WorldWideScience

Sample records for multi-band bcs superconductors

  1. Anisotropy and multi-band effects in weak-coupling superconductors

    International Nuclear Information System (INIS)

    Berger, T.L.

    1977-01-01

    The techniques of second quantization and thermodynamic Green functions are used to investigate energy gap anisotropy and multi-band effects in pure, single-crystal, weak-coupling superconductors. A generalized version of the standard Gorkov factorization is used to linearize the Green functions equations of motion. The effects of lattice periodicity and band structure are taken into account by means of Bloch wave expansions and Bloch transforms. A pairing selection rule is derived which indicates the possibility of pairing between single particle states belonging to different bands, as well as the usual Cooper pairing. It is shown that the interband gap parameter, which is coupled to the usual gap parameter by the Green functions equations of motion, can only contribute indirectly to the tunneling electric current and the thermodynamic potential. In the absence of interband pairing, the equations of motion lead to the usual BCS gap equation. Also, in the absence of interband pairing, the gap parameter is found to be equal to the diagonal matrix element of the superconductor pair potential between electronic Bloch states. An essentially temperature independent anisotropy function which contains all angular dependence of the gap is shown to evolve naturally from this formalism. The overall temperature dependence of the gap is investigated and it is found that with a change of temperature, the magnitude of the gap in different directions changes in the same ration. The ordinary Markowitz-Kadanoff model is shown to be inappropriate for the case of a multi-band superconductor and a generalized version of this model is introduced and discussed. A special case of this model is considered which leads to gap discontinuities at Brillouin zone boundaries

  2. Thermodynamic parameters of single- or multi-band superconductors derived from self-field critical currents

    Energy Technology Data Exchange (ETDEWEB)

    Talantsev, Evgueni [Robinson Research Institute, Victoria University of Wellington, Lower Hutt (New Zealand); Crump, Wayne P.; Tallon, Jeffery L. [Robinson Research Institute, Victoria University of Wellington, Lower Hutt (New Zealand); MacDiarmid Institute for Advanced Materials and Nanotechnology, Lower Hutt (New Zealand)

    2017-12-15

    Key questions for any superconductor include: what is its maximum dissipation-free electrical current (its 'critical current') and can this be used to extract fundamental thermodynamic parameters? Present models focus on depinning of magnetic vortices and implicate materials engineering to maximise pinning performance. But recently we showed that the self-field critical current for thin films is a universal property, independent of microstructure, controlled only by the penetration depth. Here, using an extended BCS-like model, we calculate the penetration depth from the temperature dependence of the superconducting energy gap thus allowing us to fit self-field critical current data. In this way we extract from the T-dependent gap a set of key thermodynamic parameters, the ground-state penetration depth, energy gap and jump in electronic specific heat. Our fits to 79 available data sets, from zinc nanowires to compressed sulphur hydride with critical temperatures of 0.65 to 203 K, respectively, are excellent and the extracted parameters agree well with reported bulk values. Samples include thin films, wires or nanowires of single- or multi-band s-wave and d-wave superconductors of either type I or type II. For multiband or multiphase samples we accurately recover individual band contributions and phase fractions. (copyright 2017 by WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  3. Effective Ginzburg–Landau free energy functional for multi-band isotropic superconductors

    International Nuclear Information System (INIS)

    Grigorishin, Konstantin V.

    2016-01-01

    Highlights: • The intergradient coupling of order parameters in a two-band superconductor plays important role and cannot be neglected. • A two-band superconductor must be characterized with a single coherence length and a single Ginzburg–Landau parameter. • Type-1.5 superconductors are impossible. • The free energy functional for a multi-band superconductor can be reduced to the effective single-band Ginzburg–Landau functional. - Abstract: It has been shown that interband mixing of gradients of two order parameters (drag effect) in an isotropic bulk two-band superconductor plays important role – such a quantity of the intergradients coupling exists that the two-band superconductor is characterized with a single coherence length and a single Ginzburg–Landau (GL) parameter. Other quantities or neglecting of the drag effect lead to existence of two coherence lengths and dynamical instability due to violation of the phase relations between the order parameters. Thus so-called type-1.5 superconductors are impossible. An approximate method for solving of set of GL equations for a multi-band superconductor has been developed: using the result about the drag effect it has been shown that the free-energy functional for a multi-band superconductor can be reduced to the GL functional for an effective single-band superconductor.

  4. Quasiclassical description of multi-band superconductors with two order parameters

    Energy Technology Data Exchange (ETDEWEB)

    Moor, Andreas

    2014-05-19

    This Thesis deals with multi-band superconductors with two order parameters, i.e., the superconductivity and the spin-density wave, also touching on one-band superconductors with a charge-density wave, as well as with only the superconducting order parameter. Quasiclassical description of suchlike structures is developed and applied to investigation of various effects, inter alia, the Josephson and the proximity effects, the Knight shift, the Larkin-Ovchinnikov-Fulde-Ferrell-like state, and the interplay of the order parameters in coexistence regime. The applicability of the developed approach to pnictides is discussed.

  5. Multi-band description of the specific heat and thermodynamic critical field in MgB2 superconductor

    Science.gov (United States)

    Szcześniak, R.; Jarosik, M. W.; Tarasewicz, P.; Durajski, A. P.

    2018-05-01

    The thermodynamic properties of MgB2 superconductor can be explained using the multi-band models. In the present paper we have examined the experimental data available in literature and we have found out that it is possible to reproduce the measured values of the superconducting energy gaps, the thermodynamic critical magnetic field and specific heat jump within the framework of two-band Eliashberg formalism and appropriate defined free energy difference between superconducting and normal state. Moreover, we found that the obtained results differ significantly from the predictions of the conventional Bardeen-Cooper-Schrieffer theory.

  6. Twisting Anderson pseudospins with light: Quench dynamics in THz-pumped BCS superconductors

    OpenAIRE

    Chou, Yang-Zhi; Liao, Yunxiang; Foster, Matthew S.

    2016-01-01

    We study the preparation (pump) and the detection (probe) of far-from-equilibrium BCS superconductor dynamics in THz pump-probe experiments. In a recent experiment [R. Matsunaga, Y. I. Hamada, K. Makise, Y. Uzawa, H. Terai, Z. Wang, and R. Shimano, Phys. Rev. Lett. {\\bf 111}, 057002 (2013)], an intense monocycle THz pulse with center frequency $\\omega \\simeq \\Delta$ was injected into a superconductor with BCS gap $\\Delta$; the subsequent post-pump evolution was detected via the optical conduc...

  7. Fermi points and topological quantum phase transitions in a multi-band superconductor.

    Science.gov (United States)

    Puel, T O; Sacramento, P D; Continentino, M A

    2015-10-28

    The importance of models with an exact solution for the study of materials with non-trivial topological properties has been extensively demonstrated. The Kitaev model plays a guiding role in the search for Majorana modes in condensed matter systems. Also, the sp-chain with an anti-symmetric mixing among the s and p bands is a paradigmatic example of a topological insulator with well understood properties. Interestingly, these models share the same universality class for their topological quantum phase transitions. In this work we study a two-band model of spinless fermions with attractive inter-band interactions. We obtain its zero temperature phase diagram, which presents a rich variety of phases including a Weyl superconductor and a topological insulator. The transition from the topological to the trivial superconducting phase has critical exponents different from those of Kitaev's model.

  8. Twisting Anderson pseudospins with light: Quench dynamics in THz-pumped BCS superconductors

    Science.gov (United States)

    Chou, Yang-Zhi; Liao, Yunxiang; Foster, Matthew

    We study the preparation and the detection of coherent far-from-equilibrium BCS superconductor dynamics in THz pump-probe experiments. In a recent experiment, an intense monocycle THz pulse with center frequency ω = Δ was injected into a superconductor with BCS gap Δ the post-pump evolution was detected via the optical conductivity. It was argued that nonlinear coupling of the pump to the Anderson pseudospins of the superconductor induces coherent dynamics of the Higgs mode Δ (t) . We validate this picture in a 2D BCS model with a combination of exact numerics and the Lax reduction, and we compute the dynamical phase diagram. The main effect of the pump is to scramble the orientations of Anderson pseudospins along the Fermi surface by twisting them in the xy-plane. We show that more intense pulses can induce a far-from-equilibrium gapless phase (phase I), originally predicted in the context of interaction quenches. We show that the THz pump can reach phase I at much lower energy densities than an interaction quench, and we demonstrate that Lax reduction provides a quantitative tool for computing coherent BCS dynamics. We also compute the optical conductivity for the states discussed here.

  9. Twisting Anderson pseudospins with light: Quench dynamics in terahertz-pumped BCS superconductors

    Science.gov (United States)

    Chou, Yang-Zhi; Liao, Yunxiang; Foster, Matthew S.

    2017-03-01

    We study the preparation (pump) and the detection (probe) of far-from-equilibrium BCS superconductor dynamics in THz pump-probe experiments. In a recent experiment [R. Matsunaga, Y. I. Hamada, K. Makise, Y. Uzawa, H. Terai, Z. Wang, and R. Shimano, Phys. Rev. Lett. 111, 057002 (2013), 10.1103/PhysRevLett.111.057002], an intense monocycle THz pulse with center frequency ω ≃Δ was injected into a superconductor with BCS gap Δ ; the subsequent postpump evolution was detected via the optical conductivity. It was argued that nonlinear coupling of the pump to the Anderson pseudospins of the superconductor induces coherent dynamics of the Higgs (amplitude) mode Δ (t ) . We validate this picture in a two-dimensional BCS model with a combination of exact numerics and the Lax reduction method, and we compute the nonequilibrium phase diagram as a function of the pump intensity. The main effect of the pump is to scramble the orientations of Anderson pseudospins along the Fermi surface by twisting them in the x y plane. We show that more intense pump pulses can induce a far-from-equilibrium phase of gapless superconductivity ("phase I"), originally predicted in the context of interaction quenches in ultracold atoms. We show that the THz pump method can reach phase I at much lower energy densities than an interaction quench, and we demonstrate that Lax reduction (tied to the integrability of the BCS Hamiltonian) provides a general quantitative tool for computing coherent BCS dynamics. We also calculate the Mattis-Bardeen optical conductivity for the nonequilibrium states discussed here.

  10. BCS superconductors: The out-of-equilibrium response to a laser pulse

    Science.gov (United States)

    Avella, Adolfo

    2018-05-01

    The dynamics of a 2D d-wave BCS superconductor driven out-of-equilibrium by a perpendicularly-impinging polarized laser pulse is analyzed on varying the laser pulse characteristics. The observed effects include: oscillations both in the amplitude and in the phase of the superconducting order parameter, suppression of the superconductivity, but also its enhancement with a strong dependence on all varying parameters and, in particular, on the polarization in plane of the applied vector potential and on the value of its frequency. This study opens up the possibility to distinguish very clearly the behavior of the nodal and anti-nodal non-thermal excitations and to tackle some of the puzzling results of the current experimental scenario in the field.

  11. PdTe: a 4.5 K type-II BCS superconductor

    International Nuclear Information System (INIS)

    Tiwari, Brajesh; Goyal, Reena; Jha, Rajveer; Awana, V P S; Dixit, Ambesh

    2015-01-01

    We report on the structure and physical properties of the polycrystalline PdTe superconductor, which is synthesized by the solid state reaction route via the quartz vacuum encapsulation technique at 750 °C. The as synthesized compound is crystallized in hexagonal crystal structure with P63/mmc space group. Both transport and magnetic measurements showed that PdTe is a bulk superconductor below 4.5 K. Isothermal magnetization (MH) and magneto-transport (R(T)H) measurements provided the values of the lower (H c1 ) and upper (H c2 ) critical fields as 250 Oe and 1200 Oe respectively at 2 K, establishing that the compound is clearly a type-II superconductor. The coherence length (ξ 0 ) and Ginzburg–Landau parameter (κ) are estimated from the experimentally determined upper and lower critical fields, and are 449 Å and 1.48 respectively. Thermodynamic heat capacity measurements under different magnetic fields, i.e. C p (T)H, showed a clear transition at 4.5 K (T c ), which shifts gradually to lower temperatures with application of field. The values of Debye temperature (Θ D ) and electronic specific heat coefficient (γ) obtained from C p (T) data are found to be 203 K and 6.01 mJ mol −1 K −2 . The observed specific heat jump (ΔC/γT c ) is 1.33, thus suggesting a possible weak coupling case for the PdTe superconductor. (paper)

  12. Brillouin-Wigner theory of mixed-valence impurities in BCS superconductor: Tc/TcO and ΔC/ΔCO

    International Nuclear Information System (INIS)

    Li Jun; Gong Changde.

    1986-08-01

    The (lowest order) Brillouin-Wigner perturbational expansion theory is adopted to describe the mixed-valence impurities in the BCS superconductor. Two substantial quantities characterizing the superconducting state, i.e. the reduced transition temperature T c /T cO and the reduced specific heat jump ΔC/ΔC O are calculated numerically as a function of the impurity concentration x and the energy level difference E f between two 4f configurations. A comparison with the experimental data of the Th 1-x Ce x and Th 1-x U x alloy is also included with a more reasonable fitting than Kaiser's theory. (author)

  13. BCS 50 years

    CERN Document Server

    Feldman, Dimitri

    2011-01-01

    The BCS theory of superconductivity developed in 1957 by Bardeen, Cooper and Schrieffer has been remarkably successful in explaining the properties of superconductors. In addition, concepts from BCS have been incorporated into diverse fields of physics, from nuclear physics and dense quark matter to the current standard model. Practical applications include SQUIDs, magnetic resonance imaging, superconducting electronics and the transmission of electricity. This invaluable book is a compilation of both a historical account and a discussion of the current state of theory and experiment. With con

  14. Superconductors

    International Nuclear Information System (INIS)

    1988-01-01

    The chapter 6.3 p. 143 to 153 of this book deals with superconductors 19 items are briefly presented with address of manufacturer or laboratory to contact, mainly in the USA or Japan. In particular magnets, films, high temperature superconductors and various applications are presented [fr

  15. Superconductors

    CERN Document Server

    Narlikar, A V

    2014-01-01

    Superconductors is neither about basic aspects of superconductivity nor about its applications, but its mainstay is superconducting materials. Unusual and unconventional features of a large variety of novel superconductors are presented and their technological potential as practical superconductors assessed. The book begins with an introduction to basic aspects of superconductivity. The presentation is readily accessible to readers from a diverse range of scientific and technical disciplines, such as metallurgy, materials science, materials engineering, electronic and device engineering, and chemistry. The derivation of mathematical formulas and equations has been kept to a minimum and, wherever necessary, short appendices with essential mathematics have been added at the end of the text. The book is not meant to serve as an encyclopaedia, describing each and every superconductor that exists, but focuses on important milestones in their exciting development.

  16. Superconductors

    International Nuclear Information System (INIS)

    Ekin, J.W.

    1983-01-01

    This chapter attempts to provide an introductory guide to interpreting handbook data on practical, high-current, superconducting materials, principally for magnet applications. An overview is given of the properties and operational limits of superconductive materials, as well as techniques used to fabricate practical superconducting wires. Topics considered include critical temperature, critical magnetic field, Type I and Type II superconductors, upper critical field values for practical materials, the temperature dependence of critical field and upper critical field, critical current, critical current density values for practical materials, the measurement of critical current, composite fabrication, stability, ac losses, eddy current loss, hysteretic loss, mechanical properties, critical current degradation, and superconducting materals selection and composite design

  17. Relativistic BCS-BEC Crossover at Quark Level

    Directory of Open Access Journals (Sweden)

    Zhuang P.

    2010-10-01

    Full Text Available The non-relativistic G0G formalism of BCS-BEC crossover at finite temperature is extended to relativistic fermion systems. The theory recovers the BCS mean field approximation at zero temperature and the non-relativistic results in a proper limit. For massive fermions, when the coupling strength increases, there exist two crossovers from the weak coupling BCS superfluid to the non-relativistic BEC state and then to the relativistic BEC state. For color superconductivity at moderate baryon density, the matter is in the BCS-BEC crossover region, and the behavior of the pseudogap is quite similar to that found in high temperature superconductors.

  18. Localized superconductors

    International Nuclear Information System (INIS)

    Ma, M.; Lee, P.A.

    1985-01-01

    We study the effects of Anderson localization on superconductivity by using a Bardeen-Cooper-Schrieffer (BCS)-type trial wave function which pairs electrons in exact time-reversed eigenstates of the single-particle Hamiltonian. Within this approximation, and neglecting localization effects on the effective Coulomb repulsion and the electron-phonon coupling, we find that superconductivity persists below the mobility edge. In fact, Anderson's theorem is valid in the localized phase as long as rhoΔ 0 L/sup d/ > 1 (rho is the density of states averaged over +- Δ 0 of the Fermi energy, Δ 0 the BCS gap parameter, and L the localization length). Hence the gap order parameter Δ(r) remains uniform in space at the BCS value Δ 0 . The superfluid density and response to electromagnetic perturbations, however, show marked differences from the ''dirty superconductor'' regime. For rhoΔ 0 L/sup d/ < 1, Δ(r) fluctuates spatially and eventually drops to zero. In the limit when states are site localized, the system crosses over into the ''Anderson negative-U glass.'' Considerations beyond the trial wave-function approximation will speed up the destruction of superconductivity. The superconductor formed from localized states has the property that its quasiparticle excitations are also localized. Such excitations can be probed by observing the normal current in a tunneling junction

  19. Relativistic BCS-BEC crossover at finite temperature and its application to color superconductivity

    International Nuclear Information System (INIS)

    He Lianyi; Zhuang Pengfei

    2007-01-01

    The nonrelativistic G 0 G formalism of BCS-BEC crossover at finite temperature is extended to relativistic fermion systems. The uncondensed pairs contribute a pseudogap to the fermion excitations. The theory recovers the BCS mean field approximation at zero temperature and the nonrelativistic results in a proper limit. For massive fermions, when the coupling strength increases, there exist two crossovers from the weak coupling BCS superfluid to the nonrelativistic BEC state and then to the relativistic BEC state. For color superconductivity at moderate baryon density, the matter is in the BCS-BEC crossover region, and the behavior of the pseudogap is quite similar to that found in high temperature superconductors

  20. Multi-band Image Registration Method Based on Fourier Transform

    Institute of Scientific and Technical Information of China (English)

    庹红娅; 刘允才

    2004-01-01

    This paper presented a registration method based on Fourier transform for multi-band images which is involved in translation and small rotation. Although different band images differ a lot in the intensity and features,they contain certain common information which we can exploit. A model was given that the multi-band images have linear correlations under the least-square sense. It is proved that the coefficients have no effect on the registration progress if two images have linear correlations. Finally, the steps of the registration method were proposed. The experiments show that the model is reasonable and the results are satisfying.

  1. An unconventional colour superconductor

    International Nuclear Information System (INIS)

    Huang Mei

    2007-01-01

    Superfluidity, or superconductivity with mismatched Fermi momenta, appears in many systems such as charge-neutral dense quark matter, asymmetric nuclear matter, and in imbalanced cold atomic gases. The mismatch plays the role of breaking the Cooper pairing, and the pair-breaking state cannot be properly described in the framework of standard BCS theory. I give a brief review on recent theoretical developments in understanding unconventional colour superconductivity, including a gapless colour superconductor, chromomagnetic instabilities and the Higgs instability in the gapless phase. I also introduce a possible new framework for describing an unconventional colour superconductor

  2. The BCS-BEC Crossover

    Science.gov (United States)

    Parish, Meera M.

    2015-09-01

    This chapter presents the crossover from the Bardeen-Cooper-Schrieffer (BCS) state of weakly correlated pairs of fermions to the Bose-Einstein condensation (BEC) of diatomic molecules in the atomic Fermi gas. Our aim is to provide a pedagogical review of the BCS-BEC crossover, with an emphasis on the basic concepts, particularly those that are not generally known or are difficult to find in the literature. We shall not attempt to give an exhaustive survey of current research in the limited space here; where possible, we will direct the reader to more extensive reviews.

  3. Mass renormalization and unconventional pairing in multi-band Fe-based superconductors- a phenomenological approach

    Energy Technology Data Exchange (ETDEWEB)

    Drechsler, S.L.; Efremov, D.; Grinenko, V. [IFW-Dresden (Germany); Johnston, S. [Inst. of Quantum Matter, University of British Coulumbia, Vancouver (Canada); Rosner, H. [MPI-cPfS, Dresden, (Germany); Kikoin, K. [Tel Aviv University (Israel)

    2015-07-01

    Combining DFT calculations of the density of states and plasma frequencies with experimental thermodynamic, optical, ARPES, and dHvA data taken from the literature, we estimate both the high-energy (Coulomb, Hund's rule coupling) and the low-energy (el-boson coupling) electronic mass renormalization [H(L)EMR] for typical Fe-pnictides with T{sub c}<40 K, focusing on (K,Rb,Cs)Fe{sub 2}As{sub 2}, (Ca,Na)122, (Ba,K)122, LiFeAs, and LaFeO{sub 1-x}F{sub x}As with and without As-vacancies. Using Eliashberg theory we show that these systems can NOT be described by a very strong el-boson coupling constant λ ≥ ∝ 2, being in conflict with the HEMR as seen by DMFT, ARPES and optics. Instead, an intermediate s{sub ±} coupling regime is realized, mainly based on interband spin fluctuations from one predominant pair of bands. For (Ca,Na)122, there is also a non-negligible intraband el-phonon/orbital fluctuation intraband contribution. The coexistence of magnetic As-vacancies and high-T{sub c}=28 K for LaFeO{sub 1-x}F{sub x}As{sub 1-δ} excludes an orbital fluctuation dominated s{sub ++} scenario at least for that system. In contrast, the line nodal BaFe{sub 2}(As,P){sub 2} near the quantum critical point is found as a superstrongly coupled system. The role of a pseudo-gap is briefly discussed for some of these systems.

  4. Multi - band Persistent Scatterer Interferometry data integration for landslide analysis

    Science.gov (United States)

    Bianchini, Silvia; Mateos, Rosa; Mora, Oscar; García, Inma; Sánchez, Ciscu; Sanabria, Margarita; López, Maite; Mulas, Joaquin; Hernández, Mario; Herrera, Gerardo

    2013-04-01

    We present a methodology to perform a geomorphological assessment of ground movements over wide areas, by improving Persistent Scatterer Interferometry (PSI) analysis for landslide studies. The procedure relies on the integrated use of multi-band EO data acquired by different satellite sensors in different time intervals, to provide a detailed investigation of ground displacements. The methodology, throughout the cross-comparison and integration of PS data in different microwave bands (ALOS in L-band, ERS1/2 and ENVISAT in C-band, COSMOSKY-MED in X-band), is applied on the Tramontana Range in the northwestern part of Mallorca island (Spain), extensively affected by mass movements across time, especially during the last years. We increase the confidence degree of the available interferometric data and we homogenize all PS targets by implementing and classifying them through common criteria. Therefore, PSI results are combined with geo-thematic data and pre-existing landslide inventories of the study area, in order to improve the landslide database, providing additional information on the detected ground displacements. The results of this methodology are used to elaborate landslide activity maps, permitting to jointly exploit heterogeneous PS data for analyzing landslides at regional scale. Moreover, from a geomorphological perspective, the proposed approach exploits the implemented PS data to achieve a reliable spatial analysis of movement rates, whatever referred to certain landslide phenomena or to other natural processes, in order to perform ground motion activity maps within a wide area.

  5. Quantum Monte Carlo simulations for high-Tc superconductors

    International Nuclear Information System (INIS)

    Muramatsu, A.; Dopf, G.; Wagner, J.; Dieterich, P.; Hanke, W.

    1992-01-01

    Quantum Monte Carlo simulations for a multi-band model of high-Tc superconductors are reviewed with special emphasis on the comparison of different observabels with experiments. It is shown that a give parameter set of the three-band Hubbard model leads to a consistent description of normal-state propteries as well as pairing correlation function for the copper-oxide superconductors as a function of doping and temperature. (orig.)

  6. BCS equations in the continuum

    International Nuclear Information System (INIS)

    Sandulescu, N.; Liotta, R. J.; Wyss, R.

    1998-01-01

    The properties of nuclei close to the drip line are significantly influenced by the continuum part of the single-particle spectrum. The main role is played by the resonant states which are largely confined in the region of nuclear potential and therefore stronger coupled with the bound states in an excitation process. Resonant states are also important in the nuclei beyond the drip line. In this case the decay properties of the nucleus can be directly related to the widths of the narrow resonances occupied by the unbound nucleons. The aim of this work is to propose an alternative for evaluating the effect of the resonant part of single-particle spectrum on the pairing correlations calculated within the BCS approximation. We estimated the role of resonances in the case of the isotope 170 Sn. The Resonant-BCS (RBCS) equations are solved for the case of a seniority force. The BCS approximation based on a seniority force cannot be applied in the case of a nucleus immersed in a box if all discrete states simulating the continuum are considered. In such a case the pairing correlations will increase with the number of states in the box. In our case one can still apply a seniority force with RBCS because the effect of the continuum appears here through a finite number of physical resonances, well defined by the given mean field. Because these resonances have a spatial distribution concentrated within the region of the nuclear potential, one expects that the localization probability of nucleons, far out from the nuclear surface, to be small. The gap obtained taking correctly the contribution of resonances, according to RBCS equations, is about 1.3 MeV, while pairing gap calculated only with the bound single-particle spectrum has the value Δ = 1.10 MeV. If we introduce also the resonant states, neglecting completely their widths, the gap will increase to the value Δ = 1.880 MeV. Therefore, one cannot estimate properly the pairing correlations by supplementing the spectrum

  7. MATLAB simulation software used for the PhD thesis "Acquisition of Multi-Band Signals via Compressed Sensing

    DEFF Research Database (Denmark)

    2014-01-01

    MATLAB simulation software used for the PhD thesis "Acquisition of Multi-Band Signals via Compressed Sensing......MATLAB simulation software used for the PhD thesis "Acquisition of Multi-Band Signals via Compressed Sensing...

  8. Searching for superconductors with high critical temperature

    Energy Technology Data Exchange (ETDEWEB)

    Chao, C

    1977-08-18

    Critical temperature of superconductors can be and must be raised so that their range of application can be broadened. It was estimated that, in 3 to 5 years, superconductor electric generators might be used in nuclear submarines and/or other applications where the requirements of small volume and light weight are critical. The BCS theory was recapitulated. Possible methods of achieving higher critical temperature were proposed and discussed.

  9. A Multi-Band Photonic Phased Array Antenna for High-Data Rate Communication, Phase II

    Data.gov (United States)

    National Aeronautics and Space Administration — Multi-band phased array antenna (PAA) can reduce the number of antennas on shipboard platforms while offering significantly improved performance. In order to steer...

  10. A Multi-band Photonic Phased Array Antenna for High-Date Rate Communication, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — Multi-band phased array antenna (PAA) can reduce the number of antennas on shipboard platforms while offering significantly improved performance. In order to steer...

  11. The design and application of a multi-band IR imager

    Science.gov (United States)

    Li, Lijuan

    2018-02-01

    Multi-band IR imaging system has many applications in security, national defense, petroleum and gas industry, etc. So the relevant technologies are getting more and more attention in rent years. As we know, when used in missile warning and missile seeker systems, multi-band IR imaging technology has the advantage of high target recognition capability and low false alarm rate if suitable spectral bands are selected. Compared with traditional single band IR imager, multi-band IR imager can make use of spectral features in addition to space and time domain features to discriminate target from background clutters and decoys. So, one of the key work is to select the right spectral bands in which the feature difference between target and false target is evident and is well utilized. Multi-band IR imager is a useful instrument to collect multi-band IR images of target, backgrounds and decoys for spectral band selection study at low cost and with adjustable parameters and property compared with commercial imaging spectrometer. In this paper, a multi-band IR imaging system is developed which is suitable to collect 4 spectral band images of various scenes at every turn and can be expanded to other short-wave and mid-wave IR spectral bands combination by changing filter groups. The multi-band IR imaging system consists of a broad band optical system, a cryogenic InSb large array detector, a spinning filter wheel and electronic processing system. The multi-band IR imaging system's performance is tested in real data collection experiments.

  12. New superconductor LaRhSb

    International Nuclear Information System (INIS)

    Nishigori, S.; Moriwaki, H.; Suzuki, T.; Fujita, T.; Tanaka, H.; Takabatake, T.; Fujii, H.

    1994-01-01

    Superconductivity in LaRhSb was newly found below the transition temperature T c = 2.67 K by the measurements of the electrical resistivity, magnetic susceptibility and specific heat in magnetic fields. The characteristics of the superconductivity determined in this study indicate that LaRhSb is a type II superconductor following the BCS theory. (orig.)

  13. Interplay of Phonon and Exciton-Mediated Superconductivity in Hybrid Semiconductor-Superconductor Structures

    Science.gov (United States)

    Skopelitis, Petros; Cherotchenko, Evgenia D.; Kavokin, Alexey V.; Posazhennikova, Anna

    2018-03-01

    We predict a strong enhancement of the critical temperature in a conventional Bardeen-Cooper-Schrieffer (BCS) superconductor in the presence of a bosonic condensate of exciton polaritons. The effect depends strongly on the ratio of the cutoff frequencies for phonon and exciton-polariton mediated BCS superconductivity, respectively. We also discuss a possible design of hybrid semiconductor-superconductor structures suitable for the experimental observation of such an effect.

  14. Multi-band transmission color filters for multi-color white LEDs based visible light communication

    Science.gov (United States)

    Wang, Qixia; Zhu, Zhendong; Gu, Huarong; Chen, Mengzhu; Tan, Qiaofeng

    2017-11-01

    Light-emitting diodes (LEDs) based visible light communication (VLC) can provide license-free bands, high data rates, and high security levels, which is a promising technique that will be extensively applied in future. Multi-band transmission color filters with enough peak transmittance and suitable bandwidth play a pivotal role for boosting signal-noise-ratio in VLC systems. In this paper, multi-band transmission color filters with bandwidth of dozens nanometers are designed by a simple analytical method. Experiment results of one-dimensional (1D) and two-dimensional (2D) tri-band color filters demonstrate the effectiveness of the multi-band transmission color filters and the corresponding analytical method.

  15. Single and multi-band electromagnetic induced transparency-like metamaterials with coupled split ring resonators

    Science.gov (United States)

    Bagci, Fulya; Akaoglu, Baris

    2017-08-01

    We present a metamaterial configuration exhibiting single and multi-band electromagnetic induced transparency (EIT)-like properties. The unit cell of the single band EIT-like metamaterial consists of a multi-split ring resonator surrounded by a split ring resonator. The multi-split ring resonator acts as a quasi-dark or dark resonator, depending on the polarization of the incident wave, and the split ring resonator serves as the bright resonator. Combination of these two resonators results in a single band EIT-like transmission inside the stop band. EIT-like transmission phenomenon is also clearly observed in the measured transmission spectrum at almost the same frequencies for vertical and horizontal polarized waves, and the numerical results are verified for normal incidence. Moreover, multi-band transmission windows are created within a wide band by combining the two slightly different single band EIT-like metamaterial unit cells that exhibit two different coupling strengths inside a supercell configuration. Group indices as high as 123 for single band and 488 for tri-band transmission, accompanying with high transmission rates (over 80%), are achieved, rendering the metamaterial very suitable for multi-band slow light applications. It is shown that the group delay of the propagating wave can be increased and dynamically controlled by changing the polarization angle. Multi-band EIT-like transmission is also verified experimentally, and a good agreement with simulations is obtained. The proposed novel methodology for obtaining multi-band EIT, which takes advantage of a supercell configuration by hosting slightly different configured unit cells, can be utilized for easily formation and manipulation of multi-band transmission windows inside a stop band.

  16. Parallel LC circuit model for multi-band absorption and preliminary design of radiative cooling.

    Science.gov (United States)

    Feng, Rui; Qiu, Jun; Liu, Linhua; Ding, Weiqiang; Chen, Lixue

    2014-12-15

    We perform a comprehensive analysis of multi-band absorption by exciting magnetic polaritons in the infrared region. According to the independent properties of the magnetic polaritons, we propose a parallel inductance and capacitance(PLC) circuit model to explain and predict the multi-band resonant absorption peaks, which is fully validated by using the multi-sized structure with identical dielectric spacing layer and the multilayer structure with the same strip width. More importantly, we present the application of the PLC circuit model to preliminarily design a radiative cooling structure realized by merging several close peaks together. This omnidirectional and polarization insensitive structure is a good candidate for radiative cooling application.

  17. Comparative study of BCS-BEC crossover theories above Tc: The nature of the pseudogap in ultracold atomic Fermi gases

    International Nuclear Information System (INIS)

    Chien, C.-C.; Guo Hao; He Yan; Levin, K.

    2010-01-01

    This article presents a comparison of two finite-temperature BCS-Bose-Einstein condensation (BEC) crossover theories above the transition temperature: Nozieres-Schmitt-Rink (NSR) theory and finite-T extended BCS-Leggett theory. The comparison is cast in the form of numerical studies of the behavior of the fermionic spectral function both theoretically and as constrained by (primarily) radio frequency (rf) experiments. Both theories include pair fluctuations and exhibit pseudogap effects, although the nature of this pseudogap is very different. The pseudogap in finite-T extended BCS-Leggett theory is found to follow a BCS-like dispersion which, in turn, is associated with a broadened BCS-like self-energy, rather more similar to what is observed in high-temperature superconductors (albeit, for a d-wave case). The fermionic quasiparticle dispersion is different in NSR theory and the damping is considerably larger. We argue that the two theories are appropriate in different temperature regimes with the BCS-Leggett approach being more suitable nearer to condensation. There should, in effect, be little difference at higher T as the pseudogap becomes weaker and where the simplifying approximations used in the BCS-Leggett approach break down. On the basis of momentum-integrated rf studies of unpolarized gases, it would be difficult to distinguish which theory is the better one. A full comparison for polarized gases is not possible since it is claimed that there are inconsistencies in the NSR approach (not found in the BCS-Leggett scheme). Future experiments along the lines of momentum-resolved experiments look to be very promising in distinguishing the two theories.

  18. A Possible Path from BCS through HTS to VHTS

    Science.gov (United States)

    Chu, C. W.

    2010-03-01

    Three years after celebrating the 50th anniversary of the BCS theory and the 20th anniversary of the discovery of high temperature superconductivity (HTS), it appears to be most fitting for us to contemplate the possibility of very high temperature superconductivity (VHTS). VHTS, preferably at room temperature, if achieved, could change the world both scientifically and technologically. Unfortunately, it has long been considered by some to belong to the domain of science fiction and to occur only ``at an astronomical distance and under an astronomical pressure.'' With the advent of liquid nitrogen superconductivity in 1987, the outlook has become much brighter. Currently, there appears to be no reason, either theoretical or experimental, why VHTS would be impossible, in spite of the 2006 prediction of the death of HTS by 2010-2015 through the so-called scientometric analysis of the publication record of the previous 20 years. The recent discovery of the new class of Fe-pnictide HTSs fuels more cautious optimism. Since its inception, BCS theory has provided the basic framework for the occurrence and understanding of superconductivity, but it has failed to show where and how to find superconductivity at a higher temperature. This may be attributed to the small energy scale of superconductivity in comparison with those of other excitations in the solids. After examining existing data, we believe that a holistic multidisciplinary enlightened empirical approach appears to be the most effective way to discover novel superconductors with higher transition temperatures. In this talk, I shall present several possible approaches toward VHTS that we are currently pursuing, after briefly summarizing what has happened in the long search for HTS and VHTS.

