Universidad Carlos III de Madrid, Butarque, 15, E28911 Leganes (Spain)

    2011-04-15

    Research highlights: {yields} A local model is used to demonstrate a flip effect in the orientation of a magnet over a superconductor. {yields} A superconducting torus shape is studied. {yields} Increasing the inner radius of the torus elevates the flip effect point. {yields} There are linear piecewises in the geometrical dependency functions that help to fit the flip effect point. - Abstract: In a previous study, a general local model was used in order to demonstrate the apparition of a flip effect in the equilibrium orientation of a magnet when it is over a superconducting torus. This effect can be easily used in devices such as binary position detectors for magneto-microscopy, contactless sieves or magnetic levels amongst others. We present an initial study useful to design devices based on the flip effect between magnets and torus superconductors. It demonstrates that varying different geometrical parameters the flip effect point can be fixed. Also, it can be observed that increasing the inner radius of the torus elevates the flip effect point. A magneto-mechanical explanation of this phenomenon is exposed. For an increment of cross-section diameter occurs the same behavior. There are linear piecewises in the geometrical dependency functions that can be used for a more accurate fitting of the flip effect point.

  9. Effects of post-annealing and cobalt co-doping on superconducting properties of (Ca,Pr)Fe2As2 single crystals

    Science.gov (United States)

    Okada, T.; Ogino, H.; Yakita, H.; Yamamoto, A.; Kishio, K.; Shimoyama, J.

    2014-10-01

    In order to clarify the origin of anomalous superconductivity in (Ca,RE)Fe2As2 system, Pr doped and Pr,Co co-doped CaFe2As2 single crystals were grown by the FeAs flux method. These samples showed two-step superconducting transition with Tc1 = 25-42 K, and Tc2 < 16 K, suggesting that (Ca,RE)Fe2As2 system has two superconducting components. Post-annealing performed for these crystals in evacuated quartz ampoules at various temperatures revealed that post-annealing at ∼400 °C increased the c-axis length for all samples. This indicates that as-grown crystals have a certain level of strain, which is released by post-annealing at ∼400 °C. Superconducting properties also changed dramatically by post-annealing. After annealing at 400 °C, some of the co-doped samples showed large superconducting volume fraction corresponding to the perfect diamagnetism below Tc2 and high Jc values of 104-105 A cm-2 at 2 K in low field, indicating the bulk superconductivity of (Ca,RE)Fe2As2 phase occurred below Tc2. On the contrary, the superconducting volume fraction above Tc2 was always very small, suggesting that 40 K-class superconductivity observed in this system is originating in the local superconductivity in the crystal.

  10. Single crystals of superconducting SmFeAsO Hx : Structure and properties

    Science.gov (United States)

    Pisoni, A.; Katrych, S.; Arakcheeva, A.; Verebélyi, T.; Bokor, M.; Huang, P.; Gaál, R.; Matus, P.; Karpinski, J.; Forró, L.

    2016-07-01

    We report the synthesis, structure, and superconducting properties of single crystals of SmFeAsO Hx . The crystals were grown at high pressure and high temperature using a cubic anvil technique. 1H-NMR studies confirm the presence of H atoms in the samples. Single crystal x-ray diffraction analyses demonstrate a remarkable disorder in the S m2O2 layers induced by hydrogen incorporation and reveal that the H positions are compatible with a H2O -like geometry inside the crystals. We have measured the magnetotransport properties of SmFeAsO Hx single crystals with x =0.07 , 0.11, and 0.16 in magnetic field up to 16 T, oriented along the two main crystallographic directions. The results show an increase of the critical temperature with hydrogen content. The zero-temperature upper critical fields and the magnetic anisotropy are calculated as a function of the hydrogen content. SmFeAsO Hx crystals present significantly higher upper critical fields and magnetic anisotropies compared to SmFeAs O1 -xFx compounds.

  11. The role of various boron precursor on superconducting properties of MgB2/Fe

    Science.gov (United States)

    Safran, S.; Kılıçarslan, E.; Kılıç, A.; Gencer, A.

    2014-09-01

    The superconducting properties of Fe sheathed MgB2 wire has been studied as a function of precursor B powder particle size. The in situ processed MgB2 samples were prepared by means of conventional solid state reaction method with magnesium powder (99.8%, 325 mesh) and three different types of amorphous boron powders (purity; 98.8%, >95% and 91.9%) from two sources, Pavezyum (Turkish supplier) and Sigma Aldrich. The particle sizes of Turkish boron precursor powder were selected between 300 and 800 nm. The structural and magnetic properties of the prepared samples were investigated by means of the X-ray powder diffraction (XRD) and ac susceptibility measurements. The XRD patterns showed that the diffraction peaks for our samples belong to the main phase of the MgB2 diffraction patterns. The highest critical temperature, Tc = 38.4 K was measured for the MgB2 sample which was fabricated by using the 98.8% B. The critical current density of this sample was extracted from the magnetization measurements and Jc = 5.4 × 105 A cm-2 at 5 K and B = 2 T. We found that the sample made by using the 98.8% boron showed almost 2 times higher Jc than that of obtained from 91.9% B powder.

  12. Electronic properties and superconductivity of rapidly quenched Al-Si alloys

    Energy Technology Data Exchange (ETDEWEB)

    Chevrier, J.; Pavuna, D.; Cyrot-Lackmann, F.

    1987-12-15

    We present detailed studies of electronic properties of Al-Si alloys prepared in a nonequilibrium state by means of rapid solidification. The quenched alloys exhibit an enhanced superconducting transition temperature up to 6.2 K in an Al--Si 30 at. % alloy as well as an increased thermal slope of resistivity. Using differential scanning calorimetry, a large enthalpy variation (..delta..H = 4.1 kJ/mole for Al--Si 30 at. %) has been measured during the irreversible transition from the non- equilibrium state to the equilibrium one. This is mainly attributed to the energy difference between the metallic state of silicon atoms trapped in fcc aluminum matrix during quenching and the usual covalent state of silicon precipitates in an equilibrium state. This large energy difference is presented as the origin of a lattice instability which softens the phonon spectrum and gives rise to a stronger electron-phonon coupling. This appears to be a characteristic property of nonequilibrium Al-Si solid solutions, which is associated with the metallic state of silicon atoms. An interpretation of the T/sub c/ enhancement is proposed for both Al-Si and Al-Ge alloys based on the phonon softening in these nonequilibrium crystalline alloys.

  13. Mechanical and physical properties of Bi-2223 and Nb3Sn superconducting materials between 300 K and 7 K

    Science.gov (United States)

    Nyilas, Arman; Osamura, Kozo; Sugano, Michinaka

    2003-09-01

    Within the framework of IEC/TC90-WG5 and VAMAS/TWA16, superconducting (SC) materials are investigated with respect to their mechanical properties between 300 K and 7 K. Besides the mechanical tests, physical and electrical properties are also determined for high Tc SC-tapes. The mechanical tests comprised the characterization of tensile properties at ambient temperature as well as at 7 K of Nb3Sn-reacted strands, Bi2223 tapes, pure silver tapes, silver bars, silver alloy tapes and bare filaments extracted from Bi-2223 tapes. All these investigations are carried out using a variable temperature helium gas flow cryostat equipped with a servo hydraulic tensile machine (MTS, model 810). For the load measurements specially developed, highly sensitive cryogenic proof in situ working load cells are used. For the strain determination of the wires, a high resolution ultra-light double extensometer system with a specially developed low noise signal conditioner is used. The engineering parameters such as yield strength and elastic modulus are evaluated using the obtained data with newly developed software. For the tiny and brittle filaments load versus displacement data are obtained. A determined master line (Young's modulus versus machine compliance) established by thin 0.125 mm Ø wires of different pure metals is used for the Young's modulus estimation of filaments. For the 4 K electrical voltage-current measurements under magnetic fields of up to 13 T, an existing test facility is used for the high Tc tapes. No dependency between applied strain up to 0.3% and the critical current under magnetic field could be observed for the selected specific Bi-2223 tapes. In addition, thermal expansion curves of Bi-2223 tapes along with pure silver and silver alloy (AgMg) are determined between 290 K and 7 K using in situ working extensometers. The coefficient of thermal expansion is evaluated by the determined thermal expansion versus temperature curve.

  14. Synthesis and superconducting properties of the iron oxyarsenide TbFeAsO0.85

    OpenAIRE

    Shi, Y G; Yu, S.; Belik, A. A.; Matsushita, Y; Tanaka, M.; Katsuya, Y.; KOBAYASHI, K.; Yamaura, K.; Takayama-Muromachi, E.

    2008-01-01

    The iron oxyarsenide TbFeAsO0.85 was synthesized by a high-pressure method. A high-quality polycrystalline sample was obtained and characterized by measurements of magnetic susceptibility and electrical resistivity. Bulk superconductivity with Tc of 42 K was clearly established without an F doping usually conducted to tune on superconductivity in the iron oxypnictide.

  15. Anisotropic effect of appearing superconductivity on the electron transport in FeSe

    Science.gov (United States)

    Grigoriev, P. D.; Sinchenko, A. A.; Kesharpu, K. K.; Shakin, A.; Mogilyuk, T. I.; Orlov, A. P.; Frolov, A. V.; Lyubshin, D. S.; Chareev, D. A.; Volkova, O. S.; Vasiliev, A. N.

    2017-06-01

    A theoretical model has been proposed to describe the conductivity of a layered anisotropic normal metal containing small superconducting inclusions at an arbitrary eccentricity of spheroidal superconducting islands. The electron transport and magnetic properties of FeSe single crystals have been measured. The results indicate the existence of superconductivity at temperatures much higher than the critical superconducting transition temperature corresponding to vanishing electrical resistance. Within the proposed model, quantitative agreement has been achieved between the volume fraction of superconducting inclusions and its temperature dependence determined from the transport and magnetic measurements.

  16. Detailed magnetization study of superconducting properties of YBa2Cu3O7-x ceramic spheres

    Science.gov (United States)

    Landau, I. L.; Willems, J. B.; Hulliger, J.

    2008-03-01

    We present a magnetization study of low density YBa2Cu3O7-x ceramics carried out in magnetic fields H such that 0.5 Oe85 K, using low field magnetization measurements, we were able to evaluate the temperature dependence of λ, which turned out to be very close to predictions from conventional Ginzburg-Landau theory. Although the present samples consisted of randomly oriented grains, specifics of magnetization measurements allowed for evaluation of λab(T). Good agreement between our estimation of the grain size and the real sample structure provides evidence for the validity of this analysis of magnetization data. Measurements of the equilibrium magnetization in high magnetic fields were used for evaluation of Hc2(T). At temperatures close to Tc, the Hc2(T) dependence turned out to be linear, in agreement with Ginzburg-Landau theory. The value of the temperature at which Hc2 vanishes coincides with the superconducting critical temperature evaluated from low field measurements, which is important evidence of the validity of both approaches to the analysis of magnetization data.

  17. Temperature dependence of the critical current of the superconducting microladder in zero magnetic field: Theory and experiment

    Energy Technology Data Exchange (ETDEWEB)

    Fink, H.J. (Department of Electrical Engineering and Computer Science, University of California, Davis, Davis, California 95616 (USA)); Buisson, O.; Pannetier, B. (Centre de Recherches sur les Tres Basses Temperature, Centre National de la Recherche Scientifique, Boite Postale 166X, 38042 Grenoble CEDEX, France (FR))

    1991-05-01

    The largest supercurrent which can be injected into a superconducting microladder was calculated as a function of nodal spacing {ital scrL} and temperature for zero magnetic flux using (i) exact solutions of the Ginzburg-Landau equation in terms of Jacobian elliptic functions and (ii) approximate solutions in terms of hyperbolic functions. The agreement is good for {ital scrL}/{xi}({ital T}){lt}3, where {xi}({ital T}) is the temperature-dependent coherence length. Since solution (ii) is much simpler than solution (i), it is of considerable value when calculating critical currents of micronets with nodal spacings comparable to {xi}({ital T}). We find that the temperature-dependent critical current deviates significantly from the classical 3/2 power law of the Ginzburg-Landau theory. Preliminary experiments on a submicrometer ladder confirm such deviations.

  18. Origin of dc voltage in type II superconducting flux pumps: field, field rate of change, and current density dependence of resistivity

    Science.gov (United States)

    Geng, J.; Matsuda, K.; Fu, L.; Fagnard, J.-F.; Zhang, H.; Zhang, X.; Shen, B.; Dong, Q.; Baghdadi, M.; Coombs, T. A.

    2016-03-01

    Superconducting flux pumps are the kind of devices which can generate direct current into superconducting circuit using external magnetic field. The key point is how to induce a dc voltage across the superconducting load by ac fields. Giaever (1966 IEEE Spectr. 3 117) pointed out flux motion in superconductors will induce a dc voltage, and demonstrated a rectifier model which depended on breaking superconductivity. van de Klundert et al (1981 Cryogenics 21 195, 267) in their review(s) described various configurations for flux pumps all of which relied on inducing the normal state in at least part of the superconductor. In this letter, following their work, we reveal that a variation in the resistivity of type II superconductors is sufficient to induce a dc voltage in flux pumps and it is not necessary to break superconductivity. This variation in resistivity is due to the fact that flux flow is influenced by current density, field intensity, and field rate of change. We propose a general circuit analogy for travelling wave flux pumps, and provide a mathematical analysis to explain the dc voltage. Several existing superconducting flux pumps which rely on the use of a travelling magnetic wave can be explained using the analysis enclosed. This work can also throw light on the design and optimization of flux pumps.

  19. Superconductivity in transition metals.

    Science.gov (United States)

    Slocombe, Daniel R; Kuznetsov, Vladimir L; Grochala, Wojciech; Williams, Robert J P; Edwards, Peter P

    2015-03-13

    A qualitative account of the occurrence and magnitude of superconductivity in the transition metals is presented, with a primary emphasis on elements of the first row. Correlations of the important parameters of the Bardeen-Cooper-Schrieffer theory of superconductivity are highlighted with respect to the number of d-shell electrons per atom of the transition elements. The relation between the systematics of superconductivity in the transition metals and the periodic table high-lights the importance of short-range or chemical bonding on the remarkable natural phenomenon of superconductivity in the chemical elements. A relationship between superconductivity and lattice instability appears naturally as a balance and competition between localized covalent bonding and so-called broken covalency, which favours d-electron delocalization and superconductivity. In this manner, the systematics of superconductivity and various other physical properties of the transition elements are related and unified.

  20. Effect of rapid heating, quenching and transformation conditions on the superconducting properties and microstructure of Jelly-Roll processed Nb3Al superconductors

    Science.gov (United States)

    Fukuzaki, T.; Takeuchi, T.; Banno, N.; Tagawa, K.; Tatsumi, N.; Ogiwara, H.; Wada, H.

    2002-10-01

    A Jelly-Roll processed Nb3Al superconductor with excellent superconducting properties has been fabricated by the process of rapid heating, quenching and transformation (RHQT). In order to fabricate a long length of wire with homogeneous superconducting properties, the optimization of the RHQT conditions is particularly important because RHQT conditions determine the final microstructure and superconducting properties. In this paper, we have studied the variation of microstructure and superconducting properties with RHQ and transformation annealing conditions, to determine the optimum processing condition. In the study of the RHQ treatment, we found that the RHQ conditions are divided into four regions according to the joule heating current (IRHQ). In the optimum region, the wire is quenched from the temperature in which a bcc solid solution extends to more than 25 at%Al, and the scatter of critical current density (Jc) after transformation annealing is almost negligible. In the study of the deformation and transformation heat treatment, we have found that the deformation of the supersaturated solid solution improves the resultant superconducting properties, and prevents degradation of superconducting properties that occurs when the temperature ramp-up rate is slow.

  1. Effect of the BSCCO superconducting properties by tiny Y2O3 addition

    Science.gov (United States)

    Dong, Yan; Sun, Aimin; Xu, Bin; Zhang, Hongtao; Zhang, Meng

    2016-09-01

    In this paper, the effect of tiny Y2O3 addition in (Bi,Pb)-2223 superconductor prepared by solid state reaction technique was studied. The properties of samples have been investigated via X-ray diffraction (XRD), resistance-temperature (R-T) curve, scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS). XRD data indicated that all samples are multiphase and the major phases are high-temperature phases and low-temperature phases. The volume fraction of (Bi,Pb)-2223 is not great change with tiny Y2O3 addition. All samples exhibit superconducting phase with the critical transition temperature and one-step transition, however, the transition width was decreased with the Y2O3 addition up to 0.04 wt.% and sharp increased with the excessive oxide addition. SEM pictures show that the Y2O3 appeared on the flake-type grains surface obviously, but the number and size of the hole between grains are decreased in the 0.04 wt.% addition.

  2. SRF test facility for the superconducting LINAC ``RAON'' — RRR property and e-beam welding

    Science.gov (United States)

    Jung, Yoochul; Hyun, Myungook; Joo, Jongdae; Joung, Mijoung

    2015-02-01

    Equipment, such as a vacuum furnace, high pressure rinse (HPR), eddy current test (ECT) and buffered chemical polishing (BCP), are installed in the superconducting radio frequency (SRF) test facility. Three different sizes of cryostats (diameters of 600 mm for a quarter wave resonator (QWR), 900 mm for a half wave resonator (HWR), and 1200 mm for single spoke resonator 1&2 (SSR 1&2)) for vertical RF tests are installed for testing cavities. We confirmed that as-received niobium sheets (ASTM B393, RRR300) good electrical properties because they showed average residual resistance ratio (RRR) values higher than 300. However, serious RRR degradation occurred after joining two pieces of Nb by e-beam welding because the average RRR values of the samples were ˜179, which was only ˜60% of as-received RRR value. From various e-beam welding experiments in which the welding current and a speed at a fixed welding voltage were changed, we confirmed that good welding results were obtained at a 53 mA welding current and a 20-mm/s welding speed at a fixed welding voltage of 150 kV.

  3. EPW: Electron-phonon coupling, transport and superconducting properties using maximally localized Wannier functions

    Science.gov (United States)

    Poncé, S.; Margine, E. R.; Verdi, C.; Giustino, F.

    2016-12-01

    The EPW (Electron-Phonon coupling using Wannier functions) software is a Fortran90 code that uses density-functional perturbation theory and maximally localized Wannier functions for computing electron-phonon couplings and related properties in solids accurately and efficiently. The EPW v4 program can be used to compute electron and phonon self-energies, linewidths, electron-phonon scattering rates, electron-phonon coupling strengths, transport spectral functions, electronic velocities, resistivity, anisotropic superconducting gaps and spectral functions within the Migdal-Eliashberg theory. The code now supports spin-orbit coupling, time-reversal symmetry in non-centrosymmetric crystals, polar materials, and k and q-point parallelization. Considerable effort was dedicated to optimization and parallelization, achieving almost a ten times speedup with respect to previous releases. A computer test farm was implemented to ensure stability and portability of the code on the most popular compilers and architectures. Since April 2016, version 4 of the EPW code is fully integrated in and distributed with the Quantum ESPRESSO package, and can be downloaded through QE-forge at http://qe-forge.org/gf/project/q-e.

  4. International round robin test for mechanical properties of REBCO superconductive tapes at room temperature

    Science.gov (United States)

    Osamura, K.; Shin, H.-S.; Weiss, K.-P.; Nyilas, A.; Nijhuis, A.; Yamamoto, K.; Machiya, S.; Nishijima, G.

    2014-08-01

    An international round robin test was promoted to establish a test method for room temperature mechanical properties of commercial REBCO superconductive tapes. Seven laboratories practiced a tensile test under the direction of guideline REBCO13 for four different kinds of REBCO tape. From the stress versus strain curve, the modulus of elasticity and the 0.2% proof strength were measured. The scatter of measured values was analyzed by evaluating the RSU (relative standard uncertainty). To judge the major contribution to scattering, an F test was applied. The major source of RSUs was estimated to be the influence of inter-laboratory scattering. In order to reduce the overall scattering, it is suggested that the REBCO13 guideline should be modified with respect to the following three experimental factors. The window determining acceptable data should be narrowed, and the initial strain rate should be suppressed to less than 1 × 10-4 (s-1). Repeated thickness measurement is recommended to reduce the standard uncertainty.

  5. Transport properties and anisotropy of superconducting (Li1-x Fe x )OHFeSe single crystals

    Science.gov (United States)

    Wang, Chunlei; Yi, Xiaolei; Qiu, Yang; Tang, Qingbin; Zhang, Xinwei; Luo, Yongsong; Yu, Benhai

    2016-05-01

    Large size single crystals of (Li1-x Fe x )OHFeSe have been synthesized via a hydrothermal ion-exchange technique using K0.8Fe2Se2 single crystals as the main raw material. The onset superconducting transition temperature is up to 40.3 K. The critical current density is as large as 1.9 × 105 A cm-2 at 5 K and self field. The upper critical fields have been determined by analyzing the relationship between resistivity and temperature under different applied fields along c-axis and ab-plane, respectively. An anisotropic factor about 11 is obtained, which is further confirmed by fitting the data obtained from the angle-dependent resistivity according to the anisotropic Ginzburg-Landau theory. The flux pinning potential (U 0/k B) is as large as 6429 and 3115 K at 0.1 T in H//ab and H//c orientation, respectively. However, the flux pinning potentials are very sensitive to the applied magnetic field and will fast decrease with increase of the magnetic field in both directions, which are obviously different from the Ba1-x K x Fe2As2 superconductor indicating a different flux pinning mechanism in the two kinds of superconductors.

  6. Thermodynamic Properties of Fast Ramped Superconducting Accelerator Magnets for the Fair Project

    Science.gov (United States)

    Fischer, E.; Mierau, A.; Schnizer, P.; Bleile, A.; Gärtner, W.; Guymenuk, O.; Khodzhibagiyan, H.; Schroeder, C.; Sikler, G.; Stafiniak, A.

    2010-04-01

    The 100 Tm synchrotron SIS 100 is the core component of the international Facility of Antiproton and Ion Research (FAIR) to be built at GSI Darmstadt. The 108 bending magnets are 3 m long 2 T superferric dipoles providing a nominal ramp rate of 4 T/s within a usable aperture of 115 mmṡ60 mm. An intensive R&D period was conducted to minimise the AC losses to lower operation costs and to guarantee a safe thermal stability for long term continuous cycling with a maximum repetition frequency of 1 Hz. The latter requirement is strictly limited by the overall heat flow originated by eddy currents and hysteresis losses in iron yoke and coil as well as by its hydraulic resistance respective to the forced two phase helium cooling flow within the hollow superconducting cable. Recently three full size dipoles—and one quadrupole magnets were built and intensive tests have been started in the end of 2008 at the GSI cryogenic test facility. We present the measured thermodynamic parameters of the first tested dipole: AC losses depending on Bmax and dB/dt for various characteristic ramping modes and conclude for necessary optimisations toward the final design of the series magnets.

  7. Upper critical field, pressure-dependent superconductivity and electronic anisotropy of Sm4Fe2As2Te(1-x)O(4-y)F(y).

    Science.gov (United States)

    Pisoni, A; Katrych, S; Szirmai, P; Náfrádi, B; Gaál, R; Karpinski, J; Forró, L

    2016-03-23

    We present a detailed study of the electrical transport properties of a recently discovered iron-based superconductor: Sm4Fe2As2Te0.72O2.8F1.2. We followed the temperature dependence of the upper critical field by resistivity measurement of single crystals in magnetic fields up to 16 T, oriented along the two main crystallographic directions. This material exhibits a zero-temperature upper critical field of 90 T and 65 T parallel and perpendicular to the Fe2As2 planes, respectively. An unprecedented superconducting magnetic anisotropy γH=H(c2)(ab)/H(c2)(c) ~ 14 is observed near Tc, and it decreases at lower temperatures as expected in multiband superconductors. Direct measurement of the electronic anisotropy was performed on microfabricated samples, showing a value of ρ(c)/ρ(ab)(300K) ~ 5 that rises up to 19 near Tc . Finally, we have studied the pressure and temperature dependence of the in-plane resistivity. The critical temperature decreases linearly upon application of hydrostatic pressure (up to 2 GPa) similarly to overdoped cuprate superconductors. The resistivity shows saturation at high temperatures, suggesting that the material approaches the Mott-Ioffe-Regel limit for metallic conduction. Indeed, we have successfully modelled the resistivity in the normal state with a parallel resistor model that is widely accepted for this state. All the measured quantities suggest strong pressure dependence of the density of states.

  8. Quench Property of Twisted-Pair MgB$_2$ Superconducting Cables in Helium Gas

    CERN Document Server

    Spurrell, J; Falorio, I; Pelegrin, J; Ballarino, A; Yang, Y

    2015-01-01

    CERN's twisted-pair superconducting cable is a novel design which offers filament transposition, low cable inductance and is particularly suited for tape conductors such as 2G YBCO coated conductors, Ag-sheathed Bi2223 tapes and Ni/Monel-sheathed MgB2 tapes. A typical design of such twistedpair cables consists of multiple superconducting tapes intercalated with thin copper tapes as additional stabilizers. The copper tapes are typically not soldered to the superconducting tapes so that sufficient flexibility is retained for the twisting of the tape assembly. The electrical and thermal contacts between the copper and superconducting tapes are an important parameter for current sharing, cryogenic stability and quench propagation. Using an MgB2 twisted-pair cable assembly manufactured at CERN, we have carried out minimum quench energy (MQE) and propagation velocity (vp) measurements with point-like heat deposition localized within a tape. Furthermore, different contacts between the copper and superconductor aroun...

  9. Accelerator physics and radiometric properties of superconducting wavelength shifters; Beschleunigerphysik und radiometrische Eigenschaften supraleitender Wellenlaengenschieber

    Energy Technology Data Exchange (ETDEWEB)

    Scheer, Michael

    2008-11-17

    Subject of this thesis is the operation of wave-length shifters at electron storage rings and their use in radiometry. The basic aspects of the radiometry, the technical requirements, the influence of wave-length shifters on the storage ring, and results of first measurements are presented for a device installed at BESSY. Most of the calculations are carried out by the program WAVE, which has been developed within this thesis. WAVE allows to calculate the synchrotron radiation spectra of wavelength shifters within an relative uncertainty of 1/100000. The properties of wave-length shifters in terms of accelerator physics as well as a generating function for symplectic tracking calculations can also be calculated by WAVE. The later was implemented in the tracking code BETA to investigate the influence of insertion devices on the dynamic aperture and emittance of the storage ring. These studies led to the concept of alternating low- and high-beta-sections at BESSY-II, which allow to operate superconducting insertion devices without a significant distortion of the magnetic optics. To investigate the experimental aspects of the radiometry at wave-length shifters, a program based on the Monte-Carlo-code GEANT4 has been developed. It allows to simulate the radiometrical measurements and the absorption properties of detectors. With the developed codes first radiometrical measurements by the PTB have been analysed. A comparison of measurements and calculations show a reasonable agreement with deviations of about five percent in the spectral range of 40-60 keV behind a 1-mm-Cu filter. A better agreement was found between 20 keV and 80 keV without Cu filter. In this case the measured data agreed within a systematic uncertainty of two percent with the results of the calculations. (orig.)

  10. Magnetotransport Properties in High-Quality Ultrathin Two-Dimensional Superconducting Mo2C Crystals.

    Science.gov (United States)

    Wang, Libin; Xu, Chuan; Liu, Zhibo; Chen, Long; Ma, Xiuliang; Cheng, Hui-Ming; Ren, Wencai; Kang, Ning

    2016-04-26

    Ultrathin transition metal carbides are a class of developing two-dimensional (2D) materials with superconductivity and show great potentials for electrical energy storage and other applications. Here, we report low-temperature magnetotransport measurements on high-quality ultrathin 2D superconducting α-Mo2C crystals synthesized by a chemical vapor deposition method. The magnetoresistance curves exhibit reproducible oscillations at low magnetic fields for temperature far below the superconducting transition temperature of the crystals. We interpret the oscillatory magnetoresistance as a consequence of screening currents circling around the boundary of triangle-shaped terraces found on the surface of ultrathin Mo2C crystals. As the sample thickness decreases, the Mo2C crystals exhibit negative magnetoresistance deep in the superconducting transition regime, which reveals strong phase fluctuations of the superconducting order parameters associated with the superconductor-insulator transition. Our results demonstrate that the ultrathin superconducting Mo2C crystals provide an interesting system for studying rich transport phenomena in a 2D crystalline superconductor with enhanced quantum fluctuations.

  11. Structural and superconducting properties of YBa2Cu3-xMxOy (M=Ag, Al

    Directory of Open Access Journals (Sweden)

    S Falahati

    2009-08-01

    Full Text Available   Samples of YBa2Cu3-xAgxOy with x=0, 0.1, 0.15, 0.2, 0.3 and samples of YBa2Cu3-xAlxOy with x=0, 0.01, 0.02, 0.03 and 0.045 are prepared by the sol-gel method. Structural and superconducting properties of samples are studied by electrical resistivity (R-T, X-ray diffraction (XRD and scanning electron microscopy (SEM. All the samples show transition to superconducting state and the transition temperatures of the samples increased with increasing Ag doping up to x=0.15. R-T measurements show a small decrease of TC (zero with increasing Al doping up to x=0.02, and followed by a faster decrease with increasing doping concentration. YBCO grains are better linked with increasing Ag doping. So, Ag has positive effects in superconducting properties of YBCO. The crystal structure of samples was refined by MAUD. These results show tha, Ag is substituted for Cu(1 in YBCO. According to these analysis, we introduce x=0.15 as the optimum value for doping concentration .

  12. The Effect of Temperature Dependence of AC Losses in a Bi-2223/Ag Insert of an 8-T Superconducting Magnet

    DEFF Research Database (Denmark)

    Wang, Lei; Wang, Qiuliang; Wang, Hui;

    2016-01-01

    A conduction-cooled split-gap superconducting magnet system with a center field of 8 T has been designed and fabricated in the Institute of Electrical Engineering, Chinese Academy of Sciences. The system consists of two Bi-2223/Ag coils and six NbTi coils. Due to a large aspect ratio of the high...... dependence relations of the critical current density .1c are considered. The calculations are carried out in three steps. First, to estimate the magnitude of ac losses rapidly in the Bi-2223/Ag coils, the ac losses are calculated when the Bi-2223/Ag and NbTi coils are simultaneously charged, in which...... the temperature distribution is not considered. Second, the temperature variation is considered to calculate the ac losses under the same operating conditions with those in the first case. Finally, the NbTi coils are charged first, followed by the Bi-2223/Ag coils; the ac losses calculated are less than those...

  13. Size-dependent superconducting state of individual nanosized Pb islands grown on Si(111) by tunneling spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Liu Jiepeng; Wu Xuefeng; Ming Fangfei; Zhang Xieqiu; Wang Kedong; Xiao Xudong [Department of Physics, Chinese University of Hong Kong, Shatin, NT (Hong Kong); Wang Bing, E-mail: xdxiao@phy.cuhk.edu.hk [Hefei National Laboratory for Physical Sciences at Microscales, University of Science and Technology of China, Hefei, Anhui 230026 (China)

    2011-07-06

    By measuring the temperature-dependent tunneling spectroscopy of a set of flat-top Pb islands from 3.2 to 15 K, the limiting size of a nine-monolayer-thick Pb island with superconductivity above 3.2 K was determined to be {approx} 30 nm{sup 2}, in good agreement with the Anderson criterion. Further analysis indicates that the zero-temperature energy gap decreases significantly faster than the transition temperature when the Pb island size approaches this limit. This leads to a decrease of 2{Delta}(0)/k{sub B}T{sub C} from 4.5 to 3.3, thus showing that the Pb island superconductors undergo a change from strong to weak electron-phonon coupling.

  14. Nonstationary Superconductivity: Quantum Dissipation and Time-Dependent Ginzburg-Landau Equation

    Directory of Open Access Journals (Sweden)

    Anatoly A. Barybin

    2011-01-01

    Full Text Available Transport equations of the macroscopic superfluid dynamics are revised on the basis of a combination of the conventional (stationary Ginzburg-Landau equation and Schrödinger's equation for the macroscopic wave function (often called the order parameter by using the well-known Madelung-Feynman approach to representation of the quantum-mechanical equations in hydrodynamic form. Such an approach has given (a three different contributions to the resulting chemical potential for the superfluid component, (b a general hydrodynamic equation of superfluid motion, (c the continuity equation for superfluid flow with a relaxation term involving the phenomenological parameters GL and GL, (d a new version of the time-dependent Ginzburg-Landau equation for the modulus of the order parameter which takes into account dissipation effects and reflects the charge conservation property for the superfluid component. The conventional Ginzburg-Landau equation also follows from our continuity equation as a particular case of stationarity. All the results obtained are mutually consistent within the scope of the chosen phenomenological description and, being model-neutral, applicable to both the low-c and high-c superconductors.

  15. Solvent dependent photophysical properties of dimethoxy curcumin

    Science.gov (United States)

    Barik, Atanu; Indira Priyadarsini, K.

    2013-03-01

    Dimethoxy curcumin (DMC) is a methylated derivative of curcumin. In order to know the effect of ring substitution on photophysical properties of curcumin, steady state absorption and fluorescence spectra of DMC were recorded in organic solvents with different polarity and compared with those of curcumin. The absorption and fluorescence spectra of DMC, like curcumin, are strongly dependent on solvent polarity and the maxima of DMC showed red shift with increase in solvent polarity function (Δf), but the above effect is prominently observed in case of fluorescence maxima. From the dependence of Stokes' shift on solvent polarity function the difference between the excited state and ground state dipole moment was estimated as 4.9 D. Fluorescence quantum yield (ϕf) and fluorescence lifetime (τf) of DMC were also measured in different solvents at room temperature. The results indicated that with increasing solvent polarity, ϕf increased linearly, which has been accounted for the decrease in non-radiative rate by intersystem crossing (ISC) processes.

  16. Elimination of bubbles and improvement of the superconducting properties in MgB2 films annealed using electron beam

    Science.gov (United States)

    Xu, Zhuang; Kong, Xiangdong; Han, Li; Pang, Hua; Wu, Yue; Gao, Zhaoshun; Li, Xiaona

    2017-03-01

    MgB2 superconducting films can be readily obtained using the electron-beam annealing method. However, many bubbles existing in the film severely damage the surface morphology, which is known as the deleterious current-limiting mechanism. Based on morphology images and energy-dispersive spectroscopy spectra, we found that, during the annealing process, solid Mg-rich layers evaporate to form Mg vapour in the precursor film, resulting in bubbles in the film. By reducing the cycle thickness of the precursor film, we obtained MgB2 films with better properties. The root-mean-square surface roughness was 2.7 nm over a 10 × 10 μm area for a 100 nm-thick film, and the critical current density at 20 K was increased to 3.8 × 106 A cm‑2. These MgB2 films are suitable for fabricating MgB2 superconducting devices.

  17. High-Temperature Superconductivity

    Science.gov (United States)

    Tanaka, Shoji

    2006-12-01

    A general review on high-temperature superconductivity was made. After prehistoric view and the process of discovery were stated, the special features of high-temperature superconductors were explained from the materials side and the physical properties side. The present status on applications of high-temperature superconductors were explained on superconducting tapes, electric power cables, magnets for maglev trains, electric motors, superconducting quantum interference device (SQUID) and single flux quantum (SFQ) devices and circuits.

  18. Superconductivity in Ca-doped graphene laminates

    Science.gov (United States)

    Chapman, J.; Su, Y.; Howard, C. A.; Kundys, D.; Grigorenko, A. N.; Guinea, F.; Geim, A. K.; Grigorieva, I. V.; Nair, R. R.

    2016-01-01

    Despite graphene’s long list of exceptional electronic properties and many theoretical predictions regarding the possibility of superconductivity in graphene, its direct and unambiguous experimental observation has not been achieved. We searched for superconductivity in weakly interacting, metal decorated graphene crystals assembled into so-called graphene laminates, consisting of well separated and electronically decoupled graphene crystallites. We report robust superconductivity in all Ca-doped graphene laminates. They become superconducting at temperatures (Tc) between ≈4 and ≈6 K, with Tc’s strongly dependent on the confinement of the Ca layer and the induced charge carrier concentration in graphene. We find that Ca is the only dopant that induces superconductivity in graphene laminates above 1.8 K among several dopants used in our experiments, such as potassium, caesium and lithium. By revealing the tunability of the superconducting response through doping and confinement of the metal layer, our work shows that achieving superconductivity in free-standing, metal decorated monolayer graphene is conditional on an optimum confinement of the metal layer and sufficient doping, thereby bringing its experimental realization within grasp. PMID:26979564

  19. Superconductivity in Ca-doped graphene laminates

    Science.gov (United States)

    Chapman, J.; Su, Y.; Howard, C. A.; Kundys, D.; Grigorenko, A. N.; Guinea, F.; Geim, A. K.; Grigorieva, I. V.; Nair, R. R.

    2016-03-01

    Despite graphene’s long list of exceptional electronic properties and many theoretical predictions regarding the possibility of superconductivity in graphene, its direct and unambiguous experimental observation has not been achieved. We searched for superconductivity in weakly interacting, metal decorated graphene crystals assembled into so-called graphene laminates, consisting of well separated and electronically decoupled graphene crystallites. We report robust superconductivity in all Ca-doped graphene laminates. They become superconducting at temperatures (Tc) between ≈4 and ≈6 K, with Tc’s strongly dependent on the confinement of the Ca layer and the induced charge carrier concentration in graphene. We find that Ca is the only dopant that induces superconductivity in graphene laminates above 1.8 K among several dopants used in our experiments, such as potassium, caesium and lithium. By revealing the tunability of the superconducting response through doping and confinement of the metal layer, our work shows that achieving superconductivity in free-standing, metal decorated monolayer graphene is conditional on an optimum confinement of the metal layer and sufficient doping, thereby bringing its experimental realization within grasp.

  20. Superconducting phase transition in STM tips

    Energy Technology Data Exchange (ETDEWEB)

    Eltschka, Matthias; Jaeck, Berthold; Assig, Maximilian; Etzkorn, Markus; Ast, Christian R. [Max Planck Institute for Solid State Research, Stuttgart (Germany); Kern, Klaus [Max Planck Institute for Solid State Research, Stuttgart (Germany); Ecole Polytechnique Federale de Lausanne (Switzerland)

    2015-07-01

    The superconducting properties of systems with dimensions comparable to the London penetration depth considerably differ from macroscopic systems. We have studied the superconducting phase transition of vanadium STM tips in external magnetic fields. Employing Maki's theory we extract the superconducting parameters such as the gap or the Zeeman splitting from differential conductance spectra. While the Zeeman splitting follows the theoretical description of a system with s=1/2 and g=2, the superconducting gaps as well as the critical fields depend on the specific tip. For a better understanding of the experimental results, we solve a one dimensional Usadel equation modeling the superconducting tip as a cone with the opening angle α in an external magnetic field. We find that only a small region at the apex of the tip is superconducting in high magnetic fields and that the order of the phase transition is directly determined by α. Further, the spectral broadening increases with α indicating an intrinsic broadening mechanism due to the conical shape of the tip. Comparing these calculations to our experimental results reveals the order of the superconducting phase transition of the STM tips.

  1. Superconductivity in Ca-doped graphene laminates.

    Science.gov (United States)

    Chapman, J; Su, Y; Howard, C A; Kundys, D; Grigorenko, A N; Guinea, F; Geim, A K; Grigorieva, I V; Nair, R R

    2016-03-16

    Despite graphene's long list of exceptional electronic properties and many theoretical predictions regarding the possibility of superconductivity in graphene, its direct and unambiguous experimental observation has not been achieved. We searched for superconductivity in weakly interacting, metal decorated graphene crystals assembled into so-called graphene laminates, consisting of well separated and electronically decoupled graphene crystallites. We report robust superconductivity in all Ca-doped graphene laminates. They become superconducting at temperatures (Tc) between ≈4 and ≈6 K, with Tc's strongly dependent on the confinement of the Ca layer and the induced charge carrier concentration in graphene. We find that Ca is the only dopant that induces superconductivity in graphene laminates above 1.8 K among several dopants used in our experiments, such as potassium, caesium and lithium. By revealing the tunability of the superconducting response through doping and confinement of the metal layer, our work shows that achieving superconductivity in free-standing, metal decorated monolayer graphene is conditional on an optimum confinement of the metal layer and sufficient doping, thereby bringing its experimental realization within grasp.

  2. Effects of post-annealing and cobalt co-doping on superconducting properties of (Ca,Pr)Fe{sub 2}As{sub 2} single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Okada, T., E-mail: 8781303601@mail.ecc.u-tokyo.ac.jp; Ogino, H.; Yakita, H.; Yamamoto, A.; Kishio, K.; Shimoyama, J.

    2014-10-15

    Highlights: • Post-annealing at 400 °C killed superconductivity for Co-free sample. • Pr,Co co-doped samples maintained superconductivity even after annealing. • Two-step superconducting transition was observed via magnetization measurement. • Bulk superconductivity of low-T{sub c} component was confirmed. • Superconducting volume fraction of high-T{sub c} component was always small. - Abstract: In order to clarify the origin of anomalous superconductivity in (Ca,RE)Fe{sub 2}As{sub 2} system, Pr doped and Pr,Co co-doped CaFe{sub 2}As{sub 2} single crystals were grown by the FeAs flux method. These samples showed two-step superconducting transition with T{sub c1} = 25–42 K, and T{sub c2} < 16 K, suggesting that (Ca,RE)Fe{sub 2}As{sub 2} system has two superconducting components. Post-annealing performed for these crystals in evacuated quartz ampoules at various temperatures revealed that post-annealing at ∼400 °C increased the c-axis length for all samples. This indicates that as-grown crystals have a certain level of strain, which is released by post-annealing at ∼400 °C. Superconducting properties also changed dramatically by post-annealing. After annealing at 400 °C, some of the co-doped samples showed large superconducting volume fraction corresponding to the perfect diamagnetism below T{sub c2} and high J{sub c} values of 10{sup 4}–10{sup 5} A cm{sup −2} at 2 K in low field, indicating the bulk superconductivity of (Ca,RE)Fe{sub 2}As{sub 2} phase occurred below T{sub c2}. On the contrary, the superconducting volume fraction above T{sub c2} was always very small, suggesting that 40 K-class superconductivity observed in this system is originating in the local superconductivity in the crystal.

  3. CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES: Hofstadter's Butterfly and Phase Transition of Checkerboard Superconducting Network in a Magnetic Field

    Science.gov (United States)

    Hou, Jing-Min; Tian, Li-Jim

    2010-03-01

    We study the magnetic effect of the checkerboard superconducting wire network. Based on the de Gennes-Alexader theory, we obtain difference equations for superconducting order parameter in the wire network. Through solving these difference equations, we obtain the eigenvalues, linked to the coherence length, as a function of magnetic field. The diagram of eigenvalues shows a fractal structure, being so-called Hofstadter's butterfly. We also calculate and discuss the dependence of the transition temperature of the checkerboard superconducting wire network on the applied magnetic field, which is related to up-edge of the Hofstadter's butterfly spectrum.

  4. Study of superconducting properties of ferrocene-added MgB{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Sudesh; Varma, G.D. [Department of Physics, Indian Institute of Technology Roorkee (India); Das, S.; Bernhard, C. [Department of Physics, Fribourg Centre for Nanomaterials-FriMat, University of Fribourg (Switzerland); Shripathi, T. [UGC-DAE CSR, University Campus, Indore (India)

    2014-07-15

    In the present study, we have shown the effects of ferrocene (FeC{sub 10}H{sub 10}) addition on the superconducting properties of polycrystalline MgB{sub 2} superconductor using transport and magnetic measurements. The addition of FeC{sub 10}H{sub 10} up to 2 wt% in the MgB{sub 2} sample has shown enhanced critical current density, J{sub C} in the entire magnetic field region without affecting much the transition temperature. At 10 K, with respect to a pristine MgB{sub 2} sample, J{sub C} has improved by a factor of 6.55 at 6 T applied field for 1 wt% FeC{sub 10}H{sub 10}. An improvement in the upper critical field, H{sub C{sub 2}} and irreversibility field, H{sub irr} has also been observed up to 2 wt% addition of FeC{sub 10}H{sub 10}. The value of H{sub C{sub 2}} (0) as obtained using the Ginzburg-Landau (GL)-theory fit of the experimental data increases by almost 2 T for 2 wt% FeC{sub 10}H{sub 10}-added MgB{sub 2} as compared to the pristine samples. From X-ray photoemission spectroscopy (XPS), we observed that the Fe is present in sample in the form of ferromagnetic oxides, Fe{sub 3}O{sub 4} and γ-Fe{sub 2}O{sub 3}. These ferromagnetic inclusions provide efficient pinning centers to improve J{sub C}(H) behavior. The flux pinning mechanisms present in the FeC{sub 10}H{sub 10}-added samples are described and discussed in this paper. (copyright 2014 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  5. Studying temperature dependence of pairing gap parameter in a nucleus as a small superconducting system

    Science.gov (United States)

    Rahmatinejad, A.; Razavi, R.; Kakavand, T.