  19. BCS wave function, matrix product states, and the Ising conformal field theory

    Science.gov (United States)

    Montes, Sebastián; Rodríguez-Laguna, Javier; Sierra, Germán

    2017-11-01

    We present a characterization of the many-body lattice wave functions obtained from the conformal blocks (CBs) of the Ising conformal field theory (CFT). The formalism is interpreted as a matrix product state using continuous ancillary degrees of freedom. We provide analytic and numerical evidence that the resulting states can be written as BCS states. We give a complete proof that the translationally invariant 1D configurations have a BCS form and we find suitable parent Hamiltonians. In particular, we prove that the ground state of the finite-size critical Ising transverse field (ITF) Hamiltonian can be obtained with this construction. Finally, we study 2D configurations using an operator product expansion (OPE) approximation. We associate these states to the weak pairing phase of the p +i p superconductor via the scaling of the pairing function and the entanglement spectrum.

  20. The superconductor

    International Nuclear Information System (INIS)

    Lad, J.K.

    1979-01-01

    Techniques for fabrication of a few important superconductors like Nb, Ti and Nb 3 Sn are described. Copper or bronze or both can be used as a matrix in the superconductor. Current densities obtained for different ratios of copper to superconductor are studied. The specifications of multi-filament Nb 3 Sn superconductors are given. The relative merits of the two superconductors are discussed. The temperature range obtained is approximately 3 0 K and a magnetic field of 9T(tesla) can be achieved. (A.K.)

  1. Renormalized modes in cuprate superconductors

    Science.gov (United States)

    Gupta, Anushri; Kumari, Anita; Verma, Sanjeev K.; Indu, B. D.

    2018-04-01

    The renormalized mode frequencies are obtained with the help of quantum dynamical approach of many body phonon Green's function technique via a general Hamiltonian (excluding BCS Hamiltonian) including the effects of phonons and electrons, anharmonicities and electron-phonon interactions. The numerical estimates have been carried out to study the renormalized mode frequency of high temperature cuprate superconductor (HTS) YBa2Cu3O7-δ using modified Born-Mayer-Huggins interaction potential (MBMHP) best applicable to study the dynamical properties of all HTS.

  2. Multi-band microwave photonic satellite repeater scheme employing intensity Mach-Zehnder modulators

    Institute of Scientific and Technical Information of China (English)

    Yin Jie; Dong Tao; Zhang Bin; Hao Yan; Cao Guixing; Cheng Zijing; Xu Kun; Zhou Yue; Dai Jian

    2017-01-01

    To solve the satellite repeater's flexible and wideband frequency conversion problem,we propose a novel microwave photonic repeater system,which can convert the upload signal's carrier to six different frequencies.The scheme employs one 20 GHz bandwidth dual-drive Mach-Zehnder modulator (MZM) and two 10 GHz bandwidth MZMs.The basic principle of this scheme is filtering out two optical sidebands after the optical carrier suppression (OCS) modulation and combining two sidebands modulated by the input radio frequency (RF) signal.This structure can realize simultaneous multi-band frequency conversion with only one frequency-fixed microwave source and prevent generating harmful interference sidebands by using two corresponding optical filters after optical modulation.In the simulation,one C-band signal of 6 GHz carrier can be successfully converted to 12 GHz (Ku-band),28 GHz,34 GHz,40 GHz,46 GHz (Ka-band) and 52 GHz (V-band),which can be an attractive method to realize multi-band microwave photonic satellite repeater.Alternatively,the scheme can be configured to generate multi-band local oscillators (LOs) for widely satellite onboard clock distribution when the input RF signal is replaced by the internal clock source.

  3. Organic superconductors

    International Nuclear Information System (INIS)

    Bulaevskij, L.N.; Shchegolev, I.F.

    1986-01-01

    Main achievements in creating new organic conducting materials - synthetic metals and superconductors, are considered. The processes of superconductivity occurrence in organic materials are discussed. It is shown that conjugated bonds between C and H atoms in organic molecules play an important role in this case. At present ''crystal direction'' in organic superconductor synthesis is mainly developed. Later on, organic superconductor crystals are supposed to be introduced into usual polymers, e.g. polyethylene

  4. Experimental constraints on theories of high Tc superconductors

    International Nuclear Information System (INIS)

    Little, W.A.

    1989-01-01

    Recent experiments on the high-T c superconductors have begun to narrow the possible theoretical explanations of the phenomenon. Experimental evidence on the size, structure and symmetry of the charge carriers will be reviewed; evidence for and against strong coupling; and, recent results on a search for direct evidence of magnetic signature in the coupling mechanism will be presented. The authors show how these experiments impose strong constraints on the theories of these superconductors. A new type of experiment is also discussed which appears capable of identifying the true nature of the coupling mechanism if the superconductors prove to be BCS-like in nature

  5. BCS superconductivity for weakly coupled clusters

    International Nuclear Information System (INIS)

    Friedel, J.

    1992-01-01

    BCS superconductivity is expected to have fairly high critical temperatures when clusters of moderate sizes are weakly coupled to form a crystal. This remark extends to quasi zerodimensional cases, a remark initially made by Labbe for quasi one-dimensional ones and by Hirsch, Bok and Labbe for quasi twodimensional ones. Possible applications are envisaged for twodimensional clusters (fullerene) or threedimensional ones (metal clusters, Chevrel phases). Conditions for optimal applicability of the scheme are somewhat restricted. (orig.)

  6. Pattern-based compression of multi-band image data for landscape analysis

    CERN Document Server

    Myers, Wayne L; Patil, Ganapati P

    2006-01-01

    This book describes an integrated approach to using remotely sensed data in conjunction with geographic information systems for landscape analysis. Remotely sensed data are compressed into an analytical image-map that is compatible with the most popular geographic information systems as well as freeware viewers. The approach is most effective for landscapes that exhibit a pronounced mosaic pattern of land cover. The image maps are much more compact than the original remotely sensed data, which enhances utility on the internet. As value-added products, distribution of image-maps is not affected by copyrights on original multi-band image data.

  7. RRI-GBT MULTI-BAND RECEIVER: MOTIVATION, DESIGN, AND DEVELOPMENT

    International Nuclear Information System (INIS)

    Maan, Yogesh; Deshpande, Avinash A.; Chandrashekar, Vinutha; Chennamangalam, Jayanth; Rao, K. B. Raghavendra; Somashekar, R.; Ezhilarasi, M. S.; Sujatha, S.; Kasturi, S.; Sandhya, P.; Duraichelvan, R.; Amiri, Shahram; Aswathappa, H. A.; Sarabagopalan, G.; Ananda, H. M.; Anderson, Gary; Bauserman, Jonah; Beaudet, Carla; Bloss, Marty; Barve, Indrajit V.

    2013-01-01

    We report the design and development of a self-contained multi-band receiver (MBR) system, intended for use with a single large aperture to facilitate sensitive and high time-resolution observations simultaneously in 10 discrete frequency bands sampling a wide spectral span (100-1500 MHz) in a nearly log-periodic fashion. The development of this system was primarily motivated by need for tomographic studies of pulsar polar emission regions. Although the system design is optimized for the primary goal, it is also suited for several other interesting astronomical investigations. The system consists of a dual-polarization multi-band feed (with discrete responses corresponding to the 10 bands pre-selected as relatively radio frequency interference free), a common wide-band radio frequency front-end, and independent back-end receiver chains for the 10 individual sub-bands. The raw voltage time sequences corresponding to 16 MHz bandwidth each for the two linear polarization channels and the 10 bands are recorded at the Nyquist rate simultaneously. We present the preliminary results from the tests and pulsar observations carried out with the Robert C. Byrd Green Bank Telescope using this receiver. The system performance implied by these results and possible improvements are also briefly discussed.

  8. RRI-GBT MULTI-BAND RECEIVER: MOTIVATION, DESIGN, AND DEVELOPMENT

    Energy Technology Data Exchange (ETDEWEB)

    Maan, Yogesh; Deshpande, Avinash A.; Chandrashekar, Vinutha; Chennamangalam, Jayanth; Rao, K. B. Raghavendra; Somashekar, R.; Ezhilarasi, M. S.; Sujatha, S.; Kasturi, S.; Sandhya, P.; Duraichelvan, R.; Amiri, Shahram; Aswathappa, H. A.; Sarabagopalan, G.; Ananda, H. M. [Raman Research Institute, Bangalore (India); Anderson, Gary; Bauserman, Jonah; Beaudet, Carla; Bloss, Marty [National Radio Astronomy Observatory, P.O. Box 2, Green Bank, WV (United States); Barve, Indrajit V. [Indian Institute of Astrophysics, Bangalore (India); and others

    2013-01-15

    We report the design and development of a self-contained multi-band receiver (MBR) system, intended for use with a single large aperture to facilitate sensitive and high time-resolution observations simultaneously in 10 discrete frequency bands sampling a wide spectral span (100-1500 MHz) in a nearly log-periodic fashion. The development of this system was primarily motivated by need for tomographic studies of pulsar polar emission regions. Although the system design is optimized for the primary goal, it is also suited for several other interesting astronomical investigations. The system consists of a dual-polarization multi-band feed (with discrete responses corresponding to the 10 bands pre-selected as relatively radio frequency interference free), a common wide-band radio frequency front-end, and independent back-end receiver chains for the 10 individual sub-bands. The raw voltage time sequences corresponding to 16 MHz bandwidth each for the two linear polarization channels and the 10 bands are recorded at the Nyquist rate simultaneously. We present the preliminary results from the tests and pulsar observations carried out with the Robert C. Byrd Green Bank Telescope using this receiver. The system performance implied by these results and possible improvements are also briefly discussed.

  9. Ginzburg–Landau theory of mesoscopic multi-band Josephson junctions

    Energy Technology Data Exchange (ETDEWEB)

    Romeo, F.; De Luca, R., E-mail: rdeluca@unisa.it

    2017-05-15

    Highlights: • We generalize, in the realm of the Ginzburg–Landau theory, the de Gennes matching-matrix method for the interface order parameters to describe the superconducting properties of multi-band mesoscopic Josephson junctions. • The results are in agreement with a microscopic treatment of nanobridge junctions. • Thermal stability of the nanobridge junction is discussed in connection with recent experiments on iron-based grain-boundary junctions. - Abstract: A Ginzburg–Landau theory for multi-band mesoscopic Josephson junctions has been developed. The theory, obtained by generalizing the de Gennes matching-matrix method for the interface order parameters, allows the study of the phase dynamics of various types of mesoscopic Josephson junctions. As a relevant application, we studied mesoscopic double-band junctions also in the presence of a superconducting nanobridge interstitial layer. The results are in agreement with a microscopic treatment of the same system. Furthermore, thermal stability of the nanobridge junction is discussed in connection with recent experiments on iron-based grain-boundary junctions.

  10. A reconfigurable frequency-selective surface for dual-mode multi-band filtering applications

    Science.gov (United States)

    Majidzadeh, Maryam; Ghobadi, Changiz; Nourinia, Javad

    2017-03-01

    A reconfigurable single-layer frequency-selective surface (FSS) with dual-mode multi-band modes of operation is presented. The proposed structure is printed on a compact 10 × 10 mm2 FR4 substrate with the thickness of 1.6 mm. A simple square loop is printed on the front side while another one along with two defected vertical arms is deployed on the backside. To realise the reconfiguration, two pin diodes are embedded on the backside square loop. Suitable insertion of conductive elements along with pin diodes yields in dual-mode multi-band rejection of applicable in service frequency ranges. The first operating mode due to diodes' 'ON' state provides rejection of 2.4 GHz WLAN in 2-3 GHz, 5.2/5.8 GHz WLAN and X band in 5-12 GHz, and a part of Ku band in 13.9-16 GHz. In diodes 'OFF' state, the FSS blocks WLAN in 4-7.3 GHz, X band in 8-12.7 GHz as well as part of Ku band in 13.7-16.7 GHz. As well, high attenuation of incident waves is observed by a high shielding effectiveness (SE) in the blocked frequency bands. Also, a stable behaviour against different polarisations and angles of incidence is obtained. Comprehensive studies are conducted on a fabricated prototype to assess its performance from which encouraging results are obtained.

  11. Briefing on superconductor developments

    International Nuclear Information System (INIS)

    Larbalestier, D.

    1987-01-01

    In this paper, the author covers the technology of the new oxide superconductors and how they might relate to the existing superconductors. He discusses old-fashioned superconductors; the material science of superconductors; the new oxide superconductors; and the future of oxide superconductors. 13 figures, 1 table

  12. Oxide superconductors

    International Nuclear Information System (INIS)

    Cava, R.J.

    2000-01-01

    This article briefly reviews ceramic superconductors from historical and materials perspectives. It describes the factors that distinguish high-temperature cuprate superconductors from most electronic ceramics and places them in the context of other families of superconducting materials. Finally, it describes some of the scientific issues presently being actively pursued in the search for the mechanism for high-temperature superconductivity and the directions of research into new superconducting ceramics in recent years

  13. Superfluid response in heavy fermion superconductors

    Science.gov (United States)

    Zhong, Yin; Zhang, Lan; Shao, Can; Luo, Hong-Gang

    2017-10-01

    Motivated by a recent London penetration depth measurement [H. Kim, et al., Phys. Rev. Lett. 114, 027003 (2015)] and novel composite pairing scenario [O. Erten, R. Flint, and P. Coleman, Phys. Rev. Lett. 114, 027002 (2015)] of the Yb-doped heavy fermion superconductor CeCoIn5, we revisit the issue of superfluid response in the microscopic heavy fermion lattice model. However, from the literature, an explicit expression for the superfluid response function in heavy fermion superconductors is rare. In this paper, we investigate the superfluid density response function in the celebrated Kondo-Heisenberg model. To be specific, we derive the corresponding formalism from an effective fermionic large- N mean-field pairing Hamiltonian whose pairing interaction is assumed to originate from the effective local antiferromagnetic exchange interaction. Interestingly, we find that the physically correct, temperature-dependent superfluid density formula can only be obtained if the external electromagnetic field is directly coupled to the heavy fermion quasi-particle rather than the bare conduction electron or local moment. Such a unique feature emphasizes the key role of the Kondo-screening-renormalized heavy quasi-particle for low-temperature/energy thermodynamics and transport behaviors. As an important application, the theoretical result is compared to an experimental measurement in heavy fermion superconductors CeCoIn5 and Yb-doped Ce1- x Yb x CoIn5 with fairly good agreement and the transition of the pairing symmetry in the latter material is explained as a simple doping effect. In addition, the requisite formalism for the commonly encountered nonmagnetic impurity and non-local electrodynamic effect are developed. Inspired by the success in explaining classic 115-series heavy fermion superconductors, we expect the present theory will be applied to understand other heavy fermion superconductors such as CeCu2Si2 and more generic multi-band superconductors.

  14. Multi-Band Multi-Tone Tunable Millimeter-Wave Frequency Synthesizer For Satellite Beacon Transmitter

    Science.gov (United States)

    Simons, Rainee N.; Wintucky, Edwin G.

    2016-01-01

    This paper presents the design and test results of a multi-band multi-tone tunable millimeter-wave frequency synthesizer, based on a solid-state frequency comb generator. The intended application of the synthesizer is in a satellite beacon transmitter for radio wave propagation studies at K-band (18 to 26.5 GHz), Q-band (37 to 42 GHz), and E-band (71 to 76 GHz). In addition, the architecture for a compact beacon transmitter, which includes the multi-tone synthesizer, polarizer, horn antenna, and power/control electronics, has been investigated for a notional space-to-ground radio wave propagation experiment payload on a small satellite. The above studies would enable the design of robust high throughput multi-Gbps data rate future space-to-ground satellite communication links.

  15. Multi-band microwave metamaterial absorber based on coplanar Jerusalem crosses

    Science.gov (United States)

    Wang, Guo-Dong; Liu, Ming-Hai; Hu, Xi-Wei; Kong, Ling-Hua; Cheng, Li-Li; Chen, Zhao-Quan

    2014-01-01

    The influence of the gap on the absorption performance of the conventional split ring resonator (SRR) absorber is investigated at microwave frequencies. Our simulated results reveal that the geometry of the square SRR can be equivalent to a Jerusalem cross (JC) resonator and its corresponding metamaterial absorber (MA) is changed to a JC absorber. The JC MA exhibits an experimental absorption peak of 99.1% at 8.72 GHz, which shows an excellent agreement with our simulated results. By simply assembling several JCs with slightly different geometric parameters next to each other into a unit cell, a perfect multi-band absorption can be effectively obtained. The experimental results show that the MA has four distinct and strong absorption peaks at 8.32 GHz, 9.8 GHz, 11.52 GHz and 13.24 GHz. Finally, the multi-reflection interference theory is introduced to interpret the absorption mechanism.

  16. Multi-band circular polarizer based on a twisted triple split-ring resonator

    International Nuclear Information System (INIS)

    Wu Song; Huang Xiao-Jun; Yang He-Lin; Xiao Bo-Xun; Jin Yan

    2014-01-01

    A multi-band circular polarizer using a twisted triple split-ring resonator (TSRR) is presented and studied numerically and experimentally. At four distinct resonant frequencies, the incident linearly polarized wave can be transformed into left/right-handed circularly polarized waves. Numerical simulation results show that a y-polarized wave can be converted into a right-handed circularly polarized wave at 5.738 GHz and 9.218 GHz, while a left-handed circularly polarized wave is produced at 7.292 GHz and 10.118 GHz. The experimental results are in agreement with the numerical results. The surface current distributions are investigated to illustrate the polarization transformation mechanism. Furthermore, the influences of the structure parameters of the circular polarizer on transmission spectra are discussed as well. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

  17. Multi-band Microwave Antennas and Devices based on Generalized Negative-Refractive-Index Transmission Lines

    Science.gov (United States)

    Ryan, Colan Graeme Matthew

    Focused on the quad-band generalized negative-refractive-index transmission line (G-NRI-TL), this thesis presents a variety of novel printed G-NRI-TL multi-band microwave device and antenna prototypes. A dual-band coupled-line coupler, an all-pass G-NRI-TL bridged-T circuit, a dual-band metamaterial leaky-wave antenna, and a multi-band G-NRI-TL resonant antenna are all new developments resulting from this research. In addition, to continue the theme of multi-band components, negative-refractive-index transmission lines are used to create a dual-band circularly polarized transparent patch antenna and a two-element wideband decoupled meander antenna system. High coupling over two independently-specified frequency bands is the hallmark of the G-NRI-TL coupler: it is 0.35lambda0 long but achieves approximately -3 dB coupling over both bands with a maximum insertion loss of 1 dB. This represents greater design flexibility than conventional coupled-line couplers and less loss than subsequent G-NRI-TL couplers. The single-ended bridged-T G-NRI-TL offers a metamaterial unit cell with an all-pass magnitude response up to 8 GHz, while still preserving the quad-band phase response of the original circuit. It is shown how the all-pass response leads to wider bandwidths and improved matching in quad-band inverters, power dividers, and hybrid couplers. The dual-band metamaterial leaky-wave antenna presented here was the first to be reported in the literature, and it allows broadside radiation at both 2 GHz and 6 GHz without experiencing the broadside stopband common to conventional periodic antennas. Likewise, the G-NRI-TL resonant antenna is the first reported instance of such a device, achieving quad-band operation between 2.5 GHz and 5.6 GHz, with a minimum radiation efficiency of 80%. Negative-refractive-index transmission line loading is applied to two devices: an NRI-TL meander antenna achieves a measured 52% impedance bandwidth, while a square patch antenna incorporates

  18. Radio frequency electromagnetic field compliance assessment of multi-band and MIMO equipped radio base stations.

    Science.gov (United States)

    Thors, Björn; Thielens, Arno; Fridén, Jonas; Colombi, Davide; Törnevik, Christer; Vermeeren, Günter; Martens, Luc; Joseph, Wout

    2014-05-01

    In this paper, different methods for practical numerical radio frequency exposure compliance assessments of radio base station products were investigated. Both multi-band base station antennas and antennas designed for multiple input multiple output (MIMO) transmission schemes were considered. For the multi-band case, various standardized assessment methods were evaluated in terms of resulting compliance distance with respect to the reference levels and basic restrictions of the International Commission on Non-Ionizing Radiation Protection. Both single frequency and multiple frequency (cumulative) compliance distances were determined using numerical simulations for a mobile communication base station antenna transmitting in four frequency bands between 800 and 2600 MHz. The assessments were conducted in terms of root-mean-squared electromagnetic fields, whole-body averaged specific absorption rate (SAR) and peak 10 g averaged SAR. In general, assessments based on peak field strengths were found to be less computationally intensive, but lead to larger compliance distances than spatial averaging of electromagnetic fields used in combination with localized SAR assessments. For adult exposure, the results indicated that even shorter compliance distances were obtained by using assessments based on localized and whole-body SAR. Numerical simulations, using base station products employing MIMO transmission schemes, were performed as well and were in agreement with reference measurements. The applicability of various field combination methods for correlated exposure was investigated, and best estimate methods were proposed. Our results showed that field combining methods generally considered as conservative could be used to efficiently assess compliance boundary dimensions of single- and dual-polarized multicolumn base station antennas with only minor increases in compliance distances. © 2014 Wiley Periodicals, Inc.

  19. Isotope and multiband effects in layered superconductors.

    Science.gov (United States)

    Bussmann-Holder, Annette; Keller, Hugo

    2012-06-13

    In this review we consider three classes of superconductors, namely cuprate superconductors, MgB(2) and the new Fe based superconductors. All of these three systems are layered materials and multiband compounds. Their pairing mechanisms are under discussion with the exception of MgB(2), which is widely accepted to be a 'conventional' electron-phonon interaction mediated superconductor, but extending the Bardeen-Cooper-Schrieffer (BCS) theory to account for multiband effects. Cuprates and Fe based superconductors have higher superconducting transition temperatures and more complex structures. Superconductivity is doping dependent in these material classes unlike in MgB(2) which, as a pure compound, has the highest values of T(c) and a rapid suppression of superconductivity with doping takes place. In all three material classes isotope effects have been observed, including exotic ones in the cuprates, and controversial ones in the Fe based materials. Before the area of high-temperature superconductivity, isotope effects on T(c) were the signature for phonon mediated superconductivity-even when deviations from the BCS value to smaller values were observed. Since the discovery of high T(c) materials this is no longer evident since competing mechanisms might exist and other mediating pairing interactions are discussed which are of purely electronic origin. In this work we will compare the three different material classes and especially discuss the experimentally observed isotope effects of all three systems and present a rather general analysis of them. Furthermore, we will concentrate on multiband signatures which are not generally accepted in cuprates even though they are manifest in various experiments, the evidence for those in MgB(2), and indications for them in the Fe based compounds. Mostly we will consider experimental data, but when possible also discuss theoretical models which are suited to explain the data.

  20. Gravitationally bound BCS state as dark matter

    Energy Technology Data Exchange (ETDEWEB)

    Alexander, Stephon [Department of Physics, Brown University, Providence, RI 20912 (United States); Cormack, Sam, E-mail: stephon_alexander@brown.edu, E-mail: samuel.c.cormack.gr@dartmouth.edu [Department of Physics and Astronomy, Dartmouth College, Hanover, NH 03755 (United States)

    2017-04-01

    We explore the possibility that fermionic dark matter undergoes a BCS transition to form a superfluid. This requires an attractive interaction between fermions and we describe a possible source of this interaction induced by torsion. We describe the gravitating fermion system with the Bogoliubov-de Gennes formalism in the local density approximation. We solve the Poisson equation along with the equations for the density and gap energy of the fermions to find a self-gravitating, superfluid solution for dark matter halos. In order to produce halos the size of dwarf galaxies, we require a particle mass of ∼ 200 eV. We find a maximum attractive coupling strength before the halo becomes unstable. If dark matter halos do have a superfluid component, this raises the possibility that they contain vortex lines.

  1. The evidence of unconventional pairing in heavy fermion superconductors and high-Tc superconductors

    International Nuclear Information System (INIS)

    Tien, C.; Wur, C.S.; Jiang, I.M.

    1989-01-01

    Recently there has been a great deal of interest in two classes of superconductors, heavy fermion superconductors and high T c copper oxide superconductors. The behavior and nature of superconductivity in these two classes of materials are very similar. The temperature dependences of spin-lattice relaxation time (T 1 ) and spin-spin relaxation time (T 2 ) of 9 Be in UBe 13 are quite similar to those of 63 Cu and 89 Y in YBa 2 Cu 3 O 7-δ . The Knight shift of UBe 13 is unchanged during the superconducting phase transition. The Knight shift of YBa 2 Cu 3 O 7-δ changes from the value in the normal state K n /K s = 1 at T ≥ T c to K n /K s = 0.5 at T = 6 K. Both do not approach zero as expected in BCS theory. The acoustic attenuation is enhanced just below T c instead of rapid drop near T c for these two superconducting system. Neither the enhancement, the temperature variation, nor any other anomalous behaviors appear to be mirrored in EPR data for heavy Fermion superconductors and high T c superconductors. This strongly suggests that the unconventional pairing mechanism which induces superconductivity in heavy fermion materials might also involve in high T c superconductors

  2. Ceramic superconductors II

    International Nuclear Information System (INIS)

    Yan, M.F.

    1988-01-01

    This volume compiles papers on ceramic superconductors. Topics include: structural patterns in High-Tc superconductors, phase equilibria of barium oxide superconductors, localized electrons in tetragonal YBa/sub 2/Cu/sub 3/O/sub 7-δ/, lattice and defect structure and properties of rare earth/alkaline earth-copper-oxide superconductors, alternate candidates for High-Tc superconductors, perovskite-structure superconductors; superconductive thin film fabrication, and superconductor/polymer composites

  3. Making superconductors

    International Nuclear Information System (INIS)

    McDonald, W.K.

    1981-01-01

    A method is described of producing composite rod or wire of increased strength and fineness wherein the composite is formed by reducing a lamina of two metals which have been rolled to form a cylindrical billet in which one of the metals is in expanded form. The composite produced can be encased in copper and fabricated to produce a superconductor. Alloys contemplated for producing superconductors are Nb 3 Sn, Nb 3 Ga, Nb 3 Ge, Nb 3 Si, Nb-Ti, V 3 Ga, V 3 Si, V 3 Sn, V 3 Al, and V 3 Ge laminated on bronze, Al, Cu, Ta, or combinations thereof. (author)

  4. Proposed experimental test of an alternative electrodynamic theory of superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Hirsch, J.E., E-mail: jhirsch@ucsd.edu

    2015-01-15

    Highlights: • A new experimental test of electric screening in superconductors is proposed. • The electric screening length is predicted to be much larger than in normal metals. • The reason this was not seen in earlier experiments is explained. • This is not predicted by the conventional BCS theory of superconductivity. - Abstract: An alternative form of London’s electrodynamic theory of superconductors predicts that the electrostatic screening length is the same as the magnetic penetration depth. We argue that experiments performed to date do not rule out this alternative formulation and propose an experiment to test it. Experimental evidence in its favor would have fundamental implications for the understanding of superconductivity.

  5. High critical magnetic field superconductor La3S4

    International Nuclear Information System (INIS)

    Westerholt, K.; Bach, H.; Wendemuth, R.; Methfessel, S.

    1979-01-01

    A report is presented on electrical conductivity, specific heat and magnetization measurements on La 3 S 4 single crystals. The results show that La 3 S 4 is a strong coupling superconductor with a BCS coherence length of 132 A. This extremely low value makes La 3 S 4 an intrinsic high critical magnetic field superconductor with a Landau-Ginsburg parameter of 20. For the temperature gradient of the upper critical magnetic field at the transition temperature values are found up to 35 kG/K. (author)

  6. Role of Coulomb repulsion in multilayer cuprate superconductor

    International Nuclear Information System (INIS)

    Singh Chauhan, Ekta; Singh, Vipul; Masih, Piyush

    2012-01-01

    Although BCS theory completely neglects coulomb repulsion; Anderson and Morel showed very early that it plays a central role in superconductivity. Since all high T c superconductors are based on the structure of closely spaced square planner CuO 2 layers and role of interlayer interaction plays important role in enhancement of T c . Therefore the work has been dealt with 'Role of Coulomb repulsion in Multilayer Cuprate Superconductors'. An expression for transition temperature T c is obtained by using simple integration technique and is numerically solved. It has found that T c decreases with electronic repulsion. (author)

  7. Segmentation of myocardial perfusion MR sequences with multi-band Active Appearance Models driven by spatial and temporal features

    NARCIS (Netherlands)

    Baka, N.; Milles, J.; Hendriks, E.A.; Suinesiaputra, A.; Jerosh Herold, M.; Reiber, J.H.C.; Lelieveldt, B.P.F.

    2008-01-01

    This work investigates knowledge driven segmentation of cardiac MR perfusion sequences. We build upon previous work on multi-band AAMs to integrate into the segmentation both spatial priors about myocardial shape as well as temporal priors about characteristic perfusion patterns. Different temporal

  8. A two-dimensional Fermi gas in the BEC-BCS crossover

    Energy Technology Data Exchange (ETDEWEB)

    Ries, Martin Gerhard

    2016-01-21

    This thesis reports on the preparation of a 2D Fermi gas in the BEC-BCS crossover and the observation of the BKT transition into a quasi long-range ordered superfluid phase. The pair momentum distribution of the gas is probed by means of a matter-wave focusing technique which relies on time-of-flight evolution in a weak harmonic potential. This distribution holds the coherence properties of the gas. The quasi long-range ordered phase manifests itself as a sharp low-momentum peak. The temperature where it forms is identified as the transition temperature. By tuning the temperature and the interaction strength, the phase diagram of the 2D Fermi gas in the BEC-BCS crossover is mapped out. The phase coherence is investigated in a self-interference experiment. Furthermore, algebraic decay of correlations is observed in the trap average of the first order correlation function, which is obtained from the Fourier transform of the pair momentum distribution. This is in qualitative agreement with predictions of homogeneous theory for the superfluid phase in a 2D gas. The presented results provide a foundation for future experimental and theoretical studies of strongly correlated 2D Fermi gases. They might thus help to elucidate complex systems such as the electron gas in high-T{sub c} superconductors.

  9. Further test of new pairing scheme used in overhaul of BCS theory

    International Nuclear Information System (INIS)

    Zheng, X.H.; Walmsley, D.G.

    2014-01-01

    Highlights: • Explanation of a new pairing scheme to overhaul BCS theory. • Prediction of superconductor properties from normal state resistivity. • Applications to Nb, Pb, Al, Ta, Mo, Ir and W, T c between 9.5 and 0.012 K. • High accuracy compared with measured energy gap of Nb, Pb, Al and Ta. • Prediction of energy gap for Mo, Ir and W (so far not measured). - Abstract: A new electron pairing scheme, rectifying a fundamental flaw of the BCS theory, is tested extensively. It postulates that superconductivity arises solely from residual umklapp scattering when it is not in competition for the same destination electron states with normal scattering. It reconciles a long standing theoretical discrepancy in the strength of the electron–phonon interaction between the normal and superconductive states. The new scheme is exploited to calculate the superconductive electron–phonon spectral density, α 2 F(ν), entirely on the basis of normal state electrical resistivity. This leads to first principles superconductive properties (zero temperature energy gap and tunnelling conductance) in seven metals which turn out to be highly accurate when compared with known data; in other cases experimental verification is invited. The transition temperatures involved vary over almost three orders of magnitude: from 9.5 K for niobium to 0.012 K for tungsten

  10. Surface resistance of superconductors - examples from Nb - O systems

    International Nuclear Information System (INIS)

    Palmer, F.

    1988-01-01

    The observed surface resistance of most superconductors can be written as the sum of two terms. R/sub obs/ = R/sub BCS/ + R/sub res/. This paper is divided into three sections. The first section describes the BCS theory of surface resistance in terms of a simplified two-fluid model. The second section describes several possible causes of residual resistance including normal conducting materials, tunneling across cracks in the surface, and direct generation of phonons by the RF electric field. The last section describes recent experiments having to do with the effects of oxide layers on surface resistance. Layers grown in pure oxygen at room temperature were found to have little or no effect, but if these layers are heated to temperatures near 300 0 C, they can alter both the BCS resistance and the residual resistance. Heated oxide layers also increased the dependence of the residual resistance on ambient magnetic field. 31 references, 13 figures, 3 tables

  11. Inhomogeneous superconductors

    International Nuclear Information System (INIS)

    Tinkham, M.

    1978-01-01

    The coherence length xi and penetration depth lambda set the characteristic length scales in superconductors, typically 100 to 5,000 A. A lattice of flux lines, each carrying a single quantum, can penetrate type II superconductors, i.e., those for which kappa identical with lambda/xi > 1/√2. Inhomogeneities on the scale of the flux lattice spacing are required to pin the lattice to prevent dissipative flux motion. Recent work using voids as pinning centers has demonstrated this principle, but practical materials rely on cold-work, inclusions of second phases, etc., to provide the inhomogeneity. For stability against thermal fluctuations, the superconductor should have the form of many filaments of diameter 10 to 100 μm imbedded in a highly conductive normal metal matrix. Such wire is made by drawing down billets of copper containing rods of the superconductor. An alternative approach is the metallurgical one of Tsuei, which leads to thousands of superconducting filamentary segments in a copper matrix. The superconducting proximity effect causes the whole material to superconduct at low current densities. At high current densities, the range of the proximity effect is reduced so that the effective superconducting volume fraction falls below the percolation threshold, and a finite resistance arises from the copper matrix. But, because of the extremely elongated filaments, this resistance is orders of magnitude lower than that of the normal wire, and low enough to permit the possibility of technical applications

  12. Tc, 2Δ0/KBTc and parameters of phonon spectrum for amorphous superconductors

    International Nuclear Information System (INIS)

    Cao Xiaowen

    1987-04-01

    After the correlations between superconducting parameters T C and 2Δ 0 , the parameters of the phonon spectrum, λ, , 2 > and Hall coefficient R H and between the superconducting T C and the parameters of the phonon spectrum ω 0 and /ω 0 were researched analytically. It had been found that there is a maximum of the above-mentioned both superconducting and the phonon spectrum parameters in the region of R H = -3.5 to -4.0 x 10 -11 m 3 /AS and that the materials having high ω 0 is favourable to obtain amorphous superconductors with high T C as well as that the relation between T C and the degree of the lattice disorder (i.e. /ω 0 value) is linear. On the basis of the above-mentioned results, a formula of T C and 2Δ 0 /k B T C of amorphous superconductors had been given. According to both proposed formula, it is noted for the first time that amorphous superconductor of the non-transition metals and their alloys is either a typical strong coupling superconductor which has a much larger 2 Δ 0 /k B T C than BCS theory or a extreme weak coupling superconductor which has a much smaller 2 Δ 0 /k B T C than BCS theory. Of coures, they can be also a weak coupling superconductor whose 2 Δ 0 /k B T C is consistent with BCS theory or approximate to one. The reason that the measurement value of 2 Δ 0 /k BTC of the weak coupling superconductors in the crystal state deviates obviously from BCS theory has been explained

  13. Nonequilibrium Green's function formulation of quantum transport theory for multi-band semiconductors

    International Nuclear Information System (INIS)

    Zhao, Peiji; Horing, Norman J.M.; Woolard, Dwight L.; Cui, H.L.