    2016-07-01

    In this paper, we have taken the effect of small size of nucleus and static fluctuations into account in the Bardeen-Cooper-Schrieffer (BCS) theory of superconductivity calculations of 45Ti nucleus. Thermodynamic quantities of 45Ti have been extracted within the BCS model with the inclusion of the average value of the pairing gap square, extracted by the modified Ginzburg-Landau (MGL) method for small systems. Calculated values of the excitation energy and entropy within the MGL+BCS method improve the extracted results within the usual BCS model and show a smooth behavior around the critical temperature with a very good agreement with the semi-empirical values. The result of using MGL+BCS method for the heat capacity of 45Ti is compared with the corresponding semi-empirical values and the calculated values within the BCS, static path approximation (SPA) and Modified Pairing gap BCS (MPBCS) which is a method that was proposed in our previous publications. Both MGL+BCS and MPBCS avoid the discontinuity of the heat capacity curve, which is observed in the usual BCS method, and lead to an S-shaped curve with a good agreement with the semi-empirical results.

  6. Position dependent spatial and spectral resolution measurement of distributed readout superconducting imaging detectors

    Science.gov (United States)

    Hijmering, R. A.; Verhoeve, P.; Kozorezov, A. G.; Martin, D. D. E.; Wigmore, J. K.; Jerjen, I.; Venn, R.; Groot, P. J.

    2008-04-01

    We present direct measurements of spatial and spectral resolution of cryogenic distributed readout imaging detectors (DROIDs). The spatial and spectral resolutions have been experimentally determined by scanning a 10μm spot of monochromatic visible light across the detector. The influences of the photon energy, bias voltage, and absorber length and width on the spatial and spectral resolutions have been examined. The confinement of quasiparticles in the readout sensors (superconducting tunnel junctions) as well as the detector's signal amplitude can be optimized by tuning the bias voltage, thereby improving both the spatial and spectral resolutions. Changing the length of the absorber affects the spatial and spectral resolutions in opposite manner, making it an important parameter to optimize the DROID for the application at hand. The results have been used to test expressions for photon energy, position, and spatial and spectral resolutions which have been derived by using an existing one-dimensional model. The model is found to accurately describe the experimental data, but some limitations have been identified. In particular, the model's assumption that the two sensors have identical response characteristics and noise, the approximation of the detailed quasiparticle dynamics in the sensors by border conditions, and the use of a one-dimensional diffusion process is not always adequate.

  7. Statistical correlations for thermophysical properties of Supercritical Argon (SCAR) used in cooling of futuristic High Temperature Superconducting (HTS) cables

    Energy Technology Data Exchange (ETDEWEB)

    Kalsia, Mohit [School of Mechanical Engineering, Lovely Professional University, Phagwara, 144 401 (India); Dondapati, Raja Sekhar, E-mail: drsekhar@ieee.org [School of Mechanical Engineering, Lovely Professional University, Phagwara, 144 401 (India); Usurumarti, Preeti Rao [Department of Mechanical Engineering, PVK Institute of Technology, Anantpur, 515 001 (India)

    2017-05-15

    Highlights: • The developed correlations can be integrated into thermohydraulic analysis of HTS cables. • This work also explains the phenomenon of flow with less pumping power and maximum heat transfer in HTS cables. • Pumping power required to circulate the SCAR for cooling of HTS cables would be significantly lower. • For Hg-based high temperature superconductors (T{sub c} > 134 K), SCAR found to be a suitable coolant. - Abstract: High Temperature Superconducting (HTS) cables are emerging as an alternative to conventional cables in efficient power transmission. However, these HTS cables require cooling below the critical temperature of superconductors used to transmit larger currents. With the invention of high temperature superconductors whose critical temperatures are up to 134 K (Hg based), it is a great challenge to identify a suitable coolant which can carry away the heating load on the superconductors. In order to accomplish such challenge, an attempt has been made in the present work to propose supercritical Argon (SCAR) as the alternative to cool the HTS cables. Further, a statistical correlation has been developed for the thermophysical properties such as density, viscosity, specific heat and thermal conductivity of SCAR. In addition, the accuracy of developed correlations is established with the help of few statistical parameters and validated with standard database available in the literature. These temperature dependent accurate correlations are useful in predicting the pressure drop and heat transfer behaviour in HTS cables using numerical or computational techniques. In recent times, with the sophistication of computer technology, solving of various complex transport equations along with the turbulence models became popular and hence the developed correlations would benefit the technological community. It is observed that, a decrease in pressure, density and viscosity are found to be decreasing whereas the thermal conductivity and specific

  8. Structural, transport, magnetic and superconducting properties of the pseudo-quaternary intermetallic system (Y 1-xGd x)Ni 2B 2C

    Science.gov (United States)

    Massalami, M. El; Bud'ko, S. L.; Giordanengo, B.; Fontes, M. B.; Mondragon, J. C.; Baggio-Saitovitch, E. M.

    1994-12-01

    The superconducting and the magnetic phase diagram (in x-T plane) of the pseudo-quaternary (Y 1-xGd x)Ni 2B 2C series is obtained. Superconductivity is observed to be montonically degraded with Gd-concentration for x < 0.25. For higher x, two magnetic transitions are observed. The nature of these transitions and their influence on the measured physical properties will be discussed.

  9. Superconducting and normal state properties of heavily hole-doped diamond synthesized at high pressure

    Directory of Open Access Journals (Sweden)

    V.A. Sidorov, E.A. Ekimov, A.V. Rakhmanina, S.M. Stishov, E.D. Bauer and J.D. Thompson

    2006-01-01

    Full Text Available Diamonds, synthesized at high pressures and high temperatures in the presence of boron, are heavily hole-doped by incorporation of boron into the diamond lattice. These diamonds become superconducting below Tc=2–9 K. Synthesis in the systems B-C and B4C-C at P=9 GPa and T=2500–2800 K result in formation of polycrystalline carbonado-like material, whereas synthesis from B-C-H gives small single crystals and intergrowth plates. Dense superconducting bodies can be prepared by compacting these single crystal particles at P=8 GPa and T=1800 K. Specific heat and resistivity measurements in magnetic fields prove the bulk nature of superconductivity in all pressure-synthesized samples and provide a consistent set of materials parameters that favor a conventional weak-coupling electron–phonon interpretation of the superconducting mechanism at high hole doping. Schottky barrier tunneling conductance spectra, obtained with contacts fabricated at the surface of these hole-doped diamonds, indicate the appearance of superconducting gap below Tc.

  10. Structural, elastic and electronic properties of superconducting anti-perovskites MgCNi 3, ZnCNi 3 and CdCNi 3 from first principles

    Science.gov (United States)

    Shein, I. R.; Bannikov, V. V.; Ivanovskii, A. L.

    2008-01-01

    First principle total energy calculations using the full potential linearized augmented plane wave (FP-LAPW) method with the generalized gradient approximation (GGA) for the exchange-correlation potential were performed to investigate the systematic trends for structural, elastic and electronic properties of the family of superconducting anti-perovskites MCNi 3 depending from the type of M cations (M are Mg, Zn and Cd). In result the optimized lattice parameters, independent elastic constants ( C11, C12 and C44), bulk modulus B, compressibility β, shear modulus G and tetragonal shear modulus G‧ are evaluated. Further, for the first time the numerical estimates of a set of elastic parameters (bulk and shear modulus, Young’s modulus Y, Poisson’s ratio ( ν), Lamé’s coefficients ( μ, λ)) of the polycrystalline superconducting MCNi 3 ceramics (in framework of the Voigt-Reuss-Hill approximation) were performed. Besides, the band structures, densities of states (DOS), total and site-projected l-decomposed DOS at the Fermi level, the shapes of the Fermi surfaces, the Sommerfeld’s coefficients and the molar Pauli paramagnetic susceptibility for these anti-perovskites were obtained and analyzed in comparison with the available theoretical and experimental data.

  11. Effects of oxide precursors on superconducting properties of polycrystalline SmFeAsO1-xFx

    Science.gov (United States)

    Yuan, F. F.; Ding, Y.; Sun, Y.; Zhuang, J. C.; Zhou, W.; Li, G. Z.; Sumption, M.; Li, X. W.; Shi, Z. X.

    2013-12-01

    A series of polycrystalline SmFeAsO1-xFx samples were synthesized by one-step and two-step method at ambient pressure using different oxide precursors, namely As2O3, Fe2O3 and nano-Fe2O3 powder, as the source of element O. Results of X-ray diffraction and magnetic measurements manifest that starting oxides affected the phase formation and superconducting properties of SmFeAsO1-xFx. As2O3 as oxide precursor contributes to the fast formation of superconducting phase for a short period of sintering time. And samples prepared using As2O3 show higher superconducting transition temperature Tc and more stable fluorine doping level. Compared with Fe2O3, nano-Fe2O3 promotes fluorine doping into the O site. While using Fe2O3 leads to higher level of Fe and SmOF impurities. The critical current density Jcm were derived from magnetic hysteresis loops. Sample prepared using As2O3 shows higher Jcm in low temperature and high magnetic fields.

  12. Superconducting NbTiN Thin Films with Highly Uniform Properties over a 100 mm diameter Wafer

    CERN Document Server

    Thoen, D J; Haalebos, E A F; Klapwijk, T M; Baselmans, J J A; Endo, A

    2016-01-01

    Uniformity in thickness and electronic properties of superconducting niobium titanium nitride (NbTiN) thin films is a critical issue for upscaling superconducting electronics, such as microwave kinetic inductance detectors for submillimeter wave astronomy. In this article we make an experimental comparison between the uniformity of NbTiN thin films produced by two DC magnetron sputtering systems with vastly different target sizes: the Nordiko 2000 equipped with a circular 100mm diameter target, and the Evatec LLS801 with a rectangular target of 127 mm x 444.5 mm. In addition to the films deposited staticly in both systems, we have also deposited films in the LLS801 while shuttling the substrate in front of the target, with the aim of further enhancing the uniformity. Among these three setups, the LLS801 system with substrate shuttling has yielded the highest uniformity in film thickness (+/-2%), effective resistivity (decreasing by 5% from center to edge), and superconducting critical temperature (T_c = 15.0 ...

  13. Superconducting properties of very high quality NbN thin films grown by high temperature chemical vapor deposition

    Science.gov (United States)

    Hazra, D.; Tsavdaris, N.; Jebari, S.; Grimm, A.; Blanchet, F.; Mercier, F.; Blanquet, E.; Chapelier, C.; Hofheinz, M.

    2016-10-01

    Niobium nitride (NbN) is widely used in high-frequency superconducting electronics circuits because it has one of the highest superconducting transition temperatures ({T}{{c}}˜ 16.5 {{K}}) and largest gap among conventional superconductors. In its thin-film form, the T c of NbN is very sensitive to growth conditions and it still remains a challenge to grow NbN thin films (below 50 nm) with high T c. Here, we report on the superconducting properties of NbN thin films grown by high-temperature chemical vapor deposition (HTCVD). Transport measurements reveal significantly lower disorder than previously reported, characterized by a Ioffe-Regel parameter ({k}{{F}}{\\ell }) ˜ 12. Accordingly we observe {T}{{c}}˜ 17.06 {{K}} (point of 50% of normal state resistance), the highest value reported so far for films of thickness 50 nm or less, indicating that HTCVD could be particularly useful for growing high quality NbN thin films.

  14. Applied superconductivity

    CERN Document Server

    Newhouse, Vernon L

    1975-01-01

    Applied Superconductivity, Volume II, is part of a two-volume series on applied superconductivity. The first volume dealt with electronic applications and radiation detection, and contains a chapter on liquid helium refrigeration. The present volume discusses magnets, electromechanical applications, accelerators, and microwave and rf devices. The book opens with a chapter on high-field superconducting magnets, covering applications and magnet design. Subsequent chapters discuss superconductive machinery such as superconductive bearings and motors; rf superconducting devices; and future prospec

  15. Pressure Dependence of the Ginzburg-Landau Parameter in Superconducting YB6

    Science.gov (United States)

    Gabáni, S.; Orendáč, Mat.; Kušnír, J.; Gažo, E.; Pristáš, G.; Mori, T.; Flachbart, K.

    2016-12-01

    We present measurements of the superconducting critical temperature T_c , the upper critical field H_{c2} and the third critical field H_{c3} as a function of pressure in BCS type-II superconductor YB6 (T_c = 7.5 K, H_{c2}(0) = 270 mT and H_{c3}(0) = 450 mT at ambient pressure) up to 3 GPa. Magnetic susceptibility measurements down to 2 K have shown a negative pressure effect on T_c as well as on H_{c2} with slopes dT_c/dp = -0.531 K/GPa (d ln T_c/{dp} = -7.1 %/GPa) and dH_{c2}(0)/dp = -37 mT/GPa (d ln H_{c2}/{dp} = -14 %/GPa) , respectively. Parallel magnetoresistance measurements evidenced nearly the same slopes of d ln T_c/{dp} = -5.9 %/GPa (d ln H_{c3}/{dp} = -11 %/GPa) in the equal pressure range. From these results, the estimated pressure effect on the coherence length dξ (0)/{dp} = 2.05 nm/GPa together with the supposed zero pressure effect on the magnetic penetration depth (dλ (0)/{dp} ≈ 0 ) implies that the Ginzburg-Landau parameter κ (0) = {λ }(0)/{ξ }(0) decreases with pressure as dκ (0)/d{p} = -0.31/GPa. According to this decrease, a transition from type-II to type-I superconductor should be observed in YB6 at a critical pressure p_c ≈ 10 GPa.

  16. Graphene: Carbon's superconducting footprint

    Science.gov (United States)

    Vafek, Oskar

    2012-02-01

    Graphene exhibits many extraordinary properties, but superconductivity isn't one of them. Two theoretical studies suggest that by decorating the surface of graphene with the right species of dopant atoms, or by using ionic liquid gating, superconductivity could yet be induced.

  17. Properties of Superconducting Mo, Mo2n and Trilayer Mo2n-Mo-Mo2n Thin Films

    Science.gov (United States)

    Barrentine, E. M.; Stevenson, T. R.; Brown, A. D.; Lowitz, A. E.; Noroozian, O.; U-Yen, K.; Eshan, N.; Hsieh, W. T.; Moseley, S. H.; Wollack, E. J.

    2014-01-01

    We present measurements of the properties of thin film superconducting Mo, Mo2N and Mo2N/Mo/Mo2N trilayers of interest for microwave kinetic inductance detector (MKID) applications. Using microwave resonator devices, we investigate the transition temperature, energy gaps, kinetic inductance, and internal quality factors of these materials. We present an Usadel-based interpretation of the trilayer transition temperature as a function of trilayer thicknesses, and a 2-gap interpretation to understand the change in kinetic inductance and internal resonance quality factor (Q) as a function of temperature.

  18. Improvement in Superconducting Properties of MgB2 Superconductors by Nanoscale Carbon-Based Compound Doping

    Institute of Scientific and Technical Information of China (English)

    Si-Hai Zhou

    2008-01-01

    MgB2 is a relatively new superconductor; it has attracted great interest from superconductor researchers all over the world. Thorough investigations have been carried out to study the material fabrication, as well as to study the material and superconducting properties from a fundamental physics point of view. The University of Wollongong has played a very active role in this research and a leading role in the research on high critical current density and high critical magnetic fields. Our recent research on the improve- ment of critical current density and the upper critical magnetic field by carbon-based compound doping is reviewed in this paper.

  19. Effects of lattice disorder on the superconducting properties of YBa 2Cu 3O 6.9 films

    Science.gov (United States)

    Gauzzi, Andrea; Pavuna, Davor

    1994-12-01

    We report on striking sensitivity of the superconducting properties of ion-beam sputtered YBa 2Cu 3O 6.9 films to the lattice disorder (induced by varying growth temperatures). Tc decreases with increasing disorder, while the width of the resistive transition and the normal state resistivity increase. We give a quantitative significance to this trend by expressing the degree of the disorder in terms of the lattice coherence length rc is extracted from the width of X-ray diffraction rocking curves. We find that Tc saturates to the maximum of ∼ 92 K for rc > 10 nm.

  20. Synthesis and properties of a new superconducting compound (ZrCuxSe2)

    Science.gov (United States)

    Generoso, Ana Carolina; Baptista, Naiara; Renosto, Sergio; Jefferson Machado, Antonio

    2012-02-01

    Since the discovery of superconductivity in chalcogenides in Fe-Se system and in iron pnictides much attention have been give for synthesis of new materials which can exhibit superconductivity. Within this context in this work we show results which suggest the existence of a new selenite intercalate with copper atoms in the ZrCuxSe2 nominal composition, where x is 0.1 <= x <= 0.4 interval. A superconductor behavior begins in the ZrCu0.3Se2 with superconducting critical temperature close to 9.0 K. ZrSe2 is a compound which crystallize in the hexagonal symmetry with CdI2 prototype structure belongs to the space group P-32/m1. Indeed, copper is intercalating between Se-Se which have van der Walls interaction in the ZrSe2 compound. This intercalation with copper atoms, produce superconductivity in the matrix compound (ZrSe2) which is not superconductor. The copper intercalation in the matrix compound crystallizes in a LiCrS2 prototype structure.

  1. Doping effects of transition metals on superconducting properties of (Ca,RE)FeAs2

    Science.gov (United States)

    Yakita, Hiroyuki; Ogino, Hiraku; Okada, Tomoyuki; Yamamoto, Akiyasu; Kishio, Kohji; Shimoyama, Jun-Ichi; Iyo, Akira; Eisaki, Hiroshi; Sala, Alberto

    2015-03-01

    At the previous March Meeting, we reported new iron based superconductors (Ca,RE)FeAs2 (Ca112) (RE = La-Nd, Sm-Gd)[ 1 , 2 ]. Superconducting transition was observed in all samples except for Ce-doped sample, and Tc of La-doped sample exceeded 30 K. In this study, we have synthesized transition metals (TM=Mn, Co, Ni) co-doped Ca112 samples. Mn co-doping suppressed superconductivity. On the contrary, enhancement of Tc with sharp superconducting transitions was observed in most of the Co or Ni co-doped samples. Tc of Co co-doped samples decreased with a decrease in ionic radii of RE3+ from 38 K for RE = La to 29 K for RE = Gd, though Eu doped sample showed exceptionally low Tc = 21 K. Jc value of La and Co co-doped sample estimated from magnetization measurement is approximately 2.0 x 104 Acm-2at 2 K suggesting bulk superconductivity.

  2. Structural, electronic, elastic and superconducting properties of noble metal nitrides MN{sub 2} (M = Ru, Rh, Pd)

    Energy Technology Data Exchange (ETDEWEB)

    Puvaneswari, S. [Department of Physics, E.M.G. Yadava Women' s College, Madurai, Tamilnadu 625 014 (India); Rajeswarapalanichamy, R., E-mail: rrpcaspd2003@gmail.com [Department of Physics, N.M.S.S. Vellaichamy Nadar College, Madurai, Tamilnadu 625019 (India); Sudha Priyanga, G. [Department of Physics, N.M.S.S. Vellaichamy Nadar College, Madurai, Tamilnadu 625019 (India)

    2015-02-01

    The structural stability, electronic structure, elastic and superconducting properties of noble metal nitrides MN{sub 2} (M = Ru, Rh, Pd) are investigated in tetragonal (P4/mbm), fluorite (Fm3m), orthorhombic (Pnnm), pyrite (Pa-3) and hexagonal (P6/mmm) phases using first principles calculations. The calculated lattice parameters are in good agreement with other theoretical results. Among the considered structures, RhN{sub 2} and PdN{sub 2} are found to be most stable in tetragonal structure, whereas RuN{sub 2} is stable in fluorite structure. A sequence of structural phase transition is predicted under high pressure in these metal nitrides. The electronic structure reveals that these nitrides are metallic. These metal nitrides are found to be covalent, ionic and metallic in the stable phase. The observations show that these metal nitrides are mechanically stable at ambient condition. The superconducting transition temperatures for RuN{sub 2}, RhN{sub 2} and PdN{sub 2} are found to be 1.65 K, 5.01 K and 8.7 K respectively. - Highlights: • Electronic, structural and elastic properties of RuN{sub 2}, RhN{sub 2} and PdN{sub 2} are studied. • A pressure induced structural phase transition is predicted. • Electronic structure reveals that these materials exhibit metallic behavior. • High bulk modulus indicates that RuN{sub 2}, RhN{sub 2} and PdN{sub 2} are superhard materials. • Superconducting temperature values are reported.

  3. The decay properties of the trapped magnetic field in HTS bulk superconducting actuator by AC controlled magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Kim, S.B. [Department of Electrical and Electronic Engineering, Okayama University, 3-1-1, Tsushima Naka, Okayama 700-8530 (Japan); Uwani, Y., E-mail: gen422310@s.okayama-u.ac.jp [Department of Electrical and Electronic Engineering, Okayama University, 3-1-1, Tsushima Naka, Okayama 700-8530 (Japan); Joo, J.H.; Kawamoto, R. [Department of Electrical and Electronic Engineering, Okayama University, 3-1-1, Tsushima Naka, Okayama 700-8530 (Japan); Jo, Y.S. [Center for Applied Superconductivity Technology, Korea Electrotechnology Research Institute, Seongju-dong, Changwon 641-120 (Korea, Republic of)

    2011-11-15

    The electric device applications of a high temperature superconducting (HTS) bulk magnet, having stable levitation and suspension properties according to their strong flux pinning force, have been proposed and developed. We have been investigating a three-dimensional (3-D) superconducting actuator using HTS bulks to develop a non-contract transportation device which moves freely in space. It is certain for our proposed 3-D superconducting actuator to be useful as a transporter used in a clean room where silicon wafers, which do not like mechanical contact and dust, are manufactured. The proposed actuator consists of the trapped HTS bulk as a mover and two-dimensionally arranged electromagnets as a stator. Up to now, the electromagnets consisted with iron core and copper coil were used as a stator, and each electromagnet was individually controlled using DC power supplies. In our previous work, the unstable movement characteristics of HTS bulk were observed under the DC operation, and the AC electromagnets driven with AC controlled current was proposed to solve these problems. In general, the trapped magnetic field in HTS bulk was decayed by a time-varying external magnetic field. Thus, it needs to optimize the shapes of AC electromagnets and operating patterns, the decay properties of the trapped magnetic field in the HTS bulk mover by the AC magnetic field should be cleared. In this paper, the influences of the frequency, the overall operating time, the strength of magnetization field and drive current against the decay of trapped magnetic field were experimentally studied using the fabricated AC electromagnets.

  4. Superconducting optical modulator

    Science.gov (United States)

    Bunt, Patricia S.; Ference, Thomas G.; Puzey, Kenneth A.; Tanner, David B.; Tache, Nacira; Varhue, Walter J.

    2000-12-01

    An optical modulator based on the physical properties of high temperature superconductors has been fabricated and tested. The modulator was constructed form a film of Yttrium Barium Copper Oxide (YBCO) grown on undoped silicon with a buffer layer of Yttria Stabilized Zirconia. Standard lithographic procedures were used to pattern the superconducting film into a micro bridge. Optical modulation was achieved by passing IR light through the composite structure normal to the micro bridge and switching the superconducting film in the bridge region between the superconducting and non-superconducting states. In the superconducting state, IR light reflects from the superconducting film surface. When a critical current is passed through the micro bridge, it causes the film in this region to switch to the non-superconducting state allowing IR light to pass through it. Superconducting materials have the potential to switch between these two states at speeds up to 1 picosecond using electrical current. Presently, fiber optic transmission capacity is limited by the rate at which optical data can be modulated. The superconducting modulator, when combined with other components, may have the potential to increase the transmission capacity of fiber optic lines.

  5. Irreversibility line and magnetic field dependence of the critical current in superconducting MgB sub 2 bulk samples

    CERN Document Server

    Gioacchino, D D; Tripodi, P; Grimaldi, G

    2003-01-01

    The third harmonic components of the ac susceptibility of MgB sub 2 bulk samples have been measured as a function of applied magnetic fields, together with standard magnetization cycles. The irreversibility line (IL) of the magnetic field has been extracted from the onset of the third harmonic components. Using a (1 - t) supalpha glass/liquid best fit where alpha 1.27 IL shows a coherent length xi divergence with exponent nu = 0.63, which indicates a 3D behaviour. Moreover, using the numerical solution of the non-linear magnetic diffusion equation, considering the creep model in a 3D vortex glass, a good description of the vortex dynamics has been obtained. The behaviour of the magnetization amplitude (approx Hz) and the ac susceptibility signals (kHz), at different applied magnetic fields, 3.5 T < H sub d sub c < 4.5 T, and at the reduced temperature 0.86 < t < 0.93 (T = 22 K), shows that the superconducting dynamic response of vortices in the MgB sub 2 samples is not evidently dependent on the f...

  6. Detailed magnetization study of superconducting properties of YBa{sub 2}Cu{sub 3}O{sub 7-x} ceramic spheres

    Energy Technology Data Exchange (ETDEWEB)

    Landau, I L; Willems, J B; Hulliger, J [Department of Chemistry and Biochemistry, University of Berne, Freiestrasse 3, CH-3012 Berne (Switzerland)], E-mail: landau@iac.unibe.ch

    2008-03-05

    We present a magnetization study of low density YBa{sub 2}Cu{sub 3}O{sub 7-x} ceramics carried out in magnetic fields H such that 0.5 Oesuperconducting links between grains may be completely suppressed either by a magnetic field H{approx}100 Oe (at low temperatures) or by an increase of temperature to above 70 K. This property of the present samples allowed us to evaluate the ratio between the average grain size and the magnetic field penetration depth {lambda}. Furthermore, at temperatures T>85 K, using low field magnetization measurements, we were able to evaluate the temperature dependence of {lambda}, which turned out to be very close to predictions from conventional Ginzburg-Landau theory. Although the present samples consisted of randomly oriented grains, specifics of magnetization measurements allowed for evaluation of {lambda}{sub ab}(T). Good agreement between our estimation of the grain size and the real sample structure provides evidence for the validity of this analysis of magnetization data. Measurements of the equilibrium magnetization in high magnetic fields were used for evaluation of H{sub c2}(T). At temperatures close to T{sub c}, the H{sub c2}(T) dependence turned out to be linear, in agreement with Ginzburg-Landau theory. The value of the temperature at which H{sub c2} vanishes coincides with the superconducting critical temperature evaluated from low field measurements, which is important evidence of the validity of both approaches to the analysis of magnetization data.

  7. Magnetic and superconducting nanowires

    DEFF Research Database (Denmark)

    Piraux, L.; Encinas, A.; Vila, L.

    2005-01-01

    magnetic and superconducting nanowires. Using different approaches entailing measurements on both single wires and arrays, numerous interesting physical properties have been identified in relation to the nanoscopic dimensions of these materials. Finally, various novel applications of the nanowires are also...

  8. Effects of strain on the superconducting properties of niobium-tin conductors

    Energy Technology Data Exchange (ETDEWEB)

    Hoard, R.W.

    1980-11-01

    Investigations were performed to ascertain additional information on the connection between the cubic to tetragonal martensitic phase transformation and the phenomenon of superconductivity in Nb/sub 3/Sn. Of particular interest is the degradation of the critical parameters, such as T/sub c/, H/sub c2/, and J/sub c/, with mechanical straining of the superconductor. These studies yielded information that assisted in the derivation of the critical current-strain scaling laws mentioned above.

  9. Normal zone propagation in adiabatic superconducting magnets: Pt. 1; Normal zone propagation velocity in superconducting composites

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Z.P.; Iwasa, Y. (Massachusetts Inst. of Tech., Cambridge, MA (United States). Francis Bitter National Magnet Lab. Massachusetts Inst. of Tech., Cambridge, MA (United States). Plasma Fusion Center)

    1991-09-01

    A normal zone propagation model has been developed for superconducting composites under adiabatic conditions. It is based on the Whetstone-Roos model, originally developed for normal zone propagation in adiabatic wires of unclad superconductor. The model takes into account the temperature and magnetic field dependent material properties, for both superconductor and matrix metal. Analytical results agree well with experimental data. (author).

  10. Structure, texture, and properties of superconductive electrolytic niobium coatings on glassy carbon

    Science.gov (United States)

    Kolosov, V. N.; Shevyrev, A. A.

    2016-01-01

    Superconductive electrolytic niobium coatings 0.1-100 μm thick are prepared via electrochemical deposition onto SU-2000 glassy carbon substrates in (LiF + NaF + KF)eut-K2NbF7 molten salt. Their structure, texture, and residual stresses are investigated by X-ray diffraction methods. It is shown that, when depositing the coatings, the diffusion superconductive layer of niobium carbide is formed at the substrate-coating interface. The sequence of changes in the axis of the texture of niobium coating from through to a textureless state with an increase in their thickness is established. It is found that, in the interval 0.5-5 μm, the sign of the stress changes (compressive stresses change into tensile stresses) and it reaches its maximum value. With an increase in the coating thickness from 5 to 100 μm, tensile stresses decrease from 345 to 80 MPa. It is shown that the coatings formed can be used as the material for creating a working layer of a superconducting cryogenic gyroscope rotor.

  11. The Dependence of the Field Decay on the Powering History of the LHC Superconducting Dipole Magnets

    CERN Document Server

    Sammut, N; Micallef, J; Sanfilippo, S

    2006-01-01

    The decay of the allowed multipoles in the Large Hadron Collider (LHC) dipoles is expected to perturb the beam stability during the particle injection. The decay amplitude is largely affected by the powering history of the magnet and is particularly dependent on the pre-cycle flat-top current and duration as well as the pre-injection preparation duration. With possible prospects of having different genres of cycles during the LHC operation, the powering history effect must be taken into account in the Field Description Model for the LHC and must hence be corrected during machine operation. This paper presents the results of the modelling of this phenomenon.

  12. Fabrication and properties of single domain GdBCO superconducting rings by a buffer aided Gd+011 TSIG method

    Science.gov (United States)

    Yang, P. T.; Yang, W. M.; Chen, J. L.

    2017-08-01

    Single domain REBCO bulk superconductors can be fabricated by both the top-seeded melt texture growth process and the top-seeded infiltration and growth (TSIG) process. The buffer pellet technique used in these two methods has been demonstrated to act as an efficient seed and to aid the growth of the REBCO bulk superconductors. In this paper, we combined the Gd+011 TSIG method and buffer pellet technique together to fabricate single domain REBCO superconducting rings without any machining and obvious shrinkage of the final ring, which shows a satisfactory trapped field and very good magnetic shielding at the same time. It is found that (1) a single domain GdBCO ring, with inner diameter of 10 mm and outer diameter of 32 mm, has been fabricated by this method successfully. (2) The trapped field (0.32 T, 77 K) and maximum levitation force (80.1 N, 77 K) of the single domain GdBCO ring are nearly the same as the trapped field (0.33 T, 77 K) and maximum levitation force (80.2 N, 77 K) of the single domain GdBCO bulk with the same diameter and thickness, but the uniformity of trapped field is much better for the single domain GdBCO ring. (3) The single domain GdBCO ring shows very good magnetic shielding property, the magnetic flux density shielded by the superconducting ring is up to 0.40 T at 77 K, which is much higher than that of reported samples. The results indicate that the buffer aided Gd+011 TSIG method can provide an important way to fabricate high quality single domain REBCO superconducting rings directly.

  13. Synthesis of novel strontium-based cuprate superconducting thin films, and the relationship between their crystal structures and electrical properties

    Science.gov (United States)

    Chang, Kuo-Wei

    2000-12-01

    Novel Sr-based cuprate thin films were investigated to explore their potential as next generation superconducting materials. Thin films of infinite-layer compound (Sr,Ca)CuO2 (no blocking layer), cuprate oxycarbonate Sr2CuO2(CO3) (carbonate blocking layer), and Tl(Sr,Ba)2Can-1CunOy (n = 2 and 3) (thin blocking layer) were synthesized using metal-organic chemical vapor deposition. The structure and defect chemistry of the blocking layers of these cuprate compounds were found to have profound effects on the transport properties both in the normal state and the superconducting state. Phase pure, epitaxial infinite-layer compound (Sr1-xCa x)CuO2 thin films were deposited on SrTiO3(100) substrates. However, these films were always semiconducting with resistivities of the order of 1 ohm- cm and with carrier concentrations of 1017~10 19cm-3, which is two to four orders of magnitude lower than the typical superconducting cuprates. The low carrier concentration was attributed to the absence of blocking layers containing a sufficient concentration of charged defects. Transport was via variable range hopping conduction. By annealing in air, the infinite-layer compound SrCuO2 thin films reacted with the CO2 in air to generate Sr 2CuO2(CO3) thin films. Upon formation of carbonate blocking layers, charger carriers were introduced into the Sr2CuO 2(CO3) thin films through the partial substitution of carbon by copper or boron in the SrCO3 blocking layers. After oxygen annealing or upon boron substitution, the carrier concentration increased up to 10 21 cm-3. A superconducting onset temperature of 34K and a zero resistivity temperature of 20K have been observed for Sr 2CuO2(C1-xBx)O3 thin films. A critical carrier density of 0.10~0.12 holes/Cu was required to render superconductivity. The effect of crystal structure on the critical current density was investigated by measuring the vortex pinning energies of Tl2Ba2CaCu 2Oy (Tl-2212) and Tl(Sr,Ba)2Ca Cu2O y (Tl- (Sr,Ba)1212) thin

  14. Superconductivity in carbon nanomaterials

    Science.gov (United States)

    Dlugon, Katarzyna

    The purpose of this thesis is to explain the phenomenon of superconductivity in carbon nanomaterials such as graphene, fullerenes and carbon nanotubes. In the introductory chapter, there is a description of superconductivity and how it occurs at critical temperature (Tc) that is characteristic and different to every superconducting material. The discovery of superconductivity in mercury in 1911 by Dutch physicist Heike Kamerlingh Onnes is also mentioned. Different types of superconductors, type I and type II, low and high temperatures superconductors, as well as the BCS theory that was developed in 1957 by Bardeen, Cooper, and Schrieffer, are also described in detail. The BCS theory explains how Cooper's pairs are formed and how they are responsible for the superconducting properties of many materials. The following chapters explain superconductivity in doped fullerenes, graphene and carbon nanotubes, respectively. There is a thorough explanation followed by many examples of different types of carbon nanomaterials in which small changes in chemical structure cause significant changes in superconducting properties. The goal of this research was not only to take into consideration well known carbon based superconductors but also to search for the newest available materials such as the fullerene nanowhiskers discovered quite recently. There is also a presentation of fairly new ideas about inducing superconductivity in a monolayer of graphene which is more challenging than inducing superconductivity in graphite by simply intercalating metal atoms between its graphene sheets. An effort has been taken to look for any available information about carbon nanomaterials that have the potential to superconduct at room temperature, mainly because discovery of such materials would be a real revolution in the modern world, although no such materials have been discovered yet.

  15. Fabrication and superconducting properties of internal Mg diffusion processed MgB2 wires using MgB4 precursors

    Science.gov (United States)

    Xu, Da; Wang, Dongliang; Yao, Chao; Zhang, Xianping; Ma, Yanwei; Oguro, Hidetoshi; Awaji, Satoshi; Watanabe, Kazuo

    2016-10-01

    Monofilament MgB2/Nb/Monel wires were fabricated using three different MgB4 precursors by an internal Mg diffusion (IMD) process. The wire geometry and heat-treatment conditions were optimized in order to improve the critical current density (J c) of the MgB2 wire. The influences of the quality of MgB4 powders, such as the particle size and MgO impurity, on the microstructure and superconducting properties of the wires were discussed. Although there were small amounts of voids, unreacted MgB4 particles and MgO impurity existed in the superconducting layers, and the transport layer J c of the wire with the MgB4 precursor reached 3.0 × 104 A cm-2 at 4.2 K and 10 T, which was comparable to that of IMD-processed wires fabricated using boron precursors. Both the non-barrier J c and engineering J c of MgB2 wire made using a MgB4 precursor were enhanced due to the improved grain connectivity and the enlarged fill factor.

  16. Addition effects of nanoscale NiO on microstructure and superconducting properties of MgB{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Ranot, Mahipal; Jang, S. H.; Oh, Y. S.; Shinde, K. P.; Kang, S. H.; Chung, K. C. [Korea Institute of Materials Science, Changwon (Korea, Republic of)

    2016-03-15

    We have investigated the addition effect of NiO magnetic nanoparticles on crystal structure, microstructure as well as superconducting properties of MgB{sub 2}. NiO-added MgB{sub 2} samples were prepared by the solid-state reaction method. The superconducting transition temperature (Tc) of 37.91 K was obtained for pure MgB{sub 2}, and Tc was found to decrease systematically on increasing the addition level of NiO. X-ray diffraction (XRD) analysis revealed that no substitution of Ni for Mg in the lattice of MgB{sub 2} was occurred. The microstructural analysis shows that the pure MgB{sub 2} sample consists of plate shape MgB{sub 2} grains, and the grains get refined to smaller size with the addition of NiO nanoparticles. At 5 K, high values of critical current density (Jc) were obtained for small amount NiO-added MgB{sub 2} samples as compared to pure sample. The enhancement in Jc could be attributed to the refinement of MgB{sub 2} grains which leads to high density of grain boundaries in NiO-added MgB{sub 2} samples.

  17. Hydrostatic pressure effect on the superconducting properties of BaBi3 and SrBi3 single crystals

    Science.gov (United States)

    Jha, Rajveer; Avila, Marcos A.; Ribeiro, Raquel A.

    2017-02-01

    We demonstrate the superconducting properties of, and hydrostatic pressure effect on, BaBi3 and SrBi3 superconductors. We measure the dc magnetic susceptibility under hydrostatic pressure for both compounds, which shows a positive pressure coefficient of dT c/dP = 1.22 K GPa-1 for BaBi3 and a negative pressure coefficient of dT c/dP = -0.43 K GPa-1 for SrBi3. The normal state electrical resistivity shows that both compounds are highly metallic in nature. The upper critical fields H c2 evaluated by resistivity under magnetic fields ρ(T,H) are 22 kOe for BaBi3 and 2.9 kOe for SrBi3. A specific heat jump of ΔC e/γT c = 1.05 suggests weak coupling superconductivity in BaBi3, whereas ΔC e/γT c = 2.08 for SrBi3 is higher than the Bardeen-Cooper-Schrieffer theory value of 1.43, indicating a strong coupling superconductor.

  18. Structural, Magnetic, and Superconducting Properties of Caged Compounds ROs2Zn20 (R = La, Ce, Pr, and Nd)

    Science.gov (United States)

    Wakiya, Kazuhei; Onimaru, Takahiro; Matsumoto, Keisuke T.; Yamane, Yu; Nagasawa, Naohiro; Umeo, Kazunori; Kittaka, Shunichiro; Sakakibara, Toshiro; Matsushita, Yoshitaka; Takabatake, Toshiro

    2017-03-01

    The electrical resistivity, magnetization, and specific heat of the caged compounds ROs2Zn20 (R = La, Ce, Pr, and Nd) have been measured to study their structural, magnetic, and superconducting properties. These measurements indicate that the compounds undergo structural transitions at Ts = 151, 109, 87, and 62 K, respectively. The decrease in Ts along with the lanthanoid contraction suggests that the high-temperature phase is more stable for a smaller lattice volume. Analysis of the lattice specific heat of LaOs2Zn20 reveals that the Zn atom at the 16c site encapsulated in the R2Zn12 cage vibrates at a low energy of 3 meV. For CeOs2Zn20, the small magnetic susceptibility with a broad maximum indicates the valence-fluctuating state of the Ce ions. In PrOs2Zn20, the crystalline electric field ground state of the 4f2 state of the Pr3+ ion remains in a non-Kramers doublet at T > Ts, which is lifted by symmetry lowering of the Pr site at T < Ts. Thereby, the quadrupolar degrees of freedom are quenched, avoiding the long-range quadrupole order. PrOs2Zn20 and LaOs2Zn20 exhibit superconducting transitions at 0.06 and 0.07 K, respectively.

  19. Study on effect of annealing conditions on structural, magnetic and superconducting properties of MgB{sub 2} bulk samples

    Energy Technology Data Exchange (ETDEWEB)

    Phaneendra, Konduru, E-mail: phaneendra-50@yahoo.com; Asokan, K., E-mail: phaneendra-50@yahoo.com; Kanjilal, D. [Inter University Accelerator Centre, Aruna Asaf Ali Marg, Vasanth Kung, New Delhi-110067 (India); Awana, V. P. S. [Quantum Phenomena and Applications, National Physical Laboratory, K S Krishnan Marg, New Delhi-110012 (India); Sastry, S. Sreehari [Dept. of Physics, Acharya Nagarjuna University, Guntur-522510 (India)

    2014-04-24

    Effect of annealing conditions on structural, magnetic and superconducting properties of Magnesium Diboride (MgB{sub 2}) bulk superconductor samples prepared by solid state route method are compared. The samples are made by taking Magnesium and Boron powders in stoichiometric ratio, grounded well and pelletized at pressure of about 10Tonnes. These pellets are annealed in both Argon and vacuum environment separately up to 800°c for two hours. Both the samples show clear superconducting transition at Tc ∼ 38 k. This is further conformed by AC/DC magnetization (M-T), Resistivity [ρ (T, H)] measurements under magnetic field up to 14 Tesla as well. Rietveld refinement of X-ray diffraction of both samples conformed the MgB{sub 2} phase formation with P6/mmm space group symmetry. Scanning Electron Microscopy images of the surface revile more agglomeration of grains in case of Argon annealed samples. This result in more critical current density (J{sub c}) of Argon annealed samples than vacuum annealed one calculated from Bean's critical state model. This high Jc is explained in terms of more inter grain connectivity for Argon annealed sample than vacuum annealed sample.

  20. Study on effect of annealing conditions on structural, magnetic and superconducting properties of MgB2 bulk samples

    Science.gov (United States)

    Phaneendra, Konduru; Asokan, K.; Awana, V. P. S.; Sastry, S. Sreehari; Kanjilal, D.

    2014-04-01

    Effect of annealing conditions on structural, magnetic and superconducting properties of Magnesium Diboride (MgB2) bulk superconductor samples prepared by solid state route method are compared. The samples are made by taking Magnesium and Boron powders in stoichiometric ratio, grounded well and pelletized at pressure of about 10Tonnes. These pellets are annealed in both Argon and vacuum environment separately up to 800°c for two hours. Both the samples show clear superconducting transition at Tc ˜ 38 k. This is further conformed by AC/DC magnetization (M-T), Resistivity [ρ (T, H)] measurements under magnetic field up to 14 Tesla as well. Rietveld refinement of X-ray diffraction of both samples conformed the MgB2 phase formation with P6/mmm space group symmetry. Scanning Electron Microscopy images of the surface revile more agglomeration of grains in case of Argon annealed samples. This result in more critical current density (Jc) of Argon annealed samples than vacuum annealed one calculated from Bean's critical state model. This high Jc is explained in terms of more inter grain connectivity for Argon annealed sample than vacuum annealed sample.

  1. Simple One-Step Synthesis and Superconducting Properties of SmFeAsO1-x Fx

    Institute of Scientific and Technical Information of China (English)

    MA Yan-Wei; GAO Zhao-Shun; WANG Lei; QI Yan-Peng; WANG Dong-Liang; ZHANG Xian-Ping

    2009-01-01

    The recent discovery of superconductivity in REFeAsO (RE,rare-earth metal) has generated enormous interest because these materials are the first non-copper oxide superconductors with critical temperatures Tc exceeding 50 K as well as upper critical fields well above 100 T.However,for these new superconductors,very complicated synthesis routes,such as the complex two-step synthesis or high-pressure sintering,are required.Furthermore,there is the toxicity and volatility of arsenic to consider,sometimes a sealed quartz tube of arsenic exploded during annealing.We present a new method for producing high-temperature SmFeAsO1-xFx superconductors by using a one-step sintering process.Superconducting transition with the onset temperature of 54.6 K and high critical fields Hc2 (0) ≥ 200 T were confirmed in SmFeAsO0.7F0.3.At 5 K and at self field,critical current densities Jc estimated from the magnetization hysteresis using the whole sample size and the average particle size have reached 8.5×103 and 1.2×106 A/cm2,respectively.Moreover,Jc exhibited a very weak dependence on magnetic field. This simple and safe one-step synthesis technique should be effective in other rare earth derivatives of iron-based superconductors.

  2. Over Current Properties of HTC Superconducting Wire Cooled by Liquid Hydrogen

    Science.gov (United States)

    Shirai, Yasuyuki; Kobayashi, Hiroto; Takegami, Taiki; Hikawa, Kyosuke; Shiotsu, Masahiro; Tatsumoto, Hideki; Naruo, Yoshihiro; Kobayashi, Hiroaki; Inatani, Yoshifumi; Kinoshita, Katsuhiko

    An experimental setup which can energize superconducting wires immersed in LH2 was designed and made. Over current tests were carried out using MgB2 wire. Critical current and resistivity of a test MgB2 wire submerged in liquid hydrogen were measured for exponentially increasing heat input, while the transport current exceeded the critical current. The resistivity of the conductor was obtained as a function of current and the temperature of the conductor by using the transient heating method. The distribution ratio of the current through the superconductor and the sheath, and the resistivity of the MgB2 conductor itself were estimated.

  3. Temperature Dependent Electrical Properties of PZT Wafer

    Science.gov (United States)

    Basu, T.; Sen, S.; Seal, A.; Sen, A.

    2016-04-01

    The electrical and electromechanical properties of lead zirconate titanate (PZT) wafers were investigated and compared with PZT bulk. PZT wafers were prepared by tape casting technique. The transition temperature of both the PZT forms remained the same. The transition from an asymmetric to a symmetric shape was observed for PZT wafers at higher temperature. The piezoelectric coefficient (d 33) values obtained were 560 pc/N and 234 pc/N, and the electromechanical coupling coefficient (k p) values were 0.68 and 0.49 for bulk and wafer, respectively. The reduction in polarization after fatigue was only ~3% in case of PZT bulk and ~7% for PZT wafer.

  4. Structural and superconducting properties of La2−xNdxCuO4+y (0≤x≤0.5) prepared by room temperature chemical oxidation

    DEFF Research Database (Denmark)

    Rial, C.; Morán, E.; Alario-Franco, M.A.;

    1997-01-01

    The systematic characterization of the structural and superconducting properties of room temperature chemically oxidized T/O La2-xNdxCuO4+y (0 less than or equal to x less than or equal to 0.5) has been performed by neutron powder diffraction and magnetic susceptibility measurements. Similarities...

  5. Anomalous pressure dependence of the superconducting transition temperature of beta-pyrochlore AOs2O6 oxides.

    Science.gov (United States)

    Muramatsu, T; Takeshita, N; Terakura, C; Takagi, H; Tokura, Y; Yonezawa, S; Muraoka, Y; Hiroi, Z

    2005-10-14

    High-pressure effects on the superconducting transitions of beta-pyrochlore oxide superconductors AOs(2)O(6) (A = Cs,Rb,K) are studied by measuring resistivity under high pressures up to 10 GPa. The superconducting transition temperature T(c) first increases with increasing pressure in every compound and then exhibits a broad maximum at 7.6 K (6 GPa), 8.2 K (2 GPa), and 10 K (0.6 GPa) for A = Cs, Rb, and K, respectively. Finally, the superconductivity is suppressed completely at a critical pressure near 7 GPa and 6 GPa for A = Rb and K and probably above 10 GPa for A = Cs. Characteristic changes in the coefficient A of the T(2) term in resistivity and residual resistivity are observed, both of which are synchronized with the corresponding change in T(c).

  6. Estimate bond angle dependence of superconducting transition temperature in NaFeAs with the first principle methods

    Science.gov (United States)

    Sun, Tieyu; Huang, Haitao; Peng, Biaolin; Zheng, Renkui; Lam, Chi-Hang; Tang, Tao; Wang, Yu

    2016-11-01

    The change of superconducting transition temperature (Tc) with bond angle in iron-pnictides was investigated by first-principles calculation based on density functional theory. A Green's function method was adopted to estimate the maximum eigenvalue of Eliashberg equation (an indicator of Tc) for NaFeAs with different bond angles. Through calculations the band structure of NaFeAs was obtained. It was found that hole pockets could form at the center of the first Brillion zone in the band structure, which confirmed the existence of superconductivity in NaFeAs. The upper limit of the Fe-As-Fe bond angle for superconductivity was found to be 121° and the highest Tc would occur at the angle of 108°.

  7. High field transport properties of MBE processed Fe-based superconducting thin films

    Energy Technology Data Exchange (ETDEWEB)

    Iida, Kazumasa [Nagoya University (Japan); IFW Dresden (Germany)

    2015-07-01

    It has been reported that Fe-based superconductors show high upper critical fields with low anisotropies at low temperatures. Hence these materials may offer a unique possibility for high field magnet applications. However, only a few reports on high-field transport properties of Co-doped Ba-122 and Fe(Se,Te) have been published and the only one for SmFeAs(O,F) thin films to date. In order to use this material class for applications, the knowledge of in-field and its orientation dependence of transport properties in a wide range of external fields need to be clarified. In this talk, I will report on high-field (up to dc 45 T) transport properties of P-doped Ba-122, SmFeAs(O,F) and NdFeAs(O,F) thin films prepared by MBE. Although P-doped Ba-122 has the lowest T{sub c}, self-field J{sub c} of over 6 MA/cm{sup 2} at 4.2 K is recorded, which is the highest value ever reported in Fe-based superconductors. Additionally, in-field performance of P-doped Ba-122 shows comparable to those of NdFeAs(O,F) and SmFeAs(O,F) for Hc. On the other hand, both NdFeAs(O,F) and SmFeAs(O,F) exhibited higher J{sub c} for H parallel ab due to the intrinsic pinning. These results indicate that P-doped Ba-122 is the most promising candidates for high-field magnet applications.

  8. Superconducting properties of Zn and Al double-doped Mg1-x(Zn0.5Al0.5)xB2

    DEFF Research Database (Denmark)

    Xu, G.J.; Grivel, Jean-Claude; Abrahamsen, A.B.

    2004-01-01

    A series of polycrystalline samples of Mg1-x(Zn0.5Al0.5)(x)B-2 (0less than or equal toxless than or equal to0.8) were prepared by solid state reaction method and their structure, superconducting transition temperature (T-c) and transport properties were investigated by means of X-ray diffraction...... (XRD), ac susceptibility, magnetization and resistivity. The double doping leads to decreases in both the lattice parameters a and c, and the T-c decreases with increasing dopant content. A systematical comparison with Al doped- and Li, Al double doped MgB2 of structure, superconducting transition...

  9. Effect of low temperature annealing on doping level and superconducting properties for IBAD/PLD-YBCO coated conductor

    Energy Technology Data Exchange (ETDEWEB)

    Kato, J.Y. [Superconductivity Research Laboratory, ISTEC, 1-10-13 Shinonome, Koto-ku, Tokyo 135-0062 (Japan)]. E-mail: yoshioka@istec.or.jp; Chikumoto, N. [Superconductivity Research Laboratory, ISTEC, 1-10-13 Shinonome, Koto-ku, Tokyo 135-0062 (Japan); Sakai, N. [Superconductivity Research Laboratory, ISTEC, 1-10-13 Shinonome, Koto-ku, Tokyo 135-0062 (Japan); Iijima, Y. [Fujikura Ltd., 1-5-1 Kiba, Koto-ku, Tokyo 135-8512 (Japan); Kakimoto, K. [Fujikura Ltd., 1-5-1 Kiba, Koto-ku, Tokyo 135-8512 (Japan); Saitoh, T. [Fujikura Ltd., 1-5-1 Kiba, Koto-ku, Tokyo 135-8512 (Japan); Watanabe, T. [Superconductivity Research Laboratory, ISTEC, 2-4-1 Mutsuno, Atsuta-ku, Nagoya, Aichi 456-8587 (Japan); Yamada, Y. [Superconductivity Research Laboratory, ISTEC, 2-4-1 Mutsuno, Atsuta-ku, Nagoya, Aichi 456-8587 (Japan); Tajima, S. [Superconductivity Research Laboratory, ISTEC, 1-10-13 Shinonome, Koto-ku, Tokyo 135-0062 (Japan)

    2005-10-01

    The effect of low temperature annealing on the superconducting properties of PLD-YBCO tape has been investigated with varying atmosphere. The T {sub c} of the as-prepared sample is 88.5 K, for the sample post-annealed at 200 deg. C in Ar atmosphere showed 91.5 K, indicating T {sub c} is sensitive to low temperature annealing. In spite of the higher T {sub c} the J {sub c} and {mu} {sub 0} H {sub irr} for the Ar-annealed sample were lower than those for the as-prepared sample. This indicates that the as-prepared PLD-YBCO tape is in the carrier overdoped state. It was found that re-annealing in which the sample was slowly cooled from 450 deg. C in pure oxygen atmosphere could restore the J {sub c}-degradation, demonstrating that oxygen absorption-release occurred reversely.

  10. Effects of α-particle beam irradiation on superconducting properties of thin film MgB2 superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Sang Bum; Duong, Pham van; Ha, Dong Hyup; Oh, Young Hoon; Kang, Won Nam; Chai, Jong Seo [Sungkunkwan Univeversity, Suwon (Korea, Republic of); Hong, Seung Pyo; Kim, Ran Young [Kore Institute of Radiological and Medical Science, Seoul (Korea, Republic of)

    2016-06-15

    Superconducting properties of thin film MgB2 superconductors irradiated with 45 MeV α-particle beam were studied. After the irradiation, enhancement of the critical current density and pinning force was observed, scaling close to strong pinning formula. Double logarithmic plots of the maximum pinning force density with irreversible magnetic field show a power law behavior close to carbon-doped MgB2 film or polycrystals. Variation of normalized pinning force density in the reduced magnetic field suggests scaling formulas for strong pinning mechanism like planar defects. We also observed a rapid decay of critical current density as the vortex lattice constant decreases, due to the strong interaction between vortices and increasing magnetic field.

  11. Superconducting transistor

    Science.gov (United States)

    Gray, Kenneth E.

    1979-01-01

    A superconducting transistor is formed by disposing three thin films of superconducting material in a planar parallel arrangement and insulating the films from each other by layers of insulating oxides to form two tunnel junctions. One junction is biased above twice the superconducting energy gap and the other is biased at less than twice the superconducting energy gap. Injection of quasiparticles into the center film by one junction provides a current gain in the second junction.

  12. Diameter-dependent thermodynamic and elastic properties of metallic nanoparticles

    Science.gov (United States)

    Chandra, Jeewan; Kholiya, Kuldeep

    2015-04-01

    A simple theoretical model has been proposed to study the diameter-dependent properties of metallic nanoparticles, i.e. Ag, Au, Al, Ni, Pb, Cu and Fe. The diameter-dependent thermodynamic properties includes melting temperature, Debye temperature, evaporation temperature, melting enthapy and melting entropy. The model is also extended to study the diameter-dependent elastic properties including bulk modulus, Young's modulus and thermal expansion coefficient. On comparison with available experimental findings and other theoretical approaches, the results obtained with the present formulation depict a close agreement and demonstrate the validity of the method proposed in the present paper.

  13. Anelastic characterization and superconducting properties of RuSr2GdCu2O8+δ

    Directory of Open Access Journals (Sweden)

    Jurelo, A. R.

    2008-08-01

    Full Text Available Since the discovery of the high Tc superconductors, many researches have been carried out on the different properties of these materials, especially on the transition temperature into the superconducting state. The rutheno-cuprates belong to a new class of composites, which were synthesized for the first time by Bauernfeind in 1995. Bernhard and collaborators discovered, in 1999, the coexistence of the ferromagnetism and the superconductivity in this phase, which is known as antagonistic phenomenon in the electromagnetism due to spin-charge interactions established in these states. However, the physical nature of the superconducting and magnetic states is still very obscure. The non-stoichiometric (interstitial oxygen is considered as a possible cause for the non-uniformity of the sample properties. In this paper, results of mechanical spectroscopy in Ru-1212 samples are presented showing complex anelastic spectra, which were attributed to the mobility of the interstitial oxygen atoms in the Ru-1212 lattice.Desde el descubrimiento de los superconductores de alta Tc, muchas investigaciones han sido realizadas sobre las diferentes propiedades de estos materiales, especialmente sobre la temperatura de transición dentro del estado superconductor. Los cupratos de rutenio pertenecen a una nueva clase de compositos, los cuales fueron sintetizados por primera vez por Bauernfeind en 1995. Bernhard y colaboradores descubrieron, en 1999, la coexistencia del ferromagnetismo y la superconductividad en esta fase, lo cual es conocido como un fenómeno antagonistico en el electromagnetismo debido a las interacciones spin-carga establecidas en estos estados. Sin embargo, la naturaleza física de los estados superconductores y magnéticos aun no son muy claros. El oxigeno no-estequiométrico (intersticial es considerado como una causa de la no-uniformidad de las propiedades de la muestra. En este articulo, los resultados de espectroscopia mecánica en muestras

  14. Flux Pinning Properties and Magnetic Relaxation of Superconducting SmFe0.9Co0.1AsO

    Science.gov (United States)

    Zhuang, J. C.; Sun, Y.; Ding, Y.; Yuan, F. F.; Liu, J. T.; Shi, Z. X.; Li, X. W.

    2012-12-01

    Magnetic Co ion doped SmFeAsO polycrystal was synthesized via solid-state reaction. Resistivity, SEM and magnetic hysteresis loops (MHLs) were measured to investigate magnetic properties of the sample. Critical current densities as well as the flux pinning forces densities were estimated from MHLs. This paper reports for the first time the research of superconducting MHLs as well as magnetic relaxation properties of SmFe0.9Co0.1AsO. Results suggest that: (i) A tail effect in the resistivity measurement together with the rapid decrease in critical current densities at low fields shows the evidence for granularity of the sample; (ii) The asymmetry of the MHLs may be caused by the Bean-Livingstone (BL) surface pinning or granular nature, and none of theoretical models are suitable to the scaling behaviors of flux pinning forces densities; (iii) The anomalous tendency of the temperature dependence of magnetic relaxation rate as well as the effective pinning energy were observed, which may be attributed to the competition between the bulk pinning and the BL surface pinning.

  15. Dependence of Glass Mechanical Properties on Thermal and Pressure History

    DEFF Research Database (Denmark)

    Smedskjær, Morten Mattrup; Bauchy, Mathieu

    -equilibrium material, the structure and properties of glass depend not only on its composition, but also on its thermal and pressure histories. Here we review our recent findings regarding the thermal and pressure history dependence of indentation-derived mechanical properties of oxide glasses.......Predicting the properties of new glasses prior to manufacturing is a topic attracting great industrial and scientific interest. Mechanical properties are currently of particular interest given the increasing demand for stronger, thinner, and more flexible glasses in recent years. However, as a non...

  16. Superconductivity in CVD diamond films.

    Science.gov (United States)

    Takano, Yoshihiko

    2009-06-24

    A beautiful jewel of diamond is insulator. However, boron doping can induce semiconductive, metallic and superconducting properties in diamond. When the boron concentration is tuned over 3 × 10(20) cm(-3), diamonds enter the metallic region and show superconductivity at low temperatures. The metal-insulator transition and superconductivity are analyzed using ARPES, XAS, NMR, IXS, transport and magnetic measurements and so on. This review elucidates the physical properties and mechanism of diamond superconductor as a special superconductivity that occurs in semiconductors.

  17. Properties of pseudospin polarization on a graphene-based spin singlet superconducting junction

    Institute of Scientific and Technical Information of China (English)

    Jia Shuan-Wen; Wang Jun-Tao; Yang Yan-Ling; Bai Chun-Xu

    2013-01-01

    We investigate theoretically transport characteristics in a graphene-based pseudospinmagnet/superconductor junction,including the s-wave and the d-wave pairing symmetry potential in the superconducting region.It is found that the pseudospin polarization,in sharp contrast to spin polarization in the graphene-based ferromagnet/superconductor junction,holds no influence on the specular Andreev reflection for a negligible Fermi energy.Furthermore,the Fano factor is crucially affected by the zero bias state.Therefore,we suggest here that the findings could shed light on the realization of graphene-based pseudospintronics devices and provide a new way to detect the specular Andreev reflection and the zero bias state in the actual experiments.

  18. Structure of haloform intercalated C60 and its influence on superconductive properties.

    Science.gov (United States)

    Dinnebier, Robert E; Gunnarsson, Olle; Brumm, Holger; Koch, Erik; Stephens, Peter W; Huq, Ashfia; Jansen, Martin

    2002-04-05

    CHCl3 and CHBr3 intercalated C60 have attracted particular interest after a superconductivity transition temperature (Tc) of up to 117 K was discovered. We have determined the structure using synchrotron x-ray powder-diffraction and found that the expansion of the lattice mainly takes place in one dimension (triclinic b axis), leaving planes of C60 molecules on an approximately hexagonal, slightly expanded lattice. We have performed tight-binding band structure calculations for the surface layer. In spite of the slight expansion of the layers, for the range of dopings where a large Tc has been observed, the density of states at the Fermi energy is smaller for C60.2CHCl3 and C60.2CHBr3 than for C60. This suggests that the lattice expansion alone cannot explain the increase of Tc.

  19. Nb3Sn superconducting radiofrequency cavities: fabrication, results, properties, and prospects

    Science.gov (United States)

    Posen, S.; Hall, D. L.

    2017-03-01

    A microns-thick film of Nb3Sn on the inner surface of a superconducting radiofrequency (SRF) cavity has been demonstrated to substantially improve cryogenic efficiency compared to the standard niobium material, and its predicted superheating field is approximately twice as high. We review in detail the advantages of Nb3Sn coatings for SRF cavities. We describe the vapor diffusion process used to fabricate this material in the most successful experiments, and we compare the differences in the process used at different labs. We overview results of Nb3Sn SRF coatings, including CW and pulsed measurements of cavities as well as microscopic measurements. We discuss special considerations that must be practised when using Nb3Sn cavities in applications. Finally, we conclude by summarizing the state-of-the-art and describing the outlook for this alternative SRF material.

  20. Universal relation for size dependent thermodynamic properties of metallic nanoparticles.

    Science.gov (United States)

    Xiong, Shiyun; Qi, Weihong; Cheng, Yajuan; Huang, Baiyun; Wang, Mingpu; Li, Yejun

    2011-06-14

    The previous model on surface free energy has been extended to calculate size dependent thermodynamic properties (i.e., melting temperature, melting enthalpy, melting entropy, evaporation temperature, Curie temperature, Debye temperature and specific heat capacity) of nanoparticles. According to the quantitative calculation of size effects on the calculated thermodynamic properties, it is found that most thermodynamic properties of nanoparticles vary linearly with 1/D as a first approximation. In other words, the size dependent thermodynamic properties P(n) have the form of P(n) = P(b)(1 -K/D), in which P(b) is the corresponding bulk value and K is the material constant. This may be regarded as a scaling law for most of the size dependent thermodynamic properties for different materials. The present predictions are consistent literature values.

  1. Magnetic field dependence of the coupling efficiency of a superconducting transmission line due to the proximity effect

    NARCIS (Netherlands)

    Zhu, S.; Zijlstra, T.; Golubov, A.A.; Van den Bemt, M.; Baryshev, A.M.; Klapwijk, T.M.

    2009-01-01

    The coupling efficiency of a Nb superconducting transmission line has been measured using a Fourier transform spectrometer for different magnetic fields. It is found that the coupling decreases with increasing magnetic field when the frequency is close to the gap of the Nb superconductor. This is at

  2. Effects of Mn doping on temperature-dependent magnetic properties of L10 FeMnPt

    Science.gov (United States)

    Xu, D. B.; Chen, J. S.; Zhou, T. J.; Chow, G. M.

    2011-04-01

    We report the effect of Mn doping on temperature-dependent magnetic properties of L10 FeMnPt (001) epitaxial films. (001) textured L10 Fe50-xMnxPt50 (x = 0, 5, 10, 15, 20 at. %) films were prepared by cosputtering Fe, Pt, and Mn onto MgO single crystal substrates at 550 °C. θ-2θ XRD scans indicated the lattice parameter c increased whereas the ordering parameter S decreased with Mn doping. The thermal magnetic properties measured using a superconducting quantum interference device showed that Curie temperature TC could be reduced to 500 K with 15 at. % Mn doping, but Ku was decreased to 1.6 × 107 erg/cm3. The relation of temperature-dependent anisotropy and saturation magnetization showed that it did not obey the Callen-Callen theory.

  3. Coherent transport properties of a three-terminal hybrid superconducting interferometer

    Science.gov (United States)

    Vischi, F.; Carrega, M.; Strambini, E.; D'Ambrosio, S.; Bergeret, F. S.; Nazarov, Yu. V.; Giazotto, F.

    2017-02-01

    We present an exhaustive theoretical analysis of a double-loop Josephson proximity interferometer, such as the one recently realized by Strambini et al. for control of the Andreev spectrum via an external magnetic field. This system, called ω -SQUIPT, consists of a T-shaped diffusive normal metal (N ) attached to three superconductors (S ) forming a double-loop configuration. By using the quasiclassical Green-function formalism, we calculate the local normalized density of states, the Josephson currents through the device, and the dependence of the former on the length of the junction arms, the applied magnetic field, and the S /N interface transparencies. We show that by tuning the fluxes through the double loop, the system undergoes transitions from a gapped to a gapless state. We also evaluate the Josephson currents flowing in the different arms as a function of magnetic fluxes, and we explore the quasiparticle transport by considering a metallic probe tunnel-coupled to the Josephson junction and calculating its I -V characteristics. Finally, we study the performances of the ω -SQUIPT and its potential applications by investigating its electrical and magnetometric properties.

  4. Universal size dependence of the physical properties of nanomaterials

    Science.gov (United States)

    Eremin, E. N.; Yurov, V. M.; Guchenko, S. A.; Laurynas, V. Ch

    2017-06-01

    Dimensional analysis of the experimentally observed dependence of the physical properties of nanoparticles, nanofilms and nanomaterials showed that there is a universal equation that accurately describes the observed size effects. It is shown that the size factor is also a universal value and is determined only by the atomic structure of the nanomaterial. Discovered universal relationships enable us to calculate the physical properties (mechanical, electrical, magnetic, thermal, etc.) of small particles and thin films based on knowledge of the properties of bulk materials.

  5. Superconductivity in aromatic hydrocarbons

    Energy Technology Data Exchange (ETDEWEB)

    Kubozono, Yoshihiro, E-mail: kubozono@cc.okayama-u.ac.jp [Research Laboratory for Surface Science, Okayama University, Okayama 700-8530 (Japan); Research Center of New Functional Materials for Energy Production, Storage and Transport, Okayama University, Okayama 700-8530 (Japan); Japan Science and Technology Agency, ACT-C, Kawaguchi 332-0012 (Japan); Goto, Hidenori; Jabuchi, Taihei [Research Laboratory for Surface Science, Okayama University, Okayama 700-8530 (Japan); Yokoya, Takayoshi [Research Laboratory for Surface Science, Okayama University, Okayama 700-8530 (Japan); Research Center of New Functional Materials for Energy Production, Storage and Transport, Okayama University, Okayama 700-8530 (Japan); Kambe, Takashi [Department of Physics, Okayama University, Okayama 700-8530 (Japan); Sakai, Yusuke; Izumi, Masanari; Zheng, Lu; Hamao, Shino; Nguyen, Huyen L.T. [Research Laboratory for Surface Science, Okayama University, Okayama 700-8530 (Japan); Sakata, Masafumi; Kagayama, Tomoko; Shimizu, Katsuya [Center of Science and Technology under Extreme Conditions, Osaka University, Osaka 560-8531 (Japan)

    2015-07-15

    Highlights: • Aromatic superconductor is one of core research subjects in superconductivity. Superconductivity is observed in certain metal-doped aromatic hydrocarbons. Some serious problems to be solved exist for future advancement of the research. This article shows the present status of aromatic superconductors. - Abstract: ‘Aromatic hydrocarbon’ implies an organic molecule that satisfies the (4n + 2) π-electron rule and consists of benzene rings. Doping solid aromatic hydrocarbons with metals provides the superconductivity. The first discovery of such superconductivity was made for K-doped picene (K{sub x}picene, five benzene rings). Its superconducting transition temperatures (T{sub c}’s) were 7 and 18 K. Recently, we found a new superconducting K{sub x}picene phase with a T{sub c} as high as 14 K, so we now know that K{sub x}picene possesses multiple superconducting phases. Besides K{sub x}picene, we discovered new superconductors such as Rb{sub x}picene and Ca{sub x}picene. A most serious problem is that the shielding fraction is ⩽15% for K{sub x}picene and Rb{sub x}picene, and it is often ∼1% for other superconductors. Such low shielding fractions have made it difficult to determine the crystal structures of superconducting phases. Nevertheless, many research groups have expended a great deal of effort to make high quality hydrocarbon superconductors in the five years since the discovery of hydrocarbon superconductivity. At the present stage, superconductivity is observed in certain metal-doped aromatic hydrocarbons (picene, phenanthrene and dibenzopentacene), but the shielding fraction remains stubbornly low. The highest priority research area is to prepare aromatic superconductors with a high superconducting volume-fraction. Despite these difficulties, aromatic superconductivity is still a core research target and presents interesting and potentially breakthrough challenges, such as the positive pressure dependence of T{sub c} that is clearly

  6. Grain size dependent mechanical properties in nanophase materials

    Energy Technology Data Exchange (ETDEWEB)

    Siegel, R.W. [Argonne National Lab., IL (United States); Fougere, G.E. [Northwestern Univ., Evanston, IL (United States). Dept. of Materials Science and Engineering

    1995-02-01

    It has become possible in recent years to synthesize metals and ceramics under well controlled conditions with constituent grain structures on a manometer size scale (below 100 nm). These new materials have mechanical properties that are strongly grain-size dependent and often significantly different than those of their coarser grained counterparts. Nanophase metals tend to become stronger and ceramics are more easily deformed as grain size is reduced. The observed mechanical property changes appear to be related primarily to grain size limitations and the large percentage of atoms in grain boundary environments. A brief overview of our present knowledge about the grain-size dependent mechanical properties of nanophase materials is presented.

  7. Magnetic fluctuations and superconducting properties of CaKFe4As4 studied by 75As NMR

    Science.gov (United States)

    Cui, J.; Ding, Q.-P.; Meier, W. R.; Böhmer, A. E.; Kong, T.; Borisov, V.; Lee, Y.; Bud'ko, S. L.; Valentí, R.; Canfield, P. C.; Furukawa, Y.

    2017-09-01

    We report 75As nuclear magnetic resonance (NMR) studies on a new iron-based superconductor, CaKFe4As4 , with Tc=35 K. 75As NMR spectra show two distinct lines corresponding to the As(1) and As(2) sites close to the K and Ca layers, respectively, revealing that K and Ca layers are well ordered without site inversions. We found that nuclear quadrupole frequencies νQ of the As(1) and As(2) sites show an opposite temperature T dependence. Nearly T independent behavior of the Knight shifts K is observed in the normal state, and a sudden decrease in K in the superconducting (SC) state suggests spin-singlet Cooper pairs. 75As spin-lattice relaxation rates 1 /T1 show a power-law T dependence with different exponents for the two As sites. The isotropic antiferromagnetic spin fluctuations characterized by the wave vector q =(π ,0 ) or (0 ,π ) in the single-iron Brillouin zone notation are revealed by 1 /T1T and K measurements. Such magnetic fluctuations are necessary to explain the observed temperature dependence of the 75As quadrupole frequencies, as evidenced by our first-principles calculations. In the SC state, 1 /T1 shows a rapid decrease below Tc without a Hebel-Slichter peak and decreases exponentially at low T , consistent with an s± nodeless two-gap superconductor.

  8. Macroscopic states induced in superconducting media by a transport current under flux creep

    Science.gov (United States)

    Romanovskii, V. R.

    2016-08-01

    The physical features of the formation of macroscopic states of superconducting composites consisting of a superconductor and a coating under flux creep are discussed. It is demonstrated that there exist characteristic electric field strengths depending on the properties of the superconductor, cooling conditions, and characteristics of the stabilizing coating, which affect the intensity of the E-I characteristics of the superconducting composites. Analysis shows that the measurements of the critical properties of superconductors can be accompanied by a nonuniform electric field distribution over the composite cross section and high stable superheating of the superconductor, which do not lead to superconductivity breaking.

  9. Superconducting wind turbine generators

    DEFF Research Database (Denmark)

    Abrahamsen, Asger Bech; Mijatovic, Nenad; Seiler, Eugen

    2010-01-01

    , the main challenge of the superconducting direct drive technology is to prove that the reliability is superior to the alternative drive trains based on gearboxes or permanent magnets. A strategy of successive testing of superconducting direct drive trains in real wind turbines of 10 kW, 100 kW, 1 MW and 10...... offshore turbines of 8 and 10 MW have been determined from an up-scaling of an existing 5 MW turbine and the necessary properties of the superconducting drive train are discussed. We have found that the absence of the gear box is the main benefit and the reduced weight and size is secondary. However...... MW generator and it is concluded that the present production capacity of coated conductors must be increased by a factor of 36 by 2020, resulting in a ten times lower price of the tape in order to reach a realistic price level for the superconducting drive train....

  10. Effect of nonmagnetic defects on superconducting and transport properties of Ba(Fe{sub 1–x}Co{sub x}As){sub 2} high-T{sub c} superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Blokhin, I. S.; Gavrilkin, S. Yu. [Russian Academy of Sciences, Lebedev Physical Institute (Russian Federation); Gorshunov, B. P. [Russian Academy of Sciences, Prokhorov General Physics Institute (Russian Federation); Dravin, V. A. [Russian Academy of Sciences, Lebedev Physical Institute (Russian Federation); Zhukova, E. S. [Russian Academy of Sciences, Prokhorov General Physics Institute (Russian Federation); Ivanenko, O. M. [Russian Academy of Sciences, Lebedev Physical Institute (Russian Federation); Aida, K. [Leibniz Institute for Solid State and Materials Research (Germany); Krasnosvobodtsev, S. I. [Russian Academy of Sciences, Lebedev Physical Institute (Russian Federation); Kurt, F. [Leibniz Institute for Solid State and Materials Research (Germany); Mitsen, K. V., E-mail: mitsen@sci.lebedev.ru; Tsvetkov, A. Yu. [Russian Academy of Sciences, Lebedev Physical Institute (Russian Federation)

    2015-11-15

    The effect of nonmagnetic defects on superconducting and transport properties of Ba(Fe{sub 0.94}Co{sub 0.06}As){sub 2} films is studied for obtaining information on the symmetry type of the order parameter for superconducting pnictides. Such defects are generated in the film by irradiation by He{sup +} ions with an energy of 200 keV. It is found that a decrease in superconducting transition temperature T{sub c} upon an increase in the concentration of nonmagnetic defects in this compound occurs much more slowly than predicted in the model assuming s{sup ±}-wave symmetry of the order parameter. Joint analysis of the influence of nonmagnetic defects on the superconducting and magnetotransport properties of such films leads to the conclusion that superconductivity is completely suppressed in them after critical disorder is attained, which assumes the s{sup ++}-wave symmetry.

  11. Phase Diagram and Electronic Properties of High-Tc Superconducting Oxides

    Science.gov (United States)

    Pavuna, Davor

    We firstly briefly summarize some of the most relevant recent results and open questions across rather complex electronic phase diagram of cuprates. We continue with a discussion of results on thin superconducting oxide films grown by laser ablation. Systematic studies show that BSCCO-phases and LSCO-214 exhibit conductor-like Fermi edge, whereas materials containing "chains" (like YBCO-123) are prone to very rapid surface degradation, most likely related to critical oxygen loss at the outermost layers. Recently, direct ARPES dispersion measurements on in-situ grown, strained 10UC thin LSCO-214 films (Tc = 44 K) have shown the band crossing of Fermi level well before the Brillouin zone boundary. This is in contrast to the flat band observed in unstrained single crystals — and to the band flattening predicted by band calculations for in-plane compressive strain. In spite of density of states reduction near the Fermi level, the critical temperature increases in strained films with respect to unstrained crystals; this poses further challenge to HTSC theory.

  12. Applications of Superconductivity

    Science.gov (United States)

    Goodkind, John M.

    1971-01-01

    Presents a general review of current practical applications of the properties of superconducters. The devices are classified into groups according to the property that is of primary importance. The article is inteded as a first introduction for students and professionals. (Author/DS)

  13. Studies of selected properties of high-temperature superconducting tape 2G HTS SF series - the example: tape SF12050

    Directory of Open Access Journals (Sweden)

    J. Jędryka

    2013-12-01

    Full Text Available Purpose: In presented paper were characterized selected properties of high-temperature superconducting tape 2G HTS SF series - the example of the tape SF12050. Design/methodology/approach: As part of the study smples of tape SF12050 were made. At first made to measure of chemical compsition and compared with manufacturer’s information about that kind of tape. Second step of researcher were research about adhesion of the individual layers of SF12050. After then research was made about tensile strengtht what is the justification utility, as these tapes are subjected to tension at the time of their formation and winding on the transformer core. Findings: As a result of research obtained information on the chemical composition, scratch resistance, adhesion of coating on the tape and about tensile strength. On the last step studies were conducted about critical currents - Ic. Research limitations/implications: These results allow to identify the suitability of these tapes for use on a wide scale - in particular, the winding of the transformer cores. Originality/value: On the basis of studies have demonstrated applications for which the tape may be used SF12050. Given its properties – scratch resistance and tensile strenght reistance, and information about critical current, was indicated best use of that tape for trnasformers production.

  14. Field Dependence of π-Band Superconducting Gap in MgB2 Thin Films from Point-Contact Spectroscopy

    Institute of Scientific and Technical Information of China (English)

    HUANG Yan; XI Xiao-Xing; WANG Yong-Lei; SHAN Lei; JIA Ying; YANG Huan; WEN Hai-Hu; ZHUANG Cheng-Gang; LI Qi; CUI Yi

    2008-01-01

    We present the results of point-contact spectroscopy measurements on high-quality epitaxial MgB2 thin films with injected current along the c-axis. The temperature and field dependences of л-band properties with the field parallel to (H‖) or perpendicular to (H┴ ) the c-axis are investigated in detail. When a magnetic field is applied, either parallel or perpendicular to the c-axis, the density of the quasiparticle state (DOS) of the л-band proliferates quickly with increasing field, while the gap amplitude of the л-band decreases slowly, which is different from the recent theoretical calculations, showing a field dependent competition between the interband scattering and the pair-breaking effects.

  15. Propagation in a waveguide with range-dependent seabed properties.

    Science.gov (United States)

    Holland, Charles W

    2010-11-01

    The ocean environment contains features affecting acoustic propagation that vary on a wide range of time and space scales. A significant body of work over recent decades has aimed at understanding the effects of water column spatial and temporal variability on acoustic propagation. Much less is understood about the impact of spatial variability of seabed properties on propagation, which is the focus of this study. Here, a simple, intuitive expression for propagation with range-dependent boundary properties and uniform water depth is derived. It is shown that incoherent range-dependent propagation depends upon the geometric mean of the seabed plane-wave reflection coefficient and the arithmetic mean of the cycle distance. Thus, only the spatial probability distributions (pdfs) of the sediment properties are required. Also, it is shown that the propagation over a range-dependent seabed tends to be controlled by the lossiest, not the hardest, sediments. Thus, range-dependence generally leads to higher propagation loss than would be expected, due for example to lossy sediment patches and/or nulls in the reflection coefficient. In a few instances, propagation over a range-dependent seabed can be calculated using range-independent sediment properties. The theory may be useful for other (non-oceanic) waveguides.

  16. 28 September 2011 - Canadian Intellectual Property Office Policy, International and Research Office Director K. Georgaras visiting the LHC superconducting magnet test hall with Engineer M. Bajko and Senior Scientists P. Jenni and R. Voss.

    CERN Multimedia

    2011-01-01

    28 September 2011 - Canadian Intellectual Property Office Policy, International and Research Office Director K. Georgaras visiting the LHC superconducting magnet test hall with Engineer M. Bajko and Senior Scientists P. Jenni and R. Voss.

  17. Odd-parity superconductivity in bilayer transition metal dichalcogenides

    Science.gov (United States)

    Nakamura, Yasuharu; Yanase, Youichi

    2017-08-01

    Spin-orbit coupling in transition metal dichalcogenides (TMDCs) causes spin-valley locking, giving rise to unconventional optical, transport, and superconducting properties. In this paper, we propose exotic superconductivity in bilayer group-IV TMDCs by symmetry control. The sublattice-dependent "hidden" spin-orbit coupling arising from local inversion symmetry breaking in the crystal structure may stabilize the odd-parity superconductivity by purely s -wave local pairing interaction. The stability of the odd-parity superconducting state depends on the bilayer stacking. The 2 Hb stacking in MoX2 and WX2 (X =S ,Se) favors the odd-parity superconductivity due to interlayer quantum interference. On the other hand, the odd-parity superconductivity is suppressed by the 2 Ha stacking of NbSe2. Calculating the phase diagram of the tight-binding model derived from first-principles band calculations, we conclude that the intercalated bilayer MoS2 and WS2 are candidates for a new class of odd-parity superconductors by spin-orbit coupling.

  18. Effects of drawing and high-pressure sintering on the superconducting properties of (Ba,K)Fe2As2 powder-in-tube wires

    Science.gov (United States)

    Pyon, Sunseng; Yamasaki, Yuji; Kajitani, Hideki; Koizumi, Norikiyo; Tsuchiya, Yuji; Awaji, Satoshi; Watanabe, Kazuo; Tamegai, Tsuyoshi

    2015-12-01

    The evolution of the superconducting properties of round wires of (Ba,K)Fe2As2 fabricated by the powder-in-tube (PIT) method is systematically studied. After establishing the method to obtain the largest transport critical current density (J c) in round wires using the hot isostatic press technique, we investigated how the transition temperature (T c), J c, and microstructures change at each step of the wire fabrication. Unexpectedly, we find that superconducting properties of the wire core are significantly damaged by the drawing process. Systematic measurements of J c and T c of the core superconductor after each drawing and sintering process clarified the evolution of degradation by the drawing process and recovery by heat treatment.

  19. Enhanced flux pinning properties in superconducting YBa{sub 2}Cu{sub 3}O{sub 7−z} films by a novel chemical doping approach

    Energy Technology Data Exchange (ETDEWEB)

    Wang, W.T., E-mail: wtwang@swjtu.edu.cn [Key Laboratory of Magnetic Levitation and Maglev Trains (Ministry of Education of China), Superconductivity R and D Center (SRDC), Southwest Jiaotong University, Mail Stop 165, Chengdu, Sichuan 610031 (China); Pu, M.H.; Lei, M.; Zhang, H.; Wang, Z. [Key Laboratory of Magnetic Levitation and Maglev Trains (Ministry of Education of China), Superconductivity R and D Center (SRDC), Southwest Jiaotong University, Mail Stop 165, Chengdu, Sichuan 610031 (China); Zhang, H. [Department of Physics, Peking University, Beijing 100871 (China); Cheng, C.H. [Key Laboratory of Magnetic Levitation and Maglev Trains (Ministry of Education of China), Superconductivity R and D Center (SRDC), Southwest Jiaotong University, Mail Stop 165, Chengdu, Sichuan 610031 (China); Superconductivity Research Group, School of Materials Science and Engineering, University of New South Wale, Sydney, 2052 NSW (Australia); Zhao, Y., E-mail: yzhao@swjtu.edu.cn [Key Laboratory of Magnetic Levitation and Maglev Trains (Ministry of Education of China), Superconductivity R and D Center (SRDC), Southwest Jiaotong University, Mail Stop 165, Chengdu, Sichuan 610031 (China); Superconductivity Research Group, School of Materials Science and Engineering, University of New South Wale, Sydney, 2052 NSW (Australia)

    2013-10-15

    Highlights: • Pure and Co-doped YBCO films were prepared by newly-developed chemical method. • The doped films have much denser and smoother surface microstructures. • Significantly enhanced fux-pinning properties have been obtained for dilute Co-doped flm. -- Abstract: Pure and cobalt-doped superconducting YBa{sub 2}Cu{sub 3}O{sub 7−z} (YBCO) films were prepared on (0 0 l) LaAlO{sub 3} substrate by a newly developed polymer-assisted metal organic deposition method. The cobalt-doped YBCO films display much denser and smoother surface microstructures and the superconducting transition temperature T{sub c} spans a small range of 1.7 K with the doping levels. Significantly enhanced flux-pinning properties have been obtained for dilute cobalt-doped film. This may be attributed to the good grain connections and the effective flux pinning centers introduced by cobalt doping.

  20. Frequency-dependent dynamic effective properties of porous materials

    Institute of Scientific and Technical Information of China (English)

    Peijun Wei; Zhuping Huang

    2005-01-01

    The frequency-dependent dynamic effective properties (phase velocity, attenuation and elastic modulus) of porous materials are studied numerically. The coherent plane longitudinal and shear wave equations, which are obtained by averaging on the multiple scattering fields, are used to evaluate the frequency-dependent dynamic effective properties of a porous material. It is found that the prediction of the dynamic effective properties includes the size effects of voids which are not included in most prediction of the traditional static effective properties. The prediction of the dynamic effective elastic modulus at a relatively low frequency range is compared with that of the traditional static effective elastic modulus, and the dynamic effective elastic modulus is found to be very close to the Hashin-Shtrikman upper bound.

  1. Electronic structure and superconductivity of FeSe-related superconductors.

    Science.gov (United States)

    Liu, Xu; Zhao, Lin; He, Shaolong; He, Junfeng; Liu, Defa; Mou, Daixiang; Shen, Bing; Hu, Yong; Huang, Jianwei; Zhou, X J

    2015-05-13

    FeSe superconductors and their related systems have attracted much attention in the study of iron-based superconductors owing to their simple crystal structure and peculiar electronic and physical properties. The bulk FeSe superconductor has a superconducting transition temperature (Tc) of ~8 K and it can be dramatically enhanced to 37 K at high pressure. On the other hand, its cousin system, FeTe, possesses a unique antiferromagnetic ground state but is non-superconducting. Substitution of Se with Te in the FeSe superconductor results in an enhancement of Tc up to 14.5 K and superconductivity can persist over a large composition range in the Fe(Se,Te) system. Intercalation of the FeSe superconductor leads to the discovery of the AxFe2-ySe2 (A = K, Cs and Tl) system that exhibits a Tc higher than 30 K and a unique electronic structure of the superconducting phase. A recent report of possible high temperature superconductivity in single-layer FeSe/SrTiO3 films with a Tc above 65 K has generated much excitement in the community. This pioneering work opens a door for interface superconductivity to explore for high Tc superconductors. The distinct electronic structure and superconducting gap, layer-dependent behavior and insulator-superconductor transition of the FeSe/SrTiO3 films provide critical information in understanding the superconductivity mechanism of iron-based superconductors. In this paper, we present a brief review of the investigation of the electronic structure and superconductivity of the FeSe superconductor and related systems, with a particular focus on the FeSe films.

  2. Hybridization and suppression of the superconductivity in CeFeAsO1-y. Pressure and temperature dependences of the electronic structure

    Energy Technology Data Exchange (ETDEWEB)

    Yamaoka, Hitoshi [Inst. of Physical and Chemical Research (RIKEN), Wako (Japan); Jarrige, Ignace [Japan Atomic Energy Agency (JAEA), Hyogo (Japan); Ikeda-Ohno, Atsushi [Japan Atomic Energy Agency (JAEA), Hyogo (Japan); Tsutsui, Satoshi [Japan Synchrotron Radiation Research Inst., Hyogo (Japan); Lin, Jung-Fu [Univ. of Texas, Austin, TX (United States); Takeshita, Nao [National Inst. of Advanced Industrial Science adn Technology (AIST), Ibaraki (Japan); Transformative Research-Project on Iron Pnictides (TRIP), Tokyo (Japan); Miyazawa, Kiichi [National Inst. of Advanced Industrial Science adn Technology (AIST), Ibaraki (Japan); Transformative Research-Project on Iron Pnictides (TRIP), Tokyo (Japan); Tokyo Univ. of Science, Chiba (Japan); Iyo, Akira [National Inst. of Advanced Industrial Science adn Technology (AIST), Ibaraki (Japan); Transformative Research-Project on Iron Pnictides (TRIP), Tokyo (Japan); Tokyo Univ. of Science, Chiba (Japan); Kito, Hijiri [National Inst. of Advanced Industrial Science adn Technology (AIST), Ibaraki (Japan); Transformative Research-Project on Iron Pnictides (TRIP), Tokyo (Japan); Eisaki, Hiroshi [National Inst. of Advanced Industrial Science adn Technology (AIST), Ibaraki (Japan); Transformative Research-Project on Iron Pnictides (TRIP), Tokyo (Japan); Hiraoka, Nozomu [National Synchrotron Radiation Research Center, Hsinchu (Taiwan); Ishii, Hirofumi [National Synchrotron Radiation Research Center, Hsinchu (Taiwan); Tsuei, Ku-Ding [National Synchrotron Radiation Research Center, Hsinchu (Taiwan)

    2010-09-23

    Pressure and temperature dependence of the electronic structure of superconducting (SC) CeFeAsO1-y and non-SC CeFeAsO1-y have been investigated using two complementary hard x-ray spectroscopic probes at the Ce L3 edge, partial fluorescence yield x-ray absorption spectroscopy and resonant x-ray emission spectroscopy. With increasing pressure, the ratio between the intensity of the peak related to the f0 (Ce4+ ) state and that of the f1 (Ce3+ ) state, I(f0)/I(f1 ), is found to increase continuously for both compounds, indicating a continuous increase in the Ce valence. The valence of non-SC CeFeAsO1-y is found to be slightly higher than that of SC CeFeAsO1-y in the entire pressure and temperature ranges of this study. The valence of CeFeAsO1-y around 6 GPa, where the superconductivity breaks down, is estimated to be ~3.0 , but no change in the valence is observed upon cooling. The dependence of the interatomic distances on the concentration of oxygen vacancies is studied via extended absorption fine structure spectroscopy.