    2003-01-01

    We present a nonequilibrium Green's function formulation of many-body quantum transport theory for multi-band semiconductor systems with a phonon bath. The equations are expressed exactly in terms of single particle nonequilibrium Green's functions and self-energies, treating the open electron-hole system in weak interaction with the bath. A decoupling technique is employed to separate the individual band Green's function equations of motion from one another, with the band-band interaction effects embedded in ''cross-band'' self-energies. This nonequilibrium Green's function formulation of quantum transport theory is amenable to solution by parallel computing because of its formal decoupling with respect to inter-band interactions. Moreover, this formulation also permits coding the simulator of an n-band semiconductor in terms of that for an (n-1)-band system, in step with the current tendency and development of programming technology. Finally, the focus of these equations on individual bands provides a relatively direct route for the determination of carrier motion in energy bands, and to delineate the influence of intra- and inter-band interactions. A detailed description is provided for three-band semiconductor systems

  14. Independent polarization and multi-band THz absorber base on Jerusalem cross

    Science.gov (United States)

    Arezoomand, Afsaneh Saee; Zarrabi, Ferdows B.; Heydari, Samaneh; Gandji, Navid P.

    2015-10-01

    In this paper, we present the design and simulation of a single and multi-band perfect metamaterial absorber (MA) in the THz region base on Jerusalem cross (JC) and metamaterial load in unit cells. The structures consist of dual metallic layers for allowing near-perfect absorption with absorption peak of more than 99%. In this novel design, four-different shape of Jerusalem cross is presented and by adding L, U and W shape loaded to first structure, we tried to achieve a dual-band absorber. In addition, by good implementation of these loaded, we are able to control the absorption resonance at second resonance at 0.9, 0.7 and 0.85 THz respectively. In the other hand, we achieved a semi stable designing at first resonance between 0.53 and 0.58 THz. The proposed absorber has broadband polarization angle. The surface current modeled and proved the broadband polarization angle at prototype MA. The LC resonance of the metamaterial for Jerusalem cross and modified structures are extracting from equivalent circuit. As a result, proposed MA is useful for THz medical imaging and communication systems and the dual-band absorber has applications in many scientific and technological areas.

  15. Achieving a multi-band metamaterial perfect absorber via a hexagonal ring dielectric resonator

    Science.gov (United States)

    Li, Li-Yang; Wang, Jun; Du, Hong-Liang; Wang, Jia-Fu; Qu, Shao-Bo

    2015-06-01

    A multi-band absorber composed of high-permittivity hexagonal ring dielectric resonators and a metallic ground plate is designed in the microwave band. Near-unity absorptions around 9.785 GHz, 11.525 GHz, and 12.37 GHz are observed for this metamaterial absorber. The dielectric hexagonal ring resonator is made of microwave ceramics with high permittivity and low loss. The mechanism for the near-unity absorption is investigated via the dielectric resonator theory. It is found that the absorption results from electric and magnetic resonances where enhanced electromagnetic fields are excited inside the dielectric resonator. In addition, the resonance modes of the hexagonal resonator are similar to those of standard rectangle resonators and can be used for analyzing hexagonal absorbers. Our work provides a new research method as well as a solid foundation for designing and analyzing dielectric metamaterial absorbers with complex shapes. Project supported by the National Natural Science Foundation of China (Grant Nos. 61331005, 11204378, 11274389, 11304393, and 61302023), the Aviation Science Foundation of China (Grant Nos. 20132796018 and 20123196015), the Natural Science Foundation for Post-Doctoral Scientists of China (Grant Nos. 2013M532131 and 2013M532221), the Natural Science Foundation of Shaanxi Province, China (Grant No. 2013JM6005), and the Special Funds for Authors of Annual Excellent Doctoral Degree Dissertations of China (Grant No. 201242).

  16. Multi-Band Light Curves from Two-Dimensional Simulations of Gamma-Ray Burst Afterglows

    Science.gov (United States)

    MacFadyen, Andrew

    2010-01-01

    The dynamics of gamma-ray burst outflows is inherently multi-dimensional. 1.) We present high resolution two-dimensional relativistic hydrodynamics simulations of GRBs in the afterglow phase using adaptive mesh refinement (AMR). Using standard synchrotron radiation models, we compute multi-band light curves, from the radio to X-ray, directly from the 2D hydrodynamics simulation data. We will present on-axis light curves for both constant density and wind media. We will also present off-axis light curves relevant for searches for orphan afterglows. We find that jet breaks are smoothed due to both off-axis viewing and wind media effects. 2.) Non-thermal radiation mechanisms in GRB afterglows require substantial magnetic field strengths. In turbulence driven by shear instabilities in relativistic magnetized gas, we demonstrate that magnetic field is naturally amplified to half a percent of the total energy (epsilon B = 0.005). We will show high resolution three dimensional relativistic MHD simulations of this process as well as particle in cell (PIC) simulations of mildly relativistic collisionless shocks.

  17. Exposure assessment in front of a multi-band base station antenna.

    Science.gov (United States)

    Kos, Bor; Valič, Blaž; Kotnik, Tadej; Gajšek, Peter

    2011-04-01

    This study investigates occupational exposure to electromagnetic fields in front of a multi-band base station antenna for mobile communications at 900, 1800, and 2100 MHz. Finite-difference time-domain method was used to first validate the antenna model against measurement results published in the literature and then investigate the specific absorption rate (SAR) in two heterogeneous, anatomically correct human models (Virtual Family male and female) at distances from 10 to 1000 mm. Special attention was given to simultaneous exposure to fields of three different frequencies, their interaction and the additivity of SAR resulting from each frequency. The results show that the highest frequency--2100 MHz--results in the highest spatial-peak SAR averaged over 10 g of tissue, while the whole-body SAR is similar at all three frequencies. At distances > 200 mm from the antenna, the whole-body SAR is a more limiting factor for compliance to exposure guidelines, while at shorter distances the spatial-peak SAR may be more limiting. For the evaluation of combined exposure, a simple summation of spatial-peak SAR maxima at each frequency gives a good estimation for combined exposure, which was also found to depend on the distribution of transmitting power between the different frequency bands. Copyright © 2010 Wiley-Liss, Inc.

  18. Chapter 27. Superconductors

    International Nuclear Information System (INIS)

    Vavra, O.

    2007-01-01

    In this chapter author deals with superconductors and superconductivity. Different chemical materials used as high-temperature superconductors are presented. Some applications of superconductivity are presented.

  19. Ternary superconductors

    International Nuclear Information System (INIS)

    Giorgi, A.L.

    1987-01-01

    Ternary superconductors constitute a class of superconducting compounds with exceptional properties such as high transition temperatures (≅ 15.2 K), extremely high critical fields (H c2 >60 Tesla), and the coexistence of superconductivity and long-range magnetic order. This has generated great interest in the scientific community and resulted in a large number of experimental and theoretical investigations in which many new ternary compounds have been discovered. A review of some of the properties of these ternary compounds is presented with particular emphasis on the ternary molybdenum chalcogenides and the ternary rare earth transition metal tetraborides. The effect of partial substitution of a second metal atom to form pseudoternary compounds is examined as well as some of the proposed correlations between the superconducting transition temperature and the structural and electronic properties of the ternary superconductors

  20. Superconductor Dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Gömöry, F [Bratislava, Inst. Elect. Eng. (Slovakia)

    2014-07-01

    Superconductors used in magnet technology could carry extreme currents because of their ability to keep the magnetic flux motionless. The dynamics of the magnetic flux interaction with superconductors is controlled by this property. The cases of electrical transport in a round wire and the magnetization of wires of various shapes (circular, elliptical, plate) in an external magnetic field are analysed. Resistance to the magnetic field penetration means that the field produced by the superconducting magnet is no longer proportional to the supplied current. It also leads to a dissipation of electromagnetic energy. In conductors with unequal transverse dimensions, such as flat cables, the orientation with respect to the magnetic field plays an essential role. A reduction of magnetization currents can be achieved by splitting the core of a superconducting wire into fine filaments; however, new kinds of electrical currents that couple the filaments consequently appear. Basic formulas allowing qualitative analyses of various flux dynamic cases are presented.

  1. Nanostructuring superconductors by ion beams: A path towards materials engineering

    Energy Technology Data Exchange (ETDEWEB)

    Gerbaldo, Roberto; Ghigo, Gianluca; Gozzelino, Laura; Laviano, Francesco [Department of Applied Science and Technology, Politecnico di Torino c.so Duca degli Abruzzi 24, 10129 Torino, Italy and INFN Sez. Torino, via P. Giuria 1, 10125 Torino (Italy); Amato, Antonino; Rovelli, Alberto [INFN Laboratori Nazionali del Sud, via S. Sofia 62, 95125 Catania (Italy); Cherubini, Roberto [INFN Laboratori Nazionali di Legnaro, viale dell' Universita 2, 35020 Legnaro (Italy)

    2013-07-18

    The paper deals with nanostructuring of superconducting materials by means of swift heavy ion beams. The aim is to modify their structural, optical and electromagnetic properties in a controlled way, to provide possibility of making them functional for specific applications. Results are presented concerning flux pinning effects (implantation of columnar defects with nanosize cross section to enhance critical currents and irreversibility fields), confined flux-flow and vortex guidance, design of devices by locally tailoring the superconducting material properties, analysis of disorder-induced effects in multi-band superconductors. These studies were carried out on different kinds of superconducting samples, from single crystals to thin films, from superconducting oxides to magnesium diboride, to recently discovered iron-based superconductors.

  2. Chiral superconductors.

    Science.gov (United States)

    Kallin, Catherine; Berlinsky, John

    2016-05-01

    Chiral superconductivity is a striking quantum phenomenon in which an unconventional superconductor spontaneously develops an angular momentum and lowers its free energy by eliminating nodes in the gap. It is a topologically non-trivial state and, as such, exhibits distinctive topological modes at surfaces and defects. In this paper we discuss the current theory and experimental results on chiral superconductors, focusing on two of the best-studied systems, Sr2RuO4, which is thought to be a chiral triplet p-wave superconductor, and UPt3, which has two low-temperature superconducting phases (in zero magnetic field), the lower of which is believed to be chiral triplet f-wave. Other systems that may exhibit chiral superconductivity are also discussed. Key signatures of chiral superconductivity are surface currents and chiral Majorana modes, Majorana states in vortex cores, and the possibility of half-flux quantum vortices in the case of triplet pairing. Experimental evidence for chiral superconductivity from μSR, NMR, strain, polar Kerr effect and Josephson tunneling experiments are discussed.

  3. THE BIOPHARMACEUTICAL CLASSIFICATION SYSTEM (BCS): PRESENT STATUS AND FUTURE PROSPECTIVES

    OpenAIRE

    Budhwaar Vikaas; Nanda Arun

    2012-01-01

    The Biopharmaceutical classification system (BCS) was introduced By Amidon et al., (1995) as a method for classifying drug substances based on their dose/solubility ratio and intestinal permeability. It allows predicting the in vivo pharmacokinetic performance of drug products. The drug can be categorized into four classes of BCS, namely, High solubility high permeability, low solubility high permeability, High solubility low permeability and low solubility low permeability. An objective of B...

  4. Multi-band algorithms for the estimation of chlorophyll concentration in the Chesapeake Bay

    KAUST Repository

    Gilerson, Alexander

    2015-10-14

    Standard blue-green ratio algorithms do not usually work well in turbid productive waters because of the contamination of the blue and green bands by CDOM absorption and scattering by non-algal particles. One of the alternative approaches is based on the two- or three band ratio algorithms in the red/NIR part of the spectrum, which require 665, 708, 753 nm bands (or similar) and which work well in various waters all over the world. The critical 708 nm band for these algorithms is not available on MODIS and VIIRS sensors, which limits applications of this approach. We report on another approach where a combination of the 745nm band with blue-green-red bands was the basis for the new algorithms. A multi-band algorithm which includes ratios Rrs(488)/Rrs(551)and Rrs(671)/Rrs(745) and two band algorithm based on Rrs671/Rrs745 ratio were developed with the main focus on the Chesapeake Bay (USA) waters. These algorithms were tested on the specially developed synthetic datasets, well representing the main relationships between water parameters in the Bay taken from the NASA NOMAD database and available literature, on the field data collected by our group during a 2013 campaign in the Bay, as well as NASA SeaBASS data from the other group and on matchups between satellite imagery and water parameters measured by the Chesapeake Bay program. Our results demonstrate that the coefficient of determination can be as high as R2 > 0.90 for the new algorithms in comparison with R2 = 0.6 for the standard OC3V algorithm on the same field dataset. Substantial improvement was also achieved by applying a similar approach (inclusion of Rrs(667)/Rrs(753) ratio) for MODIS matchups. Results for VIIRS are not yet conclusive. © (2015) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE).

  5. Multi-band, multi-epoch observations of the transiting warm Jupiter WASP-80b

    Energy Technology Data Exchange (ETDEWEB)

    Fukui, Akihiko; Kuroda, Daisuke [Okayama Astrophysical Observatory, National Astronomical Observatory of Japan, Asakuchi, Okayama 719-0232 (Japan); Kawashima, Yui; Ikoma, Masahiro; Kurosaki, Kenji [Department of Earth and Planetary Science, Graduate School of Science, The University of Tokyo, 7-3-1 Bunkyo-ku, Tokyo 113-0033 (Japan); Narita, Norio; Nishiyama, Shogo; Takahashi, Yasuhiro H.; Nagayama, Shogo [National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588 (Japan); Onitsuka, Masahiro; Baba, Haruka; Ryu, Tsuguru [The Graduate University for Advanced Studies, 2-21-1 Osawa, Mitaka, Tokyo 181-8588 (Japan); Ita, Yoshifusa; Onozato, Hiroki [Astronomical Institute, Graduate School of Science, Tohoku University, 6-3 Aramaki Aoba, Aoba-ku, Sendai, Miyagi 980-8578 (Japan); Hirano, Teruyuki; Kawauchi, Kiyoe [Department of Earth and Planetary Sciences, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8551 (Japan); Hori, Yasunori [Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064 (United States); Nagayama, Takahiro [Department of Physics, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8602 (Japan); Tamura, Motohide [Department of Astronomy, Graduate School of Science, The University of Tokyo, and National Astronomical Observatory of Japan (Japan); Kawai, Nobuyuki, E-mail: afukui@oao.nao.ac.jp [Department of Physics, Tokyo Institute of Technology, 2-12-1, Oookayama, Meguro, Tokyo 152-8551 (Japan); and others

    2014-08-01

    WASP-80b is a warm Jupiter transiting a bright late-K/early-M dwarf, providing a good opportunity to extend the atmospheric study of hot Jupiters toward the lower temperature regime. We report multi-band, multi-epoch transit observations of WASP-80b by using three ground-based telescopes covering from optical (g', R{sub c}, and I{sub c} bands) to near-infrared (NIR; J, H, and K{sub s} bands) wavelengths. We observe 5 primary transits, each in 3 or 4 different bands simultaneously, obtaining 17 independent transit light curves. Combining them with results from previous works, we find that the observed transmission spectrum is largely consistent with both a solar abundance and thick cloud atmospheric models at a 1.7σ discrepancy level. On the other hand, we find a marginal spectral rise in the optical region compared to the NIR region at the 2.9σ level, which possibly indicates the existence of haze in the atmosphere. We simulate theoretical transmission spectra for a solar abundance but hazy atmosphere, finding that a model with equilibrium temperature of 600 K can explain the observed data well, having a discrepancy level of 1.0σ. We also search for transit timing variations, but find no timing excess larger than 50 s from a linear ephemeris. In addition, we conduct 43 day long photometric monitoring of the host star in the optical bands, finding no significant variation in the stellar brightness. Combined with the fact that no spot-crossing event is observed in the five transits, our results confirm previous findings that the host star appears quiet for spot activities, despite the indications of strong chromospheric activities.

  6. Compact multi-band frequency reconfigurable planar monopole antenna for several wireless communication applications

    Directory of Open Access Journals (Sweden)

    M. Abou Al-Alaa

    2014-05-01

    Full Text Available A compact reconfigurable multi-band monopole antenna is presented. To achieve frequency reconfigurability, a PIN diode is used. There are two states of switch. State 1: when the switch is OFF, the antenna operates at four bands: 2.45, 3, 3.69, and 5.5 GHz with impedance bandwidth of 9.95, 5.96, 12.57, and 10.76%, respectively. State 2: when a switch is ON, the antenna operates at 2.64, 3.67, 4.94, and 5.3 GHz with impedance bandwidth of 21.15, 11.76, 5.79, and 4.12%, respectively. Folded and meandered techniques are used for miniaturize antenna size. Antenna size is 15 mm × 37 mm × 0.8 mm and the radiator part is 15 mm × 9 mm × 0.8 mm. The proposed antenna is used in several applications such as Bluetooth (2400–2484 MHz, WLAN [802.11b/g/n (2.4–2.48 GHz, 802.11y (3.657–3.69 GHz, 802.11y (4.9 GHz, 802.11a/h/j/n (5.2 GHz], Wi-MAX (2.5–2.69 GHz, LTE (band 7, band 38, band 41, and band 43 and S-DMB (2605–2655 MHz. The antenna is analyzed using the transient solver of CST Microwave Studio. The proposed antenna was fabricated and tested. Measurements and simulations show good agreement.

  7. Superconductor Digital Electronics: -- Current Status, Future Prospects

    Science.gov (United States)

    Mukhanov, Oleg

    2011-03-01

    Two major applications of superconductor electronics: communications and supercomputing will be presented. These areas hold a significant promise of a large impact on electronics state-of-the-art for the defense and commercial markets stemming from the fundamental advantages of superconductivity: simultaneous high speed and low power, lossless interconnect, natural quantization, and high sensitivity. The availability of relatively small cryocoolers lowered the foremost market barrier for cryogenically-cooled superconductor electronic systems. These fundamental advantages enabled a novel Digital-RF architecture - a disruptive technological approach changing wireless communications, radar, and surveillance system architectures dramatically. Practical results were achieved for Digital-RF systems in which wide-band, multi-band radio frequency signals are directly digitized and digital domain is expanded throughout the entire system. Digital-RF systems combine digital and mixed signal integrated circuits based on Rapid Single Flux Quantum (RSFQ) technology, superconductor analog filter circuits, and semiconductor post-processing circuits. The demonstrated cryocooled Digital-RF systems are the world's first and fastest directly digitizing receivers operating with live satellite signals, enabling multi-net data links, and performing signal acquisition from HF to L-band with 30 GHz clock frequencies. In supercomputing, superconductivity leads to the highest energy efficiencies per operation. Superconductor technology based on manipulation and ballistic transfer of magnetic flux quanta provides a superior low-power alternative to CMOS and other charge-transfer based device technologies. The fundamental energy consumption in SFQ circuits defined by flux quanta energy 2 x 10-19 J. Recently, a novel energy-efficient zero-static-power SFQ technology, eSFQ/ERSFQ was invented, which retains all advantages of standard RSFQ circuits: high-speed, dc power, internal memory. The

  8. Charged vortices in high-Tc superconductors

    International Nuclear Information System (INIS)

    Matsuda, Y.; Kumagai, K.

    2002-01-01

    It is well known that a vortex in type II superconductors traps a magnetic flux. Recently the possibility that a vortex can accumulate a finite electric charge as well has come to be realized. The sign and magnitude of the vortex charge not only is closely related to the microscopic electronic structure of the vortex, but also strongly affects the dynamical properties of the vortex. In this chapter we demonstrate that a vortex in high-T c superconductors (HTSC) indeed traps a finite electronic charge, using the high resolution measurements of the nuclear quadrupole frequencies. We then discuss the vortex Hall anomaly whose relation with the vortex charging effect has recently received considerable attention. We show that the sign of the trapped charge is opposite to the sign predicted by the conventional BCS theory and deviation of the magnitude of the charge from the theory is also significant. We also show that the electronic structure of underlying system is responsible for the Hall sign in the vortex state and again the Hall sign is opposite to the sign predicted by the BCS theory. It appears that these unexpected features observed in both electrostatics and dynamics of the vortex may be attributed to the novel electronic structure of the vortex in HTSC. (orig.)

  9. Machine-learned Identification of RR Lyrae Stars from Sparse, Multi-band Data: The PS1 Sample

    Science.gov (United States)

    Sesar, Branimir; Hernitschek, Nina; Mitrović, Sandra; Ivezić, Željko; Rix, Hans-Walter; Cohen, Judith G.; Bernard, Edouard J.; Grebel, Eva K.; Martin, Nicolas F.; Schlafly, Edward F.; Burgett, William S.; Draper, Peter W.; Flewelling, Heather; Kaiser, Nick; Kudritzki, Rolf P.; Magnier, Eugene A.; Metcalfe, Nigel; Tonry, John L.; Waters, Christopher

    2017-05-01

    RR Lyrae stars may be the best practical tracers of Galactic halo (sub-)structure and kinematics. The PanSTARRS1 (PS1) 3π survey offers multi-band, multi-epoch, precise photometry across much of the sky, but a robust identification of RR Lyrae stars in this data set poses a challenge, given PS1's sparse, asynchronous multi-band light curves (≲ 12 epochs in each of five bands, taken over a 4.5 year period). We present a novel template fitting technique that uses well-defined and physically motivated multi-band light curves of RR Lyrae stars, and demonstrate that we get accurate period estimates, precise to 2 s in > 80 % of cases. We augment these light-curve fits with other features from photometric time-series and provide them to progressively more detailed machine-learned classification models. From these models, we are able to select the widest (three-fourths of the sky) and deepest (reaching 120 kpc) sample of RR Lyrae stars to date. The PS1 sample of ˜45,000 RRab stars is pure (90%) and complete (80% at 80 kpc) at high galactic latitudes. It also provides distances that are precise to 3%, measured with newly derived period-luminosity relations for optical/near-infrared PS1 bands. With the addition of proper motions from Gaia and radial velocity measurements from multi-object spectroscopic surveys, we expect the PS1 sample of RR Lyrae stars to become the premier source for studying the structure, kinematics, and the gravitational potential of the Galactic halo. The techniques presented in this study should translate well to other sparse, multi-band data sets, such as those produced by the Dark Energy Survey and the upcoming Large Synoptic Survey Telescope Galactic plane sub-survey.

  10. Multi-band morpho-Spectral Component Analysis Deblending Tool (MuSCADeT): Deblending colourful objects

    Science.gov (United States)

    Joseph, R.; Courbin, F.; Starck, J.-L.

    2016-05-01

    We introduce a new algorithm for colour separation and deblending of multi-band astronomical images called MuSCADeT which is based on Morpho-spectral Component Analysis of multi-band images. The MuSCADeT algorithm takes advantage of the sparsity of astronomical objects in morphological dictionaries such as wavelets and their differences in spectral energy distribution (SED) across multi-band observations. This allows us to devise a model independent and automated approach to separate objects with different colours. We show with simulations that we are able to separate highly blended objects and that our algorithm is robust against SED variations of objects across the field of view. To confront our algorithm with real data, we use HST images of the strong lensing galaxy cluster MACS J1149+2223 and we show that MuSCADeT performs better than traditional profile-fitting techniques in deblending the foreground lensing galaxies from background lensed galaxies. Although the main driver for our work is the deblending of strong gravitational lenses, our method is fit to be used for any purpose related to deblending of objects in astronomical images. An example of such an application is the separation of the red and blue stellar populations of a spiral galaxy in the galaxy cluster Abell 2744. We provide a python package along with all simulations and routines used in this paper to contribute to reproducible research efforts. Codes can be found at http://lastro.epfl.ch/page-126973.html

  11. THE FIRST SYSTEMATIC STUDY OF TYPE Ibc SUPERNOVA MULTI-BAND LIGHT CURVES

    International Nuclear Information System (INIS)

    Drout, Maria R.; Soderberg, Alicia M.; Gal-Yam, Avishay; Arcavi, Iair; Green, Yoav; Cenko, S. Bradley; Fox, Derek B.; Leonard, Douglas C.; Sand, David J.; Moon, Dae-Sik

    2011-01-01

    We present detailed optical photometry for 25 Type Ibc supernovae (SNe Ibc) within d ≈ 150 Mpc obtained with the robotic Palomar 60 inch telescope in 2004-2007. This study represents the first uniform, systematic, and statistical sample of multi-band SNe Ibc light curves available to date. We correct the light curves for host galaxy extinction using a new technique based on the photometric color evolution, namely, we show that the (V – R) color of extinction-corrected SNe Ibc at Δt ≈ 10 days after V-band maximum is tightly distributed, ((V – R) V10 ) = 0.26 ± 0.06 mag. Using this technique, we find that SNe Ibc typically suffer from significant host galaxy extinction, (E(B – V)) ≈ 0.4 mag. A comparison of the extinction-corrected light curves for helium-rich (Type Ib) and helium-poor (Type Ic) SNe reveals that they are statistically indistinguishable, both in luminosity and decline rate. We report peak absolute magnitudes of (M R ) = –17.9 ± 0.9 mag and (M R ) = –18.3 ± 0.6 mag for SNe Ib and Ic, respectively. Focusing on the broad-lined (BL) SNe Ic, we find that they are more luminous than the normal SNe Ibc sample, (M R ) = –19.0 ± 1.1 mag, with a probability of only 1.6% that they are drawn from the same population of explosions. By comparing the peak absolute magnitudes of SNe Ic-BL with those inferred for local engine-driven explosions (GRB-SN 1998bw, XRF-SN 2006aj, and SN 2009bb) we find a 25% probability that relativistic SNe are drawn from the overall SNe Ic-BL population. Finally, we fit analytic models to the light curves to derive typical 56 Ni masses of M Ni ≈ 0.2 and 0.5 M ☉ for SNe Ibc and SNe Ic-BL, respectively. With reasonable assumptions for the photospheric velocities, we further extract kinetic energy and ejecta mass values of M ej ≈ 2 M ☉ and E K ≈ 10 51 erg for SNe Ibc, while for SNe Ic-BL we find higher values, M ej ≈ 5 M ☉ and E K ≈ 10 52 erg. We discuss the implications for the progenitors of SNe Ibc

  12. Microscopic analysis of the non-dissipative force on a line vortex in a superconductor

    International Nuclear Information System (INIS)

    Gaitan, F.

    1994-12-01

    A microscopic analysis of the non-dissipative force F nd acting on a line vortex in a type-II superconductor at T = 0 is given. All work presented assumes a charged BCS superconductor. We first examine the Berry phase induced in the BCS superconducting ground state by movement of the vortex and show how this phase enters into the hydro-dynamic action S hyd of the superconducting condensate. Appropriate variation of S hyd gives F nd and variation of the Berry phase term is seen to contribute the Magnus or lift force of classical hydrodynamics to F nd . This analysis, based on the BCS ground state of a charged superconductor, confirms in detail the arguments of Ao and Thouless within the context of the BCS model. Our Berry phase, in the limit e → 0, is seen to reproduce the Berry phase determined by these authors for a neutral superfluid. We also provide a second, independent, determination on F nd through a microscopic derivation of the continuity equation for the condensate linear momentum. This equation yields the acceleration equation for the superflow and shows that the vortex acts as a sink for the condensate linear momentum. The rate at which momentum is lost to the vortex determines F nd in this second approach and the result obtained agrees identically with the previous Berry phase calculation. The Magnus force contribution to F nd is seen in both calculations to be a consequence of the vortex topology and motion. (author). 10 refs

  13. Theory of the electric current transmission coefficient in the superconductor-insulator-superconductor geometry

    International Nuclear Information System (INIS)

    Navani, R.

    1974-01-01

    Tunneling in the superconductor-insulator-superconductor (S'-I-S) geometry, where the two superconductors are not necessarily the same, is studied theoretically. Two different models of the S'-I-S geometry - which we call the ''initial model'' and the ''improved model'' are discussed. For the initial model the potential barrier is flat. In the improved model, however, the differing material properties of the three regions - S', I, and S - are taken into account in an approximate fashion. In addition, applied, contact, and image potentials in the insulator are included. The solid state material properties that are taken to be different are the effective electronic masses in the three regions and the Fermi energies in the two superconductors. The quasiparticle wave functions in the S', I, and S regions are determined for both models as solutions to the Bogoliubov-de Gennes equations. The electric current transmission coefficients (also the reflection coefficient for the initial model) are derived and their behavior is extensively analyzed. Their forms in the thick barrier limit - where L greater than or approximately equal to 5 A - are related to the BCS densities of states. The tunneling current density is found to depend strongly on the tunneling angle. A relation between the angular position of the tunneling current peak and the barrier thickness is given. Finally, it is shown that the choice of insulator material effects the tunneling current, and the effect is greater the thicker the insulating film

  14. Contributions to the mathematical study of BCS theory

    International Nuclear Information System (INIS)

    Deuchert, Andreas

    2016-01-01

    The results of this thesis contribute to the mathematical study of BCS theory, that is, to the study of the BCS gap equation and the BCS functional. In the first part, we investigate a recent definition of a generalized relative entropy for bounded and not necessarily compact operators, which, in the second part, is used to define and study a non-periodic version of the BCS functional with an external field. In the third part of this work, we consider the BCS functional in two spatial dimensions with a radial pair interaction and show that the translational symmetry of the model is not broken. The quantum relative entropy plays an important role in statistical mechanics and quantum information theory. Apart from its relevance in quantum physics, it has interesting mathematical properties, such as joint convexity and monotonicity. From a purely mathematical point of view, it can be interpreted as a distance measure between two matrices, or more generally two trace-class operators, A and B. Like Hartree states, BCS states are conveniently described in terms of a generalized one-particle density matrix and so it is no surprise that the need to extend the relative entropy to non-compact operators also plays a role in BCS theory. This was our initial motivation in studying this object. The generalized relative entropy of Lewin and Sabin is defined by a limiting procedure that resembles the thermodynamic limit. An important question left open in their work is whether there exists a simple formula that allows one to compute the limit without having to work with the complicated limiting procedure. Such a formula is necessary for example for trial state arguments. In Chapter 2 we answer this question affirmatively and derive such a formula. Assuming some mild regularity conditions for the operators A and B, we show that it takes a particularly simple form, which is suitable for computations. Our proof is based upon a novel integral representation of the generalized relative

  15. Contributions to the mathematical study of BCS theory

    Energy Technology Data Exchange (ETDEWEB)

    Deuchert, Andreas

    2016-09-29

    The results of this thesis contribute to the mathematical study of BCS theory, that is, to the study of the BCS gap equation and the BCS functional. In the first part, we investigate a recent definition of a generalized relative entropy for bounded and not necessarily compact operators, which, in the second part, is used to define and study a non-periodic version of the BCS functional with an external field. In the third part of this work, we consider the BCS functional in two spatial dimensions with a radial pair interaction and show that the translational symmetry of the model is not broken. The quantum relative entropy plays an important role in statistical mechanics and quantum information theory. Apart from its relevance in quantum physics, it has interesting mathematical properties, such as joint convexity and monotonicity. From a purely mathematical point of view, it can be interpreted as a distance measure between two matrices, or more generally two trace-class operators, A and B. Like Hartree states, BCS states are conveniently described in terms of a generalized one-particle density matrix and so it is no surprise that the need to extend the relative entropy to non-compact operators also plays a role in BCS theory. This was our initial motivation in studying this object. The generalized relative entropy of Lewin and Sabin is defined by a limiting procedure that resembles the thermodynamic limit. An important question left open in their work is whether there exists a simple formula that allows one to compute the limit without having to work with the complicated limiting procedure. Such a formula is necessary for example for trial state arguments. In Chapter 2 we answer this question affirmatively and derive such a formula. Assuming some mild regularity conditions for the operators A and B, we show that it takes a particularly simple form, which is suitable for computations. Our proof is based upon a novel integral representation of the generalized relative

  16. The non-equilibrium response of a superconductor to pair-breaking radiation measured over a broad frequency band

    NARCIS (Netherlands)

    De Visser, P.J.; Yates, S.J.C.; Guruswamy, T.; Goldie, D.J.; Withington, S.; Neto, A.; Llombart, N.; Baryshev, A.M.; Klapwijk, T.M.; Baselmans, J.J.A.

    2015-01-01

    We have measured the absorption of terahertz radiation in a BCS superconductor over a broad range of frequencies from 200 GHz to 1.1 THz, using a broadband antenna-lens system and a tantalum microwave resonator. From low frequencies, the response of the resonator rises rapidly to a maximum at the

  17. Ground-state fidelity in the BCS-BEC crossover

    International Nuclear Information System (INIS)

    Khan, Ayan; Pieri, Pierbiagio

    2009-01-01

    The ground-state fidelity has been introduced recently as a tool to investigate quantum phase transitions. Here, we apply this concept in the context of a crossover problem. Specifically, we calculate the fidelity susceptibility for the BCS ground-state wave function, when the intensity of the fermionic attraction is varied from weak to strong in an interacting Fermi system, through the BCS-Bose-Einstein Condensation crossover. Results are presented for contact and finite-range attractive potentials and for both continuum and lattice models. We conclude that the fidelity susceptibility can be useful also in the context of crossover problems.

  18. 10Gb/s Ultra-Wideband Wireless Transmission Based on Multi-Band Carrierless Amplitude Phase Modulation

    DEFF Research Database (Denmark)

    Puerta Ramírez, Rafael; Rommel, Simon; Vegas Olmos, Juan José

    2016-01-01

    In this paper, for the first time, a record UWB transmission of 10Gb/s is experimentally demonstrated employing a multi-band approach of carrierless amplitude phase modulation (MultiCAP). The proposed solution complies with the restrictions on the effective radiated power established by both...... the United States Federal Communications Commission and the European Electronic Communications Committee, achieving a BER below the limit for a 7% overhead FEC of 3.8 · 10−3 up to respective wireless distances of 3.5m and 2m....

  19. Comparison of HMM experts with MLP experts in the Full Combination Multi-Band Approach to Robust ASR

    OpenAIRE

    Hagen, Astrid; Morris, Andrew

    2000-01-01

    In this paper we apply the Full Combination (FC) multi-band approach, which has originally been introduced in the framework of posterior-based HMM/ANN (Hidden Markov Model/Artificial Neural Network) hybrid systems, to systems in which the ANN (or Multilayer Perceptron (MLP)) is itself replaced by a Multi Gaussian HMM (MGM). Both systems represent the most widely used statistical models for robust ASR (automatic speech recognition). It is shown how the FC formula for the likelihood--based MGMs...