  3. Superconductivity in graphite intercalation compounds

    Energy Technology Data Exchange (ETDEWEB)

    Smith, Robert P. [Cavendish Laboratory, University of Cambridge, Madingley Road, Cambridge CB3 0HE (United Kingdom); Weller, Thomas E.; Howard, Christopher A. [Department of Physics & Astronomy, University College of London, Gower Street, London WCIE 6BT (United Kingdom); Dean, Mark P.M. [Department of Condensed Matter Physics and Materials Science, Brookhaven National Laboratory, Upton, NY 11973 (United States); Rahnejat, Kaveh C. [Department of Physics & Astronomy, University College of London, Gower Street, London WCIE 6BT (United Kingdom); Saxena, Siddharth S. [Cavendish Laboratory, University of Cambridge, Madingley Road, Cambridge CB3 0HE (United Kingdom); Ellerby, Mark, E-mail: mark.ellerby@ucl.ac.uk [Department of Physics & Astronomy, University College of London, Gower Street, London WCIE 6BT (United Kingdom)

    2015-07-15

    Highlights: • Historical background of graphite intercalates. • Superconductivity in graphite intercalates and its place in the field of superconductivity. • Recent developments. • Relevant modeling of superconductivity in graphite intercalates. • Interpretations that pertain and questions that remain. - Abstract: The field of superconductivity in the class of materials known as graphite intercalation compounds has a history dating back to the 1960s (Dresselhaus and Dresselhaus, 1981; Enoki et al., 2003). This paper recontextualizes the field in light of the discovery of superconductivity in CaC{sub 6} and YbC{sub 6} in 2005. In what follows, we outline the crystal structure and electronic structure of these and related compounds. We go on to experiments addressing the superconducting energy gap, lattice dynamics, pressure dependence, and how these relate to theoretical studies. The bulk of the evidence strongly supports a BCS superconducting state. However, important questions remain regarding which electronic states and phonon modes are most important for superconductivity, and whether current theoretical techniques can fully describe the dependence of the superconducting transition temperature on pressure and chemical composition.

  4. Spin polarization dependence of quasiparticle properties in graphene

    OpenAIRE

    Qaiumzadeh, Alireza; Jahanbani, Kh.; Asgari, Reza

    2012-01-01

    We address spin polarization dependence of graphene's Fermi liquid properties quantitatively using a microscopic Random Phase Approximation theory in an interacting spin-polarized Dirac electron system. We show an enhancement of the minority-spin many-body velocity renormalization at fully spin polarization due to reduction in the electron density and consequently increase in the interaction between electrons near the Fermi surface. We also show that the spin dependence of the Fermi velocity ...

  5. Theory of temperature dependent phonon-renormalized properties

    OpenAIRE

    Monserrat, Bartomeu; Conduit, G. J.; Needs, R. J.

    2013-01-01

    We present a general harmonic theory for the temperature dependence of phonon-renormalized properties of solids. Firstly, we formulate a perturbation theory in phonon-phonon interactions to calculate the phonon renormalization of physical quantities. Secondly, we propose two new schemes for extrapolating phonon zero-point corrections from temperature dependent data that improve the accuracy by an order of magnitude compared to previous approaches. Finally, we consider the low-temperature limi...

  6. The Preparation and Properties of Niobium Superconducting Structures Prepared by Electron Beam Evaporation in Uhv

    Science.gov (United States)

    Goodchild, Martin S.

    Available from UMI in association with The British Library. This work has achieved the development of a fabrication method for the realisation of superconductor-insulator -superconductor (SIS) junctions based on niobium thin films with an artificial barrier layer. Such devices are likely to have advantages over lead alloy devices because of the enhanced mechanical and chemical stability. A principal objective was to attempt to exploit the offset mask technology developed by Dolan that has been successfully employed by Davies et.al. in the realisation of lead alloy SIS junction heterodyne mixers. In order to transfer this technology to niobium based devices it is essential that an evaporation method is used to allow shadow formation beneath the offset mask. As a result of the chemical reactivity and the low vapour pressure of niobium, a UHV system has been developed which incorporates an electrostatically focussed electron beam evaporation source. This is capable of providing deposition rates of close to 10A/sec. with a source to substrate distance of 120mm. During deposition the system pressure is below 5 times 10 ^{-9} mbar. These process parameters have been recorded, for a number of depositions, on a specially built data acquisition system controlled by a BBC microcomputer. Such recording allows detailed comparison of conditions which helps in the understanding of differences between the superconducting behaviour of various films. A further extremely important aspect of these real time measurements is that it helps to ensure optimum settings of the focus conditions of the electron beam source. The results of the depositions are extremely encouraging with critical temperatures of between 9.1 and 9.3K being achieved. These results compare well with expected values for bulk niobium. An all-metal offset mask technology has been developed to replace the photo-resist technique pioneered by Dolan. This new method is needed because the photo-resist is not compatible

  7. Influence of the introduction and formation of artificial pinning centers on the transport properties of nanostructured Nb{sub 3}Sn superconducting wires

    Energy Technology Data Exchange (ETDEWEB)

    Da Silva, L B S; Rodrigues, C A; Bormio-Nunes, C; Oliveira, N F Jr; Rodrigues, D Jr, E-mail: lucas_sarno@ppgem.eel.usp.b, E-mail: durval@demar.eel.usp.b [Superconductivity Group, Department of Materials Engineering (DEMAR) Escola de Engenharia de Lorena (EEL), Universidade de Sao Paulo - USP Polo Urbo-Industrial, Gleba AI-6 - PO Box 116 - Lorena, SP (Brazil)

    2009-05-01

    The formation of nanostructures projected to act as pinning centers is presented as a highly promising technique for the transport properties optimization of superconductors. However, due to the necessity of nanometric dimensions of these pinning centers, the heat treatment (HT) profiles must be carefully analyzed. The present work describes a methodology to optimize the HT profiles in respect to diffusion, reaction and formation of the superconducting phases. After the HT, samples were removed for micro structural characterization. Measurements of transport properties were performed to analyze the influence of the introduction of artificial pinning centers (APC) on the superconducting phase and to find the flux pinning mechanism acting in these wires. Fitting the volumetric pinning force vs. applied magnetic field (F{sub p} vs. mu{sub o}H) curves of transport properties, we could determine the type and influence of flux pinning mechanism acting in the global behavior of the samples. It was concluded that the maximum current densities were obtained when normal phases (due to the introduction of the APCs) are the most efficient pinning centers in the global behavior of the samples. The use of HT with profile 220{sup 0}C/100h+575{sup 0}C/50h+650{sup 0}C/100h was found as the best treatment for these nanostructured superconducting wires.

  8. DE GENNES PARAMETER DEPENDENCE ON SUPERCONDUCTING PROPERTIES OF MESOSCOPIC CIRCULAR SECTOR

    Directory of Open Access Journals (Sweden)

    JOSÉ JOSÉ BARBA ORTEGA

    2012-01-01

    Full Text Available Implementamos un algoritmo usando el método de variables de enlace para resolver las ecuaciones Ginzburg Landau dependientes del tiempo en un prisma superconductor con geometría circular. La muestra está rodeada por una pequeña capa de otro superconductor a mayor temperatura crítica y sometida a un campo magnético externo aplicado perpendicular a su plano. Las condiciones de contorno son tomadas en cuenta con la longitud de extrapolación de de Gennes Evaluamos la magnetización, la vorticidad, el primero y tercer campos críticos termodinámicos como función del campo magnético externo y el parámetro . Encontramos que para estas interfaces, el tercer campo crítico termodinámico y la magnetización aumentan grandemente mientras el primer campo crítico permanece prácticamente constante.

  9. Unified picture of the doping dependence of superconducting transition temperatures in alkali metal/ammonia intercalated FeSe

    OpenAIRE

    Guterding, Daniel; Jeschke, Harald O.; Hirschfeld, P. J.; Valenti, Roser

    2014-01-01

    In the recently synthesized Li$_x$(NH$_2$)$_y$(NH$_3$)$_z$Fe$_2$Se$_2$ family of iron chalcogenides a molecular spacer consisting of lithium ions, lithium amide and ammonia separates layers of FeSe. It has been shown that upon variation of the chemical composition of the spacer layer, superconducting transition temperatures can reach $T_c\\sim 44 \\mathrm{K}$, but the relative importance of the layer separation and effective doping to the $T_c$ enhancement is currently unclear. Using state of t...

  10. Characterization of Mechanical Properties of MgB$_2$ Conductor for the Superconducting Link Project at CERN

    CERN Document Server

    Sugano, M; Bartova, B; Bjoerstad, R; Scheuerlein, C; Grasso, G

    2015-01-01

    In the framework of high luminosity upgrade of Large Hadron Collider at CERN, superconducting links are being developed. MgB2 wire is a candidate conductor for use in high-current cables. Mechanical properties of this material are of key importance for the definition of the cable design and operating conditions. In this study, we evaluated the Young's modulus of MgB2 filaments extracted from ex situ processed composite wires. The wires were produced in unit lengths of about 1 km and used in high-current cables. Single fiber tensile test was carried out on filaments composed of MgB2, Nb barrier, and Nb-Ni reaction layer. From the unloading modulus of filament specimens measured with different gauge lengths, the Young's modulus of composite filaments extracted from two different strands was determined to be 114 and 122 GPa at room temperature, respectively. By using the rule-of-mixture, the Young's modulus of MgB2 was estimated to be lower than that reported for highly dense MgB2 bulks. The reason for such diff...

  11. Superconducting electronics

    NARCIS (Netherlands)

    Rogalla, Horst

    1994-01-01

    During the last decades superconducting electronics has been the most prominent area of research for small scale applications of superconductivity. It has experienced quite a stormy development, from individual low frequency devices to devices with high integration density and pico second switching

  12. AlN Bandgap Temperature Dependence from its Optical Properties

    Science.gov (United States)

    2008-06-07

    AlN bandgap temperature dependence from its optical properties E. Silveira a,, J.A. Freitas b, S.B. Schujman c, L.J. Schowalter c a Depto. de Fisica ...range. The energy gap in semiconductors in general changes due to contributions from the electron–phonon interaction and due to the lattice thermal

  13. CONVERGENCE PROPERTIES OF THE DEPENDENT PRP CONJUGATE GRADIENT METHODS

    Institute of Scientific and Technical Information of China (English)

    Shujun LIAN; Changyu WANG; Lixia CAO

    2006-01-01

    In this paper, a new region of βκ with respect to βPRPκ is given. With two Armijo-type line searches, the authors investigate the global convergence properties of the dependent PRP conjugate gradient methods, which extend the global convergence results of PRP conjugate gradient method proved by Grippo and Lucidi (1997) and Dai and Yuan (2002).

  14. Transport and superconducting properties of RNi2B2C (R=Y,nLu) single crystals

    Science.gov (United States)

    Rathnayaka, K. D. D.; Bhatnagar, A. K.; Parasiris, A.; Naugle, D. G.; Canfield, P. C.; Cho, B. K.

    1997-04-01

    The in-plane resistivity, in-plane absolute thermopower, and upper critical field measurements are reported for single-crystal samples of YNi2B2C and LuNi2B2C superconductors. The in-plane resistivity shows metallic behavior and varies approximately linearly with temperature near room temperature (RT) but shows nearly quadratic behavior in temperature at low temperatures. The YNi2B2C and LuNi2B2C single-crystal samples exhibit large transverse magnetoresistance (~6-8 % at 45 kOe) in the ab plane. The absolute thermopower S(T) is negative from RT to the superconducting transition temperature Tc. Its magnitude at RT is a few times of the value for a typical good metal. S(T) is approximately linear in temperature between ~150 K and RT. Extrapolation to T=0 gives large intercepts (few μV/K) for both samples suggesting the presence of a much larger 'knee' than would be expected from electron-phonon interaction renormalization effects. The upper critical fields for H parallel and perpendicular to the c axis and the superconducting parameters derived from it do not show any anisotropy for the YNi2B2C single-crystal samples in agreement with magnetization and torque magnetometry measurements, but a small anisotropy is observed for the LuNi2B2C single crystals. The analysis shows that these are moderately strong-coupling type-II superconductors (similar to the A-15 compounds) with a value of the electron-phonon coupling parameter λ(0) approximately equal to 1.2 for YNi2B2C and 1.0 for LuNi2B2C, the Ginzburg-Landau coherence length ξ(0) approximately equal to 70 Å, and Hc2(0)~60-70 kOe. The temperature dependence of the upper critical field shows a positive curvature near Tc in disagreement with the Werthamer, Helfand, Hohenberg, and Maki (WHHM) theory but in agreement with a recent solution of the Gor'kov equation using a basis formed by Landau levels (Bahcall); however, the data show a severe disagreement between the observed low-temperature behavior of Hc2(T) and that

  15. Process depending morphology and resulting physical properties of TPU

    Energy Technology Data Exchange (ETDEWEB)

    Frick, Achim, E-mail: achim.frick@hs-aalen.de; Spadaro, Marcel, E-mail: marcel.spadaro@hs-aalen.de [Institute of Polymer Science and Processing (iPSP), Aalen University (Germany)

    2015-12-17

    Thermoplastic polyurethane (TPU) is a rubber like material with outstanding properties, e.g. for seal applications. TPU basically provides high strength, low frictional behavior and excellent wear resistance. Though, due to segmented structure of TPU, which is composed of hard segments (HSs) and soft segments (SSs), physical properties depend strongly on the morphological arrangement of the phase separated HSs at a certain ratio of HSs to SSs. It is obvious that the TPU deforms differently depending on its bulk morphology. Basically, the morphology can either consist of HSs segregated into small domains, which are well dispersed in the SS matrix or of few strongly phase separated large size HS domains embedded in the SS matrix. The morphology development is hardly ruled by the melt processing conditions of the TPU. Depending on the morphology, TPU provides quite different physical properties with respect to strength, deformation behavior, thermal stability, creep resistance and tribological performance. The paper deals with the influence of important melt processing parameters, such as temperature, pressure and shear conditions, on the resulting physical properties tested by tensile and relaxation experiments. Furthermore the morphology is studied employing differential scanning calorimeter (DSC), transmission light microscopy (TLM), scanning electron beam microscopy (SEM) and transmission electron beam microscopy (TEM) investigations. Correlations between processing conditions and resulting TPU material properties are elaborated. Flow and shear simulations contribute to the understanding of thermal and flow induced morphology development.

  16. Temperature Induced Stress Dependent Photoluminescence Properties of Nanocrystallite Zinc Oxide

    Directory of Open Access Journals (Sweden)

    V. Kumar

    2011-01-01

    Full Text Available In this paper, Temperature induced stress dependent structural, optical and photoluminescence properties of nanoscrysllites ZnO (nc-ZnO films are reported. It is seen that crystallite size, band gap and PL intensity of nc-ZnO are strongly dependent on stress. Large compressive stress has been observed at temperature 350-400 °C while minimum stress obtained at temperature 450 °C. A small amount of expensive stress is obtained at temperature 500 and 500 °C. The surface topography of the nc-ZnO films has been studied using atomic force microscopy. The optical band gap of nc-ZnO has been decreased from 3.25 to 3.23 eV as a function of temperature induced stress. The luminescence property is dependent on stress of nc-ZnO films.

  17. Superconducting properties of 3D low-density TI-bipolaron gas

    OpenAIRE

    Lakhno, V.D.

    2015-01-01

    Consideration is given to thermodynamical properties of a three-dimensional Bose-condensate of translation-invariant bipolarons (TI-bipolarons). The critical temperature of transition, energy, heat capacity and the transition heat of TI-bipolaron gas are calculated. The results obtained are used to explain experiments on high-temperature superconductors.

  18. Magnetization-orientation dependence of the superconducting transition in AF-F/S/F and S/F/F-AF type spin valve heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Zdravkov, Vladimir [Institut fuer Physik, Universitaet Augsburg, D-86159 Augsburg (Germany); D. Ghitsu Institute of the Electronic Engineering and Nanotechnologies ASM, MD 2028 Kishiniev (Moldova, Republic of); Lenk, Daniel; Kehrle, Jan; Obermeier, Guenter; Ullrich, Aladin; Mueller, Claus; Krug von Nidda, Hans-Albrecht; Horn, Siegfried; Tidecks, Reinhard [Institut fuer Physik, Universitaet Augsburg, D-86159 Augsburg (Germany); Morari, Roman; Sidorenko, Anatoli [D. Ghitsu Institute of the Electronic Engineering and Nanotechnologies ASM, MD 2028 Kishiniev (Moldova, Republic of); Tagirov, Lenar [Solid State Physics Department, Kazan Federal University, 420008 Kazan (Russian Federation)

    2013-07-01

    In F/S/F spin valve core structures, i.e. Cu{sub 41}Ni{sub 59}/Nb/Cu{sub 41}Ni{sub 59} systems, deposited on an antiferromagnetic CoO{sub x} layer, or with such a layer on top, critical temperature oscillations and reentrant superconductivity are observed, which can be well described by the theory. Introducing a Co sub-layer yields exchange bias effects, which influence the magnetic field dependence of the superconducting transition. Aging effects are studied, which especially alter the transparency of the lower F/S interface, resulting in a change of the behavior of the transition temperature as a function of the ferromagnetic layer thickness from extinction, over reentrant, to oscillating. The results are discussed in comparison to the S/F/F-AF triplet spin valve effect in a Nb/Cu{sub 41}Ni{sub 59}/nc-Nb/Co/CoO{sub x} system, where nc-Nb acts as a normal conducting spacer to decouple the ferromagnetic layers.

  19. Field-Angle-Dependent Low-Energy Excitations around a Vortex in the Superconducting Topological Insulator CuxBi2Se3

    Science.gov (United States)

    Nagai, Yuki

    2014-06-01

    We study the quasiparticle excitations around a single vortex in the superconducting topological insulator CuxBi2Se3, focusing on a superconducting state with point nodes. Inspired by the recent Knight shift measurements, we propose two ways to detect the positions of point nodes, using an explicit formula of the density of states with Kramer-Pesch approximation in the quasiclassical treatment. The zero-energy local density of states around a vortex parallel to the c-axis has a twofold shape and splits along the nodal direction with increasing energy; these behaviors can be detected by the scanning tunneling microscopy. An angular dependence of the density of states with a rotating magnetic field on the a-b plane has deep minima when the magnetic field is parallel to the directions of point nodes, which can be detected by angular-resolved heat capacity and thermal conductivity measurements. All the theoretical predictions are detectable via standard experimental techniques in magnetic fields.

  20. High-Pressure Study of the Ground- and Superconducting-State Properties of CeAu2Si2

    Science.gov (United States)

    Scheerer, Gernot W.; Giriat, Gaétan; Ren, Zhi; Lapertot, Gérard; Jaccard, Didier

    2017-06-01

    The pressure-temperature phase diagram of the new heavy-fermion superconductor CeAu2Si2 is markedly different from those studied previously. Indeed, superconductivity emerges not on the verge but deep inside the magnetic phase, and mysteriously Tc increases with the strengthening of magnetism. In this context, we have carried out ac calorimetry, resistivity, and thermoelectric power measurements on a CeAu2Si2 single crystal under high pressure. We uncover a strong link between the enhancement of superconductivity and quantum-critical-like features in the normal-state resistivity. Non-Fermi-liquid behavior is observed around the maximum of superconductivity and enhanced scattering rates are observed close to both the emergence and the maximum of superconductivity. Furthermore we observe signatures of pressure- and temperature-driven modifications of the magnetic structure inside the antiferromagnetic phase. A comparison of the features of CeAu2Si2 and its parent compounds CeCu2Si2 and CeCu2Ge2 plotted as function of the unit-cell volume leads us to propose that critical fluctuations of a valence crossover play a crucial role in the superconducting pairing mechanism. Our study illustrates the complex interplay between magnetism, valence fluctuations, and superconductivity.

  1. Effect of substitution of Ce on superconducting properties of Bi1.7Pb0.3Sr2Ca2-CeCu3O10+ system

    Indian Academy of Sciences (India)

    R R Kothawale; B N Dole; S S Shah

    2002-05-01

    We have investigated the superconducting properties of the Bi1.7Pb0.3Sr2Ca2-CeCu3O10+ system with = 0.00, 0.02, 0.04, 0.08 and 0.1 by X-ray diffraction and magnetic susceptibility. The substitution of Ce for Ca has been found to drastically change the superconducting properties of the system. X-ray diffraction studies on these compounds indicate decrease in the -parameter with increased substitution of Ce at Ca site and volume fraction of high c(2 : 2 : 2 : 3) phase decreases and low c phase increases. The magnetic susceptibility of this compound shows that the diamagnetic on set superconducting transition temperature (onset) varies from 109 K to 51 K for =0.00, 0.02, 0.04, 0.08 and 0.1. These results suggest the possible existence of Ce in a tetravalent state rather than a trivalent state in this system; that is, Ca2+ → Ce4+ replacement changes the hole carrier concentration. Hole filling is the cause of lowering c of the system.

  2. Phase slips in superconducting weak links

    Energy Technology Data Exchange (ETDEWEB)

    Kimmel, Gregory; Glatz, Andreas; Aranson, Igor S.

    2017-01-01

    Superconducting vortices and phase slips are primary mechanisms of dissipation in superconducting, superfluid, and cold-atom systems. While the dynamics of vortices is fairly well described, phase slips occurring in quasi-one- dimensional superconducting wires still elude understanding. The main reason is that phase slips are strongly nonlinear time-dependent phenomena that cannot be cast in terms of small perturbations of the superconducting state. Here we study phase slips occurring in superconducting weak links. Thanks to partial suppression of superconductivity in weak links, we employ a weakly nonlinear approximation for dynamic phase slips. This approximation is not valid for homogeneous superconducting wires and slabs. Using the numerical solution of the time-dependent Ginzburg-Landau equation and bifurcation analysis of stationary solutions, we show that the onset of phase slips occurs via an infinite period bifurcation, which is manifested in a specific voltage-current dependence. Our analytical results are in good agreement with simulations.

  3. Superconductivity-like phenomena in an ferrimagnetic endohedral fullerene with diluted magnetic surface

    Science.gov (United States)

    Kantar, Ersin

    2017-09-01

    The hysteretic properties of a Ising-type endohedral fullerene (EF) with a doped magnetic spin-1/2 particle confined within a spherical cage (by diluted magnetic spin-1 particles) are investigated by using the effective-field theory with correlations. The extrinsic and intrinsic parameters dependencies of the magnetic hysteresis curves and superconductivity-like phenomena in the Ising-type EF system have investigated. We have reported that doped magnetic core atom is chiefly responsible of the occurrence of the superconductivity-like phenomena in the system. Moreover, three superconductivity series have been presented by the temperature, surface composition and crystal field.

  4. The Environmental Dependence of Galaxy Properties at z=2

    CERN Document Server

    Tanaka, Masayuki; Venemans, Bram; Kurk, Jaron

    2010-01-01

    We report on the environmental dependence of galaxy properties at z=2.15. We construct multi-band photometric data sets in the (proto-)cluster PKS1138-26 field and in the GOODS field. We then fit spectral energy distributions of the galaxies with model templates generated with the latest stellar population synthesis code and derive physical properties of galaxies from the fits. To quantify the environmental dependence of galaxy properties, a special care is taken of systematic errors -- we use data sets that have almost the same wavelength samplings, use the same code to fit SEDs with the same set of templates, and compare relative differences between the two samples. We find that the PKS1138 galaxies have similar ages, shorter star formation time scales, lower star formation rates, and weaker dust extinction compared to the GOODS galaxies at z~2. This trend is similar to that observed locally, suggesting that the environmental dependence of galaxy properties is already partly in place as early as z=2.15. We ...

  5. High-temperature superconductivity in space-charge regions of lanthanum cuprate induced by two-dimensional doping

    Science.gov (United States)

    Baiutti, F.; Logvenov, G.; Gregori, G.; Cristiani, G.; Wang, Y.; Sigle, W.; van Aken, P. A.; Maier, J.

    2015-10-01

    The exploitation of interface effects turned out to be a powerful tool for generating exciting material properties. Such properties include magnetism, electronic and ionic transport and even superconductivity. Here, instead of using conventional homogeneous doping to enhance the hole concentration in lanthanum cuprate and achieve superconductivity, we replace single LaO planes with SrO dopant planes using atomic-layer-by-layer molecular beam epitaxy (two-dimensional doping). Electron spectroscopy and microscopy, conductivity measurements and zinc tomography reveal such negatively charged interfaces to induce layer-dependent superconductivity (Tc up to 35 K) in the space-charge zone at the side of the planes facing the substrate, where the strontium (Sr) profile is abrupt. Owing to the growth conditions, the other side exhibits instead a Sr redistribution resulting in superconductivity due to conventional doping. The present study represents a successful example of two-dimensional doping of superconducting oxide systems and demonstrates its power in this field.

  6. Nonlinearities in Microwave Superconductivity

    OpenAIRE

    Ledenyov, Dimitri O.; Ledenyov, Viktor O.

    2012-01-01

    The research is focused on the modeling of nonlinear properties of High Temperature Superconducting (HTS) thin films, using Bardeen, Cooper, Schrieffer and Lumped Element Circuit theories, with purpose to enhance microwave power handling capabilities of microwave filters and optimize design of microwave circuits in micro- and nano- electronics.

  7. Electric and magnetic properties measurement and analysis of a conventional and a superconducting power transformer

    Science.gov (United States)

    Figueira, P.; Pronto, A. G.; Vilhena, N.; Pina, J. M.

    2014-05-01

    Power transformers based on High Temperature Superconductors (HTS) technology have revealed potential for several practical applications, offering economic, environmental and operational benefits. In this work, two 650 VA single-phase transformers prototypes were developed, tested and characterized: a conventional one, using copper windings, and another with the same primary copper winding, but with a secondary winding made of HTS BSCCO tape. The two prototypes were compared regarding magnetic properties, losses, electric parameters and efficiency, and the results are presented and interpreted. Also, several measures to determine AC critical current of the HTS tape were made. The results are compared with DC critical current for the same tape.

  8. Doping - Dependent irreversible magnetic properties of Ba(Fe 1-xCo x) 2As 2 single crystals

    Science.gov (United States)

    Prozorov, R.; Tanatar, M. A.; Blomberg, E. C.; Prommapan, P.; Gordon, R. T.; Ni, N.; Bud'ko, S. L.; Canfield, P. C.

    2009-05-01

    We discuss the irreversible magnetic properties of self-flux grown Ba(Fe 1-xCo x) 2As 2 single crystals for a wide range of concentrations covering the whole phase diagram from the underdoped to the overdoped regime, x = 0.038, 0.047, 0.058, 0.071, 0.074, 0.10, 0.106 and 0.118. Samples were characterized by a magneto-optical method and show excellent spatial uniformity of the superconducting state down to at least the micrometer scale. The in-plane properties are isotropic, as expected for the tetragonal symmetry, and the overall behavior closely follows classical Bean model of the critical state. The field-dependent magnetization exhibits second peak at a temperature and doping - dependent magnetic field, H p( T, x). The evolution of this fishtail feature with doping is discussed. In particular we find that H p, measured at the same reduced temperature for different x, is a unique monotonic function of the superconducting transition temperature, T c( x), across all dopings. Magnetic relaxation is time-logarithmic and unusually fast. Similar to cuprates, there is an apparent crossover from collective elastic to plastic flux creep above H p. At high fields, the field dependence of the relaxation rate becomes doping independent. We discuss our results in the framework of the weak collective pinning and show that vortex physics in iron-based pnictide crystals is much closer to high- T c cuprates than to conventional s-wave (including MgB 2) superconductors.

  9. Mechanical properties as an indicator of interstitials in niobium for superconducting accelerator cavities

    Energy Technology Data Exchange (ETDEWEB)

    Ricker, R. E., E-mail: richard.ricker@nist.gov; Pitchure, D. J., E-mail: david.pitchure@nist.gov [Materials Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, MD 20899, US (United States); Myneni, G. R., E-mail: rao@jlab.org [Thomas Jefferson National Accelerator Facility, Newport News, VA 23606, US (United States)

    2015-12-04

    A preliminary investigation was conducted into the feasibility of using simple mechanical properties experiments to evaluate interstitial impurity uptake from processing environments. Two types of tests were examined: tensile tests and complex modulus measurements using a dynamic mechanical analyzer (DMA). For the tensile tests, samples were cut from a single crystal of niobium, with the same orientation, and then prepared following different procedures. Significant differences were observed during tensile tests, with yielding strength and strain-to-failure clearly related to interstitial uptake. When the strain rate was reduced by an order of magnitude, the strain-to-failure was reduced by 18 % indicating that interstitial hydrogen is responsible for this behavior. For the complex modulus measurement, polycrystalline samples from different locations of two different ingots were examined at a frequency of 1.0 Hz while the temperature was increased at the rate of 1.0 °C per minute. Anaelastic peaks were found for C, N, and O in all samples, but the lower limit of the system did not allow for detection of a peak for H. It is concluded that mechanical properties could be developed as a measurement tool to guide the development of processing methods for producing reduced interstitial content material, but additional research, and uncertainty analysis, is required for these tools to be reliable in this application.

  10. Substrate dependent structural and magnetic properties of pulsed laser deposited Fe3O4 thin films.

    Science.gov (United States)

    Goyal, Rajendra N; Kaur, Davinder; Pandey, Ashish K

    2010-12-01

    Nanocrystalline iron oxide thin films have been deposited on various substrates such as quartz, MgO(100), and Si(100) by pulsed laser deposition technique using excimer KrF laser (248 nm). The orientations, crystallite size and lattice parameters were studied using X-ray diffraction. The XRD results show that the films deposited on MgO and Si substrates are highly oriented and show only (400) and (311) reflections respectively. On the other hand, the orientation of the films deposited on quarts substrate changed from (311) to (400) with an increase in the substrate temperature from 400 degrees C to 600 degrees C, indicating thereby that the film growth direction is highly affected with nature of substrate and substrate temperature. The surface morphology of the deposited films was studied using Atomic Force Microscopy (AFM) and spherical ball like regular features of nanometer size grains were obtained. The magnetic properties were studied by Superconducting Quantum Interference Device (SQUID) magnetometer in the magnetic field +/- 6 Tesla. The magnetic field dependent magnetization (M-H) curves of all the Fe3O4 thin films measured at 5 K and 300 K show the ferrimagnetic nature. The electrochemical sensing of dopamine studied for these films shows that the film deposited on MgO substrate can be used as a sensing electrode.

  11. AC/RF Superconductivity

    Energy Technology Data Exchange (ETDEWEB)

    Ciovati, Gianluigi [JLAB

    2015-02-01

    This contribution provides a brief introduction to AC/RF superconductivity, with an emphasis on application to accelerators. The topics covered include the surface impedance of normal conductors and superconductors, the residual resistance, the field dependence of the surface resistance, and the superheating field.

  12. Temperature Dependence of Photoelectrical Properties of Single Selenium Nanowires

    Directory of Open Access Journals (Sweden)

    Liu Li-Ping

    2010-01-01

    Full Text Available Abstract Influence of temperature on photoconductivity of single Se nanowires has been studied. Time response of photocurrent at both room temperature and low temperature suggests that the trap states play an important role in the photoelectrical process. Further investigations about light intensity dependence on photocurrent at different temperatures reveal that the trap states significantly affect the carrier generation and recombination. This work may be valuable for improving the device optoelectronic performances by understanding the photoelectrical properties.

  13. Depth-Dependent Temporal Response Properties in Core Auditory Cortex

    OpenAIRE

    Christianson, G. Björn; Sahani, Maneesh; Linden, Jennifer F.

    2011-01-01

    The computational role of cortical layers within auditory cortex has proven difficult to establish. One hypothesis is that interlaminar cortical processing might be dedicated to analyzing temporal properties of sounds; if so, then there should be systematic depth-dependent changes in cortical sensitivity to the temporal context in which a stimulus occurs. We recorded neural responses simultaneously across cortical depth in primary auditory cortex and anterior auditory field of CBA/Ca mice, an...

  14. Magnetic and Superconducting Materials at High Pressures

    Energy Technology Data Exchange (ETDEWEB)

    Struzhkin, Viktor V. [Carnegie Inst. of Washington, Washington, DC (United States)

    2015-03-24

    The work concentrates on few important tasks in enabling techniques for search of superconducting compressed hydrogen compounds and pure hydrogen, investigation of mechanisms of high-Tc superconductivity, and exploring new superconducting materials. Along that route we performed several challenging tasks, including discovery of new forms of polyhydrides of alkali metal Na at very high pressures. These experiments help us to establish the experimental environment that will provide important information on the high-pressure properties of hydrogen-rich compounds. Our recent progress in RIXS measurements opens a whole field of strongly correlated 3d materials. We have developed a systematic approach to measure major electronic parameters, like Hubbard energy U, and charge transfer energy Δ, as function of pressure. This technique will enable also RIXS studies of magnetic excitations in iridates and other 5d materials at the L edge, which attract a lot of interest recently. We have developed new magnetic sensing technique based on optically detected magnetic resonance from NV centers in diamond. The technique can be applied to study superconductivity in high-TC materials, to search for magnetic transitions in strongly correlated and itinerant magnetic materials under pressure. Summary of Project Activities; development of high-pressure experimentation platform for exploration of new potential superconductors, metal polyhydrides (including newly discovered alkali metal polyhydrides), and already known superconductors at the limit of static high-pressure techniques; investigation of special classes of superconducting compounds (high-Tc superconductors, new superconducting materials), that may provide new fundamental knowledge and may prove important for application as high-temperature/high-critical parameter superconductors; investigation of the pressure dependence of superconductivity and magnetic/phase transformations in 3d transition metal compounds, including

  15. Development of Superconducting Strang and Cable with Improved Properties for Use in SSC Magnets

    Energy Technology Data Exchange (ETDEWEB)

    Scanlan, R.M.

    1989-02-01

    The critical current requirement for the NbTi superconductor strand was set at 2750 A/mm{sup 2} (5 T, 4.2 K) in the SSC Conceptual Design, compared with a value of 1800 A/mm{sup 2} which was specified for the strand used in the Tevatron dipoles. In addition, a filament diameter of 5 {micro}m, instead of the 9 {micro}m diameter used in the Tevatron. was chosen to reduce field distonion at injection. In order to meet the requirements for field homogeneity, the dimensional requirements for both strand and cable were also tightened. The technical solutions employed to achieve these improved properties and the resulting specifications will be discussed.

  16. Interplay between magnetism and superconductivity in iron-chalcogenide superconductors: crystal growth and characterizations

    Energy Technology Data Exchange (ETDEWEB)

    Wen Jinsheng; Birgeneau, R J [Physics Department, University of California, Berkeley, CA 94720 (United States); Xu Guangyong; Gu Genda; Tranquada, J M, E-mail: jinshengwen@berkeley.edu, E-mail: jtran@bnl.gov [Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, NY 11973 (United States)

    2011-12-15

    In this review, we present a summary of results on single crystal growth of two types of iron-chalcogenide superconductors, Fe{sub 1+y}Te{sub 1-x}Se{sub x} (11), and A{sub x}Fe{sub 2-y}Se{sub 2} (A = K, Rb, Cs, Tl, Tl/K, Tl/Rb), using Bridgman, zone-melting, vapor self-transport and flux techniques. The superconducting and magnetic properties (the latter gained mainly from neutron scattering measurements) of these materials are reviewed to demonstrate the connection between magnetism and superconductivity. It will be shown that for the 11 system, while static magnetic order around the reciprocal lattice position (0.5, 0) competes with superconductivity, spin excitations centered around (0.5, 0.5) are closely coupled to the materials' superconductivity; this is made evident by the strong correlation between the spectral weight around (0.5, 0.5) and the superconducting volume fraction. The observation of a spin resonance below the superconducting temperature, T{sub c}, and the magnetic-field dependence of the resonance emphasize the close interplay between spin excitations and superconductivity, similar to cuprate superconductors. In A{sub x}Fe{sub 2-y}Se{sub 2}, superconductivity with T{sub c} {approx} 30 K borders an antiferromagnetic insulating phase; this is closer to the behavior observed in the cuprates but differs from that in other iron-based superconductors.

  17. Interplay between magnetism and superconductivity in iron-chalcogenide superconductors: crystal growth and characterizations

    Science.gov (United States)

    Wen, Jinsheng; Xu, Guangyong; Gu, Genda; Tranquada, J. M.; Birgeneau, R. J.

    2011-12-01

    In this review, we present a summary of results on single crystal growth of two types of iron-chalcogenide superconductors, Fe1+yTe1-xSex (11), and AxFe2-ySe2 (A = K, Rb, Cs, Tl, Tl/K, Tl/Rb), using Bridgman, zone-melting, vapor self-transport and flux techniques. The superconducting and magnetic properties (the latter gained mainly from neutron scattering measurements) of these materials are reviewed to demonstrate the connection between magnetism and superconductivity. It will be shown that for the 11 system, while static magnetic order around the reciprocal lattice position (0.5, 0) competes with superconductivity, spin excitations centered around (0.5, 0.5) are closely coupled to the materials' superconductivity; this is made evident by the strong correlation between the spectral weight around (0.5, 0.5) and the superconducting volume fraction. The observation of a spin resonance below the superconducting temperature, Tc, and the magnetic-field dependence of the resonance emphasize the close interplay between spin excitations and superconductivity, similar to cuprate superconductors. In AxFe2-ySe2, superconductivity with Tc ~ 30 K borders an antiferromagnetic insulating phase; this is closer to the behavior observed in the cuprates but differs from that in other iron-based superconductors.

  18. Conductive magnetorheological elastomer: fatigue dependent impedance-mechanic coupling properties

    Science.gov (United States)

    Wang, Yu; Xuan, Shouhu; Ge, Lin; Wen, Qianqian; Gong, Xinglong

    2017-01-01

    This work investigated the relationship between the impedance properties and dynamic mechanical properties of magnetorheological elastomers (MREs) under fatigue loading. The storage modulus and the impedance properties of MREs were highly influenced by the pressure and magnetic field. Under the same experimental condition, the two characteristics exhibited similar fatigue dependent change trends. When pressure was smaller than 10 N, the capacitance of MRE could be divided into four sections with the increase of the cyclic numbers. The relative equivalent circuit model was established to fit the experimental results of the impedance spectra. Each parameter of circuit element reflected the change of fatigue loading, relative microstructure of MRE, MRE-electrode interface layer, respectively. Based on the above analysis, the real-time and nondestructive impedance method was demonstrated to be high potential on detecting the fatigue of the MRE device.

  19. Structural, elastic and electronic properties of superconducting anti-perovskites MgCNi{sub 3}, ZnCNi{sub 3} and CdCNi{sub 3} from first principles

    Energy Technology Data Exchange (ETDEWEB)

    Shein, I.R.; Bannikov, V.V. [Institute of Solid State Chemistry, Ural Branch of the Russian Academy of Sciences, 620041, Ekaterinburg (Russian Federation); Ivanovskii, A.L. [Institute of Solid State Chemistry, Ural Branch of the Russian Academy of Sciences, 620041, Ekaterinburg (Russian Federation)], E-mail: ivanovskii@ihim.uran.ru

    2008-01-01

    First principle total energy calculations using the full potential linearized augmented plane wave (FP-LAPW) method with the generalized gradient approximation (GGA) for the exchange-correlation potential were performed to investigate the systematic trends for structural, elastic and electronic properties of the family of superconducting anti-perovskites MCNi{sub 3} depending from the type of M cations (M are Mg, Zn and Cd). In result the optimized lattice parameters, independent elastic constants (C{sub 11}, C{sub 12} and C{sub 44}), bulk modulus B, compressibility {beta}, shear modulus G and tetragonal shear modulus G' are evaluated. Further, for the first time the numerical estimates of a set of elastic parameters (bulk and shear modulus, Young's modulus Y, Poisson's ratio ({nu}), Lame's coefficients ({mu}, {lambda})) of the polycrystalline superconducting MCNi{sub 3} ceramics (in framework of the Voigt-Reuss-Hill approximation) were performed. Besides, the band structures, densities of states (DOS), total and site-projected l-decomposed DOS at the Fermi level, the shapes of the Fermi surfaces, the Sommerfeld's coefficients and the molar Pauli paramagnetic susceptibility for these anti-perovskites were obtained and analyzed in comparison with the available theoretical and experimental data.

  20. Temperature-Dependent Dielectric Properties of Al/Epoxy Nanocomposites

    Science.gov (United States)

    Wang, Zijun; Zhou, Wenying; Sui, Xuezhen; Dong, Lina; Cai, Huiwu; Zuo, Jing; Chen, Qingguo

    2016-06-01

    Broadband dielectric spectroscopy was carried out to study the transition in electrical properties of Al/epoxy nanocomposites over the frequency range of 1-107 Hz and the temperature range of -20°C to 200°C. The dielectric permittivity, dissipation factor, and electrical conductivity of the nanocomposites increased with temperature and showed an abrupt increase around the glass transition temperature ( T g). The results clearly reveal an interesting transition of the electrical properties with increasing temperature: insulator below 70°C, conductor at about 70°C. The behavior of the transition in electrical properties of the nanocomposites was explored at different temperatures. The presence of relaxation peaks in the loss tangent and electric modulus spectra of the nanocomposites confirms that the chain segmental dynamics of the polymer is accompanied by the absorption of energy given to the system. It is suggested that the temperature-dependent transition of the electric properties in the nanocomposite is closely associated with the α-relaxation. The large increase in the dissipation factor and electric conductivity depends on the direct current conduction of thermally activated charge carriers resulting from the epoxy matrix above T g.

  1. Superconductivity in a chiral nanotube

    Science.gov (United States)

    Qin, F.; Shi, W.; Ideue, T.; Yoshida, M.; Zak, A.; Tenne, R.; Kikitsu, T.; Inoue, D.; Hashizume, D.; Iwasa, Y.

    2017-02-01

    Chirality of materials are known to affect optical, magnetic and electric properties, causing a variety of nontrivial phenomena such as circular dichiroism for chiral molecules, magnetic Skyrmions in chiral magnets and nonreciprocal carrier transport in chiral conductors. On the other hand, effect of chirality on superconducting transport has not been known. Here we report the nonreciprocity of superconductivity--unambiguous evidence of superconductivity reflecting chiral structure in which the forward and backward supercurrent flows are not equivalent because of inversion symmetry breaking. Such superconductivity is realized via ionic gating in individual chiral nanotubes of tungsten disulfide. The nonreciprocal signal is significantly enhanced in the superconducting state, being associated with unprecedented quantum Little-Parks oscillations originating from the interference of supercurrent along the circumference of the nanotube. The present results indicate that the nonreciprocity is a viable approach toward the superconductors with chiral or noncentrosymmetric structures.

  2. Hierarchic Models of Turbulence, Superfluidity and Superconductivity

    CERN Document Server

    Kaivarainen, A

    2000-01-01

    New models of Turbulence, Superfluidity and Superconductivity, based on new Hierarchic theory, general for liquids and solids (physics/0102086), have been proposed. CONTENTS: 1 Turbulence. General description; 2 Mesoscopic mechanism of turbulence; 3 Superfluidity. General description; 4 Mesoscopic scenario of fluidity; 5 Superfluidity as a hierarchic self-organization process; 6 Superfluidity in 3He; 7 Superconductivity: General properties of metals and semiconductors; Plasma oscillations; Cyclotron resonance; Electroconductivity; 8. Microscopic theory of superconductivity (BCS); 9. Mesoscopic scenario of superconductivity: Interpretation of experimental data in the framework of mesoscopic model of superconductivity.

  3. Spin polarization dependence of quasiparticle properties in graphene

    Science.gov (United States)

    Qaiumzadeh, A.; Jahanbani, Kh.; Asgari, Reza

    2012-06-01

    We address spin polarization dependence of graphene's Fermi liquid properties quantitatively using a microscopic random phase approximation theory in an interacting spin-polarized Dirac electron system. We show an enhancement of the minority-spin many-body velocity renormalization at fully spin polarization due to reduction in the electron density and consequently increase in the interaction between electrons near the Fermi surface. We also show that the spin dependence of the Fermi velocity in the chiral Fermi systems is different than that in a conventional two-dimensional electron liquid. In addition, we show that the ratio of the majority-to-minority-spin lifetime is smaller than unity and related directly to the polarization and electron energy. The spin-polarization dependence of the carrier Fermi velocity is of significance in various spintronic applications.

  4. Fabrication and superconducting properties of nano-SiC doped MgB2 tapes

    Institute of Scientific and Technical Information of China (English)

    ZHANG XianPing; MA YanWei; GAO ZhaoShun; YU ZhengGuang; WANG DongLiang; WATANABE K; GUO JianDong

    2007-01-01

    Nano-SiC doped MgB2 tapes were prepared by the in situ powder-in-tube method. Heat treatment was performed at 650℃ for 1 h. XRD data indicate that SiC particles had reacted with the MgB2 during sintering process. MgB2 core seemed to be denser after SiC doping, and the critical temperature was slightly depressed. The critical current density Jc of the SiC doped tapes was significantly enhanced in magnetic fields up to 14 T compared to the undoped ones. For the 5% SiC doped samples, Jc was increased by a factor of 32 at 4.2 K, 10 T. The enhancement of Jc-B properties in SiC doped MgB2 tapes is considered to be due to the enhancement of grain linkages and the introduction of effective flux pining centers. The substitution of B by C in MgB2 grains is thought to be the main reason for the improvement of the flux pinning ability in SiC doped MgB2 tapes.

  5. Electrical dissipation and material properties of in-plane anisotropic superconducting YBCO films

    CERN Document Server

    Czerwinka, P S

    2001-01-01

    vortex liquid-to-glass phase transition model (VG). In all cases, the data can be successfully collapsed when scaled under the VG algorithm forming the expected master curves for temperatures above and below the vortex-glass 'transition' temperature T sub V sub G (B). However, between film systems we observe wide variations of the critical exponent z(theta,B) and T sub V sub G (B) as a function of field strength (B) and field orientation (theta). This lack of 'universality' does not allow interpretation of the scaling as evidence for a vortex liquid-to-glass phase transition. We find quantitative evidence in support of alternative scaling models which are based upon conventional flux-flow/creep theories and distributions of vortex-pinning strength. We investigate the growth, material and electrical properties of a wide variety of YBa sub 2 Cu sub 3 O sub 7 sub - subdelta films (40-480nm). The films range from c-axis normal to c-axis parallel to the film plane and were grown upon SrTiO sub 3 (STO) and LaSrGaO ...

  6. Growth and superconducting properties of Cd-doped La(O,F)BiS2 single crystals

    Science.gov (United States)

    Nagao, Masanori; Tanaka, Masashi; Watauchi, Satoshi; Takano, Yoshihiko; Tanaka, Isao

    2017-08-01

    Cd-doped La(O,F)BiS2 single crystals were grown using a CsCl/KCl flux. The grown crystals have a plate-like shape with 1-2 mm square size in a well-developed ab-plane. The Cd doping in the crystals was successfully characterized by single crystal X-ray diffraction and electron probe microanalysis techniques. The superconductivity of La(O,F)BiS2 was gradually suppressed with Cd doping. The superconducting transition temperature with zero resistivity of La(O0.54F0.46)(Bi0.92Cd0.08)S2 was 2.3 K. The Cd doping does not change the superconducting anisotropy so much, albeit the considerable suppression of Tc.

  7. Fabrication and properties of monofilamentary MgB{sub 2} superconducting tapes

    Energy Technology Data Exchange (ETDEWEB)

    Grasso, G [INFM-LAMIA, Corso Perrone 24, 16152 Genova (Italy); Malagoli, A [INFM-LAMIA, Corso Perrone 24, 16152 Genova (Italy); Modica, M [INFM-LAMIA, Corso Perrone 24, 16152 Genova (Italy); Tumino, A [INFM-LAMIA, Corso Perrone 24, 16152 Genova (Italy); Ferdeghini, C [INFM-LAMIA, Corso Perrone 24, 16152 Genova (Italy); Siri, A S [INFM-LAMIA, Corso Perrone 24, 16152 Genova (Italy); Vignola, C [CESI SpA, Via Rubattino 54, 20134 Milan (Italy); Martini, L [CESI SpA, Via Rubattino 54, 20134 Milan (Italy); Previtali, V [INFN-LASA, Via F.lli Cervi 201, 20090 Segrate (Italy); Volpini, G [INFN-LASA, Via F.lli Cervi 201, 20090 Segrate (Italy)

    2003-02-01

    Nickel-sheathed MgB{sub 2} tapes were fabricated by means of the powder-in-tube method with a monocore configuration of the superconductor. The metallic tubes were filled with commercial reacted powders and cold-worked, respectively, by groove rolling, drawing, and rolling to flat tapes of about 4 mm in width and 0.35 mm in thickness. Portions of the manufactured conductors were heat-treated in an argon atmosphere at temperatures up to 940 deg C. Conductors were characterized by transport measurements to determine the magnetic field dependence of the critical current density, the irreversibility line, as well as to establish an initial relationship between the thermo-mechanical treatment and the current carrying capacity of the manufactured MgB{sub 2} samples. Our optimized samples for the low field operation carry a critical current density of at least 4 x 10{sup 5} A cm{sup -2} at 4.2 K, 1 T. The main outcome of this study, however, is that the optimal heat treatment condition changes if the MgB{sub 2} conductor has to be employed respectively for a low- or high-field operation. Finally, the first successful demonstration of the current carrying capability of longer MgB{sub 2} tapes is also reported in this paper.

  8. Effects of oxide precursors on superconducting properties of polycrystalline SmFeAsO{sub 1−x}F{sub x}

    Energy Technology Data Exchange (ETDEWEB)

    Yuan, F.F.; Ding, Y.; Sun, Y.; Zhuang, J.C.; Zhou, W. [Department of Physics and Key Laboratory of MEMS of the Ministry of Education, Southeast University, Nanjing 211189 (China); Li, G.Z.; Sumption, M. [Center for Superconducting and Magnetic Materials (CSMM), Department of Materials Science and Engineering, The Ohio State University, Columbus, OH 43210 (United States); Li, X.W. [School of Physics and Electronic Electrical Engineering, Huaiyin Normal University, Huaian 223300 (China); State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Science, Shanghai 200050 (China); Shi, Z.X., E-mail: zxshi@seu.edu.cn [Department of Physics and Key Laboratory of MEMS of the Ministry of Education, Southeast University, Nanjing 211189 (China)

    2013-12-15

    Highlights: •Polycrystalline SmFeAsO{sub 1−x}F{sub x} samples were prepared by different oxide precursors. •Phase formation and superconductivity of these samples were comparatively studied. •Results show that nano-Fe{sub 2}O{sub 3} and As{sub 2}O{sub 3} promote fluorine doping. -- Abstract: A series of polycrystalline SmFeAsO{sub 1−x}F{sub x} samples were synthesized by one-step and two-step method at ambient pressure using different oxide precursors, namely As{sub 2}O{sub 3}, Fe{sub 2}O{sub 3} and nano-Fe{sub 2}O{sub 3} powder, as the source of element O. Results of X-ray diffraction and magnetic measurements manifest that starting oxides affected the phase formation and superconducting properties of SmFeAsO{sub 1−x}F{sub x}. As{sub 2}O{sub 3} as oxide precursor contributes to the fast formation of superconducting phase for a short period of sintering time. And samples prepared using As{sub 2}O{sub 3} show higher superconducting transition temperature T{sub c} and more stable fluorine doping level. Compared with Fe{sub 2}O{sub 3}, nano-Fe{sub 2}O{sub 3} promotes fluorine doping into the O site. While using Fe{sub 2}O{sub 3} leads to higher level of Fe and SmOF impurities. The critical current density J{sub cm} were derived from magnetic hysteresis loops. Sample prepared using As{sub 2}O{sub 3} shows higher J{sub cm} in low temperature and high magnetic fields.

  9. Superconducting Properties and Microstructure in MgB2 Bulks, Wires and Tapes

    Institute of Scientific and Technical Information of China (English)

    冯勇; 阎果; 赵勇; 吴晓京; 周廉; 张平祥

    2003-01-01

    We prepared a series of MgB2 bulk samples under different temperatures, holding time and increasing rates in temperature by the solid state reaction. The thermodynamic behavior and phase formation in the Mg-B system were studied by using DTA,XRD and SEM. The results indicate that the formation of the MgB2 phase is very fast and the high increasing rate in temperature is necessary to obtain high quality MgB2. In addition, the effects of the Zr-doping in Mg1-xZrxB2 bulk samples fabricated by the solid state reaction at ambient pressure on phase compositions, microstructure and flux pinning behavior were investigated by using XRD, SQUID magnetometer, SEM and TEM. Critical current density Jc can be significantly enhanced by the Zr-doping and the best data are achieved in Mg0.9Zr0.1B2. For this sample, Jc values are remarkably improved to 1.83×106 A/cm2 in self-field and 5.51×105 A/cm2 in 1 T at 20 K. Also, high quality MgB2/Ta/Cu wires and tapes with and without Ti-doping, MgB2/Fe wires and 18 filament MgB2/NbZr/Cu tapes were fabricated by the powder-in-tube (PIT) method at ambient pressure. The phase compositions, microstructure features and flux pinning properties were studied. The results suggest that Fe is thebest metal for these sheaths. MgB2/Fe wires exhibit very high Jc at high temperatures and high fields. Jc values reach as high as 1.43×105 A/cm2 (4.2 K, 4 T) and 3.72×104 A/cm2 (15 K, 4 T).

  10. Effect of CuO2 planes on the structural and superconducting transport properties of [CuTl - 12(n - 1)n;n = 2,3,4] superconductor family

    Science.gov (United States)

    Muzaffar, M. Usman; Khan, Nawazish A.

    2016-06-01

    Cu0.5Tl0.5Ba2Can-1CunO2n+4-δ (n = 2, 3, 4) superconducting bulk samples have been synthesized by using two-step solid state reaction method. We investigated the effects of CuO2 planes on the structural and superconducting transport properties of [CuTl - 12(n - 1)n; n = 2, 3, 4] superconducting family. These samples were characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR) absorption spectroscopy and DC-resistivity (ρ) measurements. These samples are c-axis length oriented and have shown orthorhombic crystal structure. All the samples have shown metallic variations of resistivity from room temperature down to onset of superconductivity. The zero resistivity critical temperature Tc(R = 0) increases with the increase in superconducting planes and normal state resistivity systematically decreases, which show the density of inadvertent defects decreases in the final compound. The apical oxygen phonon modes are hardened as observed in the FTIR absorption measurements. The intrinsic microscopic superconducting parameters, such as the cross-over temperatures, coherence length along c-axis (ξc(0)) at 0 K, inter-layer coupling (J), inter-grain coupling (α) and fermi velocity (VF), were extracted from the fluctuation-induced conductivity (FIC) analysis. FIC analysis also showed the improvement in superconductivity with the increase in CuO2 planes.

  11. Inelastic x-ray scattering study of superconducting SmFeAsO1-xFy single crystals: Evidence for strong momentum-dependent doping-induced renormalizations of optical phonons

    Science.gov (United States)

    Le Tacon, M.; Forrest, T. R.; Rüegg, Ch.; Bosak, A.; Walters, A. C.; Mittal, R.; Rønnow, H. M.; Zhigadlo, N. D.; Katrych, S.; Karpinski, J.; Hill, J. P.; Krisch, M.; McMorrow, D. F.

    2009-12-01

    We report inelastic x-ray scattering experiments on the lattice dynamics in SmFeAsO and superconducting SmFeAsO0.60F0.35 single crystals. Particular attention was paid to the dispersions along the [100] direction of three optical modes close to 23 meV, polarized out of the FeAs planes. Remarkably, two of these modes are strongly renormalized upon fluorine doping. These results provide significant insight into the energy and momentum dependence of the coupling of the lattice to the electron system and underline the importance of spin-phonon coupling in the superconducting iron pnictides.

  12. Current dependence of the hot-spot response spectrum of superconducting single-photon detectors with different layouts

    Science.gov (United States)

    Charaev, I.; Semenov, A.; Doerner, S.; Gomard, G.; Ilin, K.; Siegel, M.

    2017-02-01

    We show that avoiding bends in a current-carrying superconducting nanowire enhances the probability for low energy photons to be detected and that this enhancement is entirely due to the increase in the experimentally achievable critical current. We studied nanowires shaped as either meander or spiral. The spirals had different layouts, a double-spiral layout with an S-turn in the middle and a single-spiral layout without such a turn. Nanowires were prepared from films of niobium nitride with a thickness of 5 nm. For specimens with each layout we measured the spectra of the single-photon response in the wavelength range from 400 nm to 1600 nm and defined the cut-off wavelength (λ c) beyond which the response rolls off. The largest and the smallest λ c were found for the single-spiral layout and for the meander, respectively. For all three layouts the relationship between λ c and the relative bias current falls onto a universal curve which has been predicted earlier in the framework of the modified hot-spot model. For the single-spiral layout, the efficiency of photon detection at wavelengths smaller than λ c reaches the expected absorbance of the spiral structure and the timing jitter per unit length of the nanowire has the smallest value.

  13. Prediction of Superconductivity for Oxides Based on Structural Parameters and Artificial Neural Network Method

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Superconductive properties for oxides were predicted by artificial neural network (ANN) method with structural and chemical parameters as inputs. The predicted properties include superconductivity for oxides, distributed ranges of the superconductive transition temperature (Tc) for complex oxides, and Tc values for cuprate superconductors. The calculated results indicated that the adjusted ANN can be used to predict superconductive properties for unknown oxides.

  14. Inhomogeneous superconductivity in organic conductors: the role of disorder and magnetic field.

    Science.gov (United States)

    Haddad, S; Charfi-Kaddour, S; Pouget, J-P

    2011-11-23

    Several experimental studies have shown the presence of spatially inhomogeneous phase coexistence of superconducting and non-superconducting domains in low dimensional organic superconductors. The superconducting properties of these systems are found to be strongly dependent on the amount of disorder introduced in the sample regardless of its origin. The suppression of the superconducting transition temperature T(c) shows a clear discrepancy with the result expected from the Abrikosov-Gor'kov law giving the behavior of T(c) with impurities. On the basis of the time dependent Ginzburg-Landau theory, we derive a model to account for this striking feature of T(c) in organic superconductors for different types of disorder by considering the segregated texture of the system. We show that the calculated T(c) quantitatively agrees with experiments. We also focus on the effect of superconducting fluctuations on the upper critical fields H(c2) of layered superconductors showing slab structure where superconducting domains are sandwiched by non-superconducting regions. We found that H(c2) may be strongly enhanced by such fluctuations.

  15. STRUCTURAL AND SUPERCONDUCTING PROPERTIES OF LA2-XSRXCUO4+Y (0-LESS-THAN-X-LESS-THAN-0.15) PREPARED BY ROOM-TEMPERATURE CHEMICAL OXIDATION

    DEFF Research Database (Denmark)

    Rial, C.; Morán, E.; Alario-Franco, M.A.;

    1995-01-01

    The presence of interstitial oxygen in room temperature chemically oxidized La2-xSrxCuO4+y, (0.15superconducting properties of these cuprates. The existence of a structural limit for the insertion of oxygen under the current oxidation...... conditions, related to the relieving of the internal strain of these materials, is proposed. Besides, oxidized materials show an almost constant T-c close to that corresponding to the optimum hole doping concentration. The coincidence of both features is remarked upon and discussed....

  16. On the structural properties and superconductivity of room-temperature chemically oxidized La2-xBaxCuO4+y (0<=x<=0.15)

    DEFF Research Database (Denmark)

    Rial, C.; Moran, E.; Alario-Franco, M.A.;

    1996-01-01

    The insertion of oxygen within the structure of La2-xBaxCuO4+y (x less than or equal to 0.15), by means of room-temperature chemical oxidation, modifies both the physical and the structural features of these materials, Concerning the superconducting properties, the extra oxygen gives rise...... and differences concerning the modifications induced by this oxidation process in the present series of La2-xBaxCuO4+y compounds and in equivalent La2-xSrxCuO4+y materials are discussed....

  17. Superconducting doped topological materials

    Energy Technology Data Exchange (ETDEWEB)

    Sasaki, Satoshi, E-mail: sasaki@sanken.osaka-u.ac.jp [Institute of Scientific and Industrial Research, Osaka University, Ibaraki, Osaka 567-0047 (Japan); Mizushima, Takeshi, E-mail: mizushima@mp.es.osaka-u.ac.jp [Department of Materials Engineering Science, Osaka University, Toyonaka, Osaka 560-8531 (Japan); Department of Physics, Okayama University, Okayama 700-8530 (Japan)

    2015-07-15

    Highlights: • Studies on both normal- and SC-state properties of doped topological materials. • Odd-parity pairing systems with the time-reversal-invariance. • Robust superconductivity in the presence of nonmagnetic impurity scattering. • We propose experiments to identify the existence of Majorana fermions in these SCs. - Abstract: Recently, the search for Majorana fermions (MFs) has become one of the most important and exciting issues in condensed matter physics since such an exotic quasiparticle is expected to potentially give rise to unprecedented quantum phenomena whose functional properties will be used to develop future quantum technology. Theoretically, the MFs may reside in various types of topological superconductor materials that is characterized by the topologically protected gapless surface state which are essentially an Andreev bound state. Superconducting doped topological insulators and topological crystalline insulators are promising candidates to harbor the MFs. In this review, we discuss recent progress and understanding on the research of MFs based on time-reversal-invariant superconducting topological materials to deepen our understanding and have a better outlook on both the search for and realization of MFs in these systems. We also discuss some advantages of these bulk systems to realize MFs including remarkable superconducting robustness against nonmagnetic impurities.

  18. High temperature interface superconductivity

    Energy Technology Data Exchange (ETDEWEB)

    Gozar, A., E-mail: adrian.gozar@yale.edu [Yale University, New Haven, CT 06511 (United States); Bozovic, I. [Yale University, New Haven, CT 06511 (United States); Brookhaven National Laboratory, Upton, NY 11973 (United States)

    2016-02-15

    Highlight: • This review article covers the topic of high temperature interface superconductivity. • New materials and techniques used for achieving interface superconductivity are discussed. • We emphasize the role played by the differences in structure and electronic properties at the interface with respect to the bulk of the constituents. - Abstract: High-T{sub c} superconductivity at interfaces has a history of more than a couple of decades. In this review we focus our attention on copper-oxide based heterostructures and multi-layers. We first discuss the technique, atomic layer-by-layer molecular beam epitaxy (ALL-MBE) engineering, that enabled High-T{sub c} Interface Superconductivity (HT-IS), and the challenges associated with the realization of high quality interfaces. Then we turn our attention to the experiments which shed light on the structure and properties of interfacial layers, allowing comparison to those of single-phase films and bulk crystals. Both ‘passive’ hetero-structures as well as surface-induced effects by external gating are discussed. We conclude by comparing HT-IS in cuprates and in other classes of materials, especially Fe-based superconductors, and by examining the grand challenges currently laying ahead for the field.

  19. Properties of cryocooler-cooled superconductive pulse coil (1); Chokureishiki chodendo parusu koiru no tokusei hyoka (1)

    Energy Technology Data Exchange (ETDEWEB)

    Hae, T.; Kajikawa, K.; Iwakuma, M.; Funaki, K. [Kyushu Univ., Fukuoka (Japan); Hayashi, H.; Tsutsumi, K. [Kyushu Electric Power Co., Inc., Fukuoka (Japan); Tomioka, A.; Konno, M.; Nose, S. [Fuji Electric Corp., Tokyo (Japan)

    1999-11-10

    We manufactured the pulse coil of refrigerating machine direct cooling system using oxide superconducting wire rod, and they succeeded in triangular wave continuous running of 1T and 1Hz. It aimed at future further scale-up using this pulse coil this time, and the relationship between heat quantity and coil temperature rise in the operation was evaluated. (NEDO)

  20. Pressure Dependent Electronic Properties of Organic Semiconductors from First Principles

    Science.gov (United States)

    Knuth, Franz; Carbogno, Christian; Blum, Volker; Scheffler, Matthias

    2015-03-01

    The electronic properties of organic semiconductors typically exhibit a significant dependence on the strain, stress, and pressure. In this contribution, we present the theoretical background, assessment of approximations, and results of electronic and transport properties in the framework of density-functional theory. Our implementation considers the analytical strain derivatives (stress tensor) including the contributions that stem from (a) van-der-Waals interactions and (b) the Fock-exchange in hybrid functionals. We validate our approach by investigating the geometric and electronic changes that occur in polyacetylene and anthracene under hydrostatic pressure. We show that the fraction of exact exchange included in the calculations is critical - and non-trivial to choose - for a correct description of these systems. Furthermore, we point out trends for the electrical conductivity under pressure and identify the dominant charge carriers and transport directions.

  1. Study of Time-Dependent Properties of Thermoplastics

    Directory of Open Access Journals (Sweden)

    Bolchoun A.

    2010-06-01

    Full Text Available Simple tests carried out with a common tension/compression testing machine are used to obtain timedependent properties of non-reinforced thermoplastics. These tests include ramp loadings as well as relaxation and creep tests. Two materials (PBT Celanex 2002-2 and POM Hostaform C9021, Ticona GmbH, Kelsterbach were taken for the experiments. The experiments show that an adequate description of the long-term material properties can be obtained from the short-time tests, namely from tests with constant traverse speed $L^.$. Below a model for the time-dependent mechanical behavior is presented and fitted to the obtained measured data. For the evaluation of the fitting quality long-term tests are used. Especially creep and relaxation tests with ”jumps”, i.e. rapid change of loading, are important for this purpose.

  2. Stress dependent vector magnetic properties in electrical steel

    Energy Technology Data Exchange (ETDEWEB)

    Ktena, Aphrodite, E-mail: aktena@teihal.gr [Department of Electrical Engineering, TEI of Chalkida, Psachna, Evia 34400 (Greece); Davino, Daniele; Visone, Ciro [Engineering Department, University of Sannio (Italy); Hristoforou, Evangelos [Laboratory of Metallurgy, National Technical University of Athens (Greece)

    2014-02-15

    The dependence of macroscopic magnetic properties on applied and residual stresses is promising for development of new magnetic non-destructive evaluation techniques in ferrous materials. The reliability of AC magnetometry, in determining the effect of strain on magnetic macroscopic parameters, is evaluated against scalar and vector Vibrating Sample Magnetometer measurements on strained electrical steel samples after unloading. Hysteresis loops have been measured at 0°, 30°, 45°, 60° and 90° to the direction of the applied stress. Vector magnetic properties reveal a stress-related anisotropy component, which increases with strain and deteriorates after fracture. The effect of residual stress on the saturation and remanent magnetization, as well as the differential susceptibility, is discussed with respect to data from AC magnetometry at 0.1 Hz. The results of the latter are representative of the magnetic configuration of the material under test and make it a promising candidate for NDE applications in steels.

  3. Investigation of the superconducting and normal state properties of the filled-skutterudite system PrPt4Ge12 via chemical substitution

    Science.gov (United States)

    Jeon, Inho; Huang, Kevin; Yazici, Duygu; Kanchanavatee, Noravee; White, Benjamin D.; Jang, Sooyoung; Pouse, Naveen; Maple, M. Brian; Ho, Pei-Chun

    We report a systematic chemical substitution study on the unconventional superconductor system PrPt4Ge12, which Sb ions are substituted for Ge. Polycrystalline samples of PrPt4Ge12-x Sbx up to x = 5 were synthesized and investigated by means of x-ray diffraction, electrical resistivity, magnetic susceptibility, and specific heat measurements. We observed a suppression of superconductivity with increasing Sb substitutions and evidence for a weak ``rattling'' mode associated with the Pr ions, characterized by a value of ΘE ~ 60 K. As part of a systematic study of the effect of various elemental substitutions on the properties of PrPt4Ge12, measurements of the superconducting and normal state properties of the Pr1-xEuxPt4Ge12 system are currently being performed. This work was supported by the U. S. Department of Energy, Office of Basic Energy Sciences, Division of Materials Sciences and Engineering under Grant No. DE-FG02-04-ER46105 (characterization and physical properties measurements), and the National Science Foundation under Grant No. DMR 1206553 (low-temperature measurements).

  4. Quark mass dependence of quarkonium properties at finite temperature

    CERN Document Server

    Ohno, H; Kaczmarek, O

    2014-01-01

    Quarkonium properties at finite temperature have been studied with quark masses of the charm and bottom quarks. Our simulations have been performed in quenched QCD with the $O(a)$-improved Wilson quarks on large and fine isotropic lattices with the spatial lattice extents $N_\\sigma =$ 96, 192 and the corresponding lattice spacings $a =$ 0.0190, 0.00967 fm, respectively, at temperatures in a range between about 0.7$T_c$ and 1.4$T_c$. We show temperature and quark mass dependence of quarkonium correlation functions and related physical quantities: the quark number susceptibility and the heavy quark diffusion constant.

  5. Superconducting interfaces between insulating oxides.

    Science.gov (United States)

    Reyren, N; Thiel, S; Caviglia, A D; Kourkoutis, L Fitting; Hammerl, G; Richter, C; Schneider, C W; Kopp, T; Rüetschi, A-S; Jaccard, D; Gabay, M; Muller, D A; Triscone, J-M; Mannhart, J

    2007-08-31

    At interfaces between complex oxides, electronic systems with unusual electronic properties can be generated. We report on superconductivity in the electron gas formed at the interface between two insulating dielectric perovskite oxides, LaAlO3 and SrTiO3. The behavior of the electron gas is that of a two-dimensional superconductor, confined to a thin sheet at the interface. The superconducting transition temperature of congruent with 200 millikelvin provides a strict upper limit to the thickness of the superconducting layer of congruent with 10 nanometers.

  6. Multistable current states in high-temperature superconducting composites

    Science.gov (United States)

    Romanovskii, V. R.

    2016-09-01

    Conditions for current instabilities that arise in high-temperature superconducting composites with essentially nonlinear dependences of the critical current densities and resistivity on the temperature and magnetic induction have been studied. The analysis has been conducted in terms of zero-dimensional models, which has made it possible to formulate general physical mechanisms behind the formation of currents states in superconducting composites according to the external magnetic field induction, cooling conditions, and the properties of the superconductor and cladding. The possible existence of current and temperature stable steps, as well as stable steps of the electric field strength, in the absence of the superconducting-normal transition, has been demonstrated. Reasons for instabilities under multistable current states have been discussed.

  7. Electron transport in a mesoscopic superconducting ferromagnetic hybrid conductor

    Energy Technology Data Exchange (ETDEWEB)

    Giroud, M.; Hasselbach, K.; Courtois, H.; Pannetier, B. [Centre de Recherche sur les Tres Basses Temperatures, CNRS, 38 - Grenoble (France); Mailly, D. [Laboratoire de Photonique et de Nanostructures, 91 - Marcoussis (France)

    2003-01-01

    We present electrical transport experiments performed on submicron hybrid devices made of a ferromagnetic conductor (Co) and a superconducting (Al) electrode. The sample was patterned in order to separate the contributions of the Co conductor and of the Co-Al interface. We observed a strong influence of the Al electrode superconductivity on the resistance of the Co conductor. This effect is large only when the interface is highly transparent. We characterized the dependence of the observed resistance decrease on temperature, bias current and magnetic field. As the differential resistance of the ferromagnet exhibits a non-trivial asymmetry, we claim that the magnetic domain structure plays an important role in the electron transport properties of superconducting / ferromagnetic conductors. (authors)

  8. Superconductivity in an Inhomogeneous Bundle of Metallic and Semiconducting Nanotubes

    Directory of Open Access Journals (Sweden)

    Ilya Grigorenko

    2013-01-01

    Full Text Available Using Bogoliubov-de Gennes formalism for inhomogeneous systems, we have studied superconducting properties of a bundle of packed carbon nanotubes, making a triangular lattice in the bundle's transverse cross-section. The bundle consists of a mixture of metallic and doped semiconducting nanotubes, which have different critical transition temperatures. We investigate how a spatially averaged superconducting order parameter and the critical transition temperature depend on the fraction of the doped semiconducting carbon nanotubes in the bundle. Our simulations suggest that the superconductivity in the bundle will be suppressed when the fraction of the doped semiconducting carbon nanotubes will be less than 0.5, which is the percolation threshold for a two-dimensional triangular lattice.

  9. Spin and Time-Reversal Symmetries of Superconducting Electron Pairs Probed by the Muon Spin Rotation and Relaxation Technique

    Science.gov (United States)

    Higemoto, Wataru; Aoki, Yuji; MacLaughlin, Douglas E.

    2016-09-01

    Unconventional superconductivity based on the strong correlation of electrons is one of the central issues of solid-state physics. Although many experimental techniques are appropriate for investigating unconventional superconductivity, a complete perspective has not been established yet. The symmetries of electron pairs are crucial properties for understanding the essential state of unconventional superconductivity. In this review, we discuss the investigation of the time-reversal and spin symmetries of superconducting electron pairs using the muon spin rotation and relaxation technique. By detecting a spontaneous magnetic field under zero field and/or the temperature dependence of the muon Knight shift in the superconducting phase, the time-reversal symmetry and spin parity of electron pairs have been determined for several unconventional superconductors.

  10. A study on the superconducting properties of YBa{sub 2}Cu{sub 9-x}Nb{sub x}O{sup y} thin films

    Energy Technology Data Exchange (ETDEWEB)

    Srinivas, S.; Bhatnagar, A.K. [Univ. of Hyderabad (India); Pinto, R. [Solid State Electronics Group, Bombay (India)] [and others

    1994-12-31

    Effect of niobium substitution at the copper site in YBa{sub 2}Cu{sub 9}O{sub 7-x} was studied in thin film form. The films were deposited by laser ablation technique using the targets of the YBa{sub 2}Cu{sub 3-x}Nb{sub x}O{sub y} where x = 0.0, 0.025, 0.05, 0.1, 0.2, 0.4, 0.8 and 1.0 under identical deposition conditions on SrTiO{sub 9} <100> substrates. Films were characterized by XRD, resistivity, I-V and J{sub c} measurements. Films made from x = 0.025 and 0.05 concentrations of Nb substituted targets showed relatively improved superconducting properties compared to that of undoped films. The best 7 realized for x = 0.025 Nb concentration was 1.8 x 10{sup {sigma}} A/cm{sup 2} and for 0.05 Nb concentration it was 3.2x10{sup {sigma}} A/cm{sup 2} at 77K. However, degradation of the superconducting properties, with the increase of x {ge} 0.1 Nb concentration and drastic suppression and complete loss of superconductivity was noticed for x {ge} 0.4. The growth of impurity phase YBa{sub 2}NbO{sub 6} for x = 0.1 and above of Nb concentration was noticed from XRD patterns. However, the site occupancy of Nb could not be confirmed from these studies.

  11. Y-Ba Superconducting Ceramics

    Science.gov (United States)

    Shunbao, Tian; Xiaofei, Li; Tinglian, Wen; Zuxiang, Lin; Shichun, Li; Huijun, Yu

    Polycrystalline Y-Ba-Cu-O superconducting materials have been studied. It was found that chemical composition and processing condition may play an important role in the final structure and superconducting properties. The density has been determined and compared with the calculated value according to the structure model reported by Bell Labs. The grain size and the morphology of the materials were observed by SEM.

  12. Shape-dependent light scattering properties of subwavelength silicon nanoblocks.

    Science.gov (United States)

    Ee, Ho-Seok; Kang, Ju-Hyung; Brongersma, Mark L; Seo, Min-Kyo

    2015-03-11

    We explore the shape-dependent light scattering properties of silicon (Si) nanoblocks and their physical origin. These high-refractive-index nanostructures are easily fabricated using planar fabrication technologies and support strong, leaky-mode resonances that enable light manipulation beyond the optical diffraction limit. Dark-field microscopy and a numerical modal analysis show that the nanoblocks can be viewed as truncated Si waveguides, and the waveguide dispersion strongly controls the resonant properties. This explains why the lowest-order transverse magnetic (TM01) mode resonance can be widely tuned over the entire visible wavelength range depending on the nanoblock length, whereas the wavelength-scale TM11 mode resonance does not change greatly. For sufficiently short lengths, the TM01 and TM11 modes can be made to spectrally overlap, and a substantial scattering efficiency, which is defined as the ratio of the scattering cross section to the physical cross section of the nanoblock, of ∼9.95, approaching the theoretical lowest-order single-channel scattering limit, is achievable. Control over the subwavelength-scale leaky-mode resonance allows Si nanoblocks to generate vivid structural color, manipulate forward and backward scattering, and act as excellent photonic artificial atoms for metasurfaces.

  13. Frequency-Dependent Properties of Magnetic Nanoparticle Crystals

    Energy Technology Data Exchange (ETDEWEB)

    Majetich, Sara [Carnegie Mellon Univ., Pittsburgh, PA (United States)

    2016-05-17

    In the proposed research program we will investigate the time- and frequency-dependent behavior of ordered nanoparticle assemblies, or nanoparticle crystals. Magnetostatic interactions are long-range and anisotropic, and this leads to complex behavior in nanoparticle assemblies, particularly in the time- and frequency-dependent properties. We hypothesize that the high frequency performance of composite materials has been limited because of the range of relaxation times; if a composite is a dipolar ferromagnet at a particular frequency, it should have the advantages of a single phase material, but without significant eddy current power losses. Arrays of surfactant-coated monodomain magnetic nanoparticles can exhibit long-range magnetic order that is stable over time. The magnetic domain size and location of domain walls is governed not by structural grain boundaries but by the shape of the array, due to the local interaction field. Pores or gaps within an assembly pin domain walls and limit the domain size. Measurements of the magnetic order parameter as a function of temperature showed that domains can exist at high temoerature, and that there is a collective phase transition, just as in an exchange-coupled ferromagnet. Dipolar ferromagnets are not merely of fundamental interest; they provide an interesting alternative to exchange-based ferromagnets. Dipolar ferromagnets made with high moment metallic particles in an insulating matrix could have high permeability without large eddy current losses. Such nanocomposites could someday replace the ferrites now used in phase shifters, isolators, circulators, and filters in microwave communications and radar applications. We will investigate the time- and frequency-dependent behavior of nanoparticle crystals with different magnetic core sizes and different interparticle barrier resistances, and will measure the magnetic and electrical properties in the DC, low frequency (0.1 Hz - 1 kHz), moderate frequency (10 Hz - 500

  14. Mechanical properties of fibroblasts depend on level of cancer transformation.

    Science.gov (United States)

    Efremov, Yu M; Lomakina, M E; Bagrov, D V; Makhnovskiy, P I; Alexandrova, A Y; Kirpichnikov, M P; Shaitan, K V

    2014-05-01

    Recently, it was revealed that tumor cells are significantly softer than normal cells. Although this phenomenon is well known, it is connected with many questions which are still unanswered. Among these questions are the molecular mechanisms which cause the change in stiffness and the correlation between cell mechanical properties and their metastatic potential. We studied mechanical properties of cells with different levels of cancer transformation. Transformed cells in three systems with different transformation types (monooncogenic N-RAS, viral and cells of tumor origin) were characterized according to their morphology, actin cytoskeleton and focal adhesion organization. Transformation led to reduction of cell spreading and thus decreasing the cell area, disorganization of actin cytoskeleton, lack of actin stress fibers and decline in the number and size of focal adhesions. These alterations manifested in a varying degree depending on type of transformation. Force spectroscopy by atomic force microscopy with spherical probes was carried out to measure the Young's modulus of cells. In all cases the Young's moduli were fitted well by log-normal distribution. All the transformed cell lines were found to be 40-80% softer than the corresponding normal ones. For the cell system with a low level of transformation the difference in stiffness was less pronounced than for the two other systems. This suggests that cell mechanical properties change upon transformation, and acquisition of invasive capabilities is accompanied by significant softening.

  15. Substitution effects on superconducting and normal state properties in (Mo1-xTx)3Sb7, where T = Ru and Fe

    Science.gov (United States)

    Tran, V. H.

    2016-12-01

    The effects of Ru- and Fe-doping on the physical properties of Mo3Sb7 were studied by measuring ac-susceptibility, dc-magnetization, electrical resistivity and specific heat. It is found that single-phased (Mo{}1-xRu x )3Sb7 and (Mo{}1-xFe x )3Sb7 samples are obtained for the concentrations x ≤slant 0.1. In this concentration range, the lattice parameter shrinks with increasing dopant content. The substitution effects on the superconducting and normal state properties are completely different between two investigated systems. In the Ru-based solid solution alloys, the substitution enhances the superconducting parameters T c and H c2 and also benefits the spin-gap opening at {T}* ˜ 50 K. In contrast, in the Fe-substituted samples, there is a depression of both T c and H c2, accompanied by vanishing spin-gap and low-dimensional magnetic correlation. The substitution of the Mo atoms by Ru and Fe atoms suppresses the cubic-tetragonal distortion, but presumably favours the magnetic field to induce a magnetic order below T *.

  16. Magnetic and superconducting properties of a heavy-fermion CeCoIn5 epitaxial film probed by nuclear quadrupole resonance

    Science.gov (United States)

    Yamanaka, Takayoshi; Shimozawa, Masaaki; Shishido, Hiroaki; Kitagawa, Shunsaku; Ikeda, Hiroaki; Shibauchi, Takasada; Terashima, Takahito; Matsuda, Yuji; Ishida, Kenji

    2017-08-01

    Since the progress in the fabrication techniques of thin films of exotic materials such as strongly correlated heavy-fermion compounds, microscopic studies of the magnetic and electronic properties inside the films have been needed. Herein, we report the observation of 115In nuclear quadrupole resonance (NQR) in an epitaxial film of the heavy-fermion superconductor CeCoIn5, for which the microscopic field gradient within the unit cell as well as magnetic and superconducting properties at zero field are evaluated. We find that the nuclear spin-lattice relaxation rate in the film is in excellent agreement with that of bulk crystals, whereas the NQR spectra show noticeable shifts and significant broadening indicating a change in the electric-field distribution inside the film. The analysis implies a displacement of In layers in the film, which, however, does not affect the magnetic fluctuations and superconducting pairing. This implies that inhomogeneity of the electronic field gradient in the film sample causes no pair-breaking effect.

  17. Transport and infrared properties of SmFeAs(O{sub 1-x}F{sub x}): from SDW to superconducting ordering

    Energy Technology Data Exchange (ETDEWEB)

    Tropeano, M; Fanciulli, C; Ferdeghini, C; Marre, D; Siri, A S; Putti, M [CNR-INFM-LAMIA and Dipartimento di Fisica, Via Dodecaneso 33, I-16146 Genova (Italy); Martinelli, A; Ferretti, M; Palenzona, A [CNR-INFM-LAMIA and Dipartimento di Chimica e Chimica Industriale, Via Dodecaneso 31, I-16146 Genova (Italy); Cimberle, M R [CNR-IMEM, Dipartimento di Fisica, Via Dodecaneso 33, I-16146 Genova (Italy); Mirri, C; Lupi, S; Sopracase, R; Calvani, P [CNR-INFM ' Coherentia' and Dipartimento di Fisica, Universita di Roma ' La Sapienza' , Piazzale Aldo Moro 2, I-00185 Rome (Italy); Perucchi, A [Sincrotrone Trieste S.C.p.A., S.S. 14 km 163.5, Area Science Park, I-34012 Basovizza, Trieste (Italy)

    2009-03-15

    We report measurements of resistivity, magnetoresistivity, Hall effect, Seebeck coefficient and infrared reflectivity of undoped SmFeAsO and lightly doped SmFeAs(O{sub 0.93}F{sub 0.07}) oxypnictides. All the properties measured on SmFeAsO are characterized by clear signatures of the magnetic instability. A self-consistent picture emerges in which carrier condensation occurs below the magnetic transition, due to the opening of a spin density wave (SDW) gap. This is accompanied by the mobility increase of not-gapped carriers due to the suppression of electron-electron scattering. SmFeAs(O{sub 0.93}F{sub 0.07}) exhibits an increase of the metallic character on cooling consistent with electron doping, even though at room temperature values of all the properties nearly overlap with those of SmFeAsO. However, with a decrease in temperature all anomalies related to the SDW instability are missing and the superconducting transition occurs. This suggests that doping abruptly breaks the symmetries of the Fermi surface, inhibiting the SDW formation in favor of the superconducting transition, with no substantial changes in the density of states or in the effective mass.

  18. Electronic, thermal, and superconducting properties of metal nitrides (MN) and metal carbides (MC) (M=V, Nb, Ta) compounds by first principles studies

    Energy Technology Data Exchange (ETDEWEB)

    Subhashree, G.; Sankar, S.; Krithiga, R. [Anna Univ., Chennai, Tamil Nadu (India). Condensed Matter Lab.

    2015-07-01

    Structural, electronic, and superconducting properties of carbides and nitrides of vanadium (V), niobium (Nb), and tantalum (Ta) (group V transition elements) have been studied by computing their electronic band structure characteristics. The electronic band structure calculations have been carried out based on the density functional theory (DFT) within the local density approximation (LDA) by using the tight binding linear muffin tin orbital method. The NaCl-type cubic structures of MN and MC (M=V, Nb, Ta) compounds have been confirmed from the electronic total energy minimum of these compounds. The ground state properties, such as equilibrium lattice constant (a{sub 0}), bulk modulus (B), and Wigner-Seitz radius (S{sub 0}) are determined and compared with available data. The electronic density of states reveals the metallic nature of the chosen materials. The electronic specific heat coefficient, Debye temperature, and superconducting transition temperature obtained from the band structure results are found to agree well with the earlier reported literature.

  19. Processing dependent properties of silica xerogels for interlayer dielectric applications

    Science.gov (United States)

    Jain, Anurag

    One of the current and near future research focus in microelectronics is to integrate copper with a new low dielectric constant (K) material. The traditional low K is dense SiO2 (K = 4). Introducing porosity in materials with silica backbone is promising as processing and integration methods are well known. This thesis focuses on studying silica xerogel, also known as nanoporous silica. A new low-K material has to be tested for an array of electrical, mechanical, thermal, and chemical properties before it is deemed successful to replace dense SiO2. These properties of silica xerogels are characterized using various analytical techniques and the effect of processing conditions is studied. The property data is explained by the models and mechanisms relating processing-structure-property behavior. The processing effects on thermal and mechanical properties are studied in great detail and the theories for generic porous low-K materials are developed. The xerogel films are processed at ambient conditions and crack free, thick (0.5--4 mum), highly porous (˜25--90%) films are obtained. Two methods of porosity control were used. One is the traditional single solvent (ethanol) method and another is a binary solvent (mixture of ethanol and ethylene glycol) method. The films underwent aging and silylation procedures to make the backbone stiff and hydrophobic. Sintering of xerogel films eliminates defects and organics and additional condensation reactions make matrix more connected, dense and ordered. Films were characterized for their refractive index, thickness, porosity, pore size and surface roughness. Dielectric constant measurements at 1 MHz show that K varies linearly with porosity. Dielectric loss tangents are low and breakdown strength meets the standards. FTIR and XPS analysis show that films are stable chemically and remain hydrophobic even after boiling in water. Mechanical and thermal properties of porous materials are dependent on the microstructure and various

  20. Superconducting Microelectronics.

    Science.gov (United States)

    Henry, Richard W.

    1984-01-01

    Discusses superconducting microelectronics based on the Josephson effect and its advantages over conventional integrated circuits in speed and sensitivity. Considers present uses in standards laboratories (voltage) and in measuring weak magnetic fields. Also considers future applications in superfast computer circuitry using Superconducting…

  1. Characteristics of frictional properties' dependency on afterslip propagation speed

    Science.gov (United States)

    Ariyoshi, K.; Matsuzawa, T.; Hasegawa, A.; Hino, R.; Hori, T.