  20. Coincident photoelectron spectroscopy on superconductors

    International Nuclear Information System (INIS)

    Voss, Stefan

    2011-01-01

    Aim of the performed experiments of this thesis was to attempt to detect Cooper pairs as carriers of the superconducting current directly by means of the photoelectric effect. The method of the coincident photoelectron spectroscopy aims thereby at the detection of two coherently emitted electrons by the interaction with a photon. Because electrostatic analyzers typically cover only a very small spatial angle, which goes along with very low coincidence rates, in connection with this thesis a time-of-flight projection system has been developed, which maps nearly the whole spatial angle on a position-resolving detector. The pulsed light source in form of special synchrotron radiation necessary for the measurement has been adjusted so weak, that only single photons could arrive at the sample. Spectroscoped were beside test measurements on silver layers both a lead monocrystal as representative of the classical BCS superconductors and monocrystalline Bi 2 Sr 2 CaCu 2 O 8 from the family of the high-temperature superconductors. With excitation energies up to 40 eV could be shown that sufficiently smooth and clean surfaces in the superconducting phase exhibit within the resolving power of about 0.5 eV no recognizable differences in comparison to the normally conducting phase. Beside these studies furthermore the simple photoemission at the different samples and especially in the case of the lead crystal is treated, because here no comparable results are known. Thereby the whole momentum space is discussed and the Fermi surface established as three-dimensional model, by means of which the measurement results are discussed. in the theoretical descriptions different models for the Cooper-pair production are presented, whereby to the momentum exchange with the crystal a special role is attributed, because this can only occur in direct excitations via discrete lattice vectors.

  1. Interacting bosons model and relation with BCS theory

    International Nuclear Information System (INIS)

    Diniz, R.

    1990-01-01

    The Nambu mechanism for BCS theory is extended with inclusion of quadrupole pairing in addition to the usual monopole pairing. An effective Hamiltonian is constructed and its relation to the IBM is discussed. The faced difficulties and a possible generalization of this model are discussed. (author)

  2. Software testing an ISTQB-BCS certified tester foundation guide

    CERN Document Server

    Hambling, Brian; Samaroo, Angelina; Thompson, Geoff; Williams, Peter; Hambling, Brian

    2015-01-01

    This practical guide provides insight into software testing, explaining the basics of the testing process and how to perform effective tests. It provides an overview of different techniques and how to apply them. It is the best-selling official textbook of the ISTQB-BCS Certified Tester Foundation Level.

  3. Effect of spontaneous decay of superconductor quasiparticles in the tunneling density of states

    International Nuclear Information System (INIS)

    Coffey, D.

    1993-01-01

    Superconductivity has been successfully described with either the Landau-Ginzburg theory of second order phase transitions or with strong-coupling versions of the original BCS theory for almost fifty years. Recent tunneling and photoemission data on the cuprate oxide superconductors may now provide evidence of corrections to the mean field approximation. It has been shown by Zasadzinski et al. that there is a dip at eV ≅ 3Δ 0 in the SIS tunneling conductance, which is the derivative of the current across a superconductor-insulator-superconductor junction with respect to the applied voltage, for a set of cuprate superconductors whose T c 's range from 5.5K to 100K. Recently L. Coffey and I proposed an explanation of this feature in terms of the spontaneous decay of mean field quasiparticles. We showed that corrections to the mean field approximation for a superconductor lead to different frequency thresholds for spontaneous quasiparticle decay with different superconductor order parameter symmetries. These effects lead to features in the superconductor density of states and in the SIS tunneling conductance and provide experimental evidence of d-wave symmetry for the superconductor order parameter in the cuprates. I discuss model and also evidence of quasiparticle decay in ARPES data on Bi 2 Sr 2 CaCu 2 O 8

  4. Coherent lattice vibrations in superconductors

    International Nuclear Information System (INIS)

    Kadin, Alan M.

    2008-01-01

    A recent analysis has shown that the pair wavefunction within the BCS theory may be represented in real-space as a spherical electronic orbital (on the scale of the coherence length ξ 0 ) coupled to a standing-wave lattice vibration with wavevector 2k F and a near-resonant phonon frequency. The present paper extends this picture to a coherent pattern of phonon standing-waves on the macroscopic scale, with electrons forming Bloch waves and an energy gap much like those in the classic band theory of crystals. These parallel planes form a diffractive waveguide permitting electron waves to traveling parallel to the planes, corresponding to lossless supercurrent. A similar picture may be extended to unconventional superconductors such as the cuprates, with an array of standing spin waves rather than phonons. Such coherent lattice vibrations should be universal indicators of the superconducting state, and should be observable below T c using X-ray and neutron diffraction techniques. Further implications of this picture are discussed

  5. Isominkowskian theory of Cooper Pairs in superconductors

    International Nuclear Information System (INIS)

    Animalu, A.O.E.

    1993-01-01

    Via the use of Santilli's isominkowskian space, the author presents a relativistic extension of the author's recent treatment of the Cooper Pair in superconductivity based on the Lie-isotopic lifting of quantum mechanics known as Hadronic Mechanics. The isominkowskian treatment reduces the solution of the eiganvalue problem for the quasiparticle energy spectrum to a geometric problem of specifying the metric of the isominkowskian space inside the pair in various models of ordinary high T c superconductors. The use of an intriguing realization of the metric due to Dirac reduces the dimensionality of the interior space to two yielding a spin mutation from 1/2 to zero inside a Cooper pair in two-band BCS and Hubbard models. 12 refs

  6. The disappearing momentum of the supercurrent in the superconductor-to-normal phase transformation

    Science.gov (United States)

    Hirsch, J. E.

    2016-06-01

    A superconductor in a magnetic field has surface currents that prevent the magnetic field from penetrating its interior. These currents carry kinetic energy and mechanical momentum. When the temperature is raised and the system becomes normal the currents disappear. Where do the kinetic energy and mechanical momentum of the currents go, and how? Here we propose that the answer to this question reveals a key necessary condition for materials to be superconductors, that is not part of conventional BCS-London theory: superconducting materials need to have hole carriers.

  7. Description of C isotopes within RMF+BCS approach

    International Nuclear Information System (INIS)

    Saxena, G.; Singh, D.; Kaushik, M.

    2013-01-01

    In the present investigations we have employed relativistic mean-field plus BCS (RMF + BCS) approach to carry out a systematic study for the ground state properties of even-even C Isotopes. One of the prime reason of this study has been to look into the role of low lying states in neutron rich reason near neutron drip line. It is found that irrespective of whether any resonant state exists or not, the occupancy of weakly bound neutron single particle states having low orbital angular momentum, (l = 0 or 1), with a well spread wave function due to the absence or very small strength of centrifugal barrier, helps to cause the occurrence of nuclei with widely extended neutron density. Such nuclei are found to have characteristically very small two-neutron separation energy and large neutron rms radius akin to that observed in weakly bound systems.

  8. RMF+BCS description of some traditional neutron magic isotones

    International Nuclear Information System (INIS)

    Saxena, G.; Singh, D.; Kaushik, M.

    2014-01-01

    The traditional neutron magic nuclei with N = 8, 20, 28, 50, 82 and 126, and those with neutron sub-magic number N = 40 are investigated within the relativistic mean-field plus BCS (RMF+BCS) approach. The results indicate appearance of new proton magic numbers as well as the disappearance of conventional magic numbers for nuclei with extreme isospin values. The calculated energies and densities do not indicate any tendency for the proton halo formations in any of the proton rich isotones due to Coulomb interaction and different single particle spectra. However, the potential barrier provided by the Coulomb interaction and that due to the centrifugal force may cause a long delay in the actual decay of proton rich nucleus resulting in the extended drip line. (authors)

  9. BCS-BEC crossover in a system of microcavity polaritons

    International Nuclear Information System (INIS)

    Keeling, Jonathan; Eastham, P.R.; Szymanska, M.H.; Littlewood, P.B.

    2005-01-01

    We investigate the thermodynamics and signatures of a polariton condensate over a range of densities, using a model of microcavity polaritons with internal structure. We determine a phase diagram for this system including fluctuation corrections to the mean-field theory. At low densities the condensation temperature T c behaves like that for point bosons. At higher densities, when T c approaches the Rabi splitting, T c deviates from the form for point bosons, and instead approaches the result of a BCS-like mean-field theory. This crossover occurs at densities much less than the Mott density. We show that current experiments are in a density range where the phase boundary is described by the BCS-like mean-field boundary. We investigate the influence of inhomogeneous broadening and detuning of excitons on the phase diagram

  10. Mathematical analysis of the multiband BCS gap equations in superconductivity

    Science.gov (United States)

    Yang, Yisong

    2005-01-01

    In this paper, we present a mathematical analysis for the phonon-dominated multiband isotropic and anisotropic BCS gap equations at any finite temperature T. We establish the existence of a critical temperature T so that, when TT, the only nonnegative gap solution is the zero solution, representing the normal phase. Furthermore, when T=T, we prove that the only gap solution is the zero solution and that the positive gap solution depend on the temperature TMarkowitz-Kadanoff model and we prove that the presence of anisotropic fluctuations enhances T as in the single-band case. A special consequence of these results is that the half-unity exponent isotope effect may rigorously be proved in the multiband BCS theory, isotropic or anisotropic.

  11. Utilization of multi-band OFDM modulation to increase traffic rate of phosphor-LED wireless VLC.

    Science.gov (United States)

    Yeh, Chien-Hung; Chen, Hsing-Yu; Chow, Chi-Wai; Liu, Yen-Liang

    2015-01-26

    To increase the traffic rate in phosphor-LED visible light communication (VLC), a multi-band orthogonal frequency division multiplexed (OFDM) modulation is first proposed and demonstrated. In the measurement, we do not utilize optical blue filter to increase modulation bandwidth of phosphor-LED in the VLC system. In this proposed scheme, different bands of OFDM signals are applied to different LED chips in a LED lamp, this can avoid the power fading and nonlinearity issue by applying the same OFDM signal to all the LED chips in a LED lamp. Here, the maximum increase percentages of traffic rates are 41.1%, 17.8% and 17.8% under received illuminations of 200, 500 and 1000 Lux, respectively, when the proposed three-band OFDM modulation is used in the VLC system. In addition, the analysis and verification by experiments are also performed.

  12. BCS @ 50: derivation of gap equations in different lattice geometries

    International Nuclear Information System (INIS)

    Saurabh Basu

    2007-07-01

    We rigorously derive BCS gap equations for a square, triangular and a honeycomb lattice using a two-dimensional t-J model. The gap equations in all the three lattice geometries look usual, with band indices appearing and a minor modification in the separable pair potential for the (two band) honeycomb lattice. In each case, the gap equation is solved (self consistently with the number equation) at low densities assuming singlet pairing. (author)

  13. Body condition score (BCS and metabolic status of shelter dogs

    Directory of Open Access Journals (Sweden)

    I. Andrighetto

    2010-04-01

    Full Text Available A group of 147 shelter dogs were weighted and assigned a body condition score (BCS using a 9 point scale system, in order to evaluate the prevalence of obesity in the kennel. More than 60% of the animals showed a BCS³6 (overweight and obese and this condition was mainly attributed to an excess of carbohydrates and fat in the diet. In 67/147 dogs, a blood sample was drawn and the effects of BCS, age and time spent in the shelter were evaluated on biochemical parameters. Obese dogs showed significantly higher levels of triglycerides (P<0.01, while increasing BCS determined only an increasing non significant trend on cholesterol values. Age influenced creatinine (P<0.05 and the oldest dogs scoring BCS³6 registered significant higher NEFA (P<0.05 and CK (P=0.01 levels. Time spent in the shelter did not affect any parameter. The dogs’ metabolic condition reflects the need of taking more care of the quality of feed administered in the shelters to avoid the negative health effects caused by chronic obesity.

  14. Prospects of Anderson's theorem for disordered cuprate superconductors

    Science.gov (United States)

    Ghosal, Amit; Chakraborty, Debmalya; Kaushal, Nitin

    2018-05-01

    We develop a simple pairing theory of superconductivity in strongly correlated d-wave superconductors for up to a moderate strength of disorder. Our description implements the key ideas of Anderson, originally proposed for disordered s-wave superconductors, but in addition takes care of the inherent strong electronic repulsion in these compounds, as well as the inhomogeneities. We first obtain the self-consistent one-particle states, that capture the effects of disorder exactly, and strong correlations using Gutzwiller approximation. These 'normal states' (at zero temperature) when coupled through BCS-type pairing attractions, produces results which are nearly identical to those from a more sophisticated Gutzwiller augmented Bogoliubov-de Gennes analysis.

  15. Inverse isotope effect in iron-based superconductor

    International Nuclear Information System (INIS)

    Shirage, Parasharam M.; Kihou, Kunihiro; Miyazawa, Kiichi; Lee, Chul-Ho; Kito, Hijiri; Yoshida, Yoshiyuki; Eisaki, Hiroshi; Tanaka, Yasumoto; Iyo, Akira

    2010-01-01

    We have found that (Ba, K)Fe 2 As 2 superconductor (a transition temperature, T c ∼ 38 K) shows an inverse Iron isotope effect (α Fe = -0.18 ± 0.03, where T c ∼ M -αFe and M is the iron isotope mass), i.e. the sample containing the larger iron mass depicts higher T c . Systematic studies using three types of Fe-isotopes ( 54 Fe, natural Fe and 57 Fe) reveal a clear inverse shift on T c by measurements of temperature dependent magnetization and resistivity. The inverse isotope effect that is the first case in high-T c superconductors strongly suggests that superconducting mechanism of the iron-based system is not explained by conventional BCS theory mediated by phonons.

  16. Agitation Rate and Time for Complete Dissolution in BCS Biowaivers Based on Investigation of a BCS Biowaiver for Dexketoprofen Tablets.

    Science.gov (United States)

    Garcia-Arieta, Alfredo; Gordon, John; Gwaza, Luther; Mangas-Sanjuan, V; Álvarez, Covadonga; Torrado, Juan J

    2015-09-08

    The objective of the present work is to investigate the validity of the existing requirements for BCS biowaivers of immediate release products containing a class I drug in relation to the agitation rate (50 or 75 rpm in the paddle apparatus) and the time limit for complete dissolution (30 min) in the current biowaivers in vitro dissolution tests. Further, the possibility of extensions will be examined since it has been proposed that the time limit for complete dissolution should be revised to 60 min, and also, if cone formation occurs with apparatus 2 at 50 rpm, then a higher agitation rate is acceptable to eliminate it. The development of four generic dexketoprofen immediate release tablets is described. Dexketoprofen is the eutomer of ketoprofen. According to the BCS, dexketoprofen is a class I drug. Three out of the four products failed to show bioequivalence for Cmax in the initial bioequivalence study conducted with the product despite similar but nonrapid dissolution profiles at 50 rpm in the paddle apparatus, or similar and very rapid dissolution profiles at 75 rpm. In conclusion, these data indicate that BCS biowaivers for class I drugs should be granted only when dissolution with the paddle apparatus is complete in 30 min at 50 rpm. The time limit for complete dissolution should not be extended to 60 min. Furthermore, the agitation rate should not be increased to 75 rpm, even in the case of a coning effect.

  17. Fine uniform filament superconductors

    Science.gov (United States)

    Riley, Jr., Gilbert N.; Li, Qi; Roberts, Peter R.; Antaya, Peter D.; Seuntjens, Jeffrey M.; Hancock, Steven; DeMoranville, Kenneth L.; Christopherson, Craig J.; Garrant, Jennifer H.; Craven, Christopher A.

    2002-01-01

    A multifilamentary superconductor composite having a high fill factor is formed from a plurality of stacked monofilament precursor elements, each of which includes a low density superconductor precursor monofilament. The precursor elements all have substantially the same dimensions and characteristics, and are stacked in a rectilinear configuration and consolidated to provide a multifilamentary precursor composite. The composite is thereafter thermomechanically processed to provide a superconductor composite in which each monofilament is less than about 50 microns thick.

  18. Energy gap and upper critical field of the new magnetic superconductor Mo3Sb7 found by the Andreev reflection method

    International Nuclear Information System (INIS)

    Dmitriev, V M; Rybaltchenko, L F; Ishchenko, L A; Khristenko, E V; Bukowski, Z; Troc, R

    2006-01-01

    We present the data of the point contact (PC) Andreev-reflection measurements on the new paramagnetic superconductor Mo 3 Sb 7 , which were used for finding the energy gap Δ and upper critical field H c2 for this compound. The maximum gap value, reduced to the zero temperature via the Bardeen-Cooper-Schrieffer (BCS) theory, turned out to be Δ (0) ≅ 0.32 meV, which is slightly smaller than that expected from the BCS theory, Δ BCS (0) ≅ 0.35 meV. The temperature dependence of the gap obeys the BCS theory approximately. The H c2 (0) value of about 16.5 kOe was obtained from fitting the experimental data to the conventional H(T) dependence, which is quadratic in temperature. This value is in close agreement with the result from magnetization measurements of 17.2 kOe

  19. The TRICLOBS Dynamic Multi-Band Image Data Set for the Development and Evaluation of Image Fusion Methods.

    Directory of Open Access Journals (Sweden)

    Alexander Toet

    Full Text Available The fusion and enhancement of multiband nighttime imagery for surveillance and navigation has been the subject of extensive research for over two decades. Despite the ongoing efforts in this area there is still only a small number of static multiband test images available for the development and evaluation of new image fusion and enhancement methods. Moreover, dynamic multiband imagery is also currently lacking. To fill this gap we present the TRICLOBS dynamic multi-band image data set containing sixteen registered visual (0.4-0.7μm, near-infrared (NIR, 0.7-1.0μm and long-wave infrared (LWIR, 8-14μm motion sequences. They represent different military and civilian surveillance scenarios registered in three different scenes. Scenes include (military and civilian people that are stationary, walking or running, or carrying various objects. Vehicles, foliage, and buildings or other man-made structures are also included in the scenes. This data set is primarily intended for the development and evaluation of image fusion, enhancement and color mapping algorithms for short-range surveillance applications. The imagery was collected during several field trials with our newly developed TRICLOBS (TRI-band Color Low-light OBServation all-day all-weather surveillance system. This system registers a scene in the Visual, NIR and LWIR part of the electromagnetic spectrum using three optically aligned sensors (two digital image intensifiers and an uncooled long-wave infrared microbolometer. The three sensor signals are mapped to three individual RGB color channels, digitized, and stored as uncompressed RGB (false color frames. The TRICLOBS data set enables the development and evaluation of (both static and dynamic image fusion, enhancement and color mapping algorithms. To allow the development of realistic color remapping procedures, the data set also contains color photographs of each of the three scenes. The color statistics derived from these photographs

  20. BCS-BEC crossover in spatially modulated fermionic condensates

    International Nuclear Information System (INIS)

    Sedrakian, Armen

    2011-01-01

    Several novel multi-component fermionic condensates show universal behavior under imbalance in the number of fermionic species. Here I discuss their phase structure, thermodynamics, and the transition from the weak (BCS) to strong (BEC) coupling regime. The inhomogeneous superconducting phases are illustrated on the example of the Fulde-Ferrell phase which appears in the weak coupling regime, at low temperatures and large asymmetries. The inhomogeneous phases persist through the crossover up to (and possibly beyond) the transition to the strong coupling regime.

  1. BCS-BEC crossover in spatially modulated fermionic condensates

    Energy Technology Data Exchange (ETDEWEB)

    Sedrakian, Armen, E-mail: sedrakian@th.physik.uni-frankfurt.de [Institute for Theoretical Physics, J. W. Goethe-University, Max-von-Laue-Str. 1, 60438 Frankfurt am Main (Germany)

    2011-09-16

    Several novel multi-component fermionic condensates show universal behavior under imbalance in the number of fermionic species. Here I discuss their phase structure, thermodynamics, and the transition from the weak (BCS) to strong (BEC) coupling regime. The inhomogeneous superconducting phases are illustrated on the example of the Fulde-Ferrell phase which appears in the weak coupling regime, at low temperatures and large asymmetries. The inhomogeneous phases persist through the crossover up to (and possibly beyond) the transition to the strong coupling regime.

  2. Cosmological BCS mechanism and the big bang singularity

    Science.gov (United States)

    Alexander, Stephon; Biswas, Tirthabir

    2009-07-01

    We provide a novel mechanism that resolves the big bang singularity present in Friedman-Lemaitre-Robertson-Walker space-times without the need for ghost fields. Building on the fact that a four-fermion interaction arises in general relativity when fermions are covariantly coupled, we show that at early times the decrease in scale factor enhances the correlation between pairs of fermions. This enhancement leads to a BCS-like condensation of the fermions and opens a gap dynamically driving the Hubble parameter H to zero and results in a nonsingular bounce, at least in some special cases.

  3. Superconductors with excess quasiparticles

    International Nuclear Information System (INIS)

    Elesin, V.F.; Kopaev, Y.V.

    1981-01-01

    This review presents a systematic kinetic theory of nonequilibrium phenomena in superconductors with excess quasiparticles created by electromagnetic or tunnel injection. The energy distributions of excess quasiparticles and of nonequilibrium phonons, dependence of the order parameter on the power and frequency (or intensity) of the electromagnetic field, magnetic properties of nonequilibrium superconductors, I-V curves of superconductor-insulator-superconductor junctions, and other properties are described in detail. The stability of superconducting states far from thermodynamic equilibrium is investigated and it is shown that characteristic instabilities leading to the formation of nonuniform states of a new type or phase transitions of the first kind are inherent to superconductors with excess quasiparticles. The results are compared with experimental data

  4. The non-equilibrium response of a superconductor to pair-breaking radiation measured over a broad frequency band

    Energy Technology Data Exchange (ETDEWEB)

    Visser, P. J. de, E-mail: p.j.devisser@tudelft.nl [Kavli Institute of NanoScience, Faculty of Applied Sciences, Delft University of Technology, Lorentzweg 1, 2628 CJ Delft (Netherlands); Yates, S. J. C. [SRON Netherlands Institute for Space Research, Landleven 12, 9747AD Groningen (Netherlands); Guruswamy, T.; Goldie, D. J.; Withington, S. [Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge CB3 0HE (United Kingdom); Neto, A.; Llombart, N. [Faculty of Electrical Engineering, Mathematics and Computer Science, Terahertz Sensing Group, Delft University of Technology, Mekelweg 4, 2628 CD Delft (Netherlands); Baryshev, A. M. [SRON Netherlands Institute for Space Research, Landleven 12, 9747AD Groningen (Netherlands); Kapteyn Astronomical Institute, University of Groningen, Landleven 12, 9747 AD Groningen (Netherlands); Klapwijk, T. M. [Kavli Institute of NanoScience, Faculty of Applied Sciences, Delft University of Technology, Lorentzweg 1, 2628 CJ Delft (Netherlands); Physics Department, Moscow State Pedagogical University, Moscow 119991 (Russian Federation); Baselmans, J. J. A. [SRON Netherlands Institute for Space Research, Sorbonnelaan 2, 3584 CA Utrecht (Netherlands); Faculty of Electrical Engineering, Mathematics and Computer Science, Terahertz Sensing Group, Delft University of Technology, Mekelweg 4, 2628 CD Delft (Netherlands)

    2015-06-22

    We have measured the absorption of terahertz radiation in a BCS superconductor over a broad range of frequencies from 200 GHz to 1.1 THz, using a broadband antenna-lens system and a tantalum microwave resonator. From low frequencies, the response of the resonator rises rapidly to a maximum at the gap edge of the superconductor. From there on, the response drops to half the maximum response at twice the pair-breaking energy. At higher frequencies, the response rises again due to trapping of pair-breaking phonons in the superconductor. In practice, this is a measurement of the frequency dependence of the quasiparticle creation efficiency due to pair-breaking in a superconductor. The efficiency, calculated from the different non-equilibrium quasiparticle distribution functions at each frequency, is in agreement with the measurements.

  5. The non-equilibrium response of a superconductor to pair-breaking radiation measured over a broad frequency band

    International Nuclear Information System (INIS)

    Visser, P. J. de; Yates, S. J. C.; Guruswamy, T.; Goldie, D. J.; Withington, S.; Neto, A.; Llombart, N.; Baryshev, A. M.; Klapwijk, T. M.; Baselmans, J. J. A.

    2015-01-01

    We have measured the absorption of terahertz radiation in a BCS superconductor over a broad range of frequencies from 200 GHz to 1.1 THz, using a broadband antenna-lens system and a tantalum microwave resonator. From low frequencies, the response of the resonator rises rapidly to a maximum at the gap edge of the superconductor. From there on, the response drops to half the maximum response at twice the pair-breaking energy. At higher frequencies, the response rises again due to trapping of pair-breaking phonons in the superconductor. In practice, this is a measurement of the frequency dependence of the quasiparticle creation efficiency due to pair-breaking in a superconductor. The efficiency, calculated from the different non-equilibrium quasiparticle distribution functions at each frequency, is in agreement with the measurements

  6. Multi-band photometry of trans-Neptunian objects in the Subaru Hyper Suprime-Cam survey

    Science.gov (United States)

    Terai, Tsuyoshi; Yoshida, Fumi; Ohtsuki, Keiji; Lykawka, Patryk Sofia; Takato, Naruhisa; Higuchi, Arika; Ito, Takashi; Komiyama, Yutaka; Miyazaki, Satoshi; Wang, Shiang-Yu

    2018-01-01

    We present visible multi-band photometry of trans-Neptunian objects (TNOs) observed by the Subaru Telescope in the framework of the Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP) from 2014 March to 2016 September. We measured the five broad-band (g, r, i, z, and Y) colors over the wavelength range from 0.4 μm to 1.0 μm for 30 known TNOs using the HSC-SSP survey data covering ˜500 deg2 of sky within ±30° of ecliptic latitude. This dataset allows us to investigate the correlations between the dynamical classes and visible reflectance spectra of TNOs. Our results show that the hot classical and scattered populations with orbital inclination (I) of I ≳ 6° share similar color distributions, while the cold classical population with I ≲ 6° has a different color distribution from the others. The low-I population has reflectance increasing toward longer wavelengths up to ˜0.8 μm, with a steeper slope than the high-I population at ≲ 0.6 μm. We also find a significant anti-correlation between g - r/r - i colors and inclination in the high-I population, as well as a possible bimodality in the g - i color vs. eccentricity plot.

  7. Observations of Multi-band Structures in Double Star TC-1 PEACE Electron and HIA Ion Data

    Science.gov (United States)

    Mohan Narasimhan, K.; Fazakerley, A. N.; Grimald, S.; Dandouras, I. S.; Mihaljcic, B.; Kistler, L. M.; Owen, C. J.

    2015-12-01

    Several authors have reported inner magnetosphere observations of proton distributions confined to narrow energy bands in the range 1 - 25 keV (Smith and Hoffman (1974), etc). These structures have been described as "nose structures", with reference to their appearance in energy-time spectrograms and are also known as "bands" if they occur for extended periods of time. Multi-nose structures have been observed if 2 or more noses appear at the same time (Vallat et al., 2007). Gaps between "noses" (or "bands") have been explained in terms of the competing corotation, convection and magnetic gradient drifts. Charge exchange losses in slow drift paths for steady state scenarios and the role of substorm injections have also been considered (Li et al., 2000; Ebihara et al., 2004). We analyse observations of electron and ion multi-band structures frequently seen in Double-Star TC1 PEACE and HIA data. We present results from statistical surveys conducted using data from the duration of the mission. Furthermore, using a combination of both statistics and simulations, we test previous theories as to possible formation mechanisms and explore other possible explanations.

  8. Multi-band tight-binding calculation of electronic transport in Fe/trans-polyacetylene/Fe tunnel junctions

    International Nuclear Information System (INIS)

    Abedi Ravan, B

    2012-01-01

    In this paper, the electronic transport characteristics of Fe/trans-polyacetylene/Fe magnetic tunnel junctions (MTJs) are investigated using multi-band tight-binding calculations within the framework of nonequilibrium Green function theory. A CH 2 radical is added to different positions on the polymer chain and its effects on the tunnelling magnetoresistance of the MTJ are studied. The ferromagnetic electrodes are assumed to be single-band and their tight-binding parameters are chosen in such a way as to simulate the ab initio density functional calculations of the band structure of bcc-Fe along its [001] crystallographic direction. In building the Hamiltonian of the trans-polyacetylene (t-PA) chain, we have assumed an s orbital on the H atoms and one s and three p(p x ,p y ,p z ) orbitals on the C atoms, and the dimerization effects are taken into account. It is found that moving the radical out of the centre of the polymer chain enhances the tunnelling magnetoresistance of the MTJ.

  9. Fabrication of high temperature superconductors

    Science.gov (United States)

    Balachandran, Uthamalingam; Dorris, Stephen E.; Ma, Beihai; Li, Meiya

    2003-06-17

    A method of forming a biaxially aligned superconductor on a non-biaxially aligned substrate substantially chemically inert to the biaxially aligned superconductor comprising is disclosed. A non-biaxially aligned substrate chemically inert to the superconductor is provided and a biaxially aligned superconductor material is deposited directly on the non-biaxially aligned substrate. A method forming a plume of superconductor material and contacting the plume and the non-biaxially aligned substrate at an angle greater than 0.degree. and less than 90.degree. to deposit a biaxially aligned superconductor on the non-biaxially aligned substrate is also disclosed. Various superconductors and substrates are illustrated.

  10. Particle–hole duality, integrability, and Russian doll BCS model

    Energy Technology Data Exchange (ETDEWEB)

    Bork, L.V. [Center for Fundamental and Applied Research, N. L. Dukhov All-Russia Research Institute of Automatics, 127055 Moscow (Russian Federation); Institute for Theoretical and Experimental Physics, 117218 Moscow (Russian Federation); Pogosov, W.V., E-mail: walter.pogosov@gmail.com [Center for Fundamental and Applied Research, N. L. Dukhov All-Russia Research Institute of Automatics, 127055 Moscow (Russian Federation); Institute for Theoretical and Applied Electrodynamics, Russian Academy of Sciences, 125412 Moscow (Russian Federation); Moscow Institute of Physics and Technology, Dolgoprudny, Moscow Region 141700 (Russian Federation)

    2015-08-15

    We address a generalized Richardson model (Russian doll BCS model), which is characterized by the breaking of time-reversal symmetry. This model is known to be exactly solvable and integrable. We point out that the Russian doll BCS model, on the level of Hamiltonian, is also particle–hole symmetric. This implies that the same state can be expressed both in the particle and hole representations with two different sets of Bethe roots. We then derive exact relations between Bethe roots in the two representations, which can hardly be obtained staying on the level of Bethe equations. In a quasi-classical limit, similar identities for usual Richardson model, known from literature, are recovered from our results. We also show that these relations for Richardson roots take a remarkably simple form at half-filling and for a symmetric with respect to the middle of the interaction band distribution of one-body energy levels, since, in this special case, the rapidities in the particle and hole representations up to the translation satisfy the same system of equations.

  11. Dimensional BCS-BEC crossover in ultracold Fermi gases

    Energy Technology Data Exchange (ETDEWEB)

    Boettcher, Igor

    2014-12-10

    We investigate thermodynamics and phase structure of ultracold Fermi gases, which can be realized and measured in the laboratory with modern trapping techniques. We approach the subject from a both theoretical and experimental perspective. Central to the analysis is the systematic comparison of the BCS-BEC crossover of two-component fermions in both three and two dimensions. A dimensional reduction can be achieved in experiments by means of highly anisotropic traps. The Functional Renormalization Group (FRG) allows for a description of both cases in a unified theoretical framework. In three dimensions we discuss with the FRG the influence of high momentum particles onto the density, extend previous approaches to the Unitary Fermi Gas to reach quantitative precision, and study the breakdown of superfluidity due to an asymmetry in the population of the two fermion components. In this context we also investigate the stability of the Sarma phase. For the two-dimensional system scattering theory in reduced dimension plays an important role. We present both the theoretically as well as experimentally relevant aspects thereof. After a qualitative analysis of the phase diagram and the equation of state in two dimensions with the FRG we describe the experimental determination of the phase diagram of the two-dimensional BCS-BEC crossover in collaboration with the group of S. Jochim at PI Heidelberg.

  12. Quantum critical scaling of fidelity in BCS-like model

    International Nuclear Information System (INIS)

    Adamski, Mariusz; Jedrzejewski, Janusz; Krokhmalskii, Taras

    2013-01-01

    We study scaling of the ground-state fidelity in neighborhoods of quantum critical points in a model of interacting spinful fermions—a BCS-like model. Due to the exact diagonalizability of the model, in one and higher dimensions, scaling of the ground-state fidelity can be analyzed numerically with great accuracy, not only for small systems but also for macroscopic ones, together with the crossover region between them. Additionally, in the one-dimensional case we have been able to derive a number of analytical formulas for fidelity and show that they accurately fit our numerical results; these results are reported in the paper. Besides regular critical points and their neighborhoods, where well-known scaling laws are obeyed, there is the multicritical point and critical points in its proximity where anomalous scaling behavior is found. We also consider scaling of fidelity in neighborhoods of critical points where fidelity oscillates strongly as the system size or the chemical potential is varied. Our results for a one-dimensional version of a BCS-like model are compared with those obtained recently by Rams and Damski in similar studies of a quantum spin chain—an anisotropic XY model in a transverse magnetic field. (paper)

  13. Coherence factors beyond the BCS expressions—a derivation

    International Nuclear Information System (INIS)

    Gorohovsky, G; Bettelheim, E

    2014-01-01

    We present a derivation of a previously announced result for matrix elements between exact eigenstates of the pairing Hamiltonian. Our results, which generalize the well-known Bardeen–Cooper–Schrieffer (BCS) (Bardeen et al 1957 Phys. Rev. 108 1175; 1957 Phys. Rev. 106 162) expressions for what are known as ‘coherence factors’, are derived based on the Slavnov (1989 Theor. Math. Phys. 79 502) formula for overlaps between Bethe-ansatz states, thus making use of the known connection between the exact diagonalization of the BCS Hamiltonian, due to Richardson (1963 Phys. Lett. 3 277; 1964 Nucl. Phys. A 52 221), and the algebraic Bethe ansatz. The resulting formula has a compact form after a suitable parameterization of the energy plane. Although we apply our method here to the pairing Hamiltonian, it may be adjusted to study what is termed the ‘Sutherland limit’ (Sutherland 1995 Phys. Rev. Lett. 74 816) for exactly solvable models, namely where a macroscopic number of rapidities form a large string. (paper)

  14. Absence of coherent peaks in a Z2 fractionalized BCS superconducting state

    Science.gov (United States)

    Zhong, Yin; Lu, Han-Tao; Luo, Hong-Gang

    2015-01-01

    We explore a Z2 fractionalized Bardeen-Cooper-Schrieffer (BCS) superconducting state, which is a minimal extension of usual BCS framework. It is found that this state has similar thermal and transport properties, but its single-particle feature strongly deviates from the coherent quasiparticle behavior of the classic/conventional BCS superconducting state. The fingerprint of such Z2 BCS state is the absence of the BCS coherent peaks and instead a kink in the local density of state occurs, which in principle could be probed by scanning tunneling microscopy or point-contact spectroscopy experiments. The corresponding exactly soluble models that realize the desirable Z2 fractionalized BCS state are presented. In addition, we also study the extended t-U-J model by using Z2 slave-spin representation and find that the Z2 BCS state may exist when the paring structure is fully gapped or has nodes. The prototypical wave-function of such a Z2 BCS state is also proposed, which could be taken as trial wave-function in current numerical techniques. Furthermore, the pairing mechanism of Z2 BCS state is argued from both weak and strong coupling perspective. The present work may be helpful to further study the unconventional superconductivity and its relation to non-Fermi liquids.

  15. The biowaiver extension for BCS class III drugs: the effect of dissolution rate on the bioequivalence of BCS class III immediate-release drugs predicted by computer simulation.

    Science.gov (United States)

    Tsume, Yasuhiro; Amidon, Gordon L

    2010-08-02

    The Biopharmaceutical Classification System (BCS) guidance issued by the FDA allows waivers for in vivo bioavailability and bioequivalence studies for immediate-release (IR) solid oral dosage forms only for BCS class I drugs. However, a number of drugs within BCS class III have been proposed to be eligible for biowaivers. The World Health Organization (WHO) has shortened the requisite dissolution time of BCS class III drugs on their Essential Medicine List (EML) from 30 to 15 min for extended biowaivers; however, the impact of the shorter dissolution time on AUC(0-inf) and C(max) is unknown. The objectives of this investigation were to assess the ability of gastrointestinal simulation software to predict the oral absorption of the BCS class I drugs propranolol and metoprolol and the BCS class III drugs cimetidine, atenolol, and amoxicillin, and to perform in silico bioequivalence studies to assess the feasibility of extending biowaivers to BCS class III drugs. The drug absorption from the gastrointestinal tract was predicted using physicochemical and pharmacokinetic properties of test drugs provided by GastroPlus (version 6.0). Virtual trials with a 200 mL dose volume at different drug release rates (T(85%) = 15 to 180 min) were performed to predict the oral absorption (C(max) and AUC(0-inf)) of the above drugs. Both BCS class I drugs satisfied bioequivalence with regard to the release rates up to 120 min. The results with BCS class III drugs demonstrated bioequivalence using the prolonged release rate, T(85%) = 45 or 60 min, indicating that the dissolution standard for bioequivalence is dependent on the intestinal membrane permeability and permeability profile throughout the gastrointestinal tract. The results of GastroPlus simulations indicate that the dissolution rate of BCS class III drugs could be prolonged to the point where dissolution, rather than permeability, would control the overall absorption. For BCS class III drugs with intestinal absorption patterns

  16. Epitaxial growth of Fe-based superconductor thin films

    Energy Technology Data Exchange (ETDEWEB)

    Meyer, Sven; Haenisch, Jens; Holzapfel, Bernhard [Institut fuer Technische Physik, Karlsruher Institut fuer Technologie, Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen (Germany)

    2016-07-01

    The Fe-based superconductors (FBS), discovered in 2008, are not only interesting for possible applications due to their large upper critical fields and low anisotropies, but also for basic understanding of unconventional superconductivity. With their properties, they constitute a link between the classic low-T{sub c} superconductors (low anisotropies, low thermal fluctuations, s-wave type symmetry) and the oxocuprates (T{sub c} up to 55 K, large H{sub c2}, unconventional pairing). Their multi-band nature reminds of MgB{sub 2}. We prepare thin films of FBS in the so called 122 family, namely Co- and P-doped BaFe{sub 2}As{sub 2} to investigate application relevant properties, such as critical current density J{sub c}, by pulsed laser deposition using a frequency-tripled Nd:YAG laser (λ = 355 nm). Microstructure and chemical composition will be investigated by XRD, AFM and SEM, and electrical transport using a 14 T PPMS. The results are compared to literature data on films grown at different wavelengths.

  17. Large area bulk superconductors

    Science.gov (United States)

    Miller, Dean J.; Field, Michael B.

    2002-01-01

    A bulk superconductor having a thickness of not less than about 100 microns is carried by a polycrystalline textured substrate having misorientation angles at the surface thereof not greater than about 15.degree.; the bulk superconductor may have a thickness of not less than about 100 microns and a surface area of not less than about 50 cm.sup.2. The textured substrate may have a thickness not less than about 10 microns and misorientation angles at the surface thereof not greater than about 15.degree.. Also disclosed is a process of manufacturing the bulk superconductor and the polycrystalline biaxially textured substrate material.

  18. Friction in levitated superconductors

    International Nuclear Information System (INIS)

    Brandt, E.H.

    1988-01-01

    A type I superconductor levitated above a magnet of low symmetry has a unique equilibrium position about which it may oscillate freely. In contrast, a type II superconductor has a continuous range of stable equilibrium positions and orientations where it floats rigidly without swinging or orbiting as if it were stuck in sand. A strong internal friction conspicuously indicates the existence and unpinning of flux lines in oxide superconductors levitated above liquid nitrogen. It is shown how these effects follow from the hysteretic magnetization curves and how the energy is dissipated

  19. Development of superconductor bulk for superconductor bearing

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Chan Joong; Jun, Byung Hyuk; Park, Soon Dong (and others)

    2008-08-15

    Current carrying capacity is one of the most important issues in the consideration of superconductor bulk materials for engineering applications. There are numerous applications of Y-Ba-Cu-O (YBCO) bulk superconductors e.g. magnetic levitation train, flywheel energy storage system, levitation transportation, lunar telescope, centrifugal device, magnetic shielding materials, bulk magnets etc. Accordingly, to obtain YBCO materials in the form of large, single crystals without weak-link problem is necessary. A top seeded melt growth (TSMG) process was used to fabricate single crystal YBCO bulk superconductors. The seeded and infiltration growth (IG) technique was also very promising method for the synthesis of large, single-grain YBCO bulk superconductors with good superconducting properties. 5 wt.% Ag doped Y211 green compacts were sintered at 900 .deg. C {approx} 1200 .deg.C and then a single crystal YBCO was fabricated by an infiltration method. A refinement and uniform distribution of the Y211 particles in the Y123 matrix were achieved by sintering the Ag-doped samples. This enhancement of the critical current density was ascribable to a fine dispersion of the Y211 particles, a low porosity and the presence of Ag particles. In addition, we have designed and manufactured large YBCO single domain with levitation force of 10-13 kg/cm{sup 2} using TSMG processing technique.

  20. SPATIALLY RESOLVED STAR FORMATION HISTORY ALONG THE DISK OF M82 USING MULTI-BAND PHOTOMETRIC DATA

    International Nuclear Information System (INIS)

    Rodriguez-Merino, L. H.; Rosa-Gonzalez, D.; Mayya, Y. D.

    2011-01-01

    We present results on the star formation history and extinction in the disk of M82 over spatial scales of 10'' (∼180 pc). Multi-band photometric data covering the far-ultraviolet to the near-infrared bands were fitted to a grid of synthetic spectral energy distributions. We obtained distribution functions of age and extinction for each of the 117 apertures analyzed, taking into account observational errors through Monte Carlo simulations. These distribution functions were fitted with Gaussian functions to obtain the mean ages and extinctions together with their errors. The zones analyzed include the high surface brightness complexes defined by O'Connell and Mangano. We found that these complexes share the same star formation history and extinction as the field stellar populations in the disk. There is an indication that the stellar populations are marginally older at the outer disk (450 Myr at ∼3 kpc) as compared to the inner disk (100 Myr at 0.5 kpc). For the nuclear region (radius less than 500 pc), we obtained an age of less than 10 Myr. The results obtained in this work are consistent with the idea that the 0.5-3 kpc part of the disk of M82 formed around 90% of the stellar mass in a star-forming episode that started around 450 Myr ago and lasted for about 350 Myr. We found that field stars are the major contributors to the flux over the spatial scales analyzed in this study, with the stellar cluster contribution being 7% in the nucleus and 0.7% in the disk.

  1. A multi-band semi-analytical algorithm for estimating chlorophyll-a concentration in the Yellow River Estuary, China.

    Science.gov (United States)

    Chen, Jun; Quan, Wenting; Cui, Tingwei

    2015-01-01

    In this study, two sample semi-analytical algorithms and one new unified multi-band semi-analytical algorithm (UMSA) for estimating chlorophyll-a (Chla) concentration were constructed by specifying optimal wavelengths. The three sample semi-analytical algorithms, including the three-band semi-analytical algorithm (TSA), four-band semi-analytical algorithm (FSA), and UMSA algorithm, were calibrated and validated by the dataset collected in the Yellow River Estuary between September 1 and 10, 2009. By comparing of the accuracy of assessment of TSA, FSA, and UMSA algorithms, it was found that the UMSA algorithm had a superior performance in comparison with the two other algorithms, TSA and FSA. Using the UMSA algorithm in retrieving Chla concentration in the Yellow River Estuary decreased by 25.54% NRMSE (normalized root mean square error) when compared with the FSA algorithm, and 29.66% NRMSE in comparison with the TSA algorithm. These are very significant improvements upon previous methods. Additionally, the study revealed that the TSA and FSA algorithms are merely more specific forms of the UMSA algorithm. Owing to the special form of the UMSA algorithm, if the same bands were used for both the TSA and UMSA algorithms or FSA and UMSA algorithms, the UMSA algorithm would theoretically produce superior results in comparison with the TSA and FSA algorithms. Thus, good results may also be produced if the UMSA algorithm were to be applied for predicting Chla concentration for datasets of Gitelson et al. (2008) and Le et al. (2009).

  2. A robust Multi-Band Water Index (MBWI) for automated extraction of surface water from Landsat 8 OLI imagery

    Science.gov (United States)

    Wang, Xiaobiao; Xie, Shunping; Zhang, Xueliang; Chen, Cheng; Guo, Hao; Du, Jinkang; Duan, Zheng

    2018-06-01

    Surface water is vital resources for terrestrial life, while the rapid development of urbanization results in diverse changes in sizes, amounts, and quality of surface water. To accurately extract surface water from remote sensing imagery is very important for water environment conservations and water resource management. In this study, a new Multi-Band Water Index (MBWI) for Landsat 8 Operational Land Imager (OLI) images is proposed by maximizing the spectral difference between water and non-water surfaces using pure pixels. Based on the MBWI map, the K-means cluster method is applied to automatically extract surface water. The performance of MBWI is validated and compared with six widely used water indices in 29 sites of China. Results show that our proposed MBWI performs best with the highest accuracy in 26 out of the 29 test sites. Compared with other water indices, the MBWI results in lower mean water total errors by a range of 9.31%-25.99%, and higher mean overall accuracies and kappa coefficients by 0.87%-3.73% and 0.06-0.18, respectively. It is also demonstrated for MBWI in terms of robustly discriminating surface water from confused backgrounds that are usually sources of surface water extraction errors, e.g., mountainous shadows and dark built-up areas. In addition, the new index is validated to be able to mitigate the seasonal and daily influences resulting from the variations of the solar condition. MBWI holds the potential to be a useful surface water extraction technology for water resource studies and applications.

  3. Relativistic corrections to the Cooperon mass: BCS versus BEC picture

    Energy Technology Data Exchange (ETDEWEB)

    Lipavský, P., E-mail: lipavsky@karlov.mff.cuni.cz

    2017-02-15

    Highlights: • Tate's measurement of relativistic effects on the Cooper pair mass show the increase while a decrease was expected. • This disagreement raised a question whether it has fundamental significance or is due to the details of the particular physical system being studied. • The most fundamental were speculations about gravitomagnetic forces enhanced by the Higgs mechanism. • These were recently disproved experimentally. • This paper shows that the relativistic mass corrections might be sensitive to the pairing scenario: the predicted mass decrease corresponds to the Bose–Einstein condensation of preformed Cooper pairs, while the pairing in the Bardeen–Cooper–Schrieffer condensate leads to an increase of experimentally observed magnitude. - Abstract: Relativistic corrections to the Cooperon mass are discussed for preformed Cooper pairs that become superconductive via the Bose–Einstein condensation (BEC) and for Cooperons in the Bardeen–Copper–Schrieffer (BCS) condensate. The distinction explains experimental results of Tate et al. (1989).

  4. Evaluation of Hyperspectral Multi-Band Indices to Estimate Chlorophyll-A Concentration Using Field Spectral Measurements and Satellite Data in Dianshan Lake, China

    Directory of Open Access Journals (Sweden)

    Linna Li

    2013-04-01

    Full Text Available Chlorophyll-a (Chl-a concentration is considered as a key indicator of the eutrophic status of inland water bodies. Various algorithms have been developed for estimating Chl-a in order to improve the accuracy of predictive models. The objective of this study is to assess the potential of hyperspectral multi-band indices to estimate the Chl-a concentration in Dianshan Lake, which is the largest lake in Shanghai, an international metropolis of China. Based on field spectral measurements and in-situ Chl-a concentration collected on 7–8 September 2010, hyperspectral multi-band indices were calibrated to estimate the Chl-a concentration with optimal wavelengths selected by model tuning. A three-band index accounts for 87.36% (R2 = 0.8736 of the Chl-a variation. A four-band index, which adds a wavelength in the near infrared (NIR region, results in a higher R2 (0.8997 by removing the absorption and backscattering effects of suspended solids. To test the applicability of the proposed indices for routinely monitoring of Chl-a in inland lakes, simulated Hyperion and real HJ-1A satellite data were selected to estimate the Chl-a concentration. The results show that the explanatory powers of these satellite hyperspectral multi-band indices are relatively high with R2 = 0.8559, 0.8945, 0.7969, and 0.8241 for simulated Hyperion and real HJ-1A satellite data, respectively. All of the results provide strong evidence that hyperspectral multi-band indices are promising and applicable to estimate Chl-a in eutrophic inland lakes.

  5. Kohn anomalies in superconductors

    International Nuclear Information System (INIS)

    Flatte, M.E.

    1994-01-01

    The detailed behavior of phonon dispersion curves near momenta which span the electronic Fermi sea in a superconductor is presented. An anomaly, similar to the metallic Kohn anomaly, exists in a superconductor's dispersion curves when the frequency of the photon spanning the Fermi sea exceeds twice the superconducting energy gap. This anomaly occurs at approximately the same momentum but is stronger than the normal-state Kohn anomaly. It also survives at finite temperature, unlike the metallic anomaly. Determination of Fermi-surface diameters from the location of these anomalies, therefore, may be more successful in the superconducting phase than in the normal state. However, the superconductor's anomaly fades rapidly with increased phonon frequency and becomes unobservable when the phonon frequency greatly exceeds the gap. This constraint makes these anomalies useful only in high-temperature superconductors such as La 1.85 Sr 0.15 CuO 4

  6. Topological superconductors: a review.

    Science.gov (United States)

    Sato, Masatoshi; Ando, Yoichi

    2017-07-01

    This review elaborates pedagogically on the fundamental concept, basic theory, expected properties, and materials realizations of topological superconductors. The relation between topological superconductivity and Majorana fermions are explained, and the difference between dispersive Majorana fermions and a localized Majorana zero mode is emphasized. A variety of routes to topological superconductivity are explained with an emphasis on the roles of spin-orbit coupling. Present experimental situations and possible signatures of topological superconductivity are summarized with an emphasis on intrinsic topological superconductors.

  7. Room temperature superconductors

    International Nuclear Information System (INIS)

    Sleight, A.W.

    1995-01-01

    If the Holy Grail of room temperature superconductivity could be achieved, the impact on could be enormous. However, a useful room temperature superconductor for most applications must possess a T c somewhat above room temperature and must be capable of sustaining superconductivity in the presence of magnetic fields while carrying a significant current load. The authors will return to the subject of just what characteristics one might seek for a compound to be a room temperature superconductor. 30 refs., 3 figs., 1 tab

  8. Continuous lengths of oxide superconductors

    Science.gov (United States)

    Kroeger, Donald M.; List, III, Frederick A.

    2000-01-01

    A layered oxide superconductor prepared by depositing a superconductor precursor powder on a continuous length of a first substrate ribbon. A continuous length of a second substrate ribbon is overlaid on the first substrate ribbon. Sufficient pressure is applied to form a bound layered superconductor precursor powder between the first substrate ribbon and the second substrate ribbon. The layered superconductor precursor is then heat treated to establish the oxide superconducting phase. The layered oxide superconductor has a smooth interface between the substrate and the oxide superconductor.

  9. Solution Theory of Ginzburg-Landau Theory on BCS-BEC Crossover

    Directory of Open Access Journals (Sweden)

    Shuhong Chen

    2014-01-01

    Full Text Available We establish strong solution theory of time-dependent Ginzburg-Landau (TDGL systems on BCS-BEC crossover. By the properties of Besov, Sobolev spaces, and Fourier functions and the method of bootstrapping argument, we deduce that the global existence of strong solutions to time-dependent Ginzburg-Landau systems on BCS-BEC crossover in various spatial dimensions.

  10. A simplified generator coordinate treatment with analytical projected-BCS solutions for isovector pairing collective motions

    International Nuclear Information System (INIS)

    Kyotoku, M.; Chen, H.T.

    1979-01-01

    Analytical expressions for the projected-BCS energies and reaction transition rates among the isovector pairing collective states are obtained by the recognition of symmetry properties in a class of BCS wave functions. As a consequence, a simplified generator coordinate treatment is suggested [pt

  11. Prediction of solubility and permeability class membership: provisional BCS classification of the world's top oral drugs.

    Science.gov (United States)

    Dahan, Arik; Miller, Jonathan M; Amidon, Gordon L

    2009-12-01

    The Biopharmaceutics Classification System (BCS) categorizes drugs into one of four biopharmaceutical classes according to their water solubility and membrane permeability characteristics and broadly allows the prediction of the rate-limiting step in the intestinal absorption process following oral administration. Since its introduction in 1995, the BCS has generated remarkable impact on the global pharmaceutical sciences arena, in drug discovery, development, and regulation, and extensive validation/discussion/extension of the BCS is continuously published in the literature. The BCS has been effectively implanted by drug regulatory agencies around the world in setting bioavailability/bioequivalence standards for immediate-release (IR) oral drug product approval. In this review, we describe the BCS scientific framework and impact on regulatory practice of oral drug products and review the provisional BCS classification of the top drugs on the global market. The Biopharmaceutical Drug Disposition Classification System and its association with the BCS are discussed as well. One notable finding of the provisional BCS classification is that the clinical performance of the majority of approved IR oral drug products essential for human health can be assured with an in vitro dissolution test, rather than empirical in vivo human studies.

  12. Experimental consequences of predicted charge rigidity of superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Hirsch, J.E., E-mail: jhirsch@ucsd.edu [Department of Physics, University of California, San Diego, La Jolla, CA 92093-0319 (United States)

    2012-08-15

    The theory of hole superconductivity predicts that in superconductors the charged superfluid is about a million times more rigid than the normal electron fluid. We point out that this physics should give rise to large changes in the bulk and surface plasmon dispersion relations of metals entering the superconducting state, that have not yet been experimentally detected and would be in stark contradiction with the expected behavior within conventional BCS-London theory. We also propose that this explains the puzzling experimental observations of Avramenko et al. on electron sound propagation in superconductors and the puzzling experiments of de Heer et al. detecting large electric dipole moments in small metal clusters, as well as the Tao effect on aggregation of superconducting microparticles in an electric field. Associated with the enhanced charge rigidity is a large increase in the electric screening length of superconductors at low temperatures that has not yet been experimentally detected. The physical origin of the enhanced charge rigidity and its relation to other aspects of the theory of hole superconductivity is discussed.

  13. High temperature superconductor accelerator magnets

    NARCIS (Netherlands)

    van Nugteren, J.

    2016-01-01

    For future particle accelerators bending dipoles are considered with magnetic fields exceeding 20T. This can only be achieved using high temperature superconductors (HTS). These exhibit different properties from classical low temperature superconductors and still require significant research and

  14. Ivar Giaever, Tunneling, and Superconductors

    Science.gov (United States)

    dropdown arrow Site Map A-Z Index Menu Synopsis Ivar Giaever, Tunneling, and Superconductors Resources with in Superconductors Measured by Electron Tunneling; Physical Review Letters, Vol. 5 Issue 4: 147 - 148 ; August 15, 1960 Electron Tunneling Between Two Superconductors; Physical Review Letters, Vol. 5 Issue 10

  15. Granular Superconductors and Gravity

    Science.gov (United States)

    Noever, David; Koczor, Ron

    1999-01-01

    As a Bose condensate, superconductors provide novel conditions for revisiting previously proposed couplings between electromagnetism and gravity. Strong variations in Cooper pair density, large conductivity and low magnetic permeability define superconductive and degenerate condensates without the traditional density limits imposed by the Fermi energy (approx. 10(exp -6) g cu cm). Recent experiments have reported anomalous weight loss for a test mass suspended above a rotating Type II, YBCO superconductor, with a relatively high percentage change (0.05-2.1%) independent of the test mass' chemical composition and diamagnetic properties. A variation of 5 parts per 104 was reported above a stationary (non-rotating) superconductor. In experiments using a sensitive gravimeter, bulk YBCO superconductors were stably levitated in a DC magnetic field and exposed without levitation to low-field strength AC magnetic fields. Changes in observed gravity signals were measured to be less than 2 parts in 108 of the normal gravitational acceleration. Given the high sensitivity of the test, future work will examine variants on the basic magnetic behavior of granular superconductors, with particular focus on quantifying their proposed importance to gravity.

  16. Josephson effect in high-Tc superconductors and in structures using them

    International Nuclear Information System (INIS)

    Kupriyanov, M.Yu.; Likharev, K.K.

    1990-01-01

    A review of the investigations of the Josephson effect in HTS materials and HTS Josephson structures is represented. The influence of the synthesis conditions and a surface etching on the surface properties of the HTS/Ag(Au) are briefly discussed. On the basis of these results the experimental data obtained in various types of the Josephson junctions (point contacts, tunnel junctions, weak links, break and bulk junctions and crystal type break junctions) are considered. These data are compared with theoretical results obtained from different BCS models of the Josephson junctions. It is concluded that now it is impossible to make either the conclusion on the applicability of the BCS theory for HTS superconductors or the unambiguous identification of the principal physical structure of the junctions. The directions of the future experimental investigations of the Josephson effect in HTS tunnel junctions and weak links are discussed

  17. Photothermal measurements of superconductors

    International Nuclear Information System (INIS)

    Kino, G.S.; Wu, X.D.; Kapitulnik, A.; Fishman, I.

    1993-01-01

    The authors have developed a new photothermal technique to investigate electronic phase transitions of high temperature superconductors. The phase shift of the thermal wave yields the anisotropic thermal diffusivity coefficient of the sample. The amplitude of the photothermal signal is sensitive to electronic phase transitions of the second kind. The technique is completely noncontacting and nondestructive, and is well suited to measure small and fragile single-crystal high-T c superconductors. The measurements give good agreement with fluctuation theory near the transition temperature. They have studied diffusion in, and superconducting fluctuations of, single crystals of YBa 2 Cu 3 O 7-δ and Bi 2 Sr 2 CaCu 2 O 8 . Both systems show fluctuation effects beyond Gaussian fluctuations. While YBa 2 Cu 3 O 7-δ behaves as a three-dimensional anisotropic superconductor, results on Bi 2 Sr 2 CaCu 2 O 8 indicate strong two-dimensional effects

  18. Macroscopic theory of superconductors

    International Nuclear Information System (INIS)

    Carr, W.J. Jr.

    1981-01-01

    A macroscopic theory for bulk superconductors is developed in the framework of the theory for other magnetic materials, where ''magnetization'' current is separated from ''free'' current on the basis of scale. This contrasts with the usual separation into equilibrium and nonequilibrium currents. In the present approach magnetization, on a large macroscopic scale, results from the vortex current, while the Meissner current and other surface currents are surface contributions to the Maxwell j. The results are important for the development of thermodynamics in type-II superconductors. The advantage of the description developed here is that magnetization becomes a local concept and its associated magnetic field can be given physical meaning

  19. Investigate the effect of anisotropic order parameter on the specific heat of anisotropic two-band superconductors

    International Nuclear Information System (INIS)

    Udomsamuthirun, P.; Peamsuwan, R.; Kumvongsa, C.

    2009-01-01

    The effect of anisotropic order parameter on the specific heat of anisotropic two-band superconductors in BCS weak-coupling limit is investigated. An analytical specific heat jump and the numerical specific heat are shown by using anisotropic order parameters, and the electron-phonon interaction and non-electron-phonon interaction. The two models of anisotropic order parameters are used for numerical calculation that we find little effect on the numerical results. The specific heat jump of MgB 2 , Lu 2 Fe 3 Si 5 and Nb 3 Sn superconductors can fit well with both of them. By comparing the experimental data with overall range of temperature, the best fit is Nb 3 Sn, MgB 2 , and Lu 2 Fe 3 Si 5 superconductors.

  20. Polynomial Similarity Transformation Theory: A smooth interpolation between coupled cluster doubles and projected BCS applied to the reduced BCS Hamiltonian

    Energy Technology Data Exchange (ETDEWEB)

    Degroote, M. [Rice Univ., Houston, TX (United States); Henderson, T. M. [Rice Univ., Houston, TX (United States); Zhao, J. [Rice Univ., Houston, TX (United States); Dukelsky, J. [Consejo Superior de Investigaciones Cientificas (CSIC), Madrid (Spain). Inst. de Estructura de la Materia; Scuseria, G. E. [Rice Univ., Houston, TX (United States)

    2018-01-03

    We present a similarity transformation theory based on a polynomial form of a particle-hole pair excitation operator. In the weakly correlated limit, this polynomial becomes an exponential, leading to coupled cluster doubles. In the opposite strongly correlated limit, the polynomial becomes an extended Bessel expansion and yields the projected BCS wavefunction. In between, we interpolate using a single parameter. The e ective Hamiltonian is non-hermitian and this Polynomial Similarity Transformation Theory follows the philosophy of traditional coupled cluster, left projecting the transformed Hamiltonian onto subspaces of the Hilbert space in which the wave function variance is forced to be zero. Similarly, the interpolation parameter is obtained through minimizing the next residual in the projective hierarchy. We rationalize and demonstrate how and why coupled cluster doubles is ill suited to the strongly correlated limit whereas the Bessel expansion remains well behaved. The model provides accurate wave functions with energy errors that in its best variant are smaller than 1% across all interaction stengths. The numerical cost is polynomial in system size and the theory can be straightforwardly applied to any realistic Hamiltonian.

  1. An Application of Multi-band Forced Photometry to One Square Degree of SERVS: Accurate Photometric Redshifts and Implications for Future Science

    Energy Technology Data Exchange (ETDEWEB)

    Nyland, Kristina; Lacy, Mark [National Radio Astronomy Observatory, Charlottesville, VA 22903 (United States); Sajina, Anna [Department of Physics and Astronomy, Tufts University, Medford, MA 02155 (United States); Pforr, Janine [ESA/ESTEC SCI-S, Keplerlaan 1, 2201 AZ, Noordwijk (Netherlands); Farrah, Duncan [Department of Physics, Virginia Tech, Blacksburg, VA 24061 (United States); Wilson, Gillian [Department of Physics and Astronomy, University of California-Riverside, 900 University Avenue, Riverside, CA, 92521 (United States); Surace, Jason [Spitzer Science Center, California Institute of Technology, M/S 314-6, Pasadena, CA 91125 (United States); Häußler, Boris [European Southern Observatory, Alonso de Cordova 3107, Vitacura, Casilla 19001, Santiago (Chile); Vaccari, Mattia [Department of Physics and Astronomy, University of the Western Cape, Robert Sobukwe Road, 7535 Bellville, Cape Town (South Africa); Jarvis, Matt, E-mail: knyland@nrao.edu [Department of Physics, Oxford Astrophysics, University of Oxford, Keble Road, Oxford OX1 3RH (United Kingdom)

    2017-05-01

    We apply The Tractor image modeling code to improve upon existing multi-band photometry for the Spitzer Extragalactic Representative Volume Survey (SERVS). SERVS consists of post-cryogenic Spitzer observations at 3.6 and 4.5 μ m over five well-studied deep fields spanning 18 deg{sup 2}. In concert with data from ground-based near-infrared (NIR) and optical surveys, SERVS aims to provide a census of the properties of massive galaxies out to z  ≈ 5. To accomplish this, we are using The Tractor to perform “forced photometry.” This technique employs prior measurements of source positions and surface brightness profiles from a high-resolution fiducial band from the VISTA Deep Extragalactic Observations survey to model and fit the fluxes at lower-resolution bands. We discuss our implementation of The Tractor over a square-degree test region within the XMM Large Scale Structure field with deep imaging in 12 NIR/optical bands. Our new multi-band source catalogs offer a number of advantages over traditional position-matched catalogs, including (1) consistent source cross-identification between bands, (2) de-blending of sources that are clearly resolved in the fiducial band but blended in the lower resolution SERVS data, (3) a higher source detection fraction in each band, (4) a larger number of candidate galaxies in the redshift range 5 <  z  < 6, and (5) a statistically significant improvement in the photometric redshift accuracy as evidenced by the significant decrease in the fraction of outliers compared to spectroscopic redshifts. Thus, forced photometry using The Tractor offers a means of improving the accuracy of multi-band extragalactic surveys designed for galaxy evolution studies. We will extend our application of this technique to the full SERVS footprint in the future.

  2. Proximity effect in normal-superconductor hybrids for quasiparticle traps

    Energy Technology Data Exchange (ETDEWEB)

    Hosseinkhani, Amin [Peter Grunberg Institute (PGI-2), Forschungszentrum Julich, D-52425 Julich (Germany); JARA-Institute for Quantum Information, RWTH Aachen University, D-52056 Aachen (Germany)

    2016-07-01

    Coherent transport of charges in the form of Cooper pairs is the main feature of Josephson junctions which plays a central role in superconducting qubits. However, the presence of quasiparticles in superconducting devices may lead to incoherent charge transfer and limit the coherence time of superconducting qubits. A way around this so-called ''quasiparticle poisoning'' might be using a normal-metal island to trap quasiparticles; this has motivated us to revisit the proximity effect in normal-superconductor hybrids. Using the semiclassical Usadel equations, we study the density of states (DoS) both within and away from the trap. We find that in the superconducting layer the DoS quickly approaches the BCS form; this indicates that normal-metal traps should be effective at localizing quasiparticles.

  3. Atomic site tunneling spectroscopy on high-Tc superconductors

    International Nuclear Information System (INIS)

    Hasegawa, T.; Nantoh, M.; Takagi, A.; Yamaguchi, W.; Ogino, M.; Kawasaki, M.

    1994-01-01

    Superconducting gap structures of Bi 2 Sr 2 CaCu 2 O y (BSCCO) and YBa 2 Cu 3 O y (YBCO) have been probed by scanning tunneling microscopy (STM) at cryogenic temperatures. The tunneling conductance curves observed on bulk single crystals of BSCCO and epitaxial thin films of YBCO revealed clear obershooting peaks and flat bottom regions around V=0 with quite low zero-bias conductances of ∝1%. Since the electron tunneling process in STM is essentially incoherent, the present observation is favored by the s-wave pairing mechanism. However, the conductance curves were found to be substantially smeared in comparison with the conventional spectra predicted in the BCS (isotropic s-wave) superconductors, suggesting gap anisotropy. (orig.)

  4. Role of the orbital degree of freedom in iron-based superconductors

    Science.gov (United States)

    Yi, Ming; Zhang, Yan; Shen, Zhi-Xun; Lu, Donghui

    2017-10-01

    Almost a decade has passed since the serendipitous discovery of the iron-based high temperature superconductors (FeSCs) in 2008. The fact that, as in the copper oxide high temperature superconductors, long-range antiferromagnetism in the FeSCs arises in proximity to superconductivity immediately raised the question of the degree of similarity between the two. Despite the great resemblance in their phase diagrams, there exist important differences between the FeSCs and the cuprates that need to be considered in order to paint a full picture of these two families of high temperature superconductors. One of the key differences is the multi-orbital multi-band nature of the FeSCs, which contrasts with the effective single-band nature of the cuprates. Systematic studies of orbital related phenomena in FeSCs have been largely lacking. In this review, we summarize angle-resolved photoemission spectroscopy (ARPES) measurements across various FeSC families that have been reported in literature, focusing on the systematic trends of orbital dependent electron correlations and the role of different Fe 3d orbitals in driving the nematic transition, the spin-density-wave transition, and superconductivity.

  5. Muon spin rotation studies of electronic excitations and magnetism in the vortex cores of superconductors

    International Nuclear Information System (INIS)

    Sonier, J E

    2007-01-01

    The focus of this paper is on recent progress in muon spin rotation (μSR) studies of the vortex cores in type-II superconductors. By comparison of μSR measurements of the vortex core size in a variety of materials with results from techniques that directly probe electronic states, the effect of delocalized quasiparticles on the spatial variation of field in a lattice of interacting vortices has been determined for both single-band and multi-band superconductors. These studies demonstrate the remarkable accuracy of what some still consider an exotic technique. In recent years μSR has also been used to search for magnetism in and around the vortex cores of high-temperature superconductors. As a local probe μSR is specially suited for detecting static or quasistatic magnetism having short-range or random spatial correlations. As discussed in this review, μSR experiments support a generic phase diagram of competing superconducting and magnetic order parameters, characterized by a quantum phase transition to a state where the competing order is spatially nonuniform

  6. Thermal behaviour of the ESR Relaxation time in slightly dirty superconductors

    International Nuclear Information System (INIS)

    Schwachheim, G.; Machado, S.F.; Tsallis, C.

    1978-07-01

    The thermal behaviour of the ESR relaxation rate in slightly dirty superconductors is discussed for both exchange and spin-orbit interactions between the conduction electrons and the impurities. The sensibility to the electronic density of states is exhibited by using, in a modified BCS framework, an heuristic analytic form which avoids two of three defects of a previous similar treatment. The sudden increase (decrease) of the relaxation rate immediately below the critical temperature for the exchange (spin-orbit) case is confirmed. Reasonable agreement with experimental data in LaRu 2 ; Gd is obtained [pt

  7. Mathematical aspects of the BCS theory of superconductivity and related theories

    International Nuclear Information System (INIS)

    Braeunlich, Gerhard Albert

    2014-01-01

    The present work starts with a introduction to the BCS theory, describing superconductivity and superfluidity. The main part consist of a collection of three publications and a paper included in a conference proceedings. The introduction (Chapter 1) includes a brief historical review of the research in the field of superconductivity and superfluidity. It ends with a short summary of the technical applications of superconductivity. In Chapter 2, a derivation of the BCS functional from quantum statistics is presented. Chapter 3 explains the results of the publications mentioned above. In a first work, the validity of the negligence of the direct and exchange energy in the derivation of the BCS functional is examined. Another work addresses the connection between the BCS theory and the Gross-Pitaevskii equation.