    2016-12-01

    The propagation speed of postseismic slip seems to vary from place to place. On the 2003 Tokachi-Oki earthquake (M8), the time lag is about 80 minutes for the largest aftershock (M7.4) off Tokachi [Miyazaki and Larson, 2008 GRL] and one year for the M7 earthquakes off Kushiro [Murakami et al., 2006 GRL]. Since the distance from the epicenter of mainshock to the largest aftershock and the M7 aftershocks off Kushiro is about 40 km and 160 km, respectively, these time lags means that propagation speed of the afterslip from the mainshock to the largest aftershock is significantly higher than to the M7 afteshocks off Kushiro. On the Sanriku-Haruka-Oki earthquakes, Matsuzawa et al. [2004 EPS] pointed out that propagation speed of the postseismic slip seems to be an order of 10 km/day for shallower part of the subduction plate boundary while 10 km/month for deeper part. These results indicate that propagation speed of postseismic slip depends on frictional properties and effective normal stress in addition to slip velocity. To know the frictional properties controlling the propagation speed of postseismic slip, some numerical simulations of interplate earthquakes based on a rate- and state-dependent friction law (RSF) [Dieterich, 1979 JGR; Ruina, 1983 JGR] have been recently performed. From those previous studies, the propagation speed of postseismic slip becomes lower in case of higher frictional stability, longer characteristic slip distance [Kato and Hirasawa, 1999 PAGEOPH], and higher effective normal stress [Ariyoshi et al., 2007 EPSL]. Since we have not quantitatively understood why such cases make the postseismic slip propagation slower, it is necessary to know analytical relation between the frictional properties and the propagation speed of postseismic slip. In this study, we develop an expression for the propagation speed of postseismic slip as a function of frictional properties including effective normal stress, and discuss its validity quantitatively by

  2. Temperature dependence of the flux line lattice transition into square symmetry in superconducting LuNi2B2C

    DEFF Research Database (Denmark)

    Eskildsen, M.R.; Abrahamsen, A.B.; Kogan, V.G.;

    2001-01-01

    We have investigated the temperature dependence of the H parallel to c flux line lattice structural phase transition from square to hexagonal symmetry, in the tetragonal superconductor LuNi2B2C (T-c = 16.6 K). At temperatures below 10 K the transition onset field, H-2(T), is only weakly temperature...... dependent. Above 10 K, H-2(T) rises sharply, bending away from the upper critical field. This contradicts theoretical predictions of H-2(T) merging with the upper critical field and suggests that just below the H-c2(T) curve the flux line lattice might be hexagonal....

  3. Direct method for calculating temperature-dependent transport properties

    Science.gov (United States)

    Liu, Yi; Yuan, Zhe; Wesselink, R. J. H.; Starikov, Anton A.; van Schilfgaarde, Mark; Kelly, Paul J.

    2015-06-01

    We show how temperature-induced disorder can be combined in a direct way with first-principles scattering theory to study diffusive transport in real materials. Excellent (good) agreement with experiment is found for the resistivity of Cu, Pd, Pt (and Fe) when lattice (and spin) disorder are calculated from first principles. For Fe, the agreement with experiment is limited by how well the magnetization (of itinerant ferromagnets) can be calculated as a function of temperature. By introducing a simple Debye-like model of spin disorder parameterized to reproduce the experimental magnetization, the temperature dependence of the average resistivity, the anisotropic magnetoresistance, and the spin polarization of a Ni80Fe20 alloy are calculated and found to be in good agreement with existing data. Extension of the method to complex, inhomogeneous materials as well as to the calculation of other finite-temperature physical properties within the adiabatic approximation is straightforward.

  4. Superconductivity and mechanical properties of SmBa2Cu3O7-δ added with nano-crystalline ZnFe2O4

    Science.gov (United States)

    Abdeen, W.; El Tahan, A.; Awad, R.; Abou Aly, A. I.; El-Maghraby, E. M.; Khalaf, A.

    2016-06-01

    The effect of nanosized ZnFe2O4 addition on the physical properties of polycrystalline SmBa2Cu3O7-δ superconductor was studied. Superconducting samples of the type (ZnFe2O4) x SmBa2Cu3O7-δ, x = 0.00, 0.01, 0.02, 0.04, 0.06, 0.08, 0.10, 0.15 and 0.20 wt% were prepared by the solid-state reaction method. The characterization and superconductivity investigation were carried out using X-ray powder diffraction, XRD, scanning electron microscope, SEM, energy-dispersive X-ray, EDX, dc electrical resistivity and transport critical current density at 77 K. Improvements in the volume fraction, superconducting transition temperature, Tc, and transport critical current density, Jc, were observed as x increased from 0.00 up to 0.08 wt% and then they decreased with further increase in nanosized ZnFe2O4 addition. The Vickers microhardness number, H v, and elastic parameters have been measured at room temperature. The ultrasonic pulse-echo technique at 4 MHz was used to determine the elastic parameters. H v and the elastic parameters were observed to increase with increasing x. The enhancement of the elastic parameters may be due to the hindrance of dislocation motion with nanosized ZnFe2O4 addition. Moreover, Debye temperatures ( θ D) were calculated and it was found that their values increased with increasing nanosized ZnFe2O4 addition. The elastic parameters of the samples were computed and corrected to zero porosity using different models. Finally, the relationship between Young's modulus and H v was estimated for different models.

  5. Induced spin-triplet pairing in the coexistence state of antiferromagnetism and singlet superconductivity: Collective modes and microscopic properties

    Science.gov (United States)

    Almeida, D. E.; Fernandes, R. M.; Miranda, E.

    2017-07-01

    The close interplay between superconductivity and antiferromagnetism in several quantum materials can lead to the appearance of an unusual thermodynamic state in which both orders coexist microscopically, despite their competing nature. A hallmark of this coexistence state is the emergence of a spin-triplet superconducting gap component, called a π triplet, which is spatially modulated by the antiferromagnetic wave vector, reminiscent of a pair density wave. In this paper, we investigate the impact of these π -triplet degrees of freedom on the phase diagram of a system with competing antiferromagnetic and superconducting orders. Although we focus on a microscopic two-band model that has been widely employed in studies of iron pnictides, most of our results follow from a Ginzburg-Landau analysis, and as such should be applicable to other systems of interest, such as cuprates and heavy fermion materials. The Ginzburg-Landau functional reveals not only that the π -triplet gap amplitude couples trilinearly with the singlet gap amplitude and the staggered magnetization magnitude but also that the π -triplet d -vector couples linearly with the magnetization direction. While in the mean-field level this coupling forces the d -vector to align parallel or antiparallel to the magnetization, in the fluctuation regime it promotes two additional collective modes—a Goldstone mode related to the precession of the d -vector around the magnetization and a massive mode, related to the relative angle between the two vectors, which is nearly degenerate with a Leggett-like mode associated with the phase difference between the singlet and triplet gaps. We also investigate the impact of magnetic fluctuations on the superconducting-antiferromagnetic phase diagram, showing that due to their coupling with the π -triplet order parameter the coexistence region is enhanced. This effect stems from the fact that the π -triplet degrees of freedom promote an effective attraction between

  6. Temperature-dependence of the superconducting condensate and gap in Bi 2Sr 2Ca 1Cu 2O 8+ z

    Science.gov (United States)

    Ma, Jian; Quitmann, C.; Kelley, R. J.; Alméras, P.; Berger, H.; Margaritondo, G.; Onellion, M.

    1994-12-01

    Using high energy resolution angle-resolved photoemission, we have measured both the superconducting gap and the photoemission superconducting condensate spectral area of Bi 2Sr 2Ca 1Cu 1O 8+ z as a function of temperature in two different locations of the Brillouin zone. We found that the size of superconducting gap along the Γ- X direction decreases to values indistinguishable from zero for which the gap retains virtually full value along the Γ - M¯ direction. The increased gap anisotropy with increasing temperature is in contrast to what happens for conventional anisotropic superconductors such as lead.

  7. Temperature-dependence of the superconducting condensate and gap in Bi2Sr2Ca1Cu2O8+x

    Science.gov (United States)

    Quitmann, C.; Kelly, R. J.; Onellion, M.; Alméras, P.; Berger, H.; Margaritondo, G.

    1994-12-01

    Using high energy resolution angle-resolved photoemission, we have measured both the superconducting gap and the photoemission superconducting condensate spectral area of Bi2Sr2Ca1Cu1O8+x as a function of temperature in two different locations of the Brillouin zone. We found that the size of superconducting gap along the Γ - X direction decreases to values indistinguishable from zero for which the gap retains virtually full value along the Γ - M direction. The increased gap anisotropy with increasing temperature is in contrast to what happens for conventional anisotropic superconductors such as lead.>

  8. Superconducting Radio Frequency Technology: An Overview

    Energy Technology Data Exchange (ETDEWEB)

    Peter Kneisel

    2003-06-01

    Superconducting RF cavities are becoming more often the choice for larger scale particle accelerator projects such as linear colliders, energy recovery linacs, free electron lasers or storage rings. Among the many advantages compared to normal conducting copper structures, the superconducting devices dissipate less rf power, permit higher accelerating gradients in CW operation and provide better quality particle beams. In most cases these accelerating cavities are fabricated from high purity bulk niobium, which has superior superconducting properties such as critical temperature and critical magnetic field when compared to other superconducting materials. Research during the last decade has shown, that the metallurgical properties--purity, grain structure, mechanical properties and oxidation behavior--have significant influence on the performance of these accelerating devices. This contribution attempts to give a short overview of the superconducting RF technology with emphasis on the importance of the material properties of the high purity niobium.

  9. Size-dependent magnetic properties of branchlike nickel oxide nanocrystals

    Science.gov (United States)

    Liu, Dan; Li, Dongsheng; Yang, Deren

    2017-01-01

    Branchlike nickel oxide nanocrystals with narrow size distribution are obtained by a solution growth method. The size-dependent of magnetic properties of the nickel oxides were investigated. The results of magnetic characterization indicate that the NiO nanocrystals with size below 12.8 nm show very weak ferromagnetic state at room temperature due to the uncompensated spins. Both of the average blocking temperature (Tb) and the irreversible temperature (Tirr) increase with the increase of nanoparticle sizes, while both the remnant magnetization and the coercivity at 300 K increase with the decrease of the particle sizes. Moreover, the disappearance of two-magnon (2M) band and redshift of one-phonon longitudinal (1LO) and two-phonon LO in vibrational properties due to size reduction are observed. Compared to the one with the spherical morphological, it is also found that nano-structured nickel oxides with the branchlike morphology have larger remnant magnetization and the coercivity at 5 K due to their larger surface-to-volume ratio and greater degree of broken symmetry at the surface or the higher proportion of broken bonds.

  10. Length-dependent mechanical properties of gold nanowires.

    Science.gov (United States)

    Han, Jing; Fang, Liang; Sun, Jiapeng; Han, Ying; Sun, Kun

    2012-12-01

    The well-known "size effect" is not only related to the diameter but also to the length of the small volume materials. It is unfortunate that the length effect on the mechanical behavior of nanowires is rarely explored in contrast to the intensive studies of the diameter effect. The present paper pays attention to the length-dependent mechanical properties of 〈111〉-oriented single crystal gold nanowires employing the large-scale molecular dynamics simulation. It is discovered that the ultrashort Au nanowires exhibit a new deformation and failure regime-high elongation and high strength. The constrained dislocation nucleation and transient dislocation slipping are observed as the dominant mechanism for such unique combination of high strength and high elongation. A mechanical model based on image force theory is developed to provide an insight to dislocation nucleation and capture the yield strength and nucleation site of first partial dislocation indicated by simulation results. Increasing the length of the nanowires, the ductile-to-brittle transition is confirmed. And the new explanation is suggested in the predict model of this transition. Inspired by the superior properties, a new approach to strengthen and toughen nanowires-hard/soft/hard sandwich structured nanowires is suggested. A preliminary evidence from the molecular dynamics simulation corroborates the present opinion.

  11. Helical superconducting black holes.

    Science.gov (United States)

    Donos, Aristomenis; Gauntlett, Jerome P

    2012-05-25

    We construct novel static, asymptotically five-dimensional anti-de Sitter black hole solutions with Bianchi type-VII(0) symmetry that are holographically dual to superconducting phases in four spacetime dimensions with a helical p-wave order. We calculate the precise temperature dependence of the pitch of the helical order. At zero temperature the black holes have a vanishing entropy and approach domain wall solutions that reveal homogenous, nonisotropic dual ground states with an emergent scaling symmetry.

  12. Thermal dependence of passive electrical properties of lizard muscle fibres.

    Science.gov (United States)

    Adams, B A

    1987-11-01

    1. The thermal dependence of passive electrical properties was determined for twitch fibres from the white region of the iliofibularis (IF) muscle of Anolis cristatellus (15-35 degrees C) and Sceloporus occidentalis (15-40 degrees C), and for twitch fibres from the white (15-45 degrees C) and red (15-40 degrees C) regions of the IF of Dipsosaurus dorsalis. These species differ in thermal ecology, with Anolis being the least thermophilic and Dipsosaurus the most thermophilic. 2. Iliofibularis fibres from the three species reacted similarly to changing temperature. As temperature was increased, input resistance (Rin) decreased (average R10 = 0.7), length constant (L) decreased (average R10 = 0.9), time constant (tau) decreased (average R10 = 0.8), sarcoplasmic resistivity (Rs) decreased (average R10 = 0.8) and apparent membrane resistance (Rm) decreased (average R10 = 0.7). In contrast, apparent membrane capacitance (Cm) increased with increasing temperature (average R10 = 1.3). 3. Rin, L, tau and apparent Rm were lowest in fibres from Anolis (the least thermophilic species) and highest in fibres from Dipsosaurus (the most thermophilic species). Anolis had the largest and Dipsosaurus the smallest diameter fibres (126 and 57 micron, respectively). Apparent Cm was highest in fibres from Sceloporus, which had fibres of intermediate diameter (101 micron). Rs did not differ significantly among species. 4. The effect of temperature on the passive electrical properties of these lizard fibres was similar to that reported for muscle fibres from other ectothermic animals (crustaceans, insects, fish and amphibians) but qualitatively different from that reported for some mammalian (cat tenuissimus, goat intercostal) fibres. The changes that occur in the passive electrical properties render the fibres less excitable as temperature increases.

  13. Dependence of Barred Galaxy Fraction on Galaxy Properties and Environment

    CERN Document Server

    Lee, Gwang-Ho; Lee, Myung Gyoon; Choi, Yun-Young

    2011-01-01

    We investigate the dependence of occurrence of bars in galaxies on galaxy properties and environment. We use a volume-limited sample of 33,391 galaxies brighter than $M_{r}=-19.5+5$log$h$ at $0.02\\le z\\le0.05489$, drawn from the SDSS DR 7. We classify the galaxies into early and late types, and identify bars by visual inspection. Among 10,674 late-type galaxies with axis ratio $b/a>0.60$, we find 3,240 barred galaxies ($f_{bar}=30.4%$) which divide into 2,542 strong bars ($f_{SB1}=23.8%$) and 698 weak bars ($f_{SB2}=6.5%$). We find that $f_{SB1}$ increases as $u-r$ color becomes redder, and that it has a maximum value at intermediate velocity dispersion ($\\sigma\\simeq$150 km s$^{-1}$). This trend suggests that strong bars are dominantly hosted by intermediate-mass systems. Weak bars prefer bluer galaxies with lower mass and lower concentration. In the case of strong bars, their dependence on the concentration index appears only for massive galaxies with $\\sigma>150$ km s${}^{-1}$. We also find that $f_{bar}$ ...

  14. The Dependence of the Pairwise Velocity Dispersion on Galaxy Properties

    CERN Document Server

    Li, C; Kauffmann, G; Börner, G; White, S D M; Cheng, F Z; Li, Cheng; Kauffmann, Guinevere; Boerner, Gerhard; White, Simon D.M.

    2006-01-01

    (abridged) We present measurements of the pairwise velocity dispersion (PVD) for different classes of galaxies in the Sloan Digital Sky Survey. For a sample of about 200,000 galaxies, we study the dependence of the PVD on galaxy properties such as luminosity, stellar mass (M_*), colour (g-r), 4000A break strength (D4000), concentration index (C), and stellar surface mass density (\\mu_*). The luminosity dependence of the PVD is in good agreement with the results of Jing & B\\"orner (2004) for the 2dFGRS catalog. The value of \\sigma_{12} measured at k=1 h/Mpc decreases as a function of increasing galaxy luminosity for galaxies fainter than L*, before increasing again for the most luminous galaxies in our sample. This behaviour is not reproduced using standard halo occupation distribution (HOD) models. Each of the galaxy subsamples selected according to luminosity or stellar mass is divided into two further subsamples according to colour, D4000, C and \\mu_*. We find that galaxies with redder colours and highe...

  15. Superconductivity in all its states

    CERN Multimedia

    Globe Info

    2011-01-01

    Temporary exhibition at the Saint-Genis-Pouilly Tourist Office. For the 100th anniversary of its discovery, take a plunge into the amazing world of superconductivity. Some materials, when cooled down to extreme temperatures, acquire a remarkable property -  they become superconducting. Superconductivity is a rare example of a quantum effect that can be witnessed on the macroscopic scale and is today at the heart of much research. In laboratories, researchers try to gain a better understanding of its origins, study new superconducting materials, explore the phenomenon at the nanometric scale and pursue their indefatigable search for new applications. Monday to Friday: 09:00 a.m. to 12:00 and 2:30 p.m. to 6:30 p.m. Saturday: 10:00 a.m. to 12:00 noon » Open to all – Admission free For further information: +33 (0)4 50 42 29 37

  16. Superconductivity in Layered Organic Metals

    Directory of Open Access Journals (Sweden)

    Jochen Wosnitza

    2012-04-01

    Full Text Available In this short review, I will give an overview on the current understanding of the superconductivity in quasi-two-dimensional organic metals. Thereby, I will focus on charge-transfer salts based on bis(ethylenedithiotetrathiafulvalene (BEDT-TTF or ET for short. In these materials, strong electronic correlations are clearly evident, resulting in unique phase diagrams. The layered crystallographic structure leads to highly anisotropic electronic as well as superconducting properties. The corresponding very high orbital critical field for in-plane magnetic-field alignment allows for the occurrence of the Fulde–Ferrell– Larkin–Ovchinnikov state as evidenced by thermodynamic measurements. The experimental picture on the nature of the superconducting state is still controversial with evidence both for unconventional as well as for BCS-like superconductivity.

  17. Recent advances in fullerene superconductivity

    CERN Document Server

    Margadonna, S

    2002-01-01

    Superconducting transition temperatures in bulk chemically intercalated fulleride salts reach 33 K at ambient pressure and in hole-doped C sub 6 sub 0 derivatives in field-effect-transistor (FET) configurations, they reach 117 K. These advances pose important challenges for our understanding of high-temperature superconductivity in these highly correlated organic metals. Here we review the structures and properties of intercalated fullerides, paying particular attention to the correlation between superconductivity and interfullerene separation, orientational order/disorder, valence state, orbital degeneracy, low-symmetry distortions, and metal-C sub 6 sub 0 interactions. The metal-insulator transition at large interfullerene separations is discussed in detail. An overview is also given of the exploding field of gate-induced superconductivity of fullerenes in FET electronic devices.

  18. Temperature dependence of the electrical properties of hydrogen titanate nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Alves, Diego C. B.; Brandão, Frederico D.; Krambrock, Klaus; Ferlauto, Andre S. [Departamento de Física, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais 31270-901 (Brazil); Fonseca, Fabio C. [Instituto de Pesquisas Energéticas e Nucleares, IPEN/CNEN-SP, 05508-000 São Paulo (Brazil)

    2014-11-14

    The temperature dependence of the electrical properties of hydrogen-rich titanate nanotubes (H-TNTs) in the 90–270 °C range was investigated by impedance spectroscopy. Three types of dominant conduction were found which depend on the previous thermal treatment of the samples. For untreated samples, at low temperatures (T < 100 °C), electrical conductivity is relatively high (>10{sup −4} S/cm at T ≈ 90 °C) and is dominated by protonic transport within structural water molecules. For thermal annealing in inert atmosphere up to 150 °C, water molecules are released from the nanotube structure resulting in a dehydrated H{sub 2}Ti{sub 3}O{sub 7} phase. Such phase has a low, thermally-dependent, electrical conductivity (10{sup −8} S/cm at T ≈ 90 °C) with activation energy of 0.68 eV. For samples annealed up to 260 °C, loss of OH groups, and consequent generation of oxygen vacancies, occurs that result in the non-stoichiometric H{sub 2(1−z)}Ti{sub 3}O{sub 7−z} phase. This phase has much higher conductivity (10{sup −5} S/cm at T ≈ 90 °C) and lower associated activation energy (0.40 eV). The generation of oxygen vacancies is confirmed by electron paramagnetic resonance measurements at room temperature, which revealed the presence of single-electron-trapped oxygen vacancies. The activation energy value found is consistent with the thermal ionization energy of the oxygen vacancies. Such defect formation represents the initial stage of the phase transformation from titanate to TiO{sub 2} (B). X-ray diffraction and Raman spectroscopy measurements also support such interpretation.

  19. Momentum Dependence of Superconducting Gap, Strong-Coupling Dispersion Kink, And Tightly Bound Cooper Pairs in the High-T(C)(Sr,Ba)(1-X)(K,Na)(X)Fe(2) As(2) Superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Wray, L.; Qian, D.; Hsieh, D.; Xia, Y.; Li, L.; Checkelsky, J.G.; Pasupathy, A.; Gomes, K.K.; Parker, C.V.; Fedorov, A.V.; Chen, G.F.; Luo, J.L.; Yazdani, A.; Ong, N.P.; Wang, N.L.; Hasan, M.Z.

    2009-05-28

    We present a systematic angle-resolved photoemission spectroscopic study of the high-T{sub c} superconductor class (Sr/Ba){sub 1-x}K{sub x}Fe{sub 2}As{sub 2}. By utilizing a photon-energy-modulation contrast and scattering geometry we report the Fermi surface and the momentum dependence of the superconducting gap, {triangle}(k{open_square}). A prominent quasiparticle dispersion kink reflecting strong scattering processes is observed in a binding-energy range of 25--55 meV in the superconducting state, and the coherence length or the extent of the Cooper pair wave function is found to be about 20 {angstrom}, which is uncharacteristic of a superconducting phase realized by the BCS-phonon-retardation mechanism. The observed 40{+-}15 meV kink likely reflects contributions from the frustrated spin excitations in a J{sub 1}-J{sub 2} magnetic background and scattering from the soft phonons. Results taken collectively provide direct clues to the nature of the pairing potential including an internal phase-shift factor in the superconducting order parameter which leads to a Brillouin zone node in a strong-coupling setting.

  20. Superconducting proximity effect in a mesoscopic ferromagnetic wire

    OpenAIRE

    Giroud, M.; Courtois, H.; Hasselbach, K.; Mailly, D.; Pannetier, B.

    1998-01-01

    We present an experimental study of the transport properties of a ferromagnetic metallic wire (Co) in metallic contact with a superconductor (Al). As the temperature is decreased below the Al superconducting transition, the Co resistance exhibits a significant dependence on both temperature and voltage. The differential resistance data show that the decay length for the proximity effect is much larger than we would simply expect from the exchange field of the ferromagnet.

  1. Influence of substitutional disorder on the electrical transport and the superconducting properties of Fe{sub 1+z}Te{sub 1−x−y}Se{sub x}S{sub y}

    Energy Technology Data Exchange (ETDEWEB)

    Rodríguez, M.G. [Laboratorio de Bajas Temperaturas, Departamento de Física, FCEyNUBA and IFIBA-CONICET, Buenos Aires (Argentina); Polla, G.; Ramos, C.P. [Gerencia de Investigación y Aplicaciones, CAC-CNEA, San Martín (Argentina); Acha, C., E-mail: acha@df.uba.ar [Laboratorio de Bajas Temperaturas, Departamento de Física, FCEyNUBA and IFIBA-CONICET, Buenos Aires (Argentina)

    2015-11-15

    We have carried out an investigation of the structural, magnetic, transport and superconducting properties of Fe{sub 1+z}Te{sub 1−x−y}Se{sub x}S{sub y} ceramic compounds, for z = 0 and some specific Se (0 ≤ x ≤ 0.5) and S (0 ≤ y ≤ 0.12) contents. The incorporation of Se and S to the FeTe structure produces a progressive reduction of the crystallographic parameters as well as different degrees of structural disorder associated with the differences of the ionic radius of the substituting cations. In the present study, we measure transport properties of this family of compounds and we show the direct influence of disorder in the normal and superconductor states. We notice that the structural disorder correlates with a variable range hopping conducting regime observed at temperatures T > 200 K. At lower temperatures, all the samples except the one with the highest degree of disorder show a crossover to a metallic-like regime, probably related to the transport of resilient-quasi-particles associated with the proximity of a Fermi liquid state at temperatures below the superconducting transition. Moreover, the superconducting properties are depressed only for that particular sample, in accordance to the condition that superconductivity is affected by disorder when the electronic localization length ξ{sub L} becomes smaller than the coherence length ξ{sub SC}. - Highlights: • New Fe(1 + z)Te(1−x−y)Se(x)S(y) ceramic samples were synthesized. • Structural, magnetic, transport and superconducting properties are presented. • Nonmagnetic disorder determines a VRH conduction regime near room temperature. • Superconductivity is affected by disorder.

  2. Anisotropic superconducting and normal state magnetic properties of single crystals of RNi*2*B*2*C compounds (R = Y, Gd, Dy, Ho, Er, and Tm)

    Energy Technology Data Exchange (ETDEWEB)

    Cho, Beongki [Iowa State Univ., Ames, IA (United States)

    1995-09-26

    The interaction of superconductivity with magnetism has been one of the most interesting and important phenomena in solid state physics since the 1950`s when small amounts of magnetic impurities were incorporated in superconductors. The discovery of the magnetic superconductors RNi2B2C (R = rare earth, Y) offers a new system to study this interaction. The wide ranges of superconducting transition (Tc) and antiferromagnetic (AF) ordering temperatures (TN) (0 K ≤ Tc ≤ 16 K, 0 K ≤ TN ≤ 20 K) give a good opportunity to observe a variety of interesting phenomena. Single crystals of high quality with appropriate size and mass are crucial in examining the anisotropic intrinsic properties. Single crystals have been grown successfully by an unusual high temperature flux method and characterized thoroughly by X-ray, electrical transport, magnetization, neutron scattering, scanning electron microscopy, and other measurements.

  3. Indium Substitution Effect on the Topological Crystalline Insulator Family (Pb1−xSnx1−yInyTe: Topological and Superconducting Properties

    Directory of Open Access Journals (Sweden)

    Ruidan Zhong

    2017-02-01

    Full Text Available Topological crystalline insulators (TCIs have been of great interest in the area of condensed matter physics. We investigated the effect of indium substitution on the crystal structure and transport properties in the TCI system (Pb1−xSnx1−yInyTe. For samples with a tin concentration x ≤ 50 % , the low-temperature resisitivities show a dramatic variation as a function of indium concentration: with up to ∼2% indium doping, the samples show weak-metallic behavior similar to their parent compounds; with ∼6% indium doping, samples have true bulk-insulating resistivity and present evidence for nontrivial topological surface states; with higher indium doping levels, superconductivity was observed, with a transition temperature, T c , positively correlated to the indium concentration and reaching as high as 4.7 K. We address this issue from the view of bulk electronic structure modified by the indium-induced impurity level that pins the Fermi level. The current work summarizes the indium substitution effect on (Pb,SnTe, and discusses the topological and superconducting aspects, which can be provide guidance for future studies on this and related systems.

  4. ASC 84: applied superconductivity conference. Final program and abstracts

    Energy Technology Data Exchange (ETDEWEB)

    1984-01-01

    Abstracts are given of presentations covering: superconducting device fabrication; applications of rf superconductivity; conductor stability and losses; detectors and signal processing; fusion magnets; A15 and Nb-Ti conductors; stability, losses, and various conductors; SQUID applications; new applications of superconductivity; advanced conductor materials; high energy physics applications of superconductivity; electronic materials and characterization; general superconducting electronics; ac machinery and new applications; digital devices; fusion and other large scale applications; in-situ and powder process conductors; ac applications; synthesis, properties, and characterization of conductors; superconducting microelectronics. (LEW)

  5. Superconducting LiFeAs as seen by scanning tunneling microscopy/spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Pohle, Rico; Scheffler, Martha; Schlegel, Ronny; Haenke, Torben; Baumann, Danny; Bachmann, Anne; Bombor, Dirk; Sykora, Steffen; Harnagea, Luminita; Wurmehl, Sabine; Hess, Christian; Buechner, Bernd [Institut fuer Festkoerperforschung IFW Dresden (Germany)

    2012-07-01

    Among the entire class of iron-based superconductors the material LiFeAs is of particular interest since an absence of nesting between electron and hole pockets suggests an unconventional type of pairing in this material. Using Scanning Tunnelling Microscopy (STM) and Spectroscopy (STS) we investigate topographic properties of the surface as well as the temperature dependency of the superconducting gap. The good agreement of our results with model calculations for the tunnelling conductance allows us to draw conclusions about the low energy properties of the superconducting system. Furthermore, we compare our results with Transport- and NMR-measurements.

  6. Influence of additions and radiation damage on the superconducting properties of sintered YBa 2Cu 3O 7 - gd

    Science.gov (United States)

    Koblischka, M. R.; Schuster, Th.; Kronmüller, H.

    1993-06-01

    Using the high-resolution Faraday (HRF) technique, domain patterns of sintered YBa 2Cu 3O 7 - δ samples containing additions of Ag 2O and Y 2BaCuO 5 are obtained. Similar observations are carried out on sintered YBa 2Cu 3O 7- δ samples with reduced oxygen content and on electron-irradiated samples. The penetration of flux into sintered high- Tc superconductors is found to be totally different from single crystalline materials (single crystals and epitaxial thin films) as the Abrikosov vortices penetrate the sample not as a whole thus forming a so-called flux front. Only a flux penetration into single superconducting grains is observed. From the measured flux density profiles, the intragrain critical current densities are determined locally. It is found that the chemical impurity phases do not affect the intragranular flux density distribution and the intragranular critical current density, but the decomposition of the Ag 2O leads to an improved oxygen stoichiometry in these samples. Electron irradiation is found to enhance the intragrain critical current densities, whereas the oxygen reduction leads to reduced intragrain currents. To determine the influence of the additions also on the intergrain critical current densities, standard four-point transport current measurements are carried out on the same samples. It is found that a maximum enhancement of the critical current density is obtained by the addition of 10 wt% silver oxide; however, this critical current density is drastically reduced by applying small external magnetic fields. The lower critical field of the matrix and the corresponding Josephson penetration depth are determined from transport current measurements. The Ag 2O additions and the green phase particles are found to separate the superconducting YBa 2Cu 3O 7- δ grains. The resulting larger widths of the barriers between the superconducting grains are found to cause a stronger influence of external magnetic fields on the intergrain critical

  7. Magnetic Field Reentrant Superconductivity in Aluminum Nanowires

    Science.gov (United States)

    Bretz-Sullivan, Terence; Goldman, Allen

    Reentrance to the superconducting state through the application of a magnetic field to quasi-one dimensional superconductors driven resistive by current, is counter to the expected properties of superconductors. It was not until recently that a microscopic mechanism explaining the phenomenon was proposed in which superconductivity and phase slip driven dissipation coexist in a non-equilibrium state. Here we present additional results of magnetic field induced reentrance into the superconducting state in quasi-one-dimensional aluminum nanowires with an in-plane magnetic field both transverse to, and along the wire axis. The reentrant behavior is seen in the magnetic field dependence of the I-V characteristic and resistance vs. temperature, and in the wire's magnetoresistance at 450mK. This work was supported by DOE Basic Energy Sciences Grant DE-FG02-02ER46004. Samples were fabricated at the Minnesota Nanofabrication Center. Parts of this work were carried out in the University of Minnesota Characterization Facility, a member of the Materials Research Facilities Network (www.mrfn.org) funded via the NSF MRSEC program.

  8. Color superconductivity

    Energy Technology Data Exchange (ETDEWEB)

    Wilczek, F. [Institute for Advanced Study, Princeton, NJ (United States)

    1997-09-22

    The asymptotic freedom of QCD suggests that at high density - where one forms a Fermi surface at very high momenta - weak coupling methods apply. These methods suggest that chiral symmetry is restored and that an instability toward color triplet condensation (color superconductivity) sets in. Here I attempt, using variational methods, to estimate these effects more precisely. Highlights include demonstration of a negative pressure in the uniform density chiral broken phase for any non-zero condensation, which we take as evidence for the philosophy of the MIT bag model; and demonstration that the color gap is substantial - several tens of MeV - even at modest densities. Since the superconductivity is in a pseudoscalar channel, parity is spontaneously broken.

  9. SUPERCONDUCTING PHOTOCATHODES.

    Energy Technology Data Exchange (ETDEWEB)

    SMEDLEY, J.; RAO, T.; WARREN, J.; SEKUTOWICZ, LANGNER, J.; STRZYZEWSKI, P.; LEFFERS, R.; LIPSKI, A.

    2005-10-09

    We present the results of our investigation of lead and niobium as suitable photocathode materials for superconducting RF injectors. Quantum efficiencies (QE) have been measured for a range of incident photon energies and a variety of cathode preparation methods, including various lead plating techniques on a niobium substrate. The effects of operating at ambient and cryogenic temperatures and different vacuum levels on the cathode QE have also been studied.

  10. Towards inducing superconductivity into graphene

    Science.gov (United States)

    Efetov, Dmitri K.

    dependent effective Debey temperature - the so-called Bloch-Gruneisen temperature theta BG. We also probe the transport properties of the high energy sub-bands in bilayer graphene by electrolyte gating. Furthermore we demonstrate that electrolyte gates can be used to drive intercalation reactions in graphite and present an all optical study of the reaction kinetics during the creation of the graphene derived graphite intercalation compound LiC 6, and show the general applicability of the electrolyte gates to other 2-dimensional materials such as thin films of complex oxides, where we demonstrate gating dependent conductance changes in the spin-orbit Mott insulator Sr 2IrO4. Another, entirely different approach to induce superconducting correlations into graphene is by bringing it into proximity to a superconductor. Although not intrinsic to graphene, Cooper pairs can leak in from the superconductor and exist in graphene in the form of phase-coherent electron-hole states, the so-called Andreev states. Here we demonstrate a new way of fabricating highly transparent graphene/superconductor junctions by vertical stacking of graphene and the type-II van der Waals superconductor NbSe2. Due to NbSe2's high upper critical field of Hc2=4T we are able to test a long proposed and yet not well understood regime, where proximity effect and quantum Hall effect coexist.

  11. Superconductivity an introduction

    CERN Document Server

    Kleiner, Reinhold

    2016-01-01

    The third edition of this proven text has been developed further in both scope and scale to reflect the potential for superconductivity in power engineering to increase efficiency in electricity transmission or engines. The landmark reference remains a comprehensive introduction to the field, covering every aspect from fundamentals to applications, and presenting the latest developments in organic superconductors, superconducting interfaces, quantum coherence, and applications in medicine and industry. Due to its precise language and numerous explanatory illustrations, it is suitable as an introductory textbook, with the level rising smoothly from chapter to chapter, such that readers can build on their newly acquired knowledge. The authors cover basic properties of superconductors and discuss stability and different material groups with reference to the latest and most promising applications, devoting the last third of the book to applications in power engineering, medicine, and low temperature physics. An e...

  12. Superconducting Accelerator Magnets

    CERN Document Server

    Mess, K H; Wolff, S

    1996-01-01

    The main topic of the book are the superconducting dipole and quadrupole magnets needed in high-energy accelerators and storage rings for protons, antiprotons or heavy ions. The basic principles of low-temperature superconductivity are outlined with special emphasis on the effects which are relevant for accelerator magnets. Properties and fabrication methods of practical superconductors are described. Analytical methods for field calculation and multipole expansion are presented for coils without and with iron yoke. The effect of yoke saturation and geometric distortions on field quality is studied. Persistent magnetization currents in the superconductor and eddy currents the copper part of the cable are analyzed in detail and their influence on field quality and magnet performance is investigated. Superconductor stability, quench origins and propagation and magnet protection are addressed. Some important concepts of accelerator physics are introduced which are needed to appreciate the demanding requirements ...

  13. Anisotropic s-wave superconductivity in graphite intercalation compounds: CaC{sub 6} and SrC{sub 6}

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Jun Sung; Boeri, Lilia; Kremer, Reinhard [Max-Planck-Institut fuer Festkoerperforschung, Heisenbergstrasse 1, D-70569 Stuttgart (Germany); Razavi, Feridoon [Department of Physics, Brock University, St. Catharines, Ontario, L2S 3A1 (Canada)

    2008-07-01

    We have investigated the anisotropy of the superconducting properties for newly-discovered superconducting graphite intercalation compounds, CaC{sub 6} and SrC{sub 6} using specific heat (C{sub p}). The electronic C{sub p} for CaC{sub 6} shows an exponential temperature dependence at low temperatures, consistent with a fully gapped s-wave superconducting order parameter. However, the detailed comparison with an isotropic superconducting gap model shows significant deviation between experiment and theory. From the magnetic field dependence of C{sub p}, the anisotropy of upper critical fields (H{sub c2}) for CaC{sub 6} is {proportional_to}5, consistent with that obtained from the magnetic field dependence of Sommerfeld coefficient, but much larger than that of SrC{sub 6}. In comparison with electronic structure calculations, we found that the isotropic gap model cannot explain observed superconducting properties, suggesting significant anisotropy in the superconducting gap for both CaC{sub 6} and SrC{sub 6}. Recent investigations on a directional point-contact spectroscopy on CaC{sub 6} along the c-axis and ab-plane are also discussed.

  14. Superconductivity in nanowires

    CERN Document Server

    Bezryadin, Alexey

    2012-01-01

    The importance and actuality of nanotechnology is unabated and will be for years to come. A main challenge is to understand the various properties of certain nanostructures, and how to generate structures with specific properties for use in actual applications in Electrical Engineering and Medicine.One of the most important structures are nanowires, in particular superconducting ones. They are highly promising for future electronics, transporting current without resistance and at scales of a few nanometers. To fabricate wires to certain defined standards however, is a major challenge, and so i

  15. Anisotropic superconductivity driven by kinematic interaction

    Science.gov (United States)

    Ivanov, V. A.

    2000-11-01

    We have analysed the effect of kinematic pairing on the symmetry of superconducting order parameter for a square lattice in the frame of the strongly correlated Hubbard model. It is argued that in the first perturbation order the kinematic interaction renormalizes the Hubbard-I dispersions and provides at low doping the mixed singlet (s + s*)-wave superconductivity, giving way at higher doping to the triplet p-wave superconductivity. The obtained phase diagram depends only on the hopping integral parameter. The influence of the Coulomb repulsion on the kinematic superconducting pairing has been estimated. The (s + s*)-wave gap and the thermodynamic critical magnetic field have been derived.

  16. Technique for reduction of mechanical losses in AC superconducting coils due to thermal expansion properties of various FRP bobbins

    Science.gov (United States)

    Sekine, N.; Tada, S.; Higuchi, T.; Furumura, Y.; Takao, T.; Yamanaka, A.

    2005-10-01

    We reported about reduction of mechanical losses in AC superconducting coils. The method is the use of FRP bobbins fabricated with special fibers. Since their FRPs have negative thermal expansion coefficient to the fiber direction, the FRP bobbins expand to the circumferential direction during cooling down. In case of the superconducting coils with such FRP bobbins, the winding tensions do not decrease during cooling down. Therefore, the mechanical losses are reduced by the suppression of wire's vibration. Their special FRPs are a Dyneema® fiber reinforced plastic (DFRP), a Dyneema and glass fiber reinforced plastic (DGFRP), and a Zylon® fiber reinforced plastic (ZFRP). These materials have negative thermal expansion coefficient to the fiber direction, however, the amplitudes of thermal expansion are various by the quantity or quality of the fiber. In this paper, the values of thermal expansion were actually measured, and it was discussed about the influence on the mechanical losses. At the experimental results, the mechanical loss was small, so that the thermal strain to the circumferential direction on the coil was large. Moreover, in case of the coils with sufficiently strong winding tensions at coil-operating temperature, the mechanical losses vanished.

  17. Technique for reduction of mechanical losses in AC superconducting coils due to thermal expansion properties of various FRP bobbins

    Energy Technology Data Exchange (ETDEWEB)

    Sekine, N. [Tsukamoto Laboratory, Faculty of Engineering, Yokohama National University, 79-5, Tokiwadai, Hodogaya-ku, Yokohama 240-8501 (Japan)]. E-mail: n-sekine@tsukalab.dnj.ynu.ac.jp; Tada, S. [Sophia University, 7-1, Kioicho, Chiyoda-ku, Tokyo 102-8554 (Japan); Higuchi, T. [Sophia University, 7-1, Kioicho, Chiyoda-ku, Tokyo 102-8554 (Japan); Furumura, Y. [Sophia University, 7-1, Kioicho, Chiyoda-ku, Tokyo 102-8554 (Japan); Takao, T. [Sophia University, 7-1, Kioicho, Chiyoda-ku, Tokyo 102-8554 (Japan); Yamanaka, A. [Research Center, Toyobo, Co., Ltd, 2-1-1, Katata, Otsu, Shiga 520-0292 (Japan)

    2005-10-01

    We reported about reduction of mechanical losses in AC superconducting coils. The method is the use of FRP bobbins fabricated with special fibers. Since their FRPs have negative thermal expansion coefficient to the fiber direction, the FRP bobbins expand to the circumferential direction during cooling down. In case of the superconducting coils with such FRP bobbins, the winding tensions do not decrease during cooling down. Therefore, the mechanical losses are reduced by the suppression of wire's vibration. Their special FRPs are a Dyneema[reg] fiber reinforced plastic (DFRP), a Dyneema and glass fiber reinforced plastic (DGFRP), and a Zylon[reg] fiber reinforced plastic (ZFRP). These materials have negative thermal expansion coefficient to the fiber direction, however, the amplitudes of thermal expansion are various by the quantity or quality of the fiber. In this paper, the values of thermal expansion were actually measured, and it was discussed about the influence on the mechanical losses. At the experimental results, the mechanical loss was small, so that the thermal strain to the circumferential direction on the coil was large. Moreover, in case of the coils with sufficiently strong winding tensions at coil-operating temperature, the mechanical losses vanished.

  18. Structural and superconducting properties of LaFeAs1-xSbxO1-yFy

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    We report the antimony(Sb) doping effect in a prototype system of iron-based superconductors LaFeAsO1-yFy(y=0,0.1,0.15).X-ray powder diffraction indicates that the lattice parameters increase with Sb content within the doping limit.Rietveld structural refinements show that,with the partial substitution of Sb for As,the thickness of the Fe2As2 layers increases significantly,whereas that of the La2O2 layers shrinks simultaneously.So a negative chemical pressure is indeed "applied" to the superconducting-active Fe2As2 layers,in contrast to the effect of positive chemical pressure by the phosphorus doping.Electrical resistance and magnetic susceptibility measurements indicate that,while the Sb doping hardly influences the SDW anomaly in LaFeAsO,it recovers SDW order for the optimally-doped sample of y=0.1.In the meantime,the superconducting transition temperature can be raised up to 30 K in LaFeAs1-xSbxO1-yFy with x=0.1 and y=0.15.The Sb doping effects are discussed in term of both J1-J2 model and Fermi Surface(FS) nesting scenario.

  19. Metal-insulator transition and superconductivity in heavily boron-doped diamond and related materials

    Energy Technology Data Exchange (ETDEWEB)

    Achatz, Philipp

    2009-05-15

    During this PhD project, the metal-insulator transition and superconductivity of highly boron-doped single crystal diamond and related materials have been investigated. The critical boron concentration n{sub c} for the metal-insulator transition was found to be the same as for the normal-superconductor transition. All metallic samples have been found to be superconducting and we were able to link the occurence of superconductivity to the proximity to the metal-insulator transition. For this purpose, a scaling law approach based on low temperature transport was proposed. Furthermore, we tried to study the nature of the superconductivity in highly boron doped single crystal diamond. Raman spectroscopy measurements on the isotopically substituted series suggest that the feature occuring at low wavenumbers ({approx} 500 cm{sup -1}) is the A1g vibrational mode associated with boron dimers. Usual Hall effect measurements yielded a puzzling situation in metallic boron-doped diamond samples, leading to carrier concentrations up to a factor 10 higher than the boron concentration determined by secondary ion mass spectroscopy (SIMS). The low temperature transport follows the one expected for a granular metal or insulator, depending on the interplay of intergranular and intragranular (tunneling) conductance. The metal-insulator transition takes place at a critical conductance g{sub c}. The granularity also influences significantly the superconducting properties by introducing the superconducting gap {delta} in the grain and Josephson coupling J between superconducting grains. A peak in magnetoresistance is observed which can be explained by superconducting fluctuations and the granularity of the system. Additionally we studied the low temperature transport of boron-doped Si samples grown by gas immersion laser doping, some of which yielded a superconducting transition at very low temperatures. Furthermore, preliminary results on the LO-phonon-plasmon coupling are shown for the

  20. Gate-induced superconductivity in two-dimensional atomic crystals

    Science.gov (United States)

    Saito, Yu; Nojima, Tsutomu; Iwasa, Yoshihiro

    2016-09-01

    Two-dimensional (2D) crystals are attracting growing interest in condensed matter physics, since these systems exhibit not only rich electronic and photonic properties but also exotic electronic phase transitions including superconductivity and charge density wave. Moreover, owing to the recent development of transfer methods after exfoliation and electric-double-layer transistors, superconducting 2D atomic crystals, the thicknesses of which are below 1-2 nm, have been successfully obtained. Here, we present a topical review on the recent discoveries of 2D crystalline superconductors by ionic-liquid gating and a series of their novel properties. In particular, we highlight two topics; quantum metallic states (or possible metallic ground states) and superconductivity robust against in-plane magnetic fields. These phenomena can be discussed with the effects of weakened disorder and/or broken spacial inversion symmetry leading to valley-dependent spin-momentum locking (spin-valley locking). These examples suggest the superconducting 2D crystals are new platforms for investigating the intrinsic quantum phases as well as exotic nature in 2D superconductors.

  1. Superconductivity in highly disordered NbN nanowires

    Science.gov (United States)

    Arutyunov, K. Yu; Ramos-Álvarez, A.; Semenov, A. V.; Korneeva, Yu P.; An, P. P.; Korneev, A. A.; Murphy, A.; Bezryadin, A.; Gol'tsman, G. N.

    2016-11-01

    The topic of superconductivity in strongly disordered materials has attracted significant attention. These materials appear to be rather promising for fabrication of various nanoscale devices such as bolometers and transition edge sensors of electromagnetic radiation. The vividly debated subject of intrinsic spatial inhomogeneity responsible for the non-Bardeen-Cooper-Schrieffer relation between the superconducting gap and the pairing potential is crucial both for understanding the fundamental issues of superconductivity in highly disordered superconductors, and for the operation of corresponding nanoelectronic devices. Here we report an experimental study of the electron transport properties of narrow NbN nanowires with effective cross sections of the order of the debated inhomogeneity scales. The temperature dependence of the critical current follows the textbook Ginzburg-Landau prediction for the quasi-one-dimensional superconducting channel I c ˜ (1-T/T c)3/2. We find that conventional models based on the the phase slip mechanism provide reasonable fits for the shape of R(T) transitions. Better agreement with R(T) data can be achieved assuming the existence of short ‘weak links’ with slightly reduced local critical temperature T c. Hence, one may conclude that an ‘exotic’ intrinsic electronic inhomogeneity either does not exist in our structures, or, if it does exist, it does not affect their resistive state properties, or does not provide any specific impact distinguishable from conventional weak links.

  2. Tunable superconducting nanoinductors

    Energy Technology Data Exchange (ETDEWEB)

    Annunziata, Anthony J; Santavicca, Daniel F; Frunzio, Luigi; Rooks, Michael J; Prober, Daniel E [Department of Applied Physics, Yale University, New Haven, CT 06511 (United States); Catelani, Gianluigi [Department of Physics, Yale University, New Haven, CT 06511 (United States); Frydman, Aviad, E-mail: anthony.annunziata@yale.edu, E-mail: daniel.prober@yale.edu [Department of Physics, Bar-Ilan University, Ramat Gan 52900 (Israel)

    2010-11-05

    We characterize inductors fabricated from ultra-thin, approximately 100 nm wide strips of niobium (Nb) and niobium nitride (NbN). These nanowires have a large kinetic inductance in the superconducting state. The kinetic inductance scales linearly with the nanowire length, with a typical value of 1 nH {mu}m{sup -1} for NbN and 44 pH {mu}m{sup -1} for Nb at a temperature of 2.5 K. We measure the temperature and current dependence of the kinetic inductance and compare our results to theoretical predictions. We also simulate the self-resonant frequencies of these nanowires in a compact meander geometry. These nanowire inductive elements have applications in a variety of microwave frequency superconducting circuits.

  3. Contact angle dependence of the resonant properties of sessile drops

    Science.gov (United States)

    Sharp, James

    2012-02-01

    A simple optical deflection technique was used to monitor the vibrations of microlitre sessile drops of glycerol/water mixtures with glycerol compositions ranging from 0% to 75%. A photodiode was used to detect time dependent variations in the intensity of laser light reflected from the droplets. The intensity variations were Fourier transformed to obtain information about the resonant properties of the drops (frequency and width of the resonance). These experiments were performed on a range of different substrates where the contact angle formed by the droplets varied between 38±2^o and 160±4^o. The measured resonant frequency values were found to be in agreement with a recently developed theory of vibrations which considers standing wave states along the profile length of the droplet. The widths of the resonances were also compared with theories which predict the influence of substrate effects, surface contamination effects and bulk viscous effects on the damping of capillary waves at the free surface of the droplets. These experiments indicate that the dominant source of damping in sessile liquid droplet is due to bulk viscous effects but that for small contact angles damping due to the droplet/substrate interaction becomes more important.

  4. Superconducting and mechanical properties of the bulk Bi(pb)SCCO system prepared via solid state and ammonium nitrate precipitation methods

    Science.gov (United States)

    Safran, S.; Kılıçarslan, E.; Ozturk, H.; Alp, M.; Akdogan, M.; Asikuzun, E.; Ozturk, O.; Kılıç, A.

    2015-09-01

    We have investigated the effect of preparation method on superconducting and mechanical properties of Bi(Pb)-2223 bulk samples using Bi1.85Pb0.35Sr2Ca2Cu3O10±y stoichiometry. Solid-state reaction and ammonium nitrate precipitation methods have been used for fabrication of the bulk samples. In addition, the effect of annealing time on BSCCO samples have been studied. Structural, electrical, magnetic and microhardness analyses of samples are performed by the X-ray powder diffraction (XRD), the Scanning Electron Microscopy (SEM), DC resistivity, AC susceptibility and Vickers microhardness test. The critical transition temperature, phase purity, surface morphology and crystallinity of the prepared bulk samples are compared with each other. Elasticity (E), brittleness (Bi), fracture toughness (KIC) and yield strength (Y) values are also determined according to annealing time, applied load and production parameters of materials.

  5. Thickness-Dependent Properties of YBCO Films Grown on GZO/CLO-Buffered NiW Substrates

    Science.gov (United States)

    Malmivirta, M.; Huhtinen, H.; Zhao, Y.; Grivel, J.-C.; Paturi, P.

    2017-01-01

    To study the role of novel Gd_2Zr_2O_7/Ce_{0.9}La_{0.1}O_2 buffer layer structure on a biaxially textured NiW substrate, a set of YBa_2Cu_3O_{7-δ } (YBCO) films with different thicknesses were prepared by pulsed laser deposition (PLD). Interface imperfections as well as thickness-dependent structural properties were observed in the YBCO thin films. The structure is also reflected into the improved superconducting properties with the highest critical current densities in films with intermediate thicknesses. Therefore, it can be concluded that the existing buffer layers need more optimization before they can be successfully used for films with various thicknesses. This issue is linked to the extremely susceptible growth method of PLD when compared to the commonly used chemical deposition methods. Nevertheless, PLD-grown films can give a hint on what to concentrate to be able to further improve the buffer layer structures for future coated conductor technologies.

  6. Evidence of weak superconductivity at the room-temperature grown LaAlO3/SrTiO3 interface

    DEFF Research Database (Denmark)

    Prawiroatmodjo, G. E. D. K.; Trier, Felix; Christensen, Dennis Valbjørn;

    2016-01-01

    The two-dimensional electron gas at the crystalline LaAlO3/SrTiO3 (c-LAO/STO) interface has sparked large interest due to its exotic properties, including an intriguing gate-tunable superconducting phase. While there is growing evidence of pronounced spatial inhomogeneity in the conductivity at STO......-based interfaces, the consequences for superconductivity remain largely unknown. We study interfaces based on amorphous LAO top layers grown at room temperature (a-LAO/STO) and demonstrate a superconducting phase similar to c-LAO/STO, however, with a gate-tunable critical temperature of 460 mK. The dependence...... of the superconducting critical current on temperature, magnetic field, and back-gate-controlled doping is found to be consistently described by a model of a random array of Josephson-coupled superconducting domains....

  7. Oxygen Adsorption-Desorption Behavior and Superconducting Properties of High-Tc Bi(Pb)-Sr-Ca-Cu-O

    Science.gov (United States)

    Miura, Norio; Suzuta, Hiroki; Deshimaru, Yuichi; Shimizu, Youichi; Sakashita, Hirofumi; Yamazoe, Noboru

    1989-07-01

    Temperature-programmed desorption (TPD) chromatograms revealed that a small amount of oxygen was desorbed from high-Tc Bi(Pb)-Sr-Ca-Cu-O (BPSCCO) in the temperature range from ca. 350 to ca. 650°C prior to a steep increase of oxygen desorption in the higher temperature range. The Tc of BPSCCO was significantly lowered with the progress of oxygen desorption especially in the former temperature range, and was restored to the original level when the desorbed oxygen was recovered. With no corresponding changes in X-ray powder diffraction pattern being detected, the oxygen desorbed below ca. 650°C was concluded to have strong relevance to the superconductivity of BPSCCO.

  8. Effect of starting materials on the superconducting properties of SmFeAsO1-xFx tapes

    Science.gov (United States)

    Wang, Chunlei; Yao, Chao; Zhang, Xianping; Gao, Zhaoshun; Wang, Dongliang; Wang, Chengduo; Lin, He; Ma, Yanwei; Awaji, Satoshi; Watanabe, Kazuo

    2012-03-01

    SmFeAsO1-xFx tapes were prepared using three kinds of starting materials. This showed that the starting materials have an obvious effect on the impurity phases in the final superconducting tapes. Compared with the other samples, the samples fabricated with SmAs, FeO, Fe2As, and SmF3 have the smallest arsenide impurity phases and voids. As a result, these samples possess much denser structures and better grain connectivities. Moreover, among the three kinds of sample fabricated in this work, this kind of sample has the highest zero resistivity temperature, ˜40 K, and the largest critical current density, ˜4600 A cm-2, in self-field at 4.2 K. This is the highest Jc value reported so far for SmFeAsO1-xFx wires and tapes.

  9. Superconductivity and magnetic properties in SmFe1-xCoxAsO (x=0 to 1)

    Science.gov (United States)

    Qi, Yanpeng; Wang, Lei; Gao, Zhaoshun; Wang, Dongliang; Zhang, Xianping; Yao, Chao; Wang, Chunlei; Wang, Chengduo; Ma, Yanwei

    2011-10-01

    In this paper the effects of replacing Fe with Co in SmFe1-xCoxAsO (x=0 to 1) are reported. X-ray diffraction patterns indicate that all the samples have formed the ZrCuSiAs-type structure with a space group P4/nmm and a full solid solution forms between SmFeAsO and SmCoAsO. It is found that the antiferromagnetic spin-density-wave (SDW) order in the parent compounds is rapidly suppressed by Co-doping, and superconductivity emerges as 0.05 SmFeAsO-SmCoAsO system. The systemic study in the SmFe1-xCoxAsO system would add more ingredients to the underlying physics of this material.

  10. Nonlinear elastic properties of superconducting antiperovskites MNNi 3 (M =Zn, Cd, Mg, Al, Ga, and In) from first principles

    KAUST Repository

    Liu, Lili

    2014-05-22

    We present theoretical studies for the third-order elastic constants (TOECs) of superconducting antiperovskites MNNi 3 (M = Zn, Cd, Mg, Al, Ga, and In) using the density functional theory (DFT) and homogeneous deformation method. From the nonlinear least-square fitting, the elastic constants are extracted from a polynomial fit to the calculated strain-energy data. Calculated second-order elastic constants (SOECs) are compared with the previous theoretical calculations, and a very good agreement was found. The nonlinear effects often play an important role when the finite strains are larger than approximately 2.5 %. Besides, we have computed the pressure derivatives of SOECs and provided rough estimations for the Grüneisen constants of long-wavelength acoustic modes by using the calculated TOECs. © 2014 Springer Science+Business Media New York.

  11. Information quantifiers, entropy squeezing and entanglement properties of superconducting qubit-deformed bosonic field system under dephasing effect

    Science.gov (United States)

    Berrada, K.; Al-Rajhi, M. A.

    2017-10-01

    In this paper, we present a detailed study on the evolution of some measures of nonclassicality and entanglement in the framework of the interaction between a superconducting qubit and deformed bosonic fields under decoherence effect. We compare the dynamical behavior of the different quantum quantifiers by exploiting a large set of nonlinear bosonic fields that are characterized by the deformation parameter. Additionally, we demonstrate how the connection between the appearance of the nonlinearity in the deformed field and the quantum information quantifiers. The time correlation between entropy squeezing, purity, and entanglement is examined in terms of the physical parameters involved in the whole system. Lastly, we explore the exact ranges of the physical parameters in order to combat the decoherence effect and maintain high amount of entanglement during the time evolution.

  12. Can doping graphite trigger room temperature superconductivity? Evidence for granular high-temperature superconductivity in water-treated graphite powder.

    Science.gov (United States)

    Scheike, T; Böhlmann, W; Esquinazi, P; Barzola-Quiquia, J; Ballestar, A; Setzer, A

    2012-11-14

    Granular superconductivity in powders of small graphite grains (several tens of micrometers) is demonstrated after treatment with pure water. The temperature, magnetic field and time dependence of the magnetic moment of the treated graphite powder provides evidence for the existence of superconducting vortices with some similarities to high-temperature granular superconducting oxides but even at temperatures above 300 K. Room temperature superconductivity in doped graphite or at its interfaces appears to be possible.

  13. Contextuality without nonlocality in a superconducting quantum system

    Science.gov (United States)

    Jerger, Markus; Reshitnyk, Yarema; Oppliger, Markus; Potočnik, Anton; Mondal, Mintu; Wallraff, Andreas; Goodenough, Kenneth; Wehner, Stephanie; Juliusson, Kristinn; Langford, Nathan K.; Fedorov, Arkady

    2016-10-01

    Classical realism demands that system properties exist independently of whether they are measured, while noncontextuality demands that the results of measurements do not depend on what other measurements are performed in conjunction with them. The Bell-Kochen-Specker theorem states that noncontextual realism cannot reproduce the measurement statistics of a single three-level quantum system (qutrit). Noncontextual realistic models may thus be tested using a single qutrit without relying on the notion of quantum entanglement in contrast to Bell inequality tests. It is challenging to refute such models experimentally, since imperfections may introduce loopholes that enable a realist interpretation. Here we use a superconducting qutrit with deterministic, binary-outcome readouts to violate a noncontextuality inequality while addressing the detection, individual-existence and compatibility loopholes. This evidence of state-dependent contextuality also demonstrates the fitness of superconducting quantum circuits for fault-tolerant quantum computation in surface-code architectures, currently the most promising route to scalable quantum computing.

  14. The relation between ferroelasticity and superconductivity

    Science.gov (United States)

    Molak, A.; Manka, R.

    1991-01-01

    The high-temperature superconductivity is explained widely by the layered crystal structure. The one- and two-dimensional subsystems and their interaction are investigated here. It is assumed that the high-T(sub c) superconductivity takes place in the two-dimensional subsystem and the increase of the phase transition temperature from 60 K up to 90 K is the consequence of turning on the influence of one-dimensional chains. The interaction between the two subsystems is transferred along the c axis by the phonons of breathing mode, which causes the hybridization of the electronic bonds between these subsystems. The experimental works indicate that the existence of both the chains Cu(1)-O and their interaction with the superconducting plane of Cu(2)-O modify the temperature of the transition to the superconducting state. It is seen from the neutron scattering data that the rates of the interatomic distance dependencies on temperature are changed around 240 K and 90 K. The 'zig-zag' order in Cu(1)-O chains has been postulated but, on the other hand, the vibrations with a large amplitude only were reported. The bi-stabilized situation of the oxygen ions can be caused by the change of distance between these ions and the Ba ions. It leads to the appearance of a two-well potential. Its parameters depend on temperature and the dynamics of the oxygen ions' movement. They can induce the antipolar order, which can be, however, more or less chaotic. The investigation of the ferroelastic properties of Y-Ba-Cu-O samples lead to the conclusion that they are related to jumps of ions inside the given chain and not to a diffusion between different sites in the ab plane. Researchers deduce, thus, that the fluctuating oxygen ions from these chains create dipoles in the ab plane. They can be described with the pseudo-spin formalism (- Pauli matrices). The system can be described with the Ising model. The pseudo-spins interact with phonons and influence the superconductivity in the second

  15. Mapping Dimensionality and Directionality of Electronic Behavior in CeCoIn5: the Superconducting State

    Science.gov (United States)

    Feldman, Benjamin E.; Gyenis, Andras; Randeria, Mallika T.; Peterson, Gabriel A.; Aynajian, Pegor; Bauer, Eric D.; Yazdani, Ali

    Unconventional superconductors often exhibit anisotropic physical properties that arise from the directional dependence of their order parameters. A prime example is CeCoIn5, a heavy fermion d-wave superconductor with a rich low-temperature phase diagram consisting of competing and coexisting magnetic and superconducting orders. Here we present dilution refrigerator scanning tunneling microscopy of CeCoIn5 cleaved perpendicular to its basal plane. We study superconductivity on the (100) surface, whose normal vector points along the antinode of the superconducting energy gap. The gap magnitude is similar to that observed in the basal plane, with a key difference: it does not exhibit any suppression near step edges. Application of a magnetic field along the [100] direction leads to the formation of anisotropic vortices, and the vortex lattice undergoes a transition at high field before the superconducting state gives way to a pseudogap phase. Our measurements illustrate the directional dependence of the superconducting properties in CeCoIn5, and more generally, demonstrate the utility of imaging d-wave superconductors along their nodal and antinodal directions.

  16. Superconductivity at 52.5 K in the lanthanum-barium-copper-oxide system

    Science.gov (United States)

    Chu, C. W.; Hor, P. H.; Meng, R. L.; Gao, L.; Huang, Z. J.

    1987-01-01

    The electrical properties of the (La/0/9/Ba/0.1/)CuO/4-y/ system are examined under ambient and hydrostatic pressures. The resistance, ac magnetic susceptibility, and superconductivity onset, midpoint, and intercept temperatures are measured. It is observed that at ambient pressure the resistance decreases with temperature decreases, and the ac susceptibility shows diamagnetic shifts starting at about 32 K. Under hydrostatic pressure a superconducting transition with an onset temperature of 52.5 K is observed, and the resistance increases at lower temperatures. The data reveal that the electrical properties of the La-Ba-Cu-O system are dependent on samples and preparation conditions. Various causes for the high temperature superconductivity of the system are proposed.

  17. Topological superconductivity induced by ferromagnetic metal chains

    Science.gov (United States)

    Li, Jian; Chen, Hua; Drozdov, Ilya K.; Yazdani, A.; Bernevig, B. Andrei; MacDonald, A. H.

    2014-12-01

    Recent experiments have provided evidence that one-dimensional (1D) topological superconductivity can be realized experimentally by placing transition-metal atoms that form a ferromagnetic chain on a superconducting substrate. We address some properties of this type of system by using a Slater-Koster tight-binding model to account for important features of the electronic structure of the transition-metal chains on the superconducting substrate. We predict that topological superconductivity is nearly universal when ferromagnetic transition-metal chains form straight lines on superconducting substrates and that it is possible for more complex chain structures. When the chain is weakly coupled to the substrate and is longer than superconducting coherence lengths, its proximity-induced superconducting gap is ˜Δ ESO/J where Δ is the s -wave pair potential on the chain, ESO is the spin-orbit splitting energy induced in the normal chain state bands by hybridization with the superconducting substrate, and J is the exchange splitting of the ferromagnetic chain d bands. Because of the topological character of the 1D superconducting state, Majorana end modes appear within the gaps of finite length chains. We find, in agreement with the experiment, that when the chain and substrate orbitals are strongly hybridized, Majorana end modes are substantially reduced in amplitude when separated from the chain end by less than the coherence length defined by the p -wave superconducting gap. We conclude that Pb is a particularly favorable substrate material for ferromagnetic chain topological superconductivity because it provides both strong s -wave pairing and strong Rashba spin-orbit coupling, but that there is an opportunity to optimize properties by varying the atomic composition and structure of the chain. Finally, we note that in the absence of disorder, a new chain magnetic symmetry, one that is also present in the crystalline topological insulators, can stabilize multiple

  18. Push-Pull Type Oligo(N-annulated perylene)quinodimethanes: Chain Length and Solvent-Dependent Ground States and Physical Properties.

    Science.gov (United States)

    Zeng, Zebing; Lee, Sangsu; Son, Minjung; Fukuda, Kotaro; Burrezo, Paula Mayorga; Zhu, Xiaojian; Qi, Qingbiao; Li, Run-Wei; Navarrete, Juan T López; Ding, Jun; Casado, Juan; Nakano, Masayoshi; Kim, Dongho; Wu, Jishan

    2015-07-08

    Research on stable open-shell singlet diradicaloids recently became a hot topic because of their unique optical, electronic, and magnetic properties and promising applications in materials science. So far, most reported singlet diradicaloid molecules have a symmetric structure, while asymmetric diradicaloids with an additional contribution of a dipolar zwitterionic form to the ground state were rarely studied. In this Article, a series of new push-pull type oligo(N-annulated perylene)quinodimethanes were synthesized. Their chain length and solvent-dependent ground states and physical properties were systematically investigated by various experimental methods such as steady-state and transient absorption, two-photon absorption, X-ray crystallographic analysis, electron spin resonance, superconducting quantum interference device, Raman spectroscopy, and electrochemistry. It was found that with extension of the chain length, the diradical character increases while the contribution of the zwitterionic form to the ground state becomes smaller. Because of the intramolecular charge transfer character, the physical properties of this push-pull system showed solvent dependence. In addition, density functional theory calculations on the diradical character and Hirshfeld charge were conducted to understand the chain length and solvent dependence of both symmetric and asymmetric systems. Our studies provided a comprehensive understanding on the fundamental structure- and environment-property relationships in the new asymmetric diradicaloid systems.

  19. Design and simulation of superconducting Lorentz Force Electrical Impedance Tomography (LFEIT)

    Energy Technology Data Exchange (ETDEWEB)

    Shen, Boyang, E-mail: bs506@cam.ac.uk; Fu, Lin, E-mail: lf359@cam.ac.uk; Geng, Jianzhao, E-mail: jg717@cam.ac.uk; Zhang, Xiuchang, E-mail: xz326@cam.ac.uk; Zhang, Heng, E-mail: hz301@cam.ac.uk; Dong, Qihuan, E-mail: qd210@cam.ac.uk; Li, Chao, E-mail: cl644@cam.ac.uk; Li, Jing, E-mail: jl908@cam.ac.uk; Coombs, T.A., E-mail: tac1000@cam.ac.uk

    2016-05-15

    Highlights: • Design of superconducting magnets using Halbach Array configuration. • Combination of superconducting magnets together with Lorentz Force Electrical Impedance Tomography (LFEIT) system. • Simulation of superconducting LFEIT system based on the theory of magneto-acoustic effect. - Abstract: Lorentz Force Electrical Impedance Tomography (LFEIT) is a hybrid diagnostic scanner with strong capability for biological imaging, particularly in cancer and haemorrhages detection. This paper presents the design and simulation of a novel combination: a superconducting magnet together with LFEIT system. Superconducting magnets can generate magnetic field with high intensity and homogeneity, which could significantly enhance the imaging performance. The modelling of superconducting magnets was carried out using Finite Element Method (FEM) package, COMSOL Multiphysics, which was based on Partial Differential Equation (PDE) model with H-formulation coupling B-dependent critical current density and bulk approximation. The mathematical model for LFEIT system was built based on the theory of magneto-acoustic effect. The magnetic field properties from magnet design were imported into the LFEIT model. The basic imaging of electrical signal was developed using MATLAB codes. The LFEIT model simulated two samples located in three different magnetic fields with varying magnetic strength and homogeneity.

  20. Itinerant Ferromagnetism and Superconductivity

    OpenAIRE

    Karchev, Naoum

    2004-01-01

    Superconductivity has again become a challenge following the discovery of unconventional superconductivity. Resistance-free currents have been observed in heavy-fermion materials, organic conductors and copper oxides. The discovery of superconductivity in a single crystal of $UGe_2$, $ZrZn_2$ and $URhGe$ revived the interest in the coexistence of superconductivity and ferromagnetism. The experiments indicate that: i)The superconductivity is confined to the ferromagnetic phase. ii)The ferromag...

  1. 100 years of superconductivity

    CERN Document Server

    Rogalla, Horst

    2011-01-01

    Even a hundred years after its discovery, superconductivity continues to bring us new surprises, from superconducting magnets used in MRI to quantum detectors in electronics. 100 Years of Superconductivity presents a comprehensive collection of topics on nearly all the subdisciplines of superconductivity. Tracing the historical developments in superconductivity, the book includes contributions from many pioneers who are responsible for important steps forward in the field.The text first discusses interesting stories of the discovery and gradual progress of theory and experimentation. Emphasizi

  2. 4. MESOSCOPIC SUPERCONDUCTIVITY: Proximity Action theory of superconductive nanostructures

    Science.gov (United States)

    Skvortsov, M. A.; Larkin, A. I.; Feigel'man, M. V.

    2001-10-01

    We review a novel approach to the superconductive proximity effect in disordered normal-superconducting (N-S) structures. The method is based on the multicharge Keldysh action and is suitable for the treatment of interaction and fluctuation effects. As an application of the formalism, we study the subgap conductance and noise in two-dimensional N-S systems in the presence of the electron-electron interaction in the Cooper channel. It is shown that singular nature of the interaction correction at large scales leads to a nonmonotonuos temperature, voltage and magnetic field dependence of the Andreev conductance.

  3. Theory analysis of critical-current degeneration in bended superconducting tapes of multifilament composite Bi2223/Ag

    Energy Technology Data Exchange (ETDEWEB)

    Gao, Peifeng; Wang, Xingzhe, E-mail: xzwang@lzu.edu.cn

    2015-10-15

    Highlights: • We proposed an empirical model to describe carrying-current degradation of bent Bi2223/Ag tapes. • Asymmetric damage of superconductor multifilament is taken into account. • Both the loading and unloading processes of bend deformation are captured. • Carrying-current property can be improved by designing configuration of the multifilament core. - Abstract: This paper proposed a degradation model to explore the influence of the mechanical bending deformation on the critical-current of superconducting composite Bi2223/Ag tape taking into account the asymmetric mechanical damage. With the aid of Weibull distribution function of statistical damage of filaments, the critical-current dependence upon bending strain of the superconducting tape in processes of loading and unloading is characterized. The degradation profile of critical-current in the superconducting composite tape is theoretically investigated by the proposed model for different critical damage strains and configurations of superconducting multifilament core at the cross-section. It is shown that the theoretical predictions are in reasonably good agreement with the experimental data, and the configuration of the multifilament core of the superconducting composite tape has a significant influence on the critical-current degradation. The superconducting multifilament core located near the compression region of the cross-section remarkably improves the mechanical and carrying-current capabilities of the superconducting composite tape.

  4. Foreword: Focus on Superconductivity in Semiconductors

    Directory of Open Access Journals (Sweden)

    Yoshihiko Takano

    2008-01-01

    Full Text Available Since the discovery of superconductivity in diamond, much attention has been given to the issue of superconductivity in semiconductors. Because diamond has a large band gap of 5.5 eV, it is called a wide-gap semiconductor. Upon heavy boron doping over 3×1020 cm−3, diamond becomes metallic and demonstrates superconductivity at temperatures below 11.4 K. This discovery implies that a semiconductor can become a superconductor upon carrier doping. Recently, superconductivity was also discovered in boron-doped silicon and SiC semiconductors. The number of superconducting semiconductors has increased. In 2008 an Fe-based superconductor was discovered in a research project on carrier doping in a LaCuSeO wide-gap semiconductor. This discovery enhanced research activities in the field of superconductivity, where many scientists place particular importance on superconductivity in semiconductors.This focus issue features a variety of topics on superconductivity in semiconductors selected from the 2nd International Workshop on Superconductivity in Diamond and Related Materials (IWSDRM2008, which was held at the National Institute for Materials Science (NIMS, Tsukuba, Japan in July 2008. The 1st workshop was held in 2005 and was published as a special issue in Science and Technology of Advanced Materials (STAM in 2006 (Takano 2006 Sci. Technol. Adv. Mater. 7 S1.The selection of papers describe many important experimental and theoretical studies on superconductivity in semiconductors. Topics on boron-doped diamond include isotope effects (Ekimov et al and the detailed structure of boron sites, and the relation between superconductivity and disorder induced by boron doping. Regarding other semiconductors, the superconducting properties of silicon and SiC (Kriener et al, Muranaka et al and Yanase et al are discussed, and In2O3 (Makise et al is presented as a new superconducting semiconductor. Iron-based superconductors are presented as a new series of high

  5. Magnetic Exchange Between Superconducting and Ferromagnetic Oxide Layers

    Science.gov (United States)

    Giblin, Sean; Taylor, Jon; Duffy, Jon; Dugdale, Stephen; Nakamura, T.; Santamaria, Jacobo

    2012-02-01

    The origins of high temperature superconductivity and the rich phase diagrams in complex oxides are still a matter of contention that have stimulated many novel experimental studies and observations. Recently the improvement of layer by layer growth techniques of thin films has enabled investigations of both bulk and surface properties. For most common superconductors the order parameter is thought to be antagonistic to that of the exchange mechanism in ferromagnets. Accurately grown thin fllms have enabled these competing interactions to be probed experimentally. In particular, the growth of epitaxial oxide layers, with well-characterized atomically flat interfaces, consisting of superconducting layers of YBa2Cu3O7 (YBCO) and lattice-matched ferromagnetic La2/3Ca1/3MnO3 (LCMO) has flourished. Using XMCD we demonstrate that the known superexchange between Mn and Cu across the YBCO/LCMO is modified when an apparent critical thickness of the superconducting layer is reduced. All samples show an apparent exchange below the superconducting transition but above it is dependent on the YBCO thickness. Possible origins of this behaviour will be discussed.

  6. Evidence for superconductivity in Li-decorated monolayer graphene.

    Science.gov (United States)

    Ludbrook, B M; Levy, G; Nigge, P; Zonno, M; Schneider, M; Dvorak, D J; Veenstra, C N; Zhdanovich, S; Wong, D; Dosanjh, P; Straßer, C; Stöhr, A; Forti, S; Ast, C R; Starke, U; Damascelli, A

    2015-09-22

    Monolayer graphene exhibits many spectacular electronic properties, with superconductivity being arguably the most notable exception. It was theoretically proposed that superconductivity might be induced by enhancing the electron-phonon coupling through the decoration of graphene with an alkali adatom superlattice [Profeta G, Calandra M, Mauri F (2012) Nat Phys 8(2):131-134]. Although experiments have shown an adatom-induced enhancement of the electron-phonon coupling, superconductivity has never been observed. Using angle-resolved photoemission spectroscopy (ARPES), we show that lithium deposited on graphene at low temperature strongly modifies the phonon density of states, leading to an enhancement of the electron-phonon coupling of up to λ ≃ 0.58. On part of the graphene-derived π*-band Fermi surface, we then observe the opening of a Δ ≃ 0.9-meV temperature-dependent pairing gap. This result suggests for the first time, to our knowledge, that Li-decorated monolayer graphene is indeed superconducting, with Tc ≃ 5.9 K.

  7. Size-Dependent Materials Properties Toward a Universal Equation

    Directory of Open Access Journals (Sweden)

    Guisbiers G

    2010-01-01

    Full Text Available Abstract Due to the lack of experimental values concerning some material properties at the nanoscale, it is interesting to evaluate this theoretically. Through a “top–down” approach, a universal equation is developed here which is particularly helpful when experiments are difficult to lead on a specific material property. It only requires the knowledge of the surface area to volume ratio of the nanomaterial, its size as well as the statistic (Fermi–Dirac or Bose–Einstein followed by the particles involved in the considered material property. Comparison between different existing theoretical models and the proposed equation is done.

  8. Improved Superconducting properties in the Mg11B2 low activation superconductor prepared by low-temperature sintering

    Science.gov (United States)

    Cheng, Fang; Liu, Yongchang; Ma, Zongqing; Shahriar Al Hossain, M.; Somer, M.

    2016-05-01

    Mg11B2 has a great application prospect in the superconducting coils for fusion reactor as the “low activation superconductors”. The un-doped Mg11B2 and Cu-doped Mg11B2 bulks using 11B as a boron precursor were fabricated by low-temperature sintering in present work. It was found that the prepared Mg11B2 low activation superconductors exhibit better Jc performance than all of other Mg11B2 samples reported in previous studies. As for Cu doped Mg11B2, minor Cu addition can obviously improve the Mg11B2 grain crystallization and reduce the amount of MgO impurity. Hence, improved grain connectivity and higher Jc at low fields is obtained in Cu doped Mg11B2 samples. For un-doped samples, refined grains and more MgO impurity with proper size brought about more flux pinning centers, resulting in better Jc performance at high fields.

  9. Preparation and Superconducting Properties of F-doped SmO1-xFxFeAs

    Institute of Scientific and Technical Information of China (English)

    Zhiyong Liu; Hongli Suo; Lin Ma; Min Liu; Zhiping Wu; Zhichao Guo; Luping Han; Meiling Zhou

    2011-01-01

    Here we report the fabrication and superconductivity of the iron-based arsenic oxide SmO1-xFxFeAs compound. X-ray diffraction (XRD) results prove that the lattice parameters a and c decrease systematically with increasing x in between 0<x≤0.35, but when x>0.35 the α and c increase with the decrease of x in the SmO1-xFxFeAs. The critical temperature (Tc) increases with increasing x in between 0.15≤x≤0.3, while x>0.3 the Tc decreases with the increase of x. It is found that at x=0.3 SmO0.7F0.3FeAs has the highest onset resistivity transition temperature of 55.5 K. The critical current density (Jc) value at 10 K for the obtained SmO0.7F0.3FeAs is 1.3× 105 A/cm2 (0 T). Meanwhile one can estimates Hc2(0) from the slope of the Hc2(T) curve at T=Tc (HC2 is the upper critical field), and for the 90% normal-state resistivity (ρn) criterion (Tc=55 K), Hc2(0) is determined to be ~253 T.

  10. Improved Superconducting properties in the Mg(11)B2 low activation superconductor prepared by low-temperature sintering.

    Science.gov (United States)

    Cheng, Fang; Liu, Yongchang; Ma, Zongqing; Shahriar Al Hossain, M; Somer, M

    2016-05-05

    Mg(11)B2 has a great application prospect in the superconducting coils for fusion reactor as the "low activation superconductors". The un-doped Mg(11)B2 and Cu-doped Mg(11)B2 bulks using (11)B as a boron precursor were fabricated by low-temperature sintering in present work. It was found that the prepared Mg(11)B2 low activation superconductors exhibit better Jc performance than all of other Mg(11)B2 samples reported in previous studies. As for Cu doped Mg(11)B2, minor Cu addition can obviously improve the Mg(11)B2 grain crystallization and reduce the amount of MgO impurity. Hence, improved grain connectivity and higher Jc at low fields is obtained in Cu doped Mg(11)B2 samples. For un-doped samples, refined grains and more MgO impurity with proper size brought about more flux pinning centers, resulting in better Jc performance at high fields.

  11. Superconductivity by kinetic energy saving?

    NARCIS (Netherlands)

    Van der Marel, D; Molegraaf, HJA; Presura, C; Santoso, [No Value; Hewson, AC; Zlatic,

    2003-01-01

    A brief introduction is given in the generic microscopic framework of superconductivity. The consequences for the temperature dependence of the kinetic energy, and the correlation energy are discussed for two cases: The BCS scenario and the non-Fermi liquid scenario. A quantitative comparison is mad

  12. Superconductivity by kinetic energy saving?

    NARCIS (Netherlands)

    Van der Marel, D; Molegraaf, HJA; Presura, C; Santoso, [No Value; Hewson, AC; Zlatic,

    2003-01-01

    A brief introduction is given in the generic microscopic framework of superconductivity. The consequences for the temperature dependence of the kinetic energy, and the correlation energy are discussed for two cases: The BCS scenario and the non-Fermi liquid scenario. A quantitative comparison is

  13. Superconductivity by kinetic energy saving?

    NARCIS (Netherlands)

    Van der Marel, D; Molegraaf, HJA; Presura, C; Santoso, [No Value; Hewson, AC; Zlatic,

    2003-01-01

    A brief introduction is given in the generic microscopic framework of superconductivity. The consequences for the temperature dependence of the kinetic energy, and the correlation energy are discussed for two cases: The BCS scenario and the non-Fermi liquid scenario. A quantitative comparison is mad

  14. Doping - Dependent irreversible magnetic properties of Ba(Fe{sub 1-x}Co{sub x}){sub 2}As{sub 2} single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Prozorov, R., E-mail: prozorov@ameslab.go [Ames Laboratory and Department of Physics and Astronomy, Iowa State University, Ames, IA 50011 (United States); Tanatar, M.A.; Blomberg, E.C.; Prommapan, P.; Gordon, R.T.; Ni, N.; Bud' ko, S.L.; Canfield, P.C. [Ames Laboratory and Department of Physics and Astronomy, Iowa State University, Ames, IA 50011 (United States)

    2009-05-01

    We discuss the irreversible magnetic properties of self-flux grown Ba(Fe{sub 1-x}Co{sub x}){sub 2}As{sub 2} single crystals for a wide range of concentrations covering the whole phase diagram from the underdoped to the overdoped regime, x = 0.038, 0.047, 0.058, 0.071, 0.074, 0.10, 0.106 and 0.118. Samples were characterized by a magneto-optical method and show excellent spatial uniformity of the superconducting state down to at least the micrometer scale. The in-plane properties are isotropic, as expected for the tetragonal symmetry, and the overall behavior closely follows classical Bean model of the critical state. The field-dependent magnetization exhibits second peak at a temperature and doping - dependent magnetic field, H{sub p}(T, x). The evolution of this fishtail feature with doping is discussed. In particular we find that H{sub p}, measured at the same reduced temperature for different x, is a unique monotonic function of the superconducting transition temperature, T{sub c}(x), across all dopings. Magnetic relaxation is time-logarithmic and unusually fast. Similar to cuprates, there is an apparent crossover from collective elastic to plastic flux creep above H{sub p}. At high fields, the field dependence of the relaxation rate becomes doping independent. We discuss our results in the framework of the weak collective pinning and show that vortex physics in iron-based pnictide crystals is much closer to high-T{sub c} cuprates than to conventional s-wave (including MgB{sub 2}) superconductors.

  15. Thermal instability and current-voltage scaling in superconducting fault current limiters

    Energy Technology Data Exchange (ETDEWEB)

    Zeimetz, B [Department of Materials Science and Metallurgy, Cambridge University, Pembroke Street, Cambridge CB1 3QZ (United Kingdom); Tadinada, K [Department of Engineering, Cambridge University, Trumpington Road, Cambridge CB2 1PZ (United Kingdom); Eves, D E [Department of Engineering, Cambridge University, Trumpington Road, Cambridge CB2 1PZ (United Kingdom); Coombs, T A [Department of Engineering, Cambridge University, Trumpington Road, Cambridge CB2 1PZ (United Kingdom); Evetts, J E [Department of Materials Science and Metallurgy, Cambridge University, Pembroke Street, Cambridge CB1 3QZ (United Kingdom); Campbell, A M [Department of Engineering, Cambridge University, Trumpington Road, Cambridge CB2 1PZ (United Kingdom)

    2004-04-01

    We have developed a computer model for the simulation of resistive superconducting fault current limiters in three dimensions. The program calculates the electromagnetic and thermal response of a superconductor to a time-dependent overload voltage, with different possible cooling conditions for the surfaces, and locally variable superconducting and thermal properties. We find that the cryogen boil-off parameters critically influence the stability of a limiter. The recovery time after a fault increases strongly with thickness. Above a critical thickness, the temperature is unstable even for a small applied AC voltage. The maximum voltage and maximum current during a short fault are correlated by a simple exponential law.

  16. Influence of calcium on transport properties, band spectrum and superconductivity of YBa2Cu3O(y) and YBa(1.5)La(0.5)Cu3O(y)

    Science.gov (United States)

    Gasumyants, V. E.; Vladimirskaya, E. V.; Patrina, I. B.

    1995-01-01

    The comparative investigation of transport phenomena in Y(1-x)Ca(x)Ba2Cu3O(y) (0 is less than x is less than 0.25; 6.96 is greater than y is greater than 6.87 and 6.73 is less than x is less than 6.53); Y(1-x)Ca(x)Ba(1.5)La(0.5)Cu3O(y) (0 is less than x is less than 0.5; 7.12 is greater than y is greater than 6.96) and YBa(2-x)La(x)Cu3O(y) (0 is less than x is less than 0.5; 6.95 is less than y is less than 7.21) systems have been carried out. The temperature dependencies of resistivity and thermopower have been measured. It was found that the S(T) dependencies take some additional features with Ca content increase. The results obtained have been analyzed on the basis of the phenomenological theory of electron transport in the case of the narrow conductive band. The main parameters of the band spectrum (the band filling with electrons degree and the total effective band width) have been determined. The dependencies of these from contents of substituting elements are discussed. Analyzing the results obtained simultaneously with the tendencies in oxygen content and critical temperature change we have confirmed the conclusion that the oxygen sublattice disordering has a determinant effect on band structure parameters and superconductive properties of YBa2Cu3O(y). The results obtained suggest that Ca gives rise to some peculiarities in band spectrum of this compound.

  17. High field superconducting magnets

    Science.gov (United States)

    Hait, Thomas P. (Inventor); Shirron, Peter J. (Inventor)

    2011-01-01

    A superconducting magnet includes an insulating layer disposed about the surface of a mandrel; a superconducting wire wound in adjacent turns about the mandrel to form the superconducting magnet, wherein the superconducting wire is in thermal communication with the mandrel, and the superconducting magnet has a field-to-current ratio equal to or greater than 1.1 Tesla per Ampere; a thermally conductive potting material configured to fill interstices between the adjacent turns, wherein the thermally conductive potting material and the superconducting wire provide a path for dissipation of heat; and a voltage limiting device disposed across each end of the superconducting wire, wherein the voltage limiting device is configured to prevent a voltage excursion across the superconducting wire during quench of the superconducting magnet.

  18. Gossamer high-temperature bulk superconductivity in FeSe

    Science.gov (United States)

    Sinchenko, A. A.; Grigoriev, P. D.; Orlov, A. P.; Frolov, A. V.; Shakin, A.; Chareev, D. A.; Volkova, O. S.; Vasiliev, A. N.

    2017-04-01

    Using the anisotropic electron transport and susceptibility measurements we demonstrate the appearance of inhomogeneous gossamer superconductivity in FeSe single crystals at ambient pressure and at temperature five times higher than its zero resistance Tc. We also find and quantitatively describe a general property: If inhomogeneous superconductivity in a anisotropic conductor first appears in the form of isolated superconducting islands, it reduces electric resistivity anisotropically with maximal effect along the least conducting axis. This gives a simple tool to study inhomogeneous superconductivity in various anisotropic compounds, which helps to investigate the onset of high-temperature superconductivity.

  19. Structural Dependence of Physical Properties in Sodium Boroaluminosilicate Glasses

    DEFF Research Database (Denmark)

    Zheng, Qiuju; Potuzak, Marcel; Mauro, John C.