  8. Classical spins in superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Shiba, H [Tokyo Univ.; Maki, K

    1968-08-01

    It is shown that there exists a localized excited state in the energy gap in a superconductor with a classical spin. At finite concentration localized excited states around classical spins form an impurity band. The process of growth of the impurity band and its effects on observable quantities are investigated.

  9. Superconductors and medical imaging

    International Nuclear Information System (INIS)

    Aubert, Guy

    2011-01-01

    After difficult beginnings in the 1970's, magnetic resonance imaging (MRI) has evolved to become nowadays the jewel in the crown of medical technology. Superconductors have been a key factor for the extraordinary expansion of MRI which in turn represents about 75 % of their total market. After recalling some basic principles, this article traces their common history and refers to future developments. (author)

  10. Irradiation damage in superconductors

    International Nuclear Information System (INIS)

    Quere, Y.

    1989-01-01

    Most superconductors are quite sensitive to irradiation defects. Critical temperatures may be depressed, critical currents may be increased, by irradiation, but other behaviours may be encountered. In compounds, the sublattice in which defects are created is of significant importance. 24 refs

  11. Banks-Casher-type relation for the BCS gap at high density

    OpenAIRE

    Kanazawa, Takuya; Wettig, Tilo; Yamamoto, Naoki

    2012-01-01

    We derive a new Banks-Casher-type relation which relates the density of complex Dirac eigenvalues at the origin to the BCS gap of quarks at high density. Our relation is applicable to QCD and QCD-like theories without a sign problem, such as two-color QCD and adjoint QCD with baryon chemical potential, and QCD with isospin chemical potential. It provides us with a method to measure the BCS gap through the Dirac spectrum on the lattice.

  12. The Effect of Excipients on the Permeability of BCS Class III Compounds and Implications for Biowaivers

    OpenAIRE

    Parr, Alan; Hidalgo, Ismael J.; Bode, Chris; Brown, William; Yazdanian, Mehran; Gonzalez, Mario A.; Sagawa, Kazuko; Miller, Kevin; Jiang, Wenlei; Stippler, Erika S.

    2015-01-01

    Purpose Currently, the FDA allows biowaivers for Class I (high solubility and high permeability) and Class III (high solubility and low permeability) compounds of the Biopharmaceutics Classification System (BCS). Scientific evidence should be provided to support biowaivers for BCS Class I and Class III (high solubility and low permeability) compounds. Methods Data on the effects of excipients on drug permeability are needed to demonstrate that commonly used excipients do not affect the permea...

  13. Electronic Structure of the Bismuth Family of High Temperature Superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Dunn, Lisa

    2002-03-07

    High temperature superconductivity remains the central intellectual problem in condensed matter physics fifteen years after its discovery. Angle resolved photoemission spectroscopy (ARPES) directly probes the electronic structure, and has played an important role in the field of high temperature superconductors. With the recent advances in sample growth and the photoemission technique, we are able to study the electronic structure in great detail, and address regimes that were previously inaccessible. This thesis work contains systematic photoemission studies of the electronic structure of the Bi-family of high temperature superconductors, which include the single-layer system (Bi2201), the bi-layer system (Bi2212), and the tri-layer system (Bi2223). We show that, unlike conventional BCS superconductors, phase coherence information emerges in the single particle excitation spectrum of high temperature superconductors as the superconducting peak in Bi2212. The universality and various properties of this superconducting peak are studied in various systems. We argue that the origin of the superconducting peak may provide the key to understanding the mechanism of High-Tc superconductors. In addition, we identified a new experimental energy scale in the bilayer material, the anisotropic intra-bilayer coupling energy. For a long time, it was predicted that this energy scale would cause bilayer band splitting. We observe this phenomenon, for the first time, in heavily overdoped Bi2212. This new observation requires the revision of the previous picture of the electronic excitation in the Brillouin zone boundary. As the first ARPES study of a trilayer system, various detailed electronic proper- ties of Bi2223 are examined. We show that, comparing with Bi2212, both superconducting gap and relative superconducting peak intensity become larger in Bi2223, however, the strength of the interlayer coupling within each unit cell is possibly weaker. These results suggest that the

  14. The Effect of Excipients on the Permeability of BCS Class III Compounds and Implications for Biowaivers.

    Science.gov (United States)

    Parr, Alan; Hidalgo, Ismael J; Bode, Chris; Brown, William; Yazdanian, Mehran; Gonzalez, Mario A; Sagawa, Kazuko; Miller, Kevin; Jiang, Wenlei; Stippler, Erika S

    2016-01-01

    Currently, the FDA allows biowaivers for Class I (high solubility and high permeability) and Class III (high solubility and low permeability) compounds of the Biopharmaceutics Classification System (BCS). Scientific evidence should be provided to support biowaivers for BCS Class I and Class III (high solubility and low permeability) compounds. Data on the effects of excipients on drug permeability are needed to demonstrate that commonly used excipients do not affect the permeability of BCS Class III compounds, which would support the application of biowaivers to Class III compounds. This study was designed to generate such data by assessing the permeability of four BCS Class III compounds and one Class I compound in the presence and absence of five commonly used excipients. The permeability of each of the compounds was assessed, at three to five concentrations, with each excipient in two different models: Caco-2 cell monolayers, and in situ rat intestinal perfusion. No substantial increases in the permeability of any of the compounds were observed in the presence of any of the tested excipients in either of the models, with the exception of disruption of Caco-2 cell monolayer integrity by sodium lauryl sulfate at 0.1 mg/ml and higher. The results suggest that the absorption of these four BCS Class III compounds would not be greatly affected by the tested excipients. This may have implications in supporting biowaivers for BCS Class III compounds in general.

  15. The complexity of intestinal permeability: Assigning the correct BCS classification through careful data interpretation.

    Science.gov (United States)

    Zur, Moran; Hanson, Allison S; Dahan, Arik

    2014-09-30

    While the solubility parameter is fairly straightforward when assigning BCS classification, the intestinal permeability (Peff) is more complex than generally recognized. In this paper we emphasize this complexity through the analysis of codeine, a commonly used antitussive/analgesic drug. Codeine was previously classified as a low-permeability compound, based on its lower LogP compared to metoprolol, a marker for the low-high permeability class boundary. In contrast, high fraction of dose absorbed (Fabs) was reported for codeine, which challenges the generally recognized Peff-Fabs correlation. The purpose of this study was to clarify this ambiguity through elucidation of codeine's BCS solubility/permeability class membership. Codeine's BCS solubility class was determined, and its intestinal permeability throughout the small intestine was investigated, both in vitro and in vivo in rats. Codeine was found to be unequivocally a high-solubility compound. All in vitro studies indicated that codeine's permeability is higher than metoprolol's. In vivo studies in rats showed similar permeability for both drugs throughout the entire small-intestine. In conclusion, codeine was found to be a BCS Class I compound. No Peff-Fabs discrepancy is involved in its absorption; rather, it reflects the risk of assigning BCS classification based on merely limited physicochemical characteristics. A thorough investigation using multiple experimental methods is prudent before assigning a BCS classification, to avoid misjudgment in various settings, e.g., drug discovery, formulation design, drug development and regulation. Copyright © 2013 Elsevier B.V. All rights reserved.

  16. Considerations for a Pediatric Biopharmaceutics Classification System (BCS): application to five drugs.

    Science.gov (United States)

    Gandhi, Shivani V; Rodriguez, William; Khan, Mansoor; Polli, James E

    2014-06-01

    It has been advocated that biopharmaceutic risk assessment should be conducted early in pediatric product development and synchronized with the adult product development program. However, we are unaware of efforts to classify drugs into a Biopharmaceutics Classification System (BCS) framework for pediatric patients. The objective was to classify five drugs into a potential BCS. These five drugs were selected since both oral and intravenous pharmacokinetic data were available for each drug, and covered the four BCS classes in adults. Literature searches for each drug were conducted using Medline and applied to classify drugs with respect to solubility and permeability in pediatric subpopulations. Four pediatric subpopulations were considered: neonates, infants, children, and adolescents. Regarding solubility, dose numbers were calculated using a volume for each subpopulation based on body surface area (BSA) relative to 250 ml for a 1.73 m(2) adult. Dose numbers spanned a range of values, depending upon the pediatric dose formula and subpopulation. Regarding permeability, pharmacokinetic literature data required assumptions and decisions about data collection. Using a devised pediatric BCS framework, there was agreement in adult and pediatric BCS class for two drugs, azithromycin (class 3) and ciprofloxacin (class 4). There was discordance for the three drugs that have high adult permeability since all pediatric permeabilities were low: dolasetron (class 3 in pediatric), ketoprofen (class 4 in pediatric), and voriconazole (class 4 in pediatric). A main contribution of this work is the identification of critical factors required for a pediatric BCS.

  17. Fracton pairing mechanism for unconventional superconductors: Self-assembling organic polymers and copper-oxide compounds

    DEFF Research Database (Denmark)

    Milovanov, A.V.; Juul Rasmussen, J.

    2002-01-01

    Self-assembling organic polymers and copper-oxide compounds are two classes of unconventional superconductors, whose challenging behavior does not comply with the traditional picture of Bardeen-Cooper-Schrieffer (BCS) superconductivity in regular crystals. In this paper, we propose a theoretical...... or holes) exchange fracton excitations, quantum oscillations of fractal lattices that mimic the complex microscopic organization of the unconventional superconductors. For the copper oxides, the superconducting transition temperature T-c as predicted by the fracton mechanism is of the order of similar to......150 K. We suggest that the marginal ingredient of the high-temperature superconducting phase is provided by fracton coupled holes that condensate in the conducting copper-oxygen planes owing to the intrinsic field-effect-transistor configuration of the cuprate compounds. For the gate...

  18. Microscopic model of quasiparticle wave packets in superfluids, superconductors, and paired Hall states.

    Science.gov (United States)

    Parameswaran, S A; Kivelson, S A; Shankar, R; Sondhi, S L; Spivak, B Z

    2012-12-07

    We study the structure of Bogoliubov quasiparticles, bogolons, the fermionic excitations of paired superfluids that arise from fermion (BCS) pairing, including neutral superfluids, superconductors, and paired quantum Hall states. The naive construction of a stationary quasiparticle in which the deformation of the pair field is neglected leads to a contradiction: it carries a net electrical current even though it does not move. However, treating the pair field self-consistently resolves this problem: in a neutral superfluid, a dipolar current pattern is associated with the quasiparticle for which the total current vanishes. When Maxwell electrodynamics is included, as appropriate to a superconductor, this pattern is confined over a penetration depth. For paired quantum Hall states of composite fermions, the Maxwell term is replaced by a Chern-Simons term, which leads to a dipolar charge distribution and consequently to a dipolar current pattern.

  19. Tunneling conductance in superconductor-hybrid double quantum dots Josephson junction

    Science.gov (United States)

    Chamoli, Tanuj; Ajay

    2018-05-01

    The present work deals with the theoretical model study to analyse the tunneling conductance across a superconductor hybrid double quantum dots tunnel junction (S-DQD-S). Recently, there are many experimental works where the Josephson current across such nanoscopic junction is found to be dependent on nature of the superconducting electrodes, coupling of the hybrid double quantum dot's electronic states with the electronic states of the superconductors and nature of electronic structure of the coupled dots. For this, we have attempted a theoretical model containing contributions of BCS superconducting leads, magnetic coupled quantum dot states and coupling of superconducting leads with QDs. In order to include magnetic coupled QDs the contributions of competitive Kondo and Ruderman-Kittel- Kasuya-Yosida (RKKY) interaction terms are also introduced through many body effects in the model Hamiltonian at low temperatures (where Kondo temperature TK tunnel junctions. Tunneling conductance is proportional to DOS, hence we can analyse it's behaviour with the help of DOS.

  20. Interplay between the energy gap and heat capacity in S-wave superconductor

    International Nuclear Information System (INIS)

    Gonczarek, R.; Mulak, M.

    1998-01-01

    Starting from the postulated, generalized form of the BCS gap equation, suitable for a wide class of microscopic models, the thermodynamic properties of S-wave superconductors are studied. The precise analytical formulas for the main thermodynamic quantities are given and discussed in the characteristic temperature limits. In particular the inversion of the equations defining the specific heat as a function of Δ(T), i.e. the temperature dependence of the energy gap in S-wave superconductor is presented. It makes possible a reconstruction of the energy gap as a function of temperature from the heat capacity data. As predicted, in the frame of the model, the other thermodynamic quantities from the Δ(T) function seem also to be interesting. (orig.)

  1. Calculation of TC in a normal-superconductor bilayer using the microscopic-based Usadel theory

    International Nuclear Information System (INIS)

    Martinis, John M.; Hilton, G.C.; Irwin, K.D.; Wollman, D.A.

    2000-01-01

    The Usadel equations give a theory of superconductivity, valid in the diffusive limit, that is a generalization of the microscopic equations of the BCS theory. Because the theory is expressed in a tractable and physical form, even experimentalists can analytically and numerically calculate detailed properties of superconductors in physically relevant geometries. Here, we describe the Usadel equations and review their solution in the case of predicting the transition temperature T C of a thin normal-superconductor bilayer. We also extend this calculation for thicker bilayers to show the dependence on the resistivity of the films. These results, which show a dependence on both the interface resistance and heat capacity of the films, provide important guidance on fabricating bilayers with reproducible transition temperatures

  2. Iron pnictide superconductors

    International Nuclear Information System (INIS)

    Tegel, Marcus Christian

    2011-01-01

    The scope of this dissertation therefore has not only been the synthesis of various new superconducting and non-superconducting iron pnictides of several structural families but also their in-depth crystallographic and physical characterisation. In Chapters 3 - 6, the family of the ZrCuSiAs-type (1111) compounds is subject of discussion. The solid solution series La(Co x Fe 1-x )PO is analysed regarding magnetic and superconducting properties and the new compounds EuMnPF and REZnPO, as well as the new superconductor parent compound SrFeAsF are presented. Chapters 7 - 9 are dedicated to the new iron arsenide superconductors of the ThCr 2 Si 2 -type (122 family). Therein, also the discovery of the first superconductor in this structural family, Ba 0.6 K 0.4 Fe 2 As 2 , is unveiled. A detailed examination of the complete solid solution series (Ba 1-x K x )Fe 2 As 2 is presented. Moreover, the crystallographic phase transitions of the closely related compounds SrFe 2 As 2 and EuFe 2 As 2 are characterised and the superconductors Sr 1-x K x Fe 2 As 2 and Ca 1-x Na x Fe 2 As 2 are examined for magnetic and phononic excitations. In Chapter 10, the redetermined crystal structure of the superconductor Fe(Se 1-x Te x ) (11-type) is presented from a chemist's point of view. Chapters 11 - 14 look into the superconducting and non-superconducting iron arsenides of more complex structural families (32522-type and 21311-type). Therein, crystallographic and magnetic details of Sr 3 Sc 2 O 5 Fe 2 As 2 are presented and Ba 2 ScO 3 FeAs and Sr 2 CrO 3 FeAs, the first two members of the new 21311-type are portrayed. Sr 2 CrO 3 FeAs is looked at in close detail with various methods, so e.g. the spin structure of the magnetically ordered compound is solved and a possible reason for the absence of superconductivity in this compound is given. Finally, the superconductor Sr 2 VO 3 FeAs is scrutinised and necessary prerequisites for superconductivity in this compound are suggested. (orig.)

  3. "Fluctuoscopy" of Superconductors

    Science.gov (United States)

    Varlamov, A. A.

    Study of fluctuation phenomena in superconductors (SCs) is the subject of great fundamental and practical importance. Understanding of their physics allowed to clear up the fundamental properties of SC state. Being predicted in 1968, one of the fluctuation effects, namely paraconductivity, was experimentally observed almost simultaneously. Since this time, fluctuations became a noticeable part of research in the field of superconductivity, and a variety of fluctuation effects have been discovered. The new wave of interest to fluctuations (FL) in superconductors was generated by the discovery of cuprate oxide superconductors (high-temperature superconductors, HTS), where, due to extremely short coherence length and low effective dimensionality of the electron system, superconductive fluctuations manifest themselves in a wide range of temperatures. Moreover, anomalous properties of the normal state of HTS were attributed by many theorists to strong FL in these systems. Being studied in the framework of the phenomenological Ginzburg-Landau theory and, more extensively, in diagrammatic microscopic approach, SC FLs side by side with other quantum corrections (weak localization, etc.) became a new tool for investigation and characterization of such new systems as HTS, disordered electron systems, granular metals, Josephson structures, artificial super-lattices, etc. The characteristic feature of SC FL is their strong dependence on temperature and magnetic fields in the vicinity of phase transition. This allows one to definitely separate the fluctuation effects from other contributions and to use them as the source of information about the microscopic parameters of a material. By their origin, SC FLs are very sensitive to relaxation processes, which break phase coherence. This allows using them for versatile characterization of SC. Today, one can speak about the " fluctuoscopy" of superconductive systems. In review, we present the qualitative picture both of thermodynamic

  4. Measuring condensate fraction in superconductors

    International Nuclear Information System (INIS)

    Chakravarty, Sudip; Kee, Hae-Young

    2000-01-01

    An analysis of off-diagonal long-range order in superconductors shows that the spin-spin correlation function is significantly influenced by the order if the order parameter is anisotropic on a microscopic scale. Thus, magnetic neutron scattering can provide a direct measurement of the condensate fraction of a superconductor. It is also argued that recent measurements in high-temperature superconductors come very close to achieving this goal. (c) 2000 The American Physical Society

  5. Processing of Mixed Oxide Superconductors

    Science.gov (United States)

    1990-07-01

    rapid changes world wide a major research centre on high Tc superconductors was awarded to Cambridge which involved moving the work and people to a...reports and paper is in the appendices. Separation Ceramic superconductors tend to be mixtures of phases, especially when first discovered. It would...properties of the superconducting state will in principle allow superconducting material to be levitated from the non superconductor and several designs

  6. Superconductor stability 90: A review

    International Nuclear Information System (INIS)

    Dresner, L.

    1990-01-01

    This paper reviews some recent developments in the field of stability of superconductors. The main topics dealt with are hydrodynamic phenomena in cable-in-conduit superconductors, namely, multiple stability, quench pressure, thermal expulsion, and thermal hydraulic quenchback, traveling normal zones in large, composite conductors, such as those intended for SMES, and the stability of vapor-cooled leads made of high-temperature superconductors. 31 refs., 5 figs

  7. High Temperature Superconductor Resonator Detectors

    Data.gov (United States)

    National Aeronautics and Space Administration — High Temperature Superconductor (HTS) infrared detectors were studied for years but never matured sufficiently for infusion into instruments. Several recent...

  8. Flux-induced Nernst effect in low-dimensional superconductors

    International Nuclear Information System (INIS)

    Berger, Jorge

    2017-01-01

    Highlights: • The Nernst effect tells us that the presence of a magnetic field and a temperature gradient in a conductor yields a transverse voltage. • The Nernst effect in superconductors, especially above their critical temperature, has been a hot topic of research during the last decades. • I predict a new effect in which a transverse voltage arises, not because of the magnetic field, but rather because of the magnetic flux enclosed by a loop with non-uniform temperature. - Abstract: A method is available that enables consistent study of the stochastic behavior of a system that obeys purely diffusive evolution equations. This method has been applied to a superconducting loop with nonuniform temperature, with average temperature close to T_c. It is found that a flux-dependent average potential difference arises along the loop, proportional to the temperature gradient and most pronounced in the direction perpendicular to this gradient. The largest voltages were obtained for fluxes close to 0.3Φ_0, average temperatures slightly below the critical temperature, thermal coherence length of the order of the perimeter of the ring, BCS coherence length that is not negligible in comparison to the thermal coherence length, and short inelastic scattering time. This effect is entirely due to thermal fluctuations. It differs essentially from the usual Nernst effect in bulk superconductors, that is induced by magnetic field rather than by magnetic flux. We also study the effect of confinement in a 2D mesoscopic film.

  9. Orbitally limited pair-density-wave phase of multilayer superconductors

    Science.gov (United States)

    Möckli, David; Yanase, Youichi; Sigrist, Manfred

    2018-04-01

    We investigate the magnetic field dependence of an ideal superconducting vortex lattice in the parity-mixed pair-density-wave phase of multilayer superconductors within a circular cell Ginzburg-Landau approach. In multilayer systems, due to local inversion symmetry breaking, a Rashba spin-orbit coupling is induced at the outer layers. This combined with a perpendicular paramagnetic (Pauli) limiting magnetic field stabilizes a staggered layer dependent pair-density-wave phase in the superconducting singlet channel. The high-field pair-density-wave phase is separated from the low-field BCS phase by a first-order phase transition. The motivating guiding question in this paper is: What is the minimal necessary Maki parameter αM for the appearance of the pair-density-wave phase of a superconducting trilayer system? To address this problem we generalize the circular cell method for the regular flux-line lattice of a type-II superconductor to include paramagnetic depairing effects. Then, we apply the model to the trilayer system, where each of the layers are characterized by Ginzburg-Landau parameter κ0 and a Maki parameter αM. We find that when the spin-orbit Rashba interaction compares to the superconducting condensation energy, the orbitally limited pair-density-wave phase stabilizes for Maki parameters αM>10 .

  10. Strong-coupling interaction in high-Tc superconductors

    International Nuclear Information System (INIS)

    Ray, D.K.

    1991-01-01

    Extensive experimental and theoretical work have been done to understand the mechanisms of superconductivity. Until 1986 when Bednorz and Muller discovered superconductivity in the copper oxide perovskite, the principal mechanism was found to be electron-phonon interaction and the characteristics of superconductivity vary depending on the strength of the electron-phonon interaction and the electronic structure. The essential characteristic of these conventional superconductors could be divided into two groups: wide band metals with low density of states N(E F ) at the Fermi energy E F and a rather weak electron-phonon coupling V obeying the universal characteristics of the BCS theory and narrow d band metals, compounds, and alloys with high values of N(E F ), electron-phonon coupling V and non negligible Coulomb interaction between the electrons. In this paper a short summary and the important results of these theories are discussed. The inherent limitations of these theories based on electron-phonon interaction will be discussed. The authors indicate the major characteristics of the new superconductors. These characteristics are difficult to explain on the basis of either the conventional electron-phonon theory or theories based on magnetic interactions alone

  11. Neutron Depolarization in Superconductors

    Science.gov (United States)

    Zhuchenko, N. K.

    1995-04-01

    The dependences of neutron depolarization on applied magnetic field are deduced along the magnetization hysteresis loop in terms of the Bean model of the critical state. The depolarization in uniaxial superconductors with the reversible magnetization, including uniaxial magnetic superconductors, is also considered. A strong depolarization is expected if the neutrons travel along the vortex lines. On calcule la dépendance en champ magnétique de la dépolarisation des neutrons le long du cycle d'hystérésis en termes du modèle critique de Bean. On considère aussi la dépolarisation dans les supraconducteurs uniaxiaux en fonction de l'aimantation réversible, y compris pour les supraconducteurs magnétiques. On attend une forte dépolarisation si les neutrons se propagent le long des vortex.

  12. Vortices and nanostructured superconductors

    CERN Document Server

    2017-01-01

    This book provides expert coverage of modern and novel aspects of the study of vortex matter, dynamics, and pinning in nanostructured and multi-component superconductors. Vortex matter in superconducting materials is a field of enormous beauty and intellectual challenge, which began with the theoretical prediction of vortices by A. Abrikosov (Nobel Laureate). Vortices, vortex dynamics, and pinning are key features in many of today’s human endeavors: from the huge superconducting accelerating magnets and detectors at the Large Hadron Collider at CERN, which opened new windows of knowledge on the universe, to the tiny superconducting transceivers using Rapid Single Flux Quanta, which have opened a revolutionary means of communication. In recent years, two new features have added to the intrinsic beauty and complexity of the subject: nanostructured/nanoengineered superconductors, and the discovery of a range of new materials showing multi-component (multi-gap) superconductivity. In this book, leading researche...

  13. Radiation behavior of superconductors

    International Nuclear Information System (INIS)

    Scanlan, R.M.; Raymond, E.L.

    1979-01-01

    High energy neutron irradiations have been performed on Nb 3 Sn superconductors to assess their behavior in a fusion reactor environment. Irradiations were performed at 4.2 K and property measurements were made without warming the samples. The critical current I/sub c/ increased with irradiation to a level about 50% above the unirradiated value at the highest fluences reached in our experiments. These results are compared with the results of other low temperature irradiations of Nb 3 Sn

  14. Unconventional Andreev reflection on the quasi-one-dimensional superconductor Nb2PdxSe5

    Directory of Open Access Journals (Sweden)

    Yeping Jiang

    2016-04-01

    Full Text Available We have carried out Andreev reflection measurements on point contact junctions between normal metal and single crystals of the quasi-one-dimensional (Q1D superconductor Nb2PdxSe5 (Tc ∼ 5.5 K. The contacts of the junctions were made on either self-cleaved surfaces or crystal edges so that the current flow directions in the two types of junctions are different, and the measurements provide a directional probe for the order parameter of the superconductor. Junctions made in both configurations show typical resistances of ∼20-30 Ohms, and a clear double-gap Andreev reflection feature was consistently observed at low temperatures. Quantitative analysis of the conductance spectrum based on a modified Blonder-Tinkham-Klapwijk (BTK model suggests that the amplitudes of two order parameters may have angular dependence in the a-c plane. Moreover, the gap to transition temperature ratio (Δ/TC for the larger gap is substantially higher than the BCS ratio expected for phonon-mediated s-wave superconductors. We argue that the anisotropic superconducting order parameter and the extremely large gap to transition temperature ratio may be associated with an unconventional pairing mechanism in the inorganic Q1D superconductor.

  15. Far infrared spectroscopy of high-Tc superconductors at the National Synchrotron Light Source

    International Nuclear Information System (INIS)

    Perkowitz, S.; Williams, G.P.

    1989-01-01

    This paper reports the first far infrared transmission spectra for micron-thick films of high-T c rare-earth superconductors such as DyBaCuO, with implications for the superconducting gap. Spectra were obtained at Brookhaven's National Synchrotron Light Source, a new high-intensity, broad-band millimeter to infrared source. The National Synchrotron Light Source at Brookhaven National Laboratory, known for powerful X-ray and UV output, is also a high-intensity (10 to 1000 times above a black body), high-brightness (intensity per solid angle), broad-band, picosecond, millimeter to infrared source. These features make it valuable for far-infrared condensed matter experiments, especially those in highly absorbing or extremely small systems. A first application has been to measure very small infrared transmissions through thick bulk-like high-T c superconducting films. Preliminary measurements through films of the conventional superconductor Nb 3 Ge established techniques. These were followed by the first measurements (to the author's knowledge) through micron-thick films of high-T c rare-earth superconductors such as DyBaCuO over 10-300 cm -1 , which includes the superconducting gap according to BCS or moderately strong-coupled theory. The authors discuss the transmission evidence bearing on the existence of a gap and other important features of high-T c superconductors, and describe the synchrotron and instrumentation features which make possible these unusual measurements

  16. Strongly disordered superconductors

    International Nuclear Information System (INIS)

    Muttalib, K.A.

    1982-01-01

    We examine some universal effects of strong non-magnetic disorder on the electron-phonon and electron-electron interactions in a superconductor. In particular we explicitly take into account the effect of slow diffusion of electrons in a disordered medium by working in an exact impurity eigenstate representation. We find that the normal diffusion of electrons characterized by a constant diffusion coefficient does not lead to any significant correction to the electron-phonon or the effective electron-electron interactions in a superconductor. We then consider sufficiently strong disorder where Anderson localization of electrons becomes important and determine the effect of localization on the electron-electron interactions. We find that due to localization, the diffusion of electrons becomes anomalous in the sense that the diffusion coefficient becomes scale dependent. This results in an increase in the effective electron-electron interaction with increasing disorder. We propose that this provides a natural explanation for the unusual sensitivity of the transition temperature T/sub c/ of the high T/sub c/ superconductors (T/sub c/ > 10 0 K) to damage effects

  17. Multi-Band (K- Q- and E-Band) Multi-Tone Millimeter-Wave Frequency Synthesizer for Radio Wave Propagation Studies

    Science.gov (United States)

    Simons, Rainee N.; Wintucky, Edwin G.

    2014-01-01

    This paper presents the design and test results of a multi-band multi-tone millimeter-wave frequency synthesizer, based on a solid-state frequency comb generator. The intended application of the synthesizer is in a space-borne transmitter for radio wave atmospheric studies at K-band (18 to 26.5 GHz), Q-band (37 to 42 GHz), and E-band (71 to 76 GHz). These studies would enable the design of robust multi-Gbps data rate space-to-ground satellite communication links. Lastly, the architecture for a compact multi-tone beacon transmitter, which includes a high frequency synthesizer, a polarizer, and a conical horn antenna, has been investigated for a notional CubeSat based space-to-ground radio wave propagation experiment.

  18. Signature of magnetic-dependent gapless odd frequency states at superconductor / ferromagnet interfaces

    Energy Technology Data Exchange (ETDEWEB)

    Robinson, Jason [Department of Materials Science, 27 Charles Babbage Road, Cambridge, CB30FS (United Kingdom)

    2015-07-01

    The theory of superconductivity developed by Bardeen, Cooper, and Schrieffer (BCS) explains the stabilisation of electron pairs into a spin-singlet, even frequency, state by the formation of an energy gap below which the density of states (DoS) is zero. At a superconductor interface with an inhomogeneous ferromagnet, a gapless odd frequency superconducting state is predicted in which the Cooper pairs are in a spin-triplet state. Although indirect evidence for such a state has been obtained, the gap structure and pairing symmetry have not so far been determined. In this talk I will present scanning tunnelling spectroscopy of Nb superconducting films proximity coupled to epitaxial Ho. These measurements reveal pronounced changes to the Nb sub-gap superconducting DoS on driving the Ho through a metamagnetic transition from a helical antiferromagnetic to a homogeneous ferromagnetic state for which a BCS-like gap is recovered. The results verify odd frequency spin-triplet superconductivity at superconductor / inhomogeneous magnet interfaces.

  19. Ultra-fast pump-probe determination of electron-phonon coupling in cuprate superconductors

    Science.gov (United States)

    Mihailovic, Dragan

    2010-03-01

    Fresh femtosecond spectroscopy experiments show the electron-phonon interaction strength λ to be 0.7 and 1.4 for YBCO and LSCO respectively and not around 0.2 as previously reported [1]. The revised estimates arise primarily from improved time-resolution, and also partly from improved modeling. Comparison with classical superconductors and pnictides shows non-monotonic correlation of λ with Tc. Systematic new measurements of the condensate vaporization energy (Uv) in cuprates [2] and pnictides reveals a power-law dependence on Tc with exponent 2. However, Uc is 16-18 times greater than the BCS condensation energy Uc, implying that a significant heat capacity of the ``bosonic glue.'' In contrast, charge-density wave systems with electronically driven ordering transitions have Uv˜Uc. The data suggest BCS and Eliashberg-based models to be inappropriate for describing the physics of high-temperature superconductors, and point towards polaron models which consider strong or intermediate λ.[4pt] [1] C.Gadermeier et al., arXiv:0902.1636[0pt] [2] P.Kusar et al., Phys. Rev. Lett. 101, 227001 (2008)

  20. Testability issues in Superconductor Electronics

    NARCIS (Netherlands)

    Kerkhoff, Hans G.; Arun, Arun J.

    2004-01-01

    An emerging technology for solutions in high-end applications in computing and telecommunication is superconductor electronics. A system-level study has been carried out to verify the feasibility of DfT in superconductor electronics. In this paper, we present how this can be realized to monitor

  1. Method for preparation of superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Barber, A.C.; McDougall, I.L.

    1975-07-10

    The invention deals with a method to prepare a superconductor consisting of a superconducting compound of at least two elements. It especially deals with superconductors which surround a superconducting intermetallic compounds of at least two elements, examples of which are Nb/sub 2/Sn and Nb/sub 3/Al.

  2. Nonmagnetic impurities in magnetic superconductors

    International Nuclear Information System (INIS)

    Mineev, V.P.

    1989-01-01

    The magnetization and magnetic field arising around the nonmagnetic impurity in magnetic superconductor with triplet pairing are found. The relationship of these results with the data of recent (gm)sR experiments in heavy fermionic superconductor U 1 - x Th x Be 13 is presented

  3. Popov approximation for composite bosons in the BCS-BEC crossover

    International Nuclear Information System (INIS)

    Pieri, P.; Strinati, G.C.

    2005-01-01

    Theoretical treatments of the BCS-BEC crossover need to provide as accurate as possible descriptions of the two regimes where the diluteness condition applies, either in terms of the constituent fermions (BCS limit) or of the composite bosons which form as bound-fermion pairs (BEC limit). This has to occur via a single fermionic theory that bridges across these two limiting representations. In this paper, we set up successive improvements of the fermionic theory, that result into composite bosons described at the level of either the Bogoliubov or the Popov approximations for pointlike bosons. This work bears on the recent experimental advances on the BCS-BEC crossover with trapped Fermi atoms, which show the need for accurate theoretical descriptions of the BEC side of the crossover

  4. Inhomogeneous condensates in dilute nuclear matter and BCS-BEC crossovers

    International Nuclear Information System (INIS)

    Stein, Martin; Sedrakian, Armen; Huang, Xu-Guang; Clark, John W; Röpke, Gerd

    2014-01-01

    We report on recent progress in understanding pairing phenomena in low-density nuclear matter at small and moderate isospin asymmetry. A rich phase diagram has been found comprising various superfluid phases that include a homogeneous and phase-separated BEC phase of deuterons at low density and a homogeneous BCS phase, an inhomogeneous LOFF phase, and a phase-separated BCS phase at higher densities. The transition from the BEC phases to the BCS phases is characterized in terms of the evolution, from strong to weak coupling, of the condensate wavefunction and the second moment of its density distribution in r-space. We briefly discuss approaches to higher-order clustering in low-density nuclear matter.

  5. Current and evolving approaches for improving the oral permeability of BCS Class III or analogous molecules.

    Science.gov (United States)

    Dave, Vivek S; Gupta, Deepak; Yu, Monica; Nguyen, Phuong; Varghese Gupta, Sheeba

    2017-02-01

    The Biopharmaceutics Classification System (BCS) classifies pharmaceutical compounds based on their aqueous solubility and intestinal permeability. The BCS Class III compounds are hydrophilic molecules (high aqueous solubility) with low permeability across the biological membranes. While these compounds are pharmacologically effective, poor absorption due to low permeability becomes the rate-limiting step in achieving adequate bioavailability. Several approaches have been explored and utilized for improving the permeability profiles of these compounds. The approaches include traditional methods such as prodrugs, permeation enhancers, ion-pairing, etc., as well as relatively modern approaches such as nanoencapsulation and nanosizing. The most recent approaches include a combination/hybridization of one or more traditional approaches to improve drug permeability. While some of these approaches have been extremely successful, i.e. drug products utilizing the approach have progressed through the USFDA approval for marketing; others require further investigation to be applicable. This article discusses the commonly studied approaches for improving the permeability of BCS Class III compounds.

  6. Coupling spin qubits via superconductors

    DEFF Research Database (Denmark)

    Leijnse, Martin; Flensberg, Karsten

    2013-01-01

    We show how superconductors can be used to couple, initialize, and read out spatially separated spin qubits. When two single-electron quantum dots are tunnel coupled to the same superconductor, the singlet component of the two-electron state partially leaks into the superconductor via crossed...... Andreev reflection. This induces a gate-controlled singlet-triplet splitting which, with an appropriate superconductor geometry, remains large for dot separations within the superconducting coherence length. Furthermore, we show that when two double-dot singlet-triplet qubits are tunnel coupled...... to a superconductor with finite charging energy, crossed Andreev reflection enables a strong two-qubit coupling over distances much larger than the coherence length....

  7. Evaluating superconductors for microwave applications

    International Nuclear Information System (INIS)

    Hammond, B.; Bybokas, J.

    1989-01-01

    It is becoming increasingly obvious that some of the earliest applications for high Tc superconductors will be in the microwave market. While this is a major opportunity for the superconductor community, it also represents a significant challenge. At DC or low frequencies a superconductor can be easily characterized by simple measurements of resistivity and magnetic susceptibility versus temperature. These parameters are fundamental to superconductor characterization and various methods exist for measuring them. The only valid way to determine the microwave characteristics of a superconductor is to measure it at microwave frequencies. It is for this reason that measuring microwave surface resistance has emerged as one of the most demanding and telling tests for materials intended for high frequency applications. In this article, the theory of microwave surface resistance is discussed. Methods for characterizing surface resistance theoretically and by practical implementation are described

  8. A modified physiological BCS for prediction of intestinal absorption in drug discovery.

    Science.gov (United States)

    Zaki, Noha M; Artursson, Per; Bergström, Christel A S

    2010-10-04

    In this study, the influence of physiologically relevant media on the compound position in a biopharmaceutical classification system (BCS) which resembled the intestinal absorption was investigated. Both solubility and permeability limited compounds (n = 22) were included to analyze the importance of each of these on the final absorption. Solubility was determined in three different dissolution media, phosphate buffer pH 6.5 (PhB 6.5), fasted state simulated intestinal fluid (FaSSIF), and fed state simulated intestinal fluid (FeSSIF) at 37 °C, and permeability values were determined using the 2/4/A1 cell line. The solubility data and membrane permeability values were used for sorting the compounds into a BCS modified to reflect the fasted and fed state. Three of the seven compounds sorted as BCS II in PhB 6.5 (high permeability, low solubility) changed their position to BCS I when dissolved in FaSSIF and/or FeSSIF (high permeability, high solubility). These were low dosed (20 mg or less) lipophilic molecules displaying solvation limited solubility. In contrast, compounds having solid-state limited solubility had a minor increase in solubility when dissolved in FaSSIF and/or FeSSIF. Although further studies are needed to enable general cutoff values, our study indicates that low dosed BCS Class II compounds which have solubility normally restricted by poor solvation may behave as BCS Class I compounds in vivo. The large series of compounds investigated herein reveals the importance of investigating solubility and dissolution under physiologically relevant conditions in all stages of the drug discovery process to push suitable compounds forward, to select proper formulations, and to reduce the risk of food effects.

  9. Iron pnictide superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Tegel, Marcus Christian

    2011-03-22

    The scope of this dissertation therefore has not only been the synthesis of various new superconducting and non-superconducting iron pnictides of several structural families but also their in-depth crystallographic and physical characterisation. In Chapters 3 - 6, the family of the ZrCuSiAs-type (1111) compounds is subject of discussion. The solid solution series La(Co{sub x}Fe{sub 1-x})PO is analysed regarding magnetic and superconducting properties and the new compounds EuMnPF and REZnPO, as well as the new superconductor parent compound SrFeAsF are presented. Chapters 7 - 9 are dedicated to the new iron arsenide superconductors of the ThCr{sub 2}Si{sub 2}-type (122 family). Therein, also the discovery of the first superconductor in this structural family, Ba{sub 0.6}K{sub 0.4}Fe{sub 2}As{sub 2}, is unveiled. A detailed examination of the complete solid solution series (Ba{sub 1-x}K{sub x})Fe{sub 2}As{sub 2} is presented. Moreover, the crystallographic phase transitions of the closely related compounds SrFe{sub 2}As{sub 2} and EuFe{sub 2}As{sub 2} are characterised and the superconductors Sr{sub 1-x}K{sub x}Fe{sub 2}As{sub 2} and Ca{sub 1-x}Na{sub x}Fe{sub 2}As{sub 2} are examined for magnetic and phononic excitations. In Chapter 10, the redetermined crystal structure of the superconductor Fe(Se{sub 1-x}Te{sub x}) (11-type) is presented from a chemist's point of view. Chapters 11 - 14 look into the superconducting and non-superconducting iron arsenides of more complex structural families (32522-type and 21311-type). Therein, crystallographic and magnetic details of Sr{sub 3}Sc{sub 2}O{sub 5}Fe{sub 2}As{sub 2} are presented and Ba{sub 2}ScO{sub 3}FeAs and Sr{sub 2}CrO{sub 3}FeAs, the first two members of the new 21311-type are portrayed. Sr{sub 2}CrO{sub 3}FeAs is looked at in close detail with various methods, so e.g. the spin structure of the magnetically ordered compound is solved and a possible reason for the absence of superconductivity in this compound is

  10. Iron pnictide superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Tegel, Marcus Christian

    2011-03-22

    The scope of this dissertation therefore has not only been the synthesis of various new superconducting and non-superconducting iron pnictides of several structural families but also their in-depth crystallographic and physical characterisation. In Chapters 3 - 6, the family of the ZrCuSiAs-type (1111) compounds is subject of discussion. The solid solution series La(Co{sub x}Fe{sub 1-x})PO is analysed regarding magnetic and superconducting properties and the new compounds EuMnPF and REZnPO, as well as the new superconductor parent compound SrFeAsF are presented. Chapters 7 - 9 are dedicated to the new iron arsenide superconductors of the ThCr{sub 2}Si{sub 2}-type (122 family). Therein, also the discovery of the first superconductor in this structural family, Ba{sub 0.6}K{sub 0.4}Fe{sub 2}As{sub 2}, is unveiled. A detailed examination of the complete solid solution series (Ba{sub 1-x}K{sub x})Fe{sub 2}As{sub 2} is presented. Moreover, the crystallographic phase transitions of the closely related compounds SrFe{sub 2}As{sub 2} and EuFe{sub 2}As{sub 2} are characterised and the superconductors Sr{sub 1-x}K{sub x}Fe{sub 2}As{sub 2} and Ca{sub 1-x}Na{sub x}Fe{sub 2}As{sub 2} are examined for magnetic and phononic excitations. In Chapter 10, the redetermined crystal structure of the superconductor Fe(Se{sub 1-x}Te{sub x}) (11-type) is presented from a chemist's point of view. Chapters 11 - 14 look into the superconducting and non-superconducting iron arsenides of more complex structural families (32522-type and 21311-type). Therein, crystallographic and magnetic details of Sr{sub 3}Sc{sub 2}O{sub 5}Fe{sub 2}As{sub 2} are presented and Ba{sub 2}ScO{sub 3}FeAs and Sr{sub 2}CrO{sub 3}FeAs, the first two members of the new 21311-type are portrayed. Sr{sub 2}CrO{sub 3}FeAs is looked at in close detail with various methods, so e.g. the spin structure of the magnetically ordered compound is solved and a possible reason for the absence of superconductivity in this compound

  11. Superconductors go organic

    International Nuclear Information System (INIS)

    Singleton, John; Mielke, Charles

    2002-01-01

    Superconductors made from organic molecules are revealing fascinating new physics and could offer huge technological potential as well. Solid-state physicists are simple people. They believe that basic research is best carried out on chemically simple materials. Traditionally they have focused on inorganic elements, alloys, and other straightforward compounds. This approach has provided some notable successes. For example, any physicist over 35 will remember the huge fuss surrounding the discovery of high-temperature cuprate superconductors in 1986, which led to the infamous 'Woodstock of physics' meeting the following year. Just before the cuprates were discovered, however, an alternative view had begun to emerge. Physical chemists such as Klaus Bechgaard, Peter Day, Gunzi Saito, Viktor Schegolev and Jack Williams were suggesting that the 'simple-materials-are-best' assumption was misplaced. They argued that some of the most exciting studies in solid-state physics can - and should - be attempted on crystalline organic materials. Although chemically complex, such materials are beautifully simple in other ways, and they can, for example, provide much more information about basic phenomena like superconductivity and magnetism than supposedly simple materials. Physicists eventually embraced these materials with enthusiasm, and the number of papers on crystalline organic metals overtook those on the high-temperature cuprate superconductors three years ago. The gap has widened ever since, and the fact that God and a billion years of evolution have produced a processor based on three-dimensional arrays of molecules, rather than silicon or gallium-arsenide chips, is taken as a good omen by those working in the field. (U.K.)

  12. Magnetic Scaling in Superconductors

    International Nuclear Information System (INIS)

    Lawrie, I.D.

    1997-01-01

    The Ginzburg-Landau-Wilson superconductor in a magnetic field B is considered in the approximation that magnetic-field fluctuations are neglected. A formulation of perturbation theory is presented in which multiloop calculations fully retaining all Landau levels are tractable. A 2-loop calculation shows that, near the zero-field critical point, the singular part of the free energy scales as F sing ∼ |t| 2-α F(B|t| -2ν ), where ν is the coherence-length exponent emdash a result which has hitherto been assumed on purely dimensional grounds. copyright 1997 The American Physical Society

  13. High temperature superconductors

    CERN Document Server

    Paranthaman, Parans

    2010-01-01

    This essential reference provides the most comprehensive presentation of the state of the art in the field of high temperature superconductors. This growing field of research and applications is currently being supported by numerous governmental and industrial initiatives in the United States, Asia and Europe to overcome grid energy distribution issues. The technology is particularly intended for densely populated areas. It is now being commercialized for power-delivery devices, such as power transmission lines and cables, motors and generators. Applications in electric utilities include current limiters, long transmission lines and energy-storage devices that will help industries avoid dips in electric power.

  14. Pinning and creep in superconductors

    International Nuclear Information System (INIS)

    Ovchinnikov, Yu.N.

    1994-01-01

    All superconductors can be separated into two large groups: type I and type II. The behaviour of these two groups in a magnetic field is quite different. The superconductors of type I, in a strong magnetic field, enter the intermediate state. Phenomenological picture of this state was given by Landau. The type II superconductors, in strong magnetic fields, form the mixed state (or Shubnikov phase). The microscopic picture of the mixed state was given by Abrikosov on the basis of Ginzburg-Landau equations. In ideal homogeneous superconductors the free energy is not changed if all the vortex structure is shifted on some distance u. The transport current will be proportional, therefore, to the electric field E. All the real superconductors, however, are inhomogeneous. Inhomogeneities interact with vortex lattice and pin it. In this new state the transport current below some critical value does not lead to the motion of the flux lattice and to the energy dissipation. The value of critical current strongly depends on the type of inhomogeneities, on the value of magnetic field and on temperature. In new layered superconductors, the critical current depends also on the orientation of the magnetic field B with respect to the layer planes. Temperature and quantum fluctuations lead to the transition between different metastable states in superconductors with current. As a result, the vortex lattice slowly moves (creep phenomenon). Below we will briefly discuss all these phenomena. (orig.)

  15. Specific heat and magnetization of a ZrB12 single crystal: characterization of a type II/1 superconductor

    OpenAIRE

    Wang, Yuxing; Lortz, Rolf; Paderno, Yuriy; Filippov, Vladimir; Abe, Satoko; Tutsch, Ulrich; Junod, Alain

    2005-01-01

    We measured the specific heat, the magnetization, and the magnetoresistance of a single crystal of ZrB12, which is superconducting below Tc ~ 6 K. The specific heat in zero field shows a BCS-type superconducting transition. The normal- to superconducting-state transition changes from first order (with a latent heat) to second order (without latent heat) with increasing magnetic field, indicating that the pure compound is a low-kappa, type-II/1 superconductor in the classification of Auer and ...

  16. Plasmons in strong superconductors

    International Nuclear Information System (INIS)

    Baldo, M.; Ducoin, C.

    2011-01-01

    We present a study of the possible plasmon excitations that can occur in systems where strong superconductivity is present. In these systems the plasmon energy is comparable to or smaller than the pairing gap. As a prototype of these systems we consider the proton component of Neutron Star matter just below the crust when electron screening is not taken into account. For the realistic case we consider in detail the different aspects of the elementary excitations when the proton, electron components are considered within the Random-Phase Approximation generalized to the superfluid case, while the influence of the neutron component is considered only at qualitative level. Electron screening plays a major role in modifying the proton spectrum and spectral function. At the same time the electron plasmon is strongly modified and damped by the indirect coupling with the superfluid proton component, even at moderately low values of the gap. The excitation spectrum shows the interplay of the different components and their relevance for each excitation modes. The results are relevant for neutrino physics and thermodynamical processes in neutron stars. If electron screening is neglected, the spectral properties of the proton component show some resemblance with the physical situation in high-T c superconductors, and we briefly discuss similarities and differences in this connection. In a general prospect, the results of the study emphasize the role of Coulomb interaction in strong superconductors.

  17. Superconductor fluxoid logic

    International Nuclear Information System (INIS)

    Andronov, A.A.; Kurin, V.V.; Levichev, M.Yu.; Ryndyk, D.A.; Vostokov, V.I.

    1993-01-01

    In recent years there has been much interest in superconductor logical devices. Our paper is devoted to the analysis of some new possibilities in this field. The main problems here are: minimization of time of logical operations and reducing of device scale. Josephson systems are quite appropriate for this purpose because of small size, short characteristic time and also small energy losses. Two different types of Josephson logic have been investigated during last years. The first type is based on hysteretic V-A characteristic of a single Josephson junction. Superconducting and resistive (with nonzero voltage) states are considered as logical zero and logical unit. The second one - rapid single flux quantum logic, has been developed recently and is based on SQUID-like bistability. Different logical states are the states with different number of magnetic flux quanta inside closed superconducting contour. Information is represented by voltage pulses with fixed ''area'' (∫ V(t)/dt). This pulses are generated when logical state of SQUID-like elementary cell changes. The fundamental role of magnetic flux quantization in this type of logic leads to the necessity of large enough self-inductance of superconductor contour and thus to limitations on minimal device dimensions. (orig.)

  18. Theory of disordered superconductors

    International Nuclear Information System (INIS)

    Wysokinski, K.I.

    1991-01-01

    The influence of disorder on the superconducting transition temperature is discussed. The main steps on the way to complete theory of disordered superconductors follows the steps in the authors' understanding of disorder and its effect on the quasiparticles in metals. Loosely speaking one can distinguish three such steps. First is the study of weakly disordered systems and this resulted in famous, celebrated Anderson theorem. The second step is ultimately connected with the coherent potential approximation as a method to study the spectrum and transport in concentrated alloys. The discovery of the role of usually neglected interferences between scattered waves in disordered conductors leading to decrease in mobility and increase of the mutual interactions between quantum particles, known as localization and interaction effects has given the new impetus to the theory of superconductivity. This is third step to be discussed in this lecture. The authors limit themselves to homogeneous bulk superconductors. In this paper some experiments on thin films as well as on copper oxides related to the presented theory are briefly mentioned

  19. Flux cutting in superconductors

    International Nuclear Information System (INIS)

    Campbell, A M

    2011-01-01

    This paper describes experiments and theories of flux cutting in superconductors. The use of the flux line picture in free space is discussed. In superconductors cutting can either be by means of flux at an angle to other layers of flux, as in longitudinal current experiments, or due to shearing of the vortex lattice as in grain boundaries in YBCO. Experiments on longitudinal currents can be interpreted in terms of flux rings penetrating axial lines. More physical models of flux cutting are discussed but all predict much larger flux cutting forces than are observed. Also, cutting is occurring at angles between vortices of about one millidegree which is hard to explain. The double critical state model and its developments are discussed in relation to experiments on crossed and rotating fields. A new experiment suggested by Clem gives more direct information. It shows that an elliptical yield surface of the critical state works well, but none of the theoretical proposals for determining the direction of E are universally applicable. It appears that, as soon as any flux flow takes place, cutting also occurs. The conclusion is that new theories are required. (perspective)

  20. Vortex cutting in superconductors

    Science.gov (United States)

    Vlasko-Vlasov, Vitalii K.; Koshelev, Alexei E.; Glatz, Andreas; Welp, Ulrich; Kwok, Wai-K.

    2015-03-01

    Unlike illusive magnetic field lines in vacuum, magnetic vortices in superconductors are real physical strings, which interact with the sample surface, crystal structure defects, and with each other. We address the complex and poorly understood process of vortex cutting via a comprehensive set of magneto-optic experiments which allow us to visualize vortex patterns at magnetization of a nearly twin-free YBCO crystal by crossing magnetic fields of different orientations. We observe a pronounced anisotropy in the flux dynamics under crossing fields and the filamentation of induced supercurrents associated with the staircase vortex structure expected in layered cuprates, flux cutting effects, and angular vortex instabilities predicted for anisotropic superconductors. At some field angles, we find formation of the vortex domains following a type-I phase transition in the vortex state accompanied by an abrupt change in the vortex orientation. To clarify the vortex cutting scenario we performed time-dependent Ginzburg-Landau simulations, which confirmed formation of sharp vortex fronts observed in the experiment and revealed a left-handed helical instability responsible for the rotation of vortices. This work was supported by the U.S. Department of Energy, Office of Science, Materials Sciences and Engineering Division.

  1. Flux Pinning in Superconductors

    CERN Document Server

    Matsushita, Teruo

    2007-01-01

    The book covers the flux pinning mechanisms and properties and the electromagnetic phenomena caused by the flux pinning common for metallic, high-Tc and MgB2 superconductors. The condensation energy interaction known for normal precipitates or grain boundaries and the kinetic energy interaction proposed for artificial Nb pins in Nb-Ti, etc., are introduced for the pinning mechanism. Summation theories to derive the critical current density are discussed in detail. Irreversible magnetization and AC loss caused by the flux pinning are also discussed. The loss originally stems from the ohmic dissipation of normal electrons in the normal core driven by the electric field induced by the flux motion. The readers will learn why the resultant loss is of hysteresis type in spite of such mechanism. The influence of the flux pinning on the vortex phase diagram in high Tc superconductors is discussed, and the dependencies of the irreversibility field are also described on other quantities such as anisotropy of supercondu...

  2. Upper critical and irreversibility fields in Ni- and Co-doped pnictide bulk superconductors

    Science.gov (United States)

    Nikolo, Martin; Singleton, John; Solenov, Dmitry; Jiang, Jianyi; Weiss, Jeremy; Hellstrom, Eric

    2018-05-01

    A comprehensive study of upper critical and irreversibility magnetic fields in Ba(Fe0.95Ni0.05)2As2 (large grain and small grain samples), Ba(Fe0.94Ni0.06)2As2, Ba(Fe0.92Co0.08)2As2, and Ba(Fe0.92Co0.09)2As2 polycrystalline bulk pnictide superconductors was made in pulsed fields of up to 65 T. The full magnetic field-temperature (H-T) phase diagrams, starting at 1.5 K, were measured. The higher temperature, upper critical field Hc2 data are well described by the one-band Werthamer, Helfand, and Hohenberg (WHH) model. At low temperatures, the experimental data depart from the fitted WHH curves, suggesting an emergence of a new phase that could be attributed to the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state. The large values of the Maki fitting parameter α indicate that the Zeeman pair breaking dominates over the orbital pair breaking and spin-paramagnetic pair-breaking effect is significant in these materials. Possible multi-band structure of these materials is lumped into effective parameters of the single-band model. Table of measured physical parameters allows us to compare these pnictide superconductors for different Co- and Ni- doping levels and granularity.

  3. Ac losses of transposed superconductors

    International Nuclear Information System (INIS)

    Eckert, D.; Enderlein, G.; Lange, F.

    1975-01-01

    Eastham and Rhodes published results of loss measurements on transposed superconducting NbTi cables and concluded basing on an extrapolation to very large numbers of wires that transposed superconductors could be used favorably in cables for power transmission. There are some reasons to question the correctness of their extrapolation. Losses were calculated for transposed superconductors in self field and got results different from those of Eastham and Rhodes. Loss measurements were performed the results of which give evidence for the correctness of our calculations. The results lead to the conclusion that the use of transposed cables of irreversible type 2 superconductors for power transmission is not advantageous

  4. Approximate energy correction for particle number summetry breaking in constrained Hartree-Fock plus BCS calculations

    International Nuclear Information System (INIS)

    Redon, N.; Meyer, J.; Meyer, M.

    1989-01-01

    An approximate restoration of the particle number symmetry, a la Lipkin-Nogami, is numerically investigated in the context of Constrained Hartree-Fock plus BCS calculations. Its effect is assessed in a variety of physical situations like potential energy landscapes in transitional nuclei, shape isomerism at low spin and fission barriers of actinide nuclei

  5. Establishing the pharmaceutical quality of Chinese herbal medicine: a provisional BCS classification.

    Science.gov (United States)

    Fong, Sophia Y K; Liu, Mary; Wei, Hai; Löbenberg, Raimar; Kanfer, Isadore; Lee, Vincent H L; Amidon, Gordon L; Zuo, Zhong

    2013-05-06

    The Biopharmaceutical Classification System (BCS), which is a scientific approach to categorize active drug ingredient based on its solubility and intestinal permeability into one of the four classes, has been used to set the pharmaceutical quality standards for drug products in western society. However, it has received little attention in the area of Chinese herbal medicine (CHM). This is likely, in part, due to the presence of multiple active components as well as lack of standardization of CHM. In this report, we apply BCS classification to CHMs provisionally as a basis for establishing improved in vitro quality standards. Based on a top-200 drugs selling list in China, a total of 31 CHM products comprising 50 official active marker compounds (AMCs) were provisionally classified according to BCS. Information on AMC content and doses of these CHM products were retrieved from the Chinese Pharmacopoeia. BCS parameters including solubility and permeability of the AMCs were predicted in silico (ACD/Laboratories). A BCS classification of CHMs according to biopharmaceutical properties of their AMCs is demonstrated to be feasible in the current study and can be used to provide a minimum set of quality standards. Our provisional results showed that 44% of the included AMCs were classified as Class III (high solubility, low permeability), followed by Class II (26%), Class I (18%), and Class IV (12%). A similar trend was observed when CHMs were classified in accordance with the BCS class of AMCs. Most (45%) of the included CHMs were classified as Class III, followed by Class II (16%), Class I (10%), and Class IV (6%); whereas 23% of the CHMs were of mixed class due to the presence of multiple individual AMCs with different BCS classifications. Moreover, about 60% of the AMCs were classified as high-solubility compounds (Class I and Class III), suggesting an important role for an in vitro dissolution test in setting quality control standards ensuring consistent

  6. Quasiparticle current in superconductor-semiconductor-superconductor junctions

    International Nuclear Information System (INIS)

    Tartakovskij, A.V.; Fistul', M.V.

    1988-01-01

    It is shown that the quasiparticle current in a superconductor-semiconductor-superconductor junction may significantly increase as a result of resonant passage of the quasiparticle along particular trajectories from periodically situated localized centers. A prediction of the theory is that with increasing junction resistance there should be a change from an excessive current to a insufficient current on the current-voltage characteristics (at high voltages). The effect of transparency of the boundaries on resonance tunneling in such junctions is also investigated

  7. Superconductor-ferromagnet-superconductor nanojunctions from perovskite materials

    International Nuclear Information System (INIS)

    Štrbík, V.; Beňačka, Š.; Gaži, Š.; Španková, M.; Šmatko, V.; Knoška, J.; Gál, N.; Chromik, Š.; Sojková, M.; Pisarčík, M.

    2017-01-01

    Highlights: • Superconductor-ferromagnet-superconductor nanojunction. • Nanojunctions prepared by Ga"3"+ focused ion beam patterning. • Indication of triplet Cooper pair component in junction superconducting current. • Qualitative agreement with theoretical model. - Abstract: The lateral superconductor-ferromagnet–superconductor (SFS) nanojunctions based on high critical temperature superconductor YBa_2Cu_3O_x (YBCO) and half-metallic ferromagnet La_0_._6_7Sr_0_._3_3MnO_3 (LSMO) thin films were prepared to investigate a possible presence of long range triplet component (LRTC) of Cooper pairs in the LSMO. We applied Ga"3"+ focused ion beam patterning to create YBCO/LSMO/YBCO lateral type nanojunctions with LSMO length as small as 40 nm. The resistivity vs. temperature, critical current density vs. temperature and resistance vs. magnetic field dependence were studied to recognize the LRTC of Cooper pairs in the LSMO. A non-monotonic temperature dependence of junction critical current density and a decrease of the SFS nanojunction resistance in increased magnetic field were observed. Only weak manifestations of LRTC and some qualitative agreement with theory were found out in SFS nanojunctions realized from the perovskite materials. The presence of equal-spin triplet component of Cooper pairs in half-metallic LSMO ferromagnet is not such apparent as in SFS junctions prepared from low temperature superconductors NbTiN and half-metallic ferromagnet CrO_2.

  8. Superconductor-ferromagnet-superconductor nanojunctions from perovskite materials

    Energy Technology Data Exchange (ETDEWEB)

    Štrbík, V., E-mail: vladimir.strbik@savba.sk [Institute of Electrical Engineering, SAS, Dúbravská Cesta 9, Bratislava (Slovakia); Beňačka, Š.; Gaži, Š.; Španková, M.; Šmatko, V. [Institute of Electrical Engineering, SAS, Dúbravská Cesta 9, Bratislava (Slovakia); Knoška, J. [Center for Free-Electron Laser Science, DESY, Notkestraße 85, 22607, Hamburg (Germany); Department of Physics, University of Hamburg, Luruper Chaussee 149, 22607, Hamburg (Germany); Gál, N.; Chromik, Š.; Sojková, M.; Pisarčík, M. [Institute of Electrical Engineering, SAS, Dúbravská Cesta 9, Bratislava (Slovakia)

    2017-02-15

    Highlights: • Superconductor-ferromagnet-superconductor nanojunction. • Nanojunctions prepared by Ga{sup 3+} focused ion beam patterning. • Indication of triplet Cooper pair component in junction superconducting current. • Qualitative agreement with theoretical model. - Abstract: The lateral superconductor-ferromagnet–superconductor (SFS) nanojunctions based on high critical temperature superconductor YBa{sub 2}Cu{sub 3}O{sub x} (YBCO) and half-metallic ferromagnet La{sub 0.67}Sr{sub 0.33}MnO{sub 3} (LSMO) thin films were prepared to investigate a possible presence of long range triplet component (LRTC) of Cooper pairs in the LSMO. We applied Ga{sup 3+} focused ion beam patterning to create YBCO/LSMO/YBCO lateral type nanojunctions with LSMO length as small as 40 nm. The resistivity vs. temperature, critical current density vs. temperature and resistance vs. magnetic field dependence were studied to recognize the LRTC of Cooper pairs in the LSMO. A non-monotonic temperature dependence of junction critical current density and a decrease of the SFS nanojunction resistance in increased magnetic field were observed. Only weak manifestations of LRTC and some qualitative agreement with theory were found out in SFS nanojunctions realized from the perovskite materials. The presence of equal-spin triplet component of Cooper pairs in half-metallic LSMO ferromagnet is not such apparent as in SFS junctions prepared from low temperature superconductors NbTiN and half-metallic ferromagnet CrO{sub 2}.

  9. Preparation of superconductor precursor powders

    Science.gov (United States)

    Bhattacharya, Raghunath

    1998-01-01

    A process for the preparation of a precursor metallic powder composition for use in the subsequent formation of a superconductor. The process comprises the steps of providing an electrodeposition bath comprising an electrolyte medium and a cathode substrate electrode, and providing to the bath one or more soluble salts of one or more respective metals which are capable of exhibiting superconductor properties upon subsequent appropriate treatment. The bath is continually energized to cause the metallic and/or reduced particles formed at the electrode to drop as a powder from the electrode into the bath, and this powder, which is a precursor powder for superconductor production, is recovered from the bath for subsequent treatment. The process permits direct inclusion of all metals in the preparation of the precursor powder, and yields an amorphous product mixed on an atomic scale to thereby impart inherent high reactivity. Superconductors which can be formed from the precursor powder include pellet and powder-in-tube products.

  10. Kinetic equations in dirty superconductors

    International Nuclear Information System (INIS)

    Kraehenbuehl, Y.

    1981-01-01

    Kinetic equations for superconductors in the dirty limit are derived using a method developed for superfluid systems, which allows a systematic expansion in small parameters; exact charge conservation is obeyed. (orig.)

  11. Polymeric conductors and superconductors

    International Nuclear Information System (INIS)

    Goodings, E.P.

    1975-01-01

    The production of electrically conductive polymers which are flexible ans capable of being shaped by normal processes, is discussed. The relation between the structure of the polymer and its ability to transport electric charge is considered. The main problem is to combine high conductivity with good processability and it is shown that stacked-planar systems are superior to conjugated polymers. Good mechanical properties have yet to be achieved. In some way the rigid pi-bonded systems must be combined with a conventional sigma-bonded polymer without destroying its flexibility and tensile properties. The structure will contain a radical ion system to provide charge carriers but it is not yet known how to design the polymer structure to give high carrier mobility. Further work is required on organic superconductors in unravelling the relationship between charge carrier mobility and the supermolecular structure of polymers. (UK)

  12. Superconductor digital electronics

    International Nuclear Information System (INIS)

    Likharev, Konstantin K.

    2012-01-01

    The objective of these notes is to offer a brief review of the history of superconductor digital electronics, and discuss prospects of its future development. Due to length restrictions, many important technical contributions could not be mentioned at all - with sincere apologies to their authors. Though an attempt has been made to give an unbiased review of the most important work all over the world, a special emphasis on the efforts in the former Soviet Union, which had not been discussed much in literature, and in which the author of this text took an active part, seemed excusable. Another important qualification is that the author phased out his own research in the field about 10 years ago, so that the last parts of the notes, devoted to present-time and future work, should be viewed as not much more than remarks by an (interested) outsider.

  13. Manufacturing of Superconductors

    DEFF Research Database (Denmark)

    Bech, Jakob Ilsted; Bay, Niels

    Superconducting tapes based on the ceramic high temperature superconductor (HTS) is a new promising product for high current applications such as electro-magnets and current transmission cables. The tapes are made by the oxide powder in tube (OPIT) method implying drawing and rolling of silver...... tubes containing ceramic powder. The final product is a composite tape, where ceramic superconducting fibres are embedded in a silver matrix. The critical current density Je [kA/cm 2 ] is the primary quality parameter of the product. The quality of the superconducting tape depends very much...... in the individual fibres. · The stresses and strains in the deformation zone are analysed. It is concluded that more detailed mechanical tests and a more detailed constitutive plasticity model is desirable in order to improve the precision of the numerical modelling. New test equipment is designed implying the new...

  14. High temperature superconductor current leads

    International Nuclear Information System (INIS)

    Zeimetz, B.; Liu, H.K.; Dou, S.X.

    1996-01-01

    Full text: The use of superconductors in high electrical current applications (magnets, transformers, generators etc.) usually requires cooling with liquid Helium, which is very expensive. The superconductor itself produces no heat, and the design of Helium dewars is very advanced. Therefore most of the heat loss, i.e. Helium consumption, comes from the current lead which connects the superconductor with its power source at room temperature. The current lead usually consists of a pair of thick copper wires. The discovery of the High Temperature Superconductors makes it possible to replace a part of the copper with superconducting material. This drastically reduces the heat losses because a) the superconductor generates no resistive heat and b) it is a very poor thermal conductor compared with the copper. In this work silver-sheathed superconducting tapes are used as current lead components. The work comprises both the production of the tapes and the overall design of the leads, in order to a) maximize the current capacity ('critical current') of the superconductor, b) minimize the thermal conductivity of the silver clad, and c) optimize the cooling conditions

  15. Hybrid molecule/superconductor assemblies

    International Nuclear Information System (INIS)

    McDevitt, J.T.; Haupt, S.G.; Riley, D.R.; Zhao, J.; Zhou, J.P., Jones, C.

    1993-01-01

    The fabrication of electronic devices from molecular materials has attracted much attention recently. Schottky diodes, molecular transistors, metal-insulator-semiconductor diodes, MIS field effect transistors and light emitting diodes have all been prepared utilizing such substances. The active elements in these devices have been constructed by depositing the molecular phase onto the surface of a metal, semiconductor or insulating substrate. With the recent discovery of high temperature superconductivity, new opportunities now exist for the study of molecule/superconductor interactions as well as for the construction of novel hybrid molecule/superconductor devices. In this paper, methods for preparing the initial two composite molecule/semiconductor devices will be reported. Consequently, light sensors based on dye-coated superconductor junctions as well as molecular switches fashioned from conductive polymer coated superconductor junctions as well as molecular switches fashioned from conductive polymer coated superconductor microbridges will be discussed. Moreover, molecule/superconductor energy and electron transfer phenomena will be illustrated also for the first time

  16. A Multi-Band Body-Worn Distributed Radio-Frequency Exposure Meter: Design, On-Body Calibration and Study of Body Morphology

    Science.gov (United States)

    Thielens, Arno; Agneessens, Sam; Van Torre, Patrick; Van den Bossche, Matthias; Eeftens, Marloes; Huss, Anke; Vermeulen, Roel; de Seze, René; Mazet, Paul; Cardis, Elisabeth; Röösli, Martin; Martens, Luc; Joseph, Wout

    2018-01-01

    A multi-band Body-Worn Distributed exposure Meter (BWDM) calibrated for simultaneous measurement of the incident power density in 11 telecommunication frequency bands, is proposed. The BDWM consists of 22 textile antennas integrated in a garment and is calibrated on six human subjects in an anechoic chamber to assess its measurement uncertainty in terms of 68% confidence interval of the on-body antenna aperture. It is shown that by using multiple antennas in each frequency band, the uncertainty of the BWDM is 22 dB improved with respect to single nodes on the front and back of the torso and variations are decreased to maximum 8.8 dB. Moreover, deploying single antennas for different body morphologies results in a variation up to 9.3 dB, which is reduced to 3.6 dB using multiple antennas for six subjects with various body mass index values. The designed BWDM, has an improved uncertainty of up to 9.6 dB in comparison to commercially available personal exposure meters calibrated on body. As an application, an average incident power density in the range of 26.7–90.8 μW·m−2 is measured in Ghent, Belgium. The measurements show that commercial personal exposure meters underestimate the actual exposure by a factor of up to 20.6. PMID:29346280

  17. Experimental study of coexistence of multi-band OFDM-UWB and OFDM-baseband signals in long-reach PONs using directly modulated lasers.