    Boroaluminosilicate glasses have found applications in many fields. The extent and nature of the mixing of network formers like SiO2, B2O3, and Al2O3 play an important role in controlling the macroscopic properties. To understand the structure-property correlations in these glasses, we study a se...... moduli, and hardness around [Al2O3]-[Na2O]=0. Moreover, there exist three compositional response regions for elastic moduli and hardness. These results are explained in terms of topological constraint theory.......Boroaluminosilicate glasses have found applications in many fields. The extent and nature of the mixing of network formers like SiO2, B2O3, and Al2O3 play an important role in controlling the macroscopic properties. To understand the structure-property correlations in these glasses, we study...... a series of sodium boroaluminosilicate glasses with various [Al2O3]/[SiO2] ratios to access different regimes of sodium behavior. We determine dynamic properties, elastic moduli, and hardness of these glasses. The results reveal an existence of local minimum for density, fragility index, Young’s and shear...

  20. Frequency Dependence of Measured Massive MIMO Channel Properties

    DEFF Research Database (Denmark)

    Oliveras Martínez, Àlex; Carvalho, Elisabeth De; Nielsen, Jesper Ødum;

    2016-01-01

    A multi-user massive MIMO measurement campaign is conducted to study the channel propagation characteristics (e.g. user correlation, sum of eigenvalues and condition number), focusing on the stability over frequencies and the impact of the array aperture. We use 3 arrays with 64 antennas (6m linear...... array, 2m linear array and 25cm by 28cm squared 2D array) serving 8 users holding a handset with 2 antennas. The study of the measurements shows that the propagation characteristics of the channel are stable for all the measured frequencies. We also observe that user proximity and user handgrip...... stabilize the studied properties of the channel across the frequencies, and in such case the larger the aperture of the array the more stable the properties. The number of base station antennas improves the propagation characteristics of the channel and stabilizes the properties in the frequency domain....

  1. Dependence of optical properties of calcium bismuthates on synthesis conditions

    Science.gov (United States)

    Shtarev, D. S.; Shtareva, A. V.

    2016-08-01

    The article studies optical properties of calcium bismuthate nanoparticles of different composition. For the first time the synthesis of these compounds was produced by the pyrolysis of organic precursors using an organic solvent. Characterization of particles was made by scanning electron microscopy and X-ray analysis. The optical properties were investigated by diffuse reflectance spectroscopy (DRS). It is shown that the type of crystal lattice of the particles of calcium bismuthate determines the possibility to control the optical properties of nanoparticles by varying their composition. The conclusions about the production process and the composition of calcium bismuthate, the most promising for use as a photocatalyst of visible light and solar cells, were made.

  2. Refinement and carbon incorporation effects on the superconducting properties of MgB{sub 2} through wet milling process of low purity boron powder

    Energy Technology Data Exchange (ETDEWEB)

    Jun, Byung-Hyuk, E-mail: bhjun@kaeri.re.kr [Neutron Science Division, Korea Atomic Energy Research Institute (KAERI), Daejeon 305-353 (Korea, Republic of); Park, Soon-Dong; Kim, Chan-Joong [Neutron Science Division, Korea Atomic Energy Research Institute (KAERI), Daejeon 305-353 (Korea, Republic of)

    2012-09-15

    Highlights: Black-Right-Pointing-Pointer Wet milling effects of B powder on the superconducting properties were investigated. Black-Right-Pointing-Pointer The C substitution for the B site in MgB{sub 2} occurred due to a toluene medium. Black-Right-Pointing-Pointer A shift of MgB{sub 2} peaks in XRD and a variation of J{sub c}-B slopes proved C incorporation. Black-Right-Pointing-Pointer The B particle size reduction could induce a small grain size in the MgB{sub 2} formation. Black-Right-Pointing-Pointer J{sub c} and H{sub c2} were enhanced by increased grain boundary pinning and lattice disorder. - Abstract: The wet milling effects of boron (B) powder on the full width at half maximum (FWHM) value of X-ray reflexes, grain size, carbon (C) substitution, critical temperature (T{sub c}), critical current density (J{sub c}), irreversibility field (H{sub irr}), and upper critical field (H{sub c2}) have been investigated for MgB{sub 2} bulk superconductors. The semi-crystalline B powder with a low purity of 95-97% was refined with different milling times of 1 to 15 h using a toluene medium. As a result of B powder milling, the particle size of the B powder decreased and the semi-crystalline phase became an amorphous phase. As the milling time increased, T{sub c} of MgB{sub 2} bulk decreased by the deterioration of the crystallinity and J{sub c} increased over the applied magnetic fields. With the refinement of the B powder, the grain boundary pinning increased due to smaller MgB{sub 2} grain size. In addition, it was found that a C substitution for the B site occurred from a toluene medium during wet milling process. The increased electron scattering due to an increase of the defects like grain boundary and lattice disorder by C substitution led to enhance the superconducting properties with an increase of the FWHM value of the MgB{sub 2} peaks and a decrease of the T{sub c}. The MgB{sub 2} prepared from B powder mechanically milled for 7 h showed the highest magnetic

  3. STRIPES AND SUPERCONDUCTIVITY IN CUPRATE SUPERCONDUCTORS

    Energy Technology Data Exchange (ETDEWEB)

    TRANQUADA, J.M.

    2005-08-22

    One type of order that has been observed to compete with superconductivity in cuprates involves alternating charge and antiferromagnetic stripes. Recent neutron scattering studies indicate that the magnetic excitation spectrum of a stripe-ordered sample is very similar to that observed in superconducting samples. In fact, it now appears that there may be a universal magnetic spectrum for the cuprates. One likely implication of this universal spectrum is that stripes of a dynamic form are present in the superconducting samples. On cooling through the superconducting transition temperature, a gap opens in the magnetic spectrum, and the weight lost at low energy piles up above the gap; the transition temperature is correlated with the size of the spin gap. Depending on the magnitude of the spin gap with respect to the magnetic spectrum, the enhanced magnetic scattering at low temperature can be either commensurate or incommensurate. Connections between stripe correlations and superconductivity are discussed.

  4. Stripes and superconductivity in cuprate superconductors

    Science.gov (United States)

    Tranquada, J. M.

    2005-08-01

    One type of order that has been observed to compete with superconductivity in cuprates involves alternating charge and antiferromagnetic stripes. Recent neutron scattering studies indicate that the magnetic excitation spectrum of a stripe-ordered sample is very similar to that observed in superconducting samples. In fact, it now appears that there may be a universal magnetic spectrum for the cuprates. One likely implication of this universal spectrum is that stripes of a dynamic form are present in the superconducting samples. On cooling through the superconducting transition temperature, a gap opens in the magnetic spectrum, and the weight lost at low energy piles up above the gap; the transition temperature is correlated with the size of the spin gap. Depending on the magnitude of the spin gap with respect to the magnetic spectrum, the enhanced magnetic scattering at low temperature can be either commensurate or incommensurate. Connections between stripe correlations and superconductivity are discussed.

  5. Development of Superconducting Wind Turbine Generators

    DEFF Research Database (Denmark)

    Jensen, Bogi Bech; Mijatovic, Nenad; Abrahamsen, Asger Bech

    2012-01-01

    (HTS); and one is a fully superconducting generator based on MgB2. It is concluded that there is large commercial interest in superconducting machines, with an increasing patenting activity. Such generators are however not without their challenges. The superconductors have to be cooled down......In this paper the commercial activities in the field of superconducting machines, particularly superconducting wind turbine generators, are reviewed and presented. Superconducting generators have the potential to provide a compact and light weight drive train at high torques and slow rotational...... to somewhere between 4K and 50K, depending on what type of superconductor is employed, which poses a significant challenge both from a construction and operation point of view. The high temperature superconductors can facilitate a higher operation temperature and simplified cooling, but the current price...

  6. Size dependence of magnetorheological properties of cobalt ferrite ferrofluid

    Energy Technology Data Exchange (ETDEWEB)

    Radhika, B.; Sahoo, Rasmita; Srinath, S., E-mail: srinath@uohyd.ac.in [School of Physics, University of Hyderabad, Hyderabad-500040 (India)

    2015-06-24

    Cobalt Ferrite nanoparticles were synthesized using co-precipitation method at reaction temperatures of 40°C and 80°C. X-Ray diffraction studies confirm cubic phase formation. The average crystallite sizes were found to be ∼30nm and ∼48nm for 40°C sample and 80°C sample respectively. Magnetic properties measured using vibrating sample magnetometer show higher coercivety and magnetization for sample prepared at 80°C. Magnetorheological properties of CoFe2O4 ferrofluids were measured and studied.

  7. Comprehensive studies for the crystal structures and electronic properties of the superconducting system Fe1 + δSe1 - xTex with \\delta \\simeq 0.037 and x \\simeq 0.55

    Science.gov (United States)

    Onoda, Masashige; Kawasaki, Yasuna; Tsubokawa, Masashi; Koyano, Tamotsu

    2010-12-01

    Structural aspects and electronic properties for the Fe1 + δSe1 - xTex system with 0.04 125Te. The crystal structures with an excess Fe site are refined precisely with obvious constraints. For the superconducting composition, the transport properties are explained in terms of the two-band model, where an electron carrier band gives a linear-in-T resistivity and another hole band leads to nearly temperature-independent behaviour. The magnetic susceptibility and the Knight shift are explained with the idea that the electron correlation is enhanced with increasing x and it is reduced with annealing. The spin-lattice relaxation rates for the normal state that show the apparent Korringa relation may also be understood in this framework. These evidences suggest that the superconductivity may emerge in a regime where the correlation is relatively weak in this system.

  8. Theory of superconductivity

    CERN Document Server

    Crisan, Mircea

    1989-01-01

    This book discusses the most important aspects of the theory. The phenomenological model is followed by the microscopic theory of superconductivity, in which modern formalism of the many-body theory is used to treat most important problems such as superconducting alloys, coexistence of superconductivity with the magnetic order, and superconductivity in quasi-one-dimensional systems. It concludes with a discussion on models for exotic and high temperature superconductivity. Its main aim is to review, as complete as possible, the theory of superconductivity from classical models and methods up t

  9. Dependence of piezoelectric properties on layer thickness for multilayer actuators

    NARCIS (Netherlands)

    Groen, W.A.; Prijs, K.; Saeed, S.

    2010-01-01

    In general, it has been reported that the piezoelectric properties in multilayer actuators decrease for layer thicknesses below 20 microns. This has been investigated for PXE55 which is a material based on PLZT-Pb(Mg 1/2W1/2)O3 and PG01 which is a low sintering version of this material. Results show

  10. Temperature dependence of poly(lactic acid) mechanical properties

    DEFF Research Database (Denmark)

    Zhou, Chengbo; Guo, Huilong; Li, Jingqing

    2016-01-01

    The mechanical properties of polymers are not only determined by their structures, but also related to the temperature field in which they are located. The yield behaviors, Young's modulus and structures of injection-molded poly(lactic acid) (PLA) samples after annealing at different temperatures...

  11. Photothermal investigation of local and depth dependent magnetic properties

    Energy Technology Data Exchange (ETDEWEB)

    Pelzl, J; Meckenstock, R, E-mail: pelzl@fks.rub.d [Institute of Experimental Physics, Solid State Spectroscopy, Ruhr-University, D-44780 Bochum (Germany)

    2010-03-01

    To achieve a spatially resolved measurement of magnetic properties two different photothermal approaches are used which rely on heat dissipated by magnetic resonance absorption or thermal modulation of the magnetic properties, respectively. The heat produced by modulated microwave absorption is detected by the classical photothermal methods such as photoacoustic effect and mirage effect. Examples comprise depth resolution of the magnetization of layered tapes and visualisation of magnetic excitations in ferrites. The second photothermal technique relies on the local modulation of magnetic properties by a thermal wave generated with an intensity modulated laser beam incident on the sample. This technique has a higher spatial resolution and sensitivity and has been used to characterize lateral magnetic properties of multilayers and spintronic media. To extend the lateral resolution of the ferromagnetic resonance detection into the nm-range techniques have been developed which are based on the detection of the modulated thermal microwave response by the thermal probe of an atomic force microscope (AFM) or by detection the thermal expansion of the magnetic sample in the course of the resonant microwave absorption with an AFM or tunnelling microscope. These thermal near field based techniques in ferromagnetic resonance have been successfully applied to image magnetic inhomogeneities around nano-structures and to measure the ferromagnetic resonance from magnetic nano-dots.

  12. Temperature dependence of the dielectric properties of rubber wood

    Science.gov (United States)

    Mohammed Firoz Kabir; Wan M. Daud; Kaida B. Khalid; Haji A.A. Sidek

    2001-01-01

    The effect of temperature on the dielectric properties of rubber wood was investigated in three anisotropic directions—longitudinal, radial, and tangential, and at different measurement frequencies. Low frequency measurements were conducted with a dielectric spectrometer, and high frequencies used microwave applied with open-ended coaxial probe sensors. Dielectric...

  13. Dependence of sand soil compressibility on soil physical properties

    Institute of Scientific and Technical Information of China (English)

    I.S.Vakhrin; G.P.Kuzmin

    2014-01-01

    A relationship between soil physical properties and its compressibility has been analyzed. The formulae to determine soil density and porosity have been substantiated in compression tests. The regularity of changes in compressibility of thawed sand soils with various degrees of water content has been experimentally identified.

  14. Density-dependent acoustic properties of PBX 9502

    Energy Technology Data Exchange (ETDEWEB)

    Brown, Geoffrey W [Los Alamos National Laboratory; Thompson, Darla G [Los Alamos National Laboratory; Deluca, Racci [Los Alamos National Laboratory; Hartline, Ernest L [Los Alamos National Laboratory; Hagelberg, Stephanie I [Los Alamos National Laboratory

    2009-07-31

    We have measured the longitudinal and shear acoustic velocities of PBX 9502 as a function of density for die-pressed samples over the range 1.795 g/cc to 1.888 g/cc. The density dependence of the velocities is linear. Thermal cycling of PBX 9502 is known to induce irreversible volume growth. We have measured this volume growth dependence on density for a subset of the pressed parts and find that the most growth occurs for the samples with lowest initial density. The acoustic velocity changes due to the volume growth are significant and reflect damage in the samples.

  15. Effects of rolling deformation processes on the properties of Ag-sheathed Sr1-xKxFe2As2 superconducting tapes

    Science.gov (United States)

    Huang, He; Zhang, Xianping; Yao, Chao; Dong, Chiheng; Zhang, Qianjun; Ma, Yanwei; Oguro, Hidetoshi; Awaji, Satoshi; Watanabe, Kazuo

    2016-06-01

    The powder-in-tube method is widely used in fabricating iron-based superconducting wires and tapes. To make tapes, a multi-pass rolling process is usually adopted. However, the multi-pass rolling process limits the efficiency of tapes. In this work, rolling deformation technique was studied systematically by fabricating Sr1-xKxFe2As2 superconducting tapes. The total rolling reduction ratio is about 80% and the difference of superconducting performance of tapes rolled by 2, 3, 5 and 7 passes has been investigated. The critical current density Jc, Vickers micro-hardness and microstructure of the superconducting core indicate that tapes after 2, 3, 5 and 7 rolling passes exhibit a similar trend. The width of the tapes and the area of superconducting cores increase with decreasing the number of rolling passes, but the transport Jc of tapes after different rolling passes seems to be the same, except for the tape rolled by 2 passes, whose transport Jc is lower than the other tapes. Concerning the geometry uniformity for the superconducting cores, the sausaging phenomenon was not observed from the photograph of longitudinal cross-section of all the samples. "Lobes" phenomenon on transverse cross-section can be suppressed through decreasing the rolling passes. Therefore, we can obtain uniform and high-performance Ag-sheathed iron-based superconducting tapes by cutting the number of rolling passes down to 3, which is more advantageous to the large-scale producing in the future.

  16. Charge ordering phenomena and superconductivity in underdoped cuprates

    Energy Technology Data Exchange (ETDEWEB)

    Tassini, Leonardo [Bayerische Akademie der Wissenschaften, Muenchen (Germany). Lehrstuhl E23 fuer Technische Physik

    2008-01-16

    In this thesis electronic properties of two prototypical copper-oxygen superconductors were studied with Raman scattering. The underdoped regime including the onset point of superconductivity p{sub sc1} was investigated. Evidence of quasi one-dimensional (1D) dynamical stripes was found. The 1D structures have a universal preferential orientation along the diagonals of the CuO{sub 2} planes below p{sub sc1}. At p{sub sc1}, lattice and electron dynamics change discontinuously. The results show that charge ordering drives the transition at p{sub sc1} and that the maximal transition temperature to superconductivity at optimal doping T{sub c}{sup MAX} depends on the type of ordering at p{sub sc1}. (orig.)

  17. Numerical calculation of transient field effects in quenching superconducting magnets

    CERN Document Server

    Schwerg, Nikolai; Russenschuck, Stephan

    2009-01-01

    The maximum obtainable magnetic induction of accelerator magnets, relying on normal conducting cables and iron poles, is limited to around 2 T because of ohmic losses and iron saturation. Using superconducting cables, and employing permeable materials merely to reduce the fringe field, this limit can be exceeded and fields of more than 10 T can be obtained. A quench denotes the sudden transition from the superconducting to the normal conducting state. The drastic increase in electrical resistivity causes ohmic heating. The dissipated heat yields a temperature rise in the coil and causes the quench to propagate. The resulting high voltages and excessive temperatures can result in an irreversible damage of the magnet - to the extend of a cable melt-down. The quench behavior of a magnet depends on numerous factors, e.g. the magnet design, the applied magnet protection measures, the external electrical network, electrical and thermal material properties, and induced eddy current losses. The analysis and optimizat...

  18. Process dependent thermoelectric properties of EDTA assisted bismuth telluride

    Science.gov (United States)

    Kulsi, Chiranjit; Kargupta, Kajari; Banerjee, Dipali

    2016-04-01

    Comparison between the structure and thermoelectric properties of EDTA (Ethylene-diamine-tetra-acetic acid) assisted bismuth telluride prepared by electrochemical deposition and hydrothermal route is reported in the present work. The prepared samples have been structurally characterized by high resolution X-ray diffraction spectra (HRXRD), field emission scanning electron microscopy (FESEM) and high resolution transmission electron microscopic images (HRTEM). Crystallite size and strain have been determined from Williamson-Hall plot of XRD which is in conformity with TEM images. Measurement of transport properties show sample in the pellet form (S1) prepared via hydrothermal route has higher value of thermoelectric power (S) than the electrodeposited film (S2). But due to a substantial increase in the electrical conductivity (σ) of the film (S2) over the pellet (S1), the power factor and the figure of merit is higher for sample S2 than the sample S1 at room temperature.

  19. Tb3+concentration dependent optical properties and energy transfer in

    Institute of Scientific and Technical Information of China (English)

    曹春燕

    2013-01-01

    By controlling the concentration of Tb3+, a series of GdF3 samples were synthesized by a hydrothermal method without any surfactant. The samples were characterized by X-ray diffraction (XRD) patterns, field emission scanning electron microscopy (FE-SEM) images, photoluminescence (PL) excitation and emission spectra as well as luminescent dynamic decay curves. The opti-cal properties of Tb3+, the concentration quenching phenomenon of Tb3+, and the energy transfer from host Gd3+to Tb3+were inves-tigated and discussed based on the concentration of Tb3+in the GdF3 samples. The experimental results suggested that the optical properties of Tb3+and the energy transfer from host Gd3+to Tb3+could be adjusted by the concentration of Tb3+in the samples.

  20. Stimulated Superconductivity at Strong Coupling

    Energy Technology Data Exchange (ETDEWEB)

    Bao, Ning; Dong, Xi; Silverstein, Eva; Torroba, Gonzalo; /Stanford U., ITP /Stanford U., Phys. Dept. /SLAC

    2011-08-12

    Stimulating a system with time dependent sources can enhance instabilities, thus increasing the critical temperature at which the system transitions to interesting low-temperature phases such as superconductivity or superfluidity. After reviewing this phenomenon in non-equilibrium BCS theory (and its marginal fermi liquid generalization) we analyze the effect in holographic superconductors. We exhibit a simple regime in which the transition temperature increases parametrically as we increase the frequency of the time-dependent source.

  1. Particle size dependent rheological property in magnetic fluid

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Jie; Pei, Lei; Xuan, Shouhu, E-mail: xuansh@ustc.edu.cn; Yan, Qifan; Gong, Xinglong, E-mail: gongxl@ustc.edu.cn

    2016-06-15

    The influence of the particle size on the rheological property of magnetic fluid was studied both by the experimental and computer simulation methods. Firstly, the magnetic fluids were prepared by dispersing Fe{sub 3}O{sub 4} nanospheres with size varied from 40 nm to 100 nm and 200 nm in the solution. Then, the rheological properties were investigated and it was found that the relative magnetorheological effects increased with increasing the particle size. Finally, the molecular dynamic simulation was used to analyze the mechanical characteristics of the magnetic fluid and the chain-like model agreed well with the experimental result. The authentic chain-like structure observed by a microscope agreed with the simulation results. The three particles composed of the similar cluster nanostructure, thus they exhibited similar magnetic property. To this end, the unique assembling microstructures was the origination of the mechanical difference. And it was found that the higher MR (magnetorheological) effects of the large particle based magnetic fluid was originated from the stronger assembling microstructure under the applying magnetic field. - Highlights: • 40 nm, 100 nm and 200 nm Fe{sub 3}O{sub 4} nanospheres were dispersed in water. • The magnetorheological effect increased with increasing the particle sizes. • Molecular dynamic simulation was used in this article.

  2. Modified Continuum Mechanics Modeling on Size-Dependent Properties of Piezoelectric Nanomaterials: A Review

    OpenAIRE

    Zhi Yan; Liying Jiang

    2017-01-01

    Piezoelectric nanomaterials (PNs) are attractive for applications including sensing, actuating, energy harvesting, among others in nano-electro-mechanical-systems (NEMS) because of their excellent electromechanical coupling, mechanical and physical properties. However, the properties of PNs do not coincide with their bulk counterparts and depend on the particular size. A large amount of efforts have been devoted to studying the size-dependent properties of PNs by using experimental characteri...

  3. Surface properties of metal-nitride and metal-carbide films deposited on Nb for radio-frequency superconductivity

    Science.gov (United States)

    Garwin, E. L.; King, F. K.; Kirby, R. E.; Aita, O.

    1987-02-01

    Various effects occur which can prevent attainment of the high Q's and/or the high gradient fields necessary for the operation of radio-frequency (rf) superconducting cavities. One of these effects, multipactor, both causes the cavity to detune during filling due to resonant secondary electron emission at the cavity walls, and lowers the quality factor (Q) by dissipative processes. TiN deposited onto the high-field regions of room-temperature Al cavities has been used at the Stanford Linear Accelerator Center to successfully reduce multipactor in the past. We have therefore studied TiN and its companion materials, NbN, NbC, and TiC, all on Nb substrates under several realistic conditions: (1) as-deposited, (2) exposed to air, and (3) electron bombarded. The studied films (up to 14-nm thickness) were sputter deposited onto sputter-cleaned Nb substrates. Results indicate that all the materials tested gave substantially the same results. The maximum secondary electron yields for as-deposited films were reduced to nearly the preoxidized values after electron bombardment (2-3×1017 electrons cm-2 in the case of NbN and NbC). X-ray photoelectron spectroscopy analysis showed that the oxides (e.g., TiO2 in the case of TiN films) formed during air exposure were slightly reduced (converted to lower oxides) by the electron-beam exposure. Auger electron spectroscopy (AES) showed a slight reduction in the surface O concentration following beam exposure. These results suggest that the chemical nature of top surface layers is responsible for the substantial changes in secondary electron yield observed upon electron-beam exposures and that AES does not reflect this change strongly because of the difficulty in extracting chemical (versus elemental) information from AES. The results indicate that any of these films would be poor choices if simply deposited and exposed to air, but, in fact, the in situ electron bombardment which occurs during cavity operation serves to reduce the

  4. Anisotropic structural and magnetic properties of the field-aligned superconducting system SmFeAsO{sub 1-x}F{sub x} (x = 0, 0.1, 0.2, 0.25 and 0.3)

    Energy Technology Data Exchange (ETDEWEB)

    You, Y B; Hsiao, T K; Chang, B C; Tai, M F; Ku, H C [Department of Physics, National Tsing Hua University, Hsinchu 30013, Taiwan (China); Hsu, Y Y [Department of Physics, National Taiwan Normal University, Taipei 10677, Taiwan (China); Wei, Z; Ruan, K Q; Li, X G, E-mail: ypyou@phys.nthu.edu.tw [Department of Physics, University of Science and Technology of China, Hefei 230026 (China)

    2011-01-01

    Anisotropic structural and magnetic properties of the field-aligned superconducting system SmFeAsO{sub 1-x}F{sub x} (x = 0, 0.1, 0.2, 0.25 and 0.3) are reported. Due to the Fe spin-orbital related anisotropic exchange coupling, all the tetragonal microcrystalline powders in epoxy were aligned at room temperature using the field-rotation method where the tetragonal ab-plane is parallel to the magnetic alignment field B{sub a} of 0.9 T and the c-axis parallels to the rotating axis. Anisotropic magnetic properties are studied through low temperature magnetic measurements along the c-axis and paralleled to the ab-plane of aligned samples in both zero-field-cooled (ZFC) and field-cooled (FC) modes. The under-doped compound (x = 0.1) is not superconducting with an antiferromagnetic Neel temperature T{sub N} {approx} 40 K, while the two optimum-doped compounds (x = 0.2 and 0.25) show high superconducting transition temperatures T{sub c} of 49K and 50K, respectively. The variation of anisotropic structural and magnetic properties for this system are discussed and compared with the previously reported 52 K anisotropic superconductor Sm{sub 0.95}La{sub 0.05}FeAsO{sub 0.85}F{sub 0.15}.

  5. Anisotropic structural and magnetic properties of the field-aligned superconducting system SmFeAsO1-xFx (x = 0, 0.1, 0.2, 0.25 and 0.3)

    Science.gov (United States)

    You, Y. B.; Hsiao, T. K.; Chang, B. C.; Tai, M. F.; Hsu, Y. Y.; Ku, H. C.; Wei, Z.; Ruan, K. Q.; Li, X. G.

    2011-01-01

    Anisotropic structural and magnetic properties of the field-aligned superconducting system SmFeAsO1-xFx (x = 0, 0.1, 0.2, 0.25 and 0.3) are reported. Due to the Fe spin-orbital related anisotropic exchange coupling, all the tetragonal microcrystalline powders in epoxy were aligned at room temperature using the field-rotation method where the tetragonal ab-plane is parallel to the magnetic alignment field Ba of 0.9 T and the c-axis parallels to the rotating axis. Anisotropic magnetic properties are studied through low temperature magnetic measurements along the c-axis and paralleled to the ab-plane of aligned samples in both zero-field-cooled (ZFC) and field-cooled (FC) modes. The under-doped compound (x = 0.1) is not superconducting with an antiferromagnetic Néel temperature TN ~ 40 K, while the two optimum-doped compounds (x = 0.2 and 0.25) show high superconducting transition temperatures Tc of 49K and 50K, respectively. The variation of anisotropic structural and magnetic properties for this system are discussed and compared with the previously reported 52 K anisotropic superconductor Sm0.95La0.05FeAsO0.85F0.15.

  6. Statistical properties of position-dependent ball-passing networks in football games

    CERN Document Server

    Narizuka, Takuma; Yamazaki, Yoshihiro

    2013-01-01

    Statistical properties of position-dependent ball-passing networks in real football games are examined. We find that the networks have the small-world property, and their degree distributions are fitted well by a truncated gamma distribution function. In order to reproduce these properties of networks, a model based on a Markov chain is proposed.

  7. Sequence-Dependent Effects on the Properties of Semiflexible Biopolymers

    CERN Document Server

    Zicong, Bela

    2008-01-01

    Using path integral technique, we show exactly that for a semiflexible biopolymer in constant extension ensemble, no matter how long the polymer and how large the external force, the effects of short range correlations in the sequence-dependent spontaneous curvatures and torsions can be incorporated into a model with well-defined mean spontaneous curvature and torsion as well as a renormalized persistence length. Moreover, for a long biopolymer with large mean persistence length, the sequence-dependent persistence lengths can be replaced by their mean. However, for a short biopolymer or for a biopolymer with small persistence lengths, inhomogeneity in persistence lengths tends to make physical observables very sensitive to details and therefore less predictable.

  8. First-principles calculations of the superconducting properties in Li-decorated monolayer graphene within the anisotropic Migdal-Eliashberg formalism

    Science.gov (United States)

    Zheng, Jing-Jing; Margine, E. R.

    2016-08-01

    The ab initio anisotropic Migdal-Eliashberg formalism has been used to examine the pairing mechanism and the nature of the superconducting gap in the recently discovered lithium-decorated monolayer graphene superconductor. Our results provide evidence that the superconducting transition in Li-decorated monolayer graphene can be explained within a standard phonon-mediated mechanism. We predict a single anisotropic superconducting gap and a critical temperature Tc=5.1 -7.6 K , in very good agreement with the experimental results.

  9. Evaluation of Trapped Magnetic Field Properties in Superconducting MgB2 Bulk Magnets of Various Shapes by Finite Element Method

    Science.gov (United States)

    Hiramatsu, Y.; Otabe, E. S.; Kiuchi, M.

    The trapped magnetic field properties of superconducting MgB2 bulk magnets with various shapes such as a triangular, a quadrangular, a hexangular bulk were calculated by the Finite Elements Method (FEM). The effect for the combination of several numbers of bulks was also investigated for several kinds of shapes to obtain large area of bulk surface in spite of one large bulk. In this calculation, the simple magnetization process replaced by the field-cool magnetization was used to obtain the equivalent distribution of the magnetic field, and the thermal equation in FEM was omitted. The trapped magnetic field for the triangular bulk by FEM was compared with the experimental result. It was found that the calculated results agreed well with the experimental result. The maximum trapped magnetic field was obtained in the cylindrical shape among several kinds of shapes. The trapped magnetic field was increased by the combination of multi-bulks. It was confirmed that the trapped magnetic field of the multi-bulks was larger than that of the single bulk. The trapped magnetic field increases with increasing the number of the bulks.

  10. Superconducting and mechanical properties of the bulk Bi(pb)SCCO system prepared via solid state and ammonium nitrate precipitation methods

    Energy Technology Data Exchange (ETDEWEB)

    Safran, S., E-mail: safran@science.ankara.edu.tr [Ankara University, Faculty of Science, Department of Physics, Tandoğan, Ankara 06100 (Turkey); Center of Excellence for Superconductivity Research, 50 Year Campus, Golbaşı, Ankara (Turkey); Kılıçarslan, E.; Ozturk, H. [Ankara University, Faculty of Science, Department of Physics, Tandoğan, Ankara 06100 (Turkey); Center of Excellence for Superconductivity Research, 50 Year Campus, Golbaşı, Ankara (Turkey); Alp, M. [Center of Excellence for Superconductivity Research, 50 Year Campus, Golbaşı, Ankara (Turkey); Akdogan, M. [Center of Excellence for Superconductivity Research, 50 Year Campus, Golbaşı, Ankara (Turkey); Abant İzzet Baysal University, Department of Physics, Bolu (Turkey); Asikuzun, E.; Ozturk, O. [Kastamonu University, Department of Physics, Kastamonu (Turkey); Kastamonu University, Research and Application Center, Kastamonu (Turkey); Kılıç, A. [Ankara University, Faculty of Science, Department of Physics, Tandoğan, Ankara 06100 (Turkey); Center of Excellence for Superconductivity Research, 50 Year Campus, Golbaşı, Ankara (Turkey)

    2015-09-01

    We have investigated the effect of preparation method on superconducting and mechanical properties of Bi(Pb)-2223 bulk samples using Bi{sub 1.85}Pb{sub 0.35}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub 10±y} stoichiometry. Solid-state reaction and ammonium nitrate precipitation methods have been used for fabrication of the bulk samples. In addition, the effect of annealing time on BSCCO samples have been studied. Structural, electrical, magnetic and microhardness analyses of samples are performed by the X-ray powder diffraction (XRD), the Scanning Electron Microscopy (SEM), DC resistivity, AC susceptibility and Vickers microhardness test. The critical transition temperature, phase purity, surface morphology and crystallinity of the prepared bulk samples are compared with each other. Elasticity (E), brittleness (B{sub i}), fracture toughness (K{sub IC}) and yield strength (Y) values are also determined according to annealing time, applied load and production parameters of materials.

  11. Manufacture, electromagnetic properties and microstructure of an 18-filament jelly-roll Nb3Al superconducting wire with rapid heating and quenching heat-treatment

    Science.gov (United States)

    Pan, X. F.; Feng, Y.; Yan, G.; Cui, L. J.; Chen, C.; Zhang, Y.; Wu, Z. X.; Liu, X. H.; Zhang, P. X.; Bai, Z. M.; Zhao, Y.; Li, L. F.

    2016-01-01

    In this paper, we have reported the manufacture of a novel simple-structured jelly-roll Nb3Al precursor long wire, and its electromagnetic properties and microstructure with different rapid heating and quenching (RHQ) heat-treatments. By comparing three processing methods, it is found that the rolling and drawing (RD) method is more suitable to the fabrication of kilometer-length Nb3Al precursor wire without annealing. Using homemade RHQ equipment, we have successfully carried out RHQ heat-treatment of Nb3Al wire samples with various heating conditions. Based on magnetization and magnetoresistivity measurements, the onset superconducting transition temperature, T c and upper critical field, H c2 (0) of optimal Nb3Al wire reach 17.9 K-18.0 K and 29.7 T, respectively. Through microstructure and composition analysis, the Nb3Al superconductor in the optimal wire displays a typical ‘layer-to-layer’ structure, which comprises alternate crystalline Nb3Al and amorphous Nb layers, and the Nb3Al grains sizes are about 100 nm-300 nm. Furthermore, many small holes are dispersed in the Nb3Al superconductor due to the diffusion reaction from Al to Nb site. The work suggests the simple-structured Nb3Al precursor wire with RHQ heat-treatment is very promising for high-field application.

  12. Improvement in microstructure and superconducting properties of single-filament powder-in-tube MgB2 wires by cold working with a swaging machine

    Science.gov (United States)

    Saito, Yusuke; Murakami, Masato; Matsumoto, Akiyoshi; Kumakura, Hiroaki

    2017-06-01

    We investigated the influence of the mechanical deformation method of wire fabrication on the microstructure and superconducting properties of single-filament in situ powder-in-tube (PIT) MgB2 wires. We employed three deformation methods to fabricate the wires: only swaging, groove rolling + roller drawing, and groove rolling + conventional drawing. We found that cold working by swaging has three advantages over the groove rolling + drawing method: (1) improved uniformity of the MgB2 core along the longitudinal direction; (2) higher mass density of the Mg + B (MgB2) core before (after) heat treatment (HT); and (3) well-developed fiber structures of Mg (MgB2) before (after) HT. These three factors greatly enhanced the critical current density (J c) values of PIT MgB2 wires. The highest J c values were obtained through mechanical deformation by swaging for both pure and carbon-doped wires. A J c value of 3.5 × 104 A cm-2 and an engineering critical current density (J e) of 1.1 × 104 A cm-2 were recorded at 4.2 K and 10 T for a swaged wire of 4.5%-carbon-coated boron powder heat-treated at 600 °C for 1 h.

  13. Technical issues of a high-Tc superconducting bulk magnet

    Science.gov (United States)

    Fujimoto, Hiroyuki

    2000-06-01

    Superconducting magnets made of high-Tc superconductors are promising for industrial applications. It is well known that REBa2Cu3O7-x superconductors prepared by melt processes have a high critical current density, Jc, at 77 K and high magnetic fields. The materials are very promising for high magnetic field applications as a superconducting permanent/bulk magnet with liquid-nitrogen refrigeration. Light rare-earth (LRE) BaCuO bulks, compared with REBaCuO bulks, exhibit a larger Jc in high magnetic fields and a much improved irreversibility field, Hirr, at 77 K. In this study, we discuss technical issues of a high-Tc superconducting bulk magnet, namely the aspects of the melt processing for bulk superconductors, their characteristic superconducting properties and mechanical properties, and trapped field properties of a superconducting bulk magnet. One of the possible applications is a superconducting bulk magnet for the magnetically levitated (Maglev) train in the future.

  14. Superconductivity in the Tungsten Bronzes

    Science.gov (United States)

    Wu, Phillip; Ishii, Satoshi; Tanabe, Kenji; Munakata, Ko; Hammond, Robert H.; Tokiwa, Kazuyasu; Geballe, Theodore H.; Beasley, Malcolm R.

    2015-03-01

    Via pulsed laser deposition and post-annealing, high quality K-doped WO3-y films with reproducible transport properties are obtained. A home built two-coil mutual inductance setup is used to probe the behavior of the films in the superconducting and normal state. The inverse penetration depths and dissipation peaks are measured as a function of temperature and field. Separately, via thin film deposition techniques, we report for the first time stable crystalline hexagonal WO3 on substrates. In order to tune the physical properties of the undoped material, we utilized an ionic liquid gating technique. We observe an insulator-to-metal transition, showing the ionic liquid gate to be a viable technique to alter the electrical transport properties of this material. By comparing the alkali and ionic liquid gated WO3, we conclude with some remarks regarding how superconductivity arises in this system.

  15. A Novel superconducting toroidal field magnet concept using advanced materials

    Science.gov (United States)

    Schwartz, J.

    1992-03-01

    The plasma physics database indicates that two distinct approaches to tokamak design may lead to commercial fusion reactors: low Aspect ratio, high plasma current, relatively low magnetic field devices, and high Aspect ratio, high field devices. The former requires significant enhancements in plasma performance, while the latter depends primarily upon technology development. The key technology for the commercialization of the high-field approach is large, high magnetic field superconducting magnets. In this paper, the physics motivation for the high field approach and key superconducting magnet (SCM) development issues are reviewed. Improved SCM performance may be obtained from improved materials and/or improved engineering. Superconducting materials ranging from NbTi to high- T c oxides are reviewed, demonstrating the broad range of potential superconducting materials. Structural material options are discussed, including cryogenic steel alloys and fiber-reinforced composite materials. Again, the breadth of options is highlighted. The potential for improved magnet engineering is quantified in terms of the Virial Theorem Limit, and two examples of approaches to highly optimized magnet configurations are discussed. The force-reduced concept, which is a finite application of the force-free solutions to Ampere's Law, appear promising for large SCMs but may be limited by the electromagnetics of a fusion plasma. The Solid Superconducting Cylinder (SSC) concept is proposed. This concept combines the unique properties of high- T c superconductors within a low- T c SCM to obtain (1) significant reductions in the structural material volume, (2) a decoupling of the tri-axial (compressive and tensile) stress state, and (3) a demountable TF magnet system. The advantages of this approach are quantified in terms of a 24 T commercial reactor TF magnet system. Significant reductions in the mechanical stress and the TF radial build are demonstrated.

  16. Disorder-dependent valley properties in monolayer WSe2

    KAUST Repository

    Tran, Kha

    2017-07-19

    We investigate the effect of disorder on exciton valley polarization and valley coherence in monolayer WSe2. By analyzing the polarization properties of photoluminescence, the valley coherence (VC) and valley polarization (VP) are quantified across the inhomogeneously broadened exciton resonance. We find that disorder plays a critical role in the exciton VC, while affecting VP less. For different monolayer samples with disorder characterized by their Stokes shift (SS), VC decreases in samples with higher SS while VP does not follow a simple trend. These two methods consistently demonstrate that VC as defined by the degree of linearly polarized photoluminescence is more sensitive to disorder, motivating further theoretical studies.

  17. Influence of the utilized precursors on the morphology and properties of YBa{sub 2}Cu{sub 3}O{sub 7−y} superconducting nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Alikhanzadeh-Arani, Sima [Plasma Physics Research Center, Science and Research Branch, Islamic Azad University, Tehran, Islamic Republic of Iran (Iran, Islamic Republic of); Salavati-Niasari, Masoud, E-mail: salavati@kashanu.ac.ir [Institute of Nano Science and Nano Technology, University of Kashan, Kashan, P.O. Box 87317-51167, Islamic Republic of Iran (Iran, Islamic Republic of); Almasi-Kashi, Mohammad [Department of Physics, University of Kashan, Kashan, 87317-51167, Islamic Republic of Iran (Iran, Islamic Republic of)

    2013-05-15

    Highlights: ► YBa{sub 2}Cu{sub 3}O{sub 7−x} (Y-123) nanoparticles was synthesized by solid state processing. ► Inorganic precursor was used in the synthesis of YBa{sub 2}Cu{sub 3}O{sub 7−x}. ► The effect of calcinations on morphology and particle size were investigated. -- Abstract: In order to prevent agglomeration of high temperature ceramic material, the solid state processing based on new and appropriate yttrium complex precursors without applying surfactant has been suggested. These have been prepared by a reaction of yttrium acetate with three coordination compositions, acetylacetone, 2-hydroxo-1-naphthaldehyde and salicylaldehyde, for forming yttrium complex types. It was found that the size and morphology of products are clearly dependent on the type of utilized precursor because the organic ligands around yttrium center in these novel precursors act like a protecting agent. Magnetic susceptibility measurements showed that T{sub c} of the superconducting nanoparticles is from 82 K to 88.4 K. The crystalline structures of the nanoparticles remained in orthorhombic symmetry. Characterizations of specimens were performed using scanning electron microscopy and transmission electron microscopy, supported by other techniques including XRD diffraction, energy dispersive X-ray, FT-IR spectrum and magnetic susceptibility measurements.

  18. Pressure-induced isostructural phase transition and correlation of FeAs coordination with the superconducting properties of 111-type Na(1-x)FeAs.

    Science.gov (United States)

    Liu, Qingqing; Yu, Xiaohui; Wang, Xiancheng; Deng, Zheng; Lv, Yuxi; Zhu, Jinlong; Zhang, Sijia; Liu, Haozhe; Yang, Wenge; Wang, Lin; Mao, Hokwang; Shen, Guoyin; Lu, Zhong-Yi; Ren, Yang; Chen, Zhiqiang; Lin, Zhijun; Zhao, Yusheng; Jin, Changqing

    2011-05-25

    The effect of pressure on the crystalline structure and superconducting transition temperature (T(c)) of the 111-type Na(1-x)FeAs system using in situ high-pressure synchrotron X-ray powder diffraction and diamond anvil cell techniques is studied. A pressure-induced tetragonal to tetragonal isostructural phase transition was found. The systematic evolution of the FeAs(4) tetrahedron as a function of pressure based on Rietveld refinements on the powder X-ray diffraction patterns was obtained. The nonmonotonic T(c)(P) behavior of Na(1-x)FeAs is found to correlate with the anomalies of the distance between the anion (As) and the iron layer as well as the bond angle of As-Fe-As for the two tetragonal phases. This behavior provides the key structural information in understanding the origin of the pressure dependence of T(c) for 111-type iron pnictide superconductors. A pressure-induced structural phase transition is also observed at 20 GPa.

  19. Magnetism and superconductivity in heavy fermion systems

    Energy Technology Data Exchange (ETDEWEB)

    Flouquet, J. (DRFMC, C.E.N.G., 38 - Grenoble (France)); Brison, J.P.; Hasselbach, K.; Taillefer, L. (C.N.R.S., 38 - Grenoble (France)); Behnia, K.; Jaccard, D. (DPMC, Geneva Univ. (Switzerland)); Visser, A. de (Natuurkundig Lab., Univ. van Amsterdam (Netherlands))

    1991-12-01

    The normal and superconducting properties of heavy fermion compounds are reviewed. The discussion is focus on the three uranium compounds: UBe{sub 13}, UPt{sub 3} and URu{sub 2}Si{sub 2}. Special attention is given: 1) to unusual (H.T) superconducting phase diagram as discovered in UPt{sub 3} where two successive superconducting phases seem to occur in zero magnetic field; 2) to the role of long range ordering as found in URu{sub 2}Si{sub 2} and UPt{sub 3}. (orig.).

  20. Towards noise engineering: Recent insights in low-frequency excess flux noise of superconducting quantum devices

    Science.gov (United States)

    Kempf, Sebastian; Ferring, Anna; Enss, Christian

    2016-10-01

    The comprehensive analysis of low-frequency excess flux noise both in terms of magnetic flux noise S Φ , 1 / f and energy sensitivity ɛ1/f of 84 superconducting quantum devices studied at temperatures below 1 K reveals a universal behavior. When analyzing data in terms of ɛ1/f, we find that noise spectra of independent devices cross each other all at certain crossing frequencies fc. Besides this main result of our paper, we further show that superconducting quantum interference device (SQUID) arrays systematically feature higher noise exponents than single SQUIDs and give evidence for a material and device type dependence of low-frequency excess flux noise. The latter results facilitate to engineer the shape of magnetic flux noise spectra and thus to experimentally modify key properties such as coherence or measurement times of superconducting quantum devices.