    Science.gov (United States)

    Morgado, José A P; Fonseca, Daniel; Cartaxo, Adolfo V T

    2011-11-07

    Transmission of coexisting Orthogonal Frequency Division Multiplexing (OFDM)-baseband (BB) and multi-band OFDM-ultra-wideband (UWB) signals along long-reach passive optical networks using directly modulated lasers (DML) is experimentally demonstrated.When optimized modulation indexes are used, bit error ratios not exceeding 5 × 10⁻⁴ can be achieved by all (OFDM-BB and three OFDM-UWB sub-bands) signals for a reach of 100 km of standard single-mode fiber (SSMF) and optical signal-to-noise ratios not lower than 25dB@0.1 nm. It is experimentally shown that, for the SSMF reach of 100km, the optimized performance of coexisting OFDM-BB and OFDM-UWB signals is mainly imposed by the combination of two effects: the SSMF dispersion-induced nonlinear distortion of the OFDM-UWB signals caused by the OFDM-BB and OFDM-UWB signals, and the further degradation of the OFDM-UWB signals with higher frequency, due to the reduced DML bandwidth.

  18. Ultra-Thin Multi-Band Polarization-Insensitive Microwave Metamaterial Absorber Based on Multiple-Order Responses Using a Single Resonator Structure

    Directory of Open Access Journals (Sweden)

    Yong Zhi Cheng

    2017-10-01

    Full Text Available We design an ultra-thin multi-band polarization-insensitive metamaterial absorber (MMA using a single circular sector resonator (CSR structure in the microwave region. Simulated results show that the proposed MMA has three distinctive absorption peaks at 3.35 GHz, 8.65 GHz, and 12.44 GHz, with absorbance of 98.8%, 99.7%, and 98.3%, respectively, which agree well with an experiment. Simulated surface current distributions of the unit-cell structure reveal that the triple-band absorption mainly originates from multiple-harmonic magnetic resonance. The proposed triple-band MMA can remain at a high absorption level for all polarization of both transverse-electric (TE and transverse-magnetic (TM modes under normal incidence. Moreover, by further optimizing the geometric parameters of the CSRs, four-band and five-band MMAs can also be obtained. Thus, our design will have potential application in detection, sensing, and stealth technology.

  19. A multi-band, multi-level, multi-electron model for efficient FDTD simulations of electromagnetic interactions with semiconductor quantum wells

    Science.gov (United States)

    Ravi, Koustuban; Wang, Qian; Ho, Seng-Tiong

    2015-08-01

    We report a new computational model for simulations of electromagnetic interactions with semiconductor quantum well(s) (SQW) in complex electromagnetic geometries using the finite-difference time-domain method. The presented model is based on an approach of spanning a large number of electron transverse momentum states in each SQW sub-band (multi-band) with a small number of discrete multi-electron states (multi-level, multi-electron). This enables accurate and efficient two-dimensional (2-D) and three-dimensional (3-D) simulations of nanophotonic devices with SQW active media. The model includes the following features: (1) Optically induced interband transitions between various SQW conduction and heavy-hole or light-hole sub-bands are considered. (2) Novel intra sub-band and inter sub-band transition terms are derived to thermalize the electron and hole occupational distributions to the correct Fermi-Dirac distributions. (3) The terms in (2) result in an explicit update scheme which circumvents numerically cumbersome iterative procedures. This significantly augments computational efficiency. (4) Explicit update terms to account for carrier leakage to unconfined states are derived, which thermalize the bulk and SQW populations to a common quasi-equilibrium Fermi-Dirac distribution. (5) Auger recombination and intervalence band absorption are included. The model is validated by comparisons to analytic band-filling calculations, simulations of SQW optical gain spectra, and photonic crystal lasers.

  20. A Multi-Band Body-Worn Distributed Radio-Frequency Exposure Meter: Design, On-Body Calibration and Study of Body Morphology

    Directory of Open Access Journals (Sweden)

    Reza Aminzadeh

    2018-01-01

    Full Text Available A multi-band Body-Worn Distributed exposure Meter (BWDM calibrated for simultaneous measurement of the incident power density in 11 telecommunication frequency bands, is proposed. The BDWM consists of 22 textile antennas integrated in a garment and is calibrated on six human subjects in an anechoic chamber to assess its measurement uncertainty in terms of 68% confidence interval of the on-body antenna aperture. It is shown that by using multiple antennas in each frequency band, the uncertainty of the BWDM is 22 dB improved with respect to single nodes on the front and back of the torso and variations are decreased to maximum 8.8 dB. Moreover, deploying single antennas for different body morphologies results in a variation up to 9.3 dB, which is reduced to 3.6 dB using multiple antennas for six subjects with various body mass index values. The designed BWDM, has an improved uncertainty of up to 9.6 dB in comparison to commercially available personal exposure meters calibrated on body. As an application, an average incident power density in the range of 26.7–90.8 μW·m − 2 is measured in Ghent, Belgium. The measurements show that commercial personal exposure meters underestimate the actual exposure by a factor of up to 20.6.

  1. Design and characterization of a low cost CubeSat multi-band optical receiver to map water ice on the lunar surface for the Lunar Flashlight mission

    Science.gov (United States)

    Vinckier, Quentin; Crabtree, Karlton; Paine, Christopher G.; Hayne, Paul O.; Sellar, Glenn R.

    2017-08-01

    Lunar Flashlight is an innovative NASA CubeSat mission dedicated to mapping water ice in the permanently shadowed regions of the Moon, which may act as cold traps for volatiles. To this end, a multi-band reflectometer will be sent to orbit the Moon. This instrument consists of an optical receiver aligned with four lasers, each of which emits sequentially at a different wavelength in the near-infrared between 1 μm and 2 μm. The receiver measures the laser light reflected from the lunar surface; continuum/absorption band ratios are then analyzed to quantify water ice in the illuminated spot. Here, we present the current state of the optical receiver design. To optimize the optical signal-to-noise ratio, we have designed the receiver so as to maximize the laser signal collected, while minimizing the stray light reaching the detector from solarilluminated areas of the lunar surface outside the field-of-view, taking into account the complex lunar topography. Characterization plans are also discussed. This highly mass- and volume-constrained mission will demonstrate several firsts, including being one of the first CubeSats performing science measurements beyond low Earth orbit.

  2. Multi-band emission in a wide wavelength range from tin oxide/Au nanocomposites grown on porous anodic alumina substrate (AAO)

    International Nuclear Information System (INIS)

    Norek, Małgorzata; Michalska-Domańska, Marta; Stępniowski, Wojciech J.; Ayala, Israel; Bombalska, Aneta; Budner, Bogusław

    2013-01-01

    The photoluminescence (PL) properties of tin oxide nanostructures are investigated. Three samples of different morphology, induced by deposition process and various geometrical features of nanoporous anodic aluminum oxide (AAO) substrate, are analyzed. X-ray photoelectronic spectroscopy (XPS) analysis reveals the presence of two forms of tin oxide on the surface of all studied samples: SnO and SnO 2 . The former form is typical for reduced surface with bridging oxygen atoms and every other row of in-plane oxygen atoms removed. The oxygen defects give rise to a strong emission in visible region. Two intense PL peaks are observed centered at about 540 (band I) and 620 (band II) nm. The origin of these bands was ascribed to the recombination of electrons from the conduction band (band I) and shallow traps levels (band II) to the surface oxygen vacancy levels. Upon deposition of Au nanoparticles on the top of tin oxide nanostructures the emission at 540 and 620 nm disappears and a new band (band III) occurs in the range >760 nm. The PL mechanism operating in the studied systems is discussed. The tin oxide/Au nanocomposites can be used as efficient multi-band light emitters in a wide (from visible to near infrared) wavelength range.

  3. Spectral density of Cooper pairs in two level quantum dot–superconductors Josephson junction

    Energy Technology Data Exchange (ETDEWEB)

    Dhyani, A., E-mail: archana.d2003@gmail.com [Department of Physics, University of Petroleum and Energy Studies, Dehradun 248007, Uttarakhand (India); Rawat, P.S. [Department of Nuclear Science and Technology, University of Petroleum and Energy Studies, Dehradun 248007, Uttarakhand (India); Tewari, B.S., E-mail: bstewari@ddn.upes.ac.in [Department of Physics, University of Petroleum and Energy Studies, Dehradun 248007, Uttarakhand (India)

    2016-09-15

    Highlights: • The present work deals with the study of the electronic spectral density of electron pairs and its effect in charge transport in superconductor-quantum dot-superconductor junctions. • The charge transfer across such junctions can be controlled by changing the positions of the dot level. • The Josephson supercurrent can also be tuned by controlling the position of quantum dot energy levels. - Abstract: In the present paper, we report the role of quantum dot energy levels on the electronic spectral density for a two level quantum dot coupled to s-wave superconducting leads. The theoretical arguments in this work are based on the Anderson model so that it necessarily includes dot energies, single particle tunneling and superconducting order parameter for BCS superconductors. The expression for single particle spectral function is obtained by using the Green's function equation of motion technique. On the basis of numerical computation of spectral function of superconducting leads, it has been found that the charge transfer across such junctions can be controlled by the positions and availability of the dot levels.

  4. Modelling of bulk superconductor magnetization

    International Nuclear Information System (INIS)

    Ainslie, M D; Fujishiro, H

    2015-01-01

    This paper presents a topical review of the current state of the art in modelling the magnetization of bulk superconductors, including both (RE)BCO (where RE = rare earth or Y) and MgB 2 materials. Such modelling is a powerful tool to understand the physical mechanisms of their magnetization, to assist in interpretation of experimental results, and to predict the performance of practical bulk superconductor-based devices, which is particularly important as many superconducting applications head towards the commercialization stage of their development in the coming years. In addition to the analytical and numerical techniques currently used by researchers for modelling such materials, the commonly used practical techniques to magnetize bulk superconductors are summarized with a particular focus on pulsed field magnetization (PFM), which is promising as a compact, mobile and relatively inexpensive magnetizing technique. A number of numerical models developed to analyse the issues related to PFM and optimise the technique are described in detail, including understanding the dynamics of the magnetic flux penetration and the influence of material inhomogeneities, thermal properties, pulse duration, magnitude and shape, and the shape of the magnetization coil(s). The effect of externally applied magnetic fields in different configurations on the attenuation of the trapped field is also discussed. A number of novel and hybrid bulk superconductor structures are described, including improved thermal conductivity structures and ferromagnet–superconductor structures, which have been designed to overcome some of the issues related to bulk superconductors and their magnetization and enhance the intrinsic properties of bulk superconductors acting as trapped field magnets. Finally, the use of hollow bulk cylinders/tubes for shielding is analysed. (topical review)

  5. Flux-induced Nernst effect in low-dimensional superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Berger, Jorge, E-mail: jorge.berger@braude.ac.il

    2017-02-15

    Highlights: • The Nernst effect tells us that the presence of a magnetic field and a temperature gradient in a conductor yields a transverse voltage. • The Nernst effect in superconductors, especially above their critical temperature, has been a hot topic of research during the last decades. • I predict a new effect in which a transverse voltage arises, not because of the magnetic field, but rather because of the magnetic flux enclosed by a loop with non-uniform temperature. - Abstract: A method is available that enables consistent study of the stochastic behavior of a system that obeys purely diffusive evolution equations. This method has been applied to a superconducting loop with nonuniform temperature, with average temperature close to T{sub c}. It is found that a flux-dependent average potential difference arises along the loop, proportional to the temperature gradient and most pronounced in the direction perpendicular to this gradient. The largest voltages were obtained for fluxes close to 0.3Φ{sub 0}, average temperatures slightly below the critical temperature, thermal coherence length of the order of the perimeter of the ring, BCS coherence length that is not negligible in comparison to the thermal coherence length, and short inelastic scattering time. This effect is entirely due to thermal fluctuations. It differs essentially from the usual Nernst effect in bulk superconductors, that is induced by magnetic field rather than by magnetic flux. We also study the effect of confinement in a 2D mesoscopic film.

  6. Coincident photoelectron spectroscopy on superconductors; Koinzidente Photoelektronenspektroskopie an Supraleitern

    Energy Technology Data Exchange (ETDEWEB)

    Voss, Stefan

    2011-07-01

    Aim of the performed experiments of this thesis was to attempt to detect Cooper pairs as carriers of the superconducting current directly by means of the photoelectric effect. The method of the coincident photoelectron spectroscopy aims thereby at the detection of two coherently emitted electrons by the interaction with a photon. Because electrostatic analyzers typically cover only a very small spatial angle, which goes along with very low coincidence rates, in connection with this thesis a time-of-flight projection system has been developed, which maps nearly the whole spatial angle on a position-resolving detector. The pulsed light source in form of special synchrotron radiation necessary for the measurement has been adjusted so weak, that only single photons could arrive at the sample. Spectroscoped were beside test measurements on silver layers both a lead monocrystal as representative of the classical BCS superconductors and monocrystalline Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8} from the family of the high-temperature superconductors. With excitation energies up to 40 eV could be shown that sufficiently smooth and clean surfaces in the superconducting phase exhibit within the resolving power of about 0.5 eV no recognizable differences in comparison to the normally conducting phase. Beside these studies furthermore the simple photoemission at the different samples and especially in the case of the lead crystal is treated, because here no comparable results are known. Thereby the whole momentum space is discussed and the Fermi surface established as three-dimensional model, by means of which the measurement results are discussed. in the theoretical descriptions different models for the Cooper-pair production are presented, whereby to the momentum exchange with the crystal a special role is attributed, because this can only occur in direct excitations via discrete lattice vectors.

  7. Influence of the projection of BCS functions on the M1 and E2 transitions in rare earths

    International Nuclear Information System (INIS)

    Fellah, M.; Hammann, T.F.

    1975-01-01

    E2 and M1 transition probabilities for odd-mass rare earth nuclei, have been calculated using both the usual BCS wave functions and the strict particle conserving, projected BCS functions. The blocking effect has been exactly and systematically taken into account. The influence of the Coriolis interaction has been studied using the first order perturbation theory. Allowance has been made for the β and γ vibrations. The unphysical effects, due to particle fluctuation in the BCS theory, are not always negligible, but are in most cases, less important than the Coriolis effect [fr

  8. RMF+BCS description of N = 32 and N = 34 shell closure

    International Nuclear Information System (INIS)

    Saxena, G.; Kumawat, M.; Singh, U.K.; Jain, S.K.; Aggarwal, Mamta; Kaushik, M.; Singh, S. Somorendro

    2017-01-01

    We have employed RMF+BCS (relativistic mean-field plus BCS) approach to study N = 32 and N = 34 shell closure with the help of ground state properties of even-even nuclei. Our present investigations include single particle energies, deformations, separation energies as well as neutron and proton densities etc. Encouraged by the recent experiments showing neutron magicity at N = 32 for Ca isotopes, we have applied RMF theory with delta function pairing along with mass dependency (1/A) for full chain of N = 32 and N = 34 isotones upto drip lines. This study predicts new doubly magic nuclei specially 48 Si which is in the same mass region in 52 Ca as the recent experiments observed

  9. Response Functions for the Two-Dimensional Ultracold Fermi Gas: Dynamical BCS Theory and Beyond

    Science.gov (United States)

    Vitali, Ettore; Shi, Hao; Qin, Mingpu; Zhang, Shiwei

    2017-12-01

    Response functions are central objects in physics. They provide crucial information about the behavior of physical systems, and they can be directly compared with scattering experiments involving particles such as neutrons or photons. Calculations of such functions starting from the many-body Hamiltonian of a physical system are challenging and extremely valuable. In this paper, we focus on the two-dimensional (2D) ultracold Fermi atomic gas which has been realized experimentally. We present an application of the dynamical BCS theory to obtain response functions for different regimes of interaction strengths in the 2D gas with zero-range attractive interaction. We also discuss auxiliary-field quantum Monte Carlo (AFQMC) methods for the calculation of imaginary time correlations in these dilute Fermi gas systems. Illustrative results are given and comparisons are made between AFQMC and dynamical BCS theory results to assess the accuracy of the latter.

  10. Phase diagram of dilute nuclear matter: Unconventional pairing and the BCS-BEC crossover

    Energy Technology Data Exchange (ETDEWEB)

    Stein, Martin; Sedrakian, Armen [Frankfurt Univ. (Germany). Inst. fuer Theoretische Physik

    2013-07-01

    We report on a comprehensive study of the phase structure of cold, dilute nuclear matter featuring a {sup 3}S{sub 1}-{sup 3}D{sub 1} condensate at non-zero isospin asymmetry, within wide ranges of temperatures and densities. We find a rich phase diagram comprising three superfluid phases, namely a LOFF phase, the ordinary BCS phase, and a heterogeneous, phase-separated BCS phase, with associated crossovers from the latter two phases to a homogeneous or phase-separated Bose-Einstein condensate of deuterons. The phase diagram contains two tri-critical points (one a Lifshitz point), which may degenerate into a single tetra-critical point for some degree of isospin asymmetry.

  11. The BCS-BEC crossover: From ultra-cold Fermi gases to nuclear systems

    Science.gov (United States)

    Strinati, Giancarlo Calvanese; Pieri, Pierbiagio; Röpke, Gerd; Schuck, Peter; Urban, Michael

    2018-04-01

    This report addresses topics and questions of common interest in the fields of ultra-cold gases and nuclear physics in the context of the BCS-BEC crossover. By this crossover, the phenomena of Bardeen-Cooper-Schrieffer (BCS) superfluidity and Bose-Einstein condensation (BEC), which share the same kind of spontaneous symmetry breaking, are smoothly connected through the progressive reduction of the size of the fermion pairs involved as the fundamental entities in both phenomena. This size ranges, from large values when Cooper pairs are strongly overlapping in the BCS limit of a weak inter-particle attraction, to small values when composite bosons are non-overlapping in the BEC limit of a strong inter-particle attraction, across the intermediate unitarity limit where the size of the pairs is comparable with the average inter-particle distance. The BCS-BEC crossover has recently been realized experimentally, and essentially in all of its aspects, with ultra-cold Fermi gases. This realization, in turn, has raised the interest of the nuclear physics community in the crossover problem, since it represents an unprecedented tool to test fundamental and unanswered questions of nuclear many-body theory. Here, we focus on the several aspects of the BCS-BEC crossover, which are of broad joint interest to both ultra-cold Fermi gases and nuclear matter, and which will likely help to solve in the future some open problems in nuclear physics (concerning, for instance, neutron stars). Similarities and differences occurring in ultra-cold Fermi gases and nuclear matter will then be emphasized, not only about the relative phenomenologies but also about the theoretical approaches to be used in the two contexts. Common to both contexts is the fact that at zero temperature the BCS-BEC crossover can be described at the mean-field level with reasonable accuracy. At finite temperature, on the other hand, inclusion of pairing fluctuations beyond mean field represents an essential ingredient

  12. Development of HANARO human factors management plan and evaluation of BCS display

    International Nuclear Information System (INIS)

    Oh, I. S.; Lee, J. W.; Lee, Y. H.

    2004-01-01

    In this study, human factors evaluation of BCS display design was performed. We adopted the suitability of design elements of BCS display as human factors evaluation measure. And, we also adopted guideline based evaluation, field survey and expert evaluation as evaluation method. The checklist was utilized for the evaluation, and the results of evaluation were well arranged in the evaluation format. We did not find out the HED (Human Engineering Discrepancy) impede safety of HANARO, except some necessary items to improve during short periods. We also provide some items of improvement for the enhancement of safety and operator's performance in the aspect of long periods. If the proposed improvement items were completely fulfilled, the more improved safety of HANARO will be secured

  13. Dynamical description of the fission process using the TD-BCS theory

    Energy Technology Data Exchange (ETDEWEB)

    Scamps, Guillaume, E-mail: scamps@nucl.phys.tohoku.ac.jp [Department of Physics, Tohoku University, Sendai 980-8578 (Japan); Simenel, Cédric [Department of Nuclear Physics, Research School of Physics and Engineering Australian National University, Canberra, Australian Capital Territory 2601 (Australia); Lacroix, Denis [Institut de Physique Nucléaire, IN2P3-CNRS, Université Paris-Sud, F-91406 Orsay Cedex (France)

    2015-10-15

    The description of fission remains a challenge for nuclear microscopic theories. The time-dependent Hartree-Fock approach with BCS pairing is applied to study the last stage of the fission process. A good agreement is found for the one-body observables: the total kinetic energy and the average mass asymmetry. The non-physical dependence of two-body observables with the initial shape is discussed.

  14. Crossover from BCS to composite boson (local pair) superconductivity in quasi-2D systems

    International Nuclear Information System (INIS)

    Gorbar, E.V.; Loktev, V.M.; Sharapov, S.G.

    1995-01-01

    The crossover from cooperative Cooper pairing to independent bound state (composite bosons) formation and condensation in quasi-2 D systems is studied. It is shown that at low carrier density the critical superconducting temperature is equal to the temperature of Bose-condensation of ideal quasi-2 D Bose-gas with heavy dynamical mass, meanwhile at high densities the BCS result remains valid. 15 refs

  15. Ferromagnet / superconductor oxide superlattices

    Science.gov (United States)

    Santamaria, Jacobo

    2006-03-01

    The growth of heterostructures combining oxide materials is a new strategy to design novel artificial multifunctional materials with interesting behaviors ruled by the interface. With the (re)discovery of colossal magnetoresistance (CMR) materials, there has been renewed interest in heterostructures involving oxide superconductors and CMR ferromagnets where ferromagnetism (F) and superconductivity (S) compete within nanometric distances from the interface. In F/S/F structures involving oxides, interfaces are especially complex and various factors like interface disorder and roughness, epitaxial strain, polarity mismatch etc., are responsible for depressed magnetic and superconducting properties at the interface over nanometer length scales. In this talk I will focus in F/S/F structures made of YBa2Cu3O7 (YBCO) and La0.7Ca0.3MnO3 (LCMO). The high degree of spin polarization of the LCMO conduction band, together with the d-wave superconductivity of the YBCO make this F/S system an adequate candidate for the search of novel spin dependent effects in transport. We show that superconductivity at the interface is depressed by various factors like charge transfer, spin injection or ferromagnetic superconducting proximity effect. I will present experiments to examine the characteristic distances of the various mechanisms of superconductivity depression. In particular, I will discuss that the critical temperature of the superconductor depends on the relative orientation of the magnetization of the F layers, giving rise to a new giant magnetoresistance effect which might be of interest for spintronic applications. Work done in collaboration with V. Peña^1, Z. Sefrioui^1, J. Garcia-Barriocanal^1, C. Visani^1, D. Arias^1, C. Leon^1 , N. Nemes^2, M. Garcia Hernandez^2, S. G. E. te Velthuis^3, A. Hoffmann^3, M. Varela^4, S. J. Pennycook^4. Work supported by MCYT MAT 2005-06024, CAM GR- MAT-0771/2004, UCM PR3/04-12399 Work at Argonne supported by the Department of Energy, Basic

  16. Topological Insulators and Superconductors for Innovative Devices

    Science.gov (United States)

    2015-03-20

    Final 3. DATES COVERED (From - To) 20120321 - 20150320 4. TITLE AND SUBTITLE Topological insulators and superconductors for innovative...locking, which hold promise for various innovative devices. Similarly, topological superconductors are associated with exotic surface states, which...298 (Rev. 8/98) Prescribed by ANSI Std. Z39.18 Final Report Title: Topological Insulators and Superconductors for Innovative Devices

  17. Detecting the BCS pairing amplitude via a sudden lattice ramp in a honeycomb lattice

    Science.gov (United States)

    Tiesinga, Eite; Nuske, Marlon; Mathey, Ludwig

    2016-05-01

    We determine the exact time evolution of an initial Bardeen-Cooper-Schrieffer (BCS) state of ultra-cold atoms in a hexagonal optical lattice. The dynamical evolution is triggered by ramping the lattice potential up, such that the interaction strength Uf is much larger than the hopping amplitude Jf. The quench initiates collective oscillations with frequency | Uf | /(2 π) in the momentum occupation numbers and imprints an oscillating phase with the same frequency on the order parameter Δ. The latter is not reproduced by treating the time evolution in mean-field theory. The momentum density-density or noise correlation functions oscillate at frequency | Uf | /(2 π) as well as its second harmonic. For a very deep lattice, with negligible tunneling energy, the oscillations of momentum occupation numbers are undamped. Non-zero tunneling after the quench leads to dephasing of the different momentum modes and a subsequent damping of the oscillations. This occurs even for a finite-temperature initial BCS state, but not for a non-interacting Fermi gas. We therefore propose to use this dephasing to detect a BCS state. Finally, we predict that the noise correlation functions in a honeycomb lattice will develop strong anti-correlations near the Dirac point. We acknowledge funding from the National Science Foundation.

  18. Temperature dependence of differential conductance in Co-based Heusler alloy Co2TiSn and superconductor Pb junctions

    Science.gov (United States)

    Ooka, Ryutaro; Shigeta, Iduru; Umetsu, Rie Y.; Nomura, Akiko; Yubuta, Kunio; Yamauchi, Touru; Kanomata, Takeshi; Hiroi, Masahiko

    2018-05-01

    We investigated temperature dependence of differential conductance G (V) in planar junctions consisting of Co-based Heusler alloy Co2TiSn and superconductor Pb. Ferromagnetic Co2TiSn was predicted to be half-metal by first-principles band calculations. The spin polarization P of Co2TiSn was deduced to be 60.0% at 1.4 K by the Andreev reflection spectroscopy. The G (V) spectral shape was smeared gradually with increasing temperature and its structure was disappeared above the superconducting transition temperature Tc. Theoretical model analysis revealed that the superconducting energy gap Δ was 1.06 meV at 1.4 K and the Tc was 6.8 K , indicating that both values were suppressed from bulk values. However, the temperature dependent Δ (T) behavior was in good agreement with that of the Bardeen-Cooper-Schrieffer (BCS) theory. The experimental results exhibit that the superconductivity of Pb attached to half-metallic Co2TiSn was kept the conventional BCS mechanism characterized strong-coupling superconductors while its superconductivity was slightly suppressed by the superconducting proximity effect at the Co2TiSn/Pb interface.

  19. Superconductors: The long road ahead

    International Nuclear Information System (INIS)

    Foner, S.; Orlando, T.P.

    1988-01-01

    Before the discovery of high-temperature superconductors, progress in superconductivity was measured by quite small increases in critical temperature, often of less than one degree. Today, there is no reason to believe that the dramatic leaps in critical temperature inaugurated by superconducting ceramics are over. Researchers may find new high-temperature superconducting materials with less severe technical limitations than the ceramics we know today. And if the day ever comes when a superconductor can be reliably manufactured to operate effectively at room temperature, then superconductors will be incorporated in a broad range of everyday household devices - motors, appliances, even children's toys - with a large consumer market. High-temperature superconductors may also cause us to extensively revise our traditional theories about how superconductivity works. Should it run out that superconductivity in ceramics involves new physical mechanisms, then these mechanisms could lead to applications never considered before. The recent discoveries have already reinvigorated superconductivity research. What was once largely the domain of a relatively small group of scientists has become a genuinely multidisciplinary realm. Now physicists, materials scientists, chemists, metallurgists, ceramists, and solid-state electronics engineers are all focusing on superconductivity. The cross-fertilization of these disciplines should contribute to further discoveries of importance to the practical application of superconductors

  20. Dual-polarization multi-band optical OFDM transmission and transceiver limitations for up to 500 Gb/s uncompensated long-haul links.

    Science.gov (United States)

    Giacoumidis, E; Jarajreh, M A; Sygletos, S; Le, S T; Farjady, F; Tsokanos, A; Hamié, A; Pincemin, E; Jaouën, Y; Ellis, A D; Doran, N J

    2014-05-05

    A number of critical issues for dual-polarization single- and multi-band optical orthogonal-frequency division multiplexing (DP-SB/MB-OFDM) signals are analyzed in dispersion compensation fiber (DCF)-free long-haul links. For the first time, different DP crosstalk removal techniques are compared, the maximum transmission-reach is investigated, and the impact of subcarrier number and high-level modulation formats are explored thoroughly. It is shown, for a bit-error-rate (BER) of 10(-3), 2000 km of quaternary phase-shift keying (QPSK) DP-MB-OFDM transmission is feasible. At high launched optical powers (LOP), maximum-likelihood decoding can extend the LOP of 40 Gb/s QPSK DP-SB-OFDM at 2000 km by 1.5 dB compared to zero-forcing. For a 100 Gb/s DP-MB-OFDM system, a high number of subcarriers contribute to improved BER but at the cost of digital signal processing computational complexity, whilst by adapting the cyclic prefix length the BER can be improved for a low number of subcarriers. In addition, when 16-quadrature amplitude modulation (16QAM) is employed the digital-to-analogue/analogue-to-digital converter (DAC/ADC) bandwidth is relaxed with a degraded BER; while the 'circular' 8QAM is slightly superior to its 'rectangular' form. Finally, the transmission of wavelength-division multiplexing DP-MB-OFDM and single-carrier DP-QPSK is experimentally compared for up to 500 Gb/s showing great potential and similar performance at 1000 km DCF-free G.652 line.

  1. Multi-band high resolution spectroscopy rules out the hot Jupiter BD+20 1790b. First data from the GIARPS Commissioning

    Science.gov (United States)

    Carleo, I.; Benatti, S.; Lanza, A. F.; Gratton, R.; Claudi, R.; Desidera, S.; Mace, G. N.; Messina, S.; Sanna, N.; Sissa, E.; Ghedina, A.; Ghinassi, F.; Guerra, J.; Harutyunyan, A.; Micela, G.; Molinari, E.; Oliva, E.; Tozzi, A.; Baffa, C.; Baruffolo, A.; Bignamini, A.; Buchschacher, N.; Cecconi, M.; Cosentino, R.; Endl, M.; Falcini, G.; Fantinel, D.; Fini, L.; Fugazza, D.; Galli, A.; Giani, E.; González, C.; González-Álvarez, E.; González, M.; Hernandez, N.; Hernandez Diaz, M.; Iuzzolino, M.; Kaplan, K. F.; Kidder, B. T.; Lodi, M.; Malavolta, L.; Maldonado, J.; Origlia, L.; Ventura, H. Perez; Puglisi, A.; Rainer, M.; Riverol, L.; Riverol, C.; San Juan, J.; Scuderi, S.; Seemann, U.; Sokal, K. R.; Sozzetti, A.; Sozzi, M.

    2018-05-01

    Context. Stellar activity is currently challenging the detection of young planets via the radial velocity (RV) technique. Aims: We attempt to definitively discriminate the nature of the RV variations for the young active K5 star BD+20 1790, for which visible (VIS) RV measurements show divergent results on the existence of a substellar companion. Methods: We compare VIS data with high precision RVs in the near-infrared (NIR) range by using the GIANO-B and IGRINS spectrographs. In addition, we present for the first time simultaneous VIS-NIR observations obtained with GIARPS (GIANO-B and HARPS-N) at Telescopio Nazionale Galileo (TNG). Orbital RVs are achromatic, so the RV amplitude does not change at different wavelengths, while stellar activity induces wavelength-dependent RV variations, which are significantly reduced in the NIR range with respect to the VIS. Results: The NIR radial velocity measurements from GIANO-B and IGRINS show an average amplitude of about one quarter with respect to previously published VIS data, as expected when the RV jitter is due to stellar activity. Coeval multi-band photometry surprisingly shows larger amplitudes in the NIR range, explainable with a mixture of cool and hot spots in the same active region. Conclusions: In this work, the claimed massive planet around BD+20 1790 is ruled out by our data. We exploited the crucial role of multi-wavelength spectroscopy when observing young active stars: thanks to facilities like GIARPS that provide simultaneous observations, this method can reach its maximum potential.

  2. A Multi-Band Analytical Algorithm for Deriving Absorption and Backscattering Coefficients from Remote-Sensing Reflectance of Optically Deep Waters

    Science.gov (United States)

    Lee, Zhong-Ping; Carder, Kendall L.

    2001-01-01

    A multi-band analytical (MBA) algorithm is developed to retrieve absorption and backscattering coefficients for optically deep waters, which can be applied to data from past and current satellite sensors, as well as data from hyperspectral sensors. This MBA algorithm applies a remote-sensing reflectance model derived from the Radiative Transfer Equation, and values of absorption and backscattering coefficients are analytically calculated from values of remote-sensing reflectance. There are only limited empirical relationships involved in the algorithm, which implies that this MBA algorithm could be applied to a wide dynamic range of waters. Applying the algorithm to a simulated non-"Case 1" data set, which has no relation to the development of the algorithm, the percentage error for the total absorption coefficient at 440 nm a (sub 440) is approximately 12% for a range of 0.012 - 2.1 per meter (approximately 6% for a (sub 440) less than approximately 0.3 per meter), while a traditional band-ratio approach returns a percentage error of approximately 30%. Applying it to a field data set ranging from 0.025 to 2.0 per meter, the result for a (sub 440) is very close to that using a full spectrum optimization technique (9.6% difference). Compared to the optimization approach, the MBA algorithm cuts the computation time dramatically with only a small sacrifice in accuracy, making it suitable for processing large data sets such as satellite images. Significant improvements over empirical algorithms have also been achieved in retrieving the optical properties of optically deep waters.

  3. MODELING THE MULTI-BAND AFTERGLOW OF GRB 130831A: EVIDENCE FOR A SPINNING-DOWN MAGNETAR DOMINATED BY GRAVITATIONAL WAVE LOSSES?

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Q.; Zong, H. S. [School of Physics, Nanjing University, Nanjing 210093 (China); Huang, Y. F., E-mail: zonghs@nju.edu.cn, E-mail: hyf@nju.edu.cn [School of Astronomy and Space Science, Nanjing University, Nanjing 210093 (China)

    2016-06-01

    The X-ray afterglow of GRB 130831A shows an “internal plateau” with a decay slope of ∼0.8, followed by a steep drop at around 10{sup 5} s with a slope of ∼6. After the drop, the X-ray afterglow continues with a much shallower decay. The optical afterglow exhibits two segments of plateaus separated by a luminous optical flare, followed by a normal decay with a slope basically consistent with that of the late-time X-ray afterglow. The decay of the internal X-ray plateau is much steeper than what we expect in the simplest magnetar model. We propose a scenario in which the magnetar undergoes gravitational-wave-driven r-mode instability, and the spin-down is dominated by gravitational wave losses up to the end of the steep plateau, so that such a relatively steep plateau can be interpreted as the internal emission of the magnetar wind and the sharp drop can be produced when the magnetar collapses into a black hole. This scenario also predicts an initial X-ray plateau lasting for hundreds of seconds with an approximately constant flux which is compatible with observation. Assuming that the magnetar wind has a negligible contribution in the optical band, we interpret the optical afterglow as the forward shock emission by invoking the energy injection from a continuously refreshed shock following the prompt emission phase. It is shown that our model can basically describe the temporal evolution of the multi-band afterglow of GRB 130831A.

  4. On the limits of consistency of Eliashberg theory and the density of states of high-Tc superconductors

    International Nuclear Information System (INIS)

    Varelogiannis, G.

    1997-01-01

    We make a detailed study of the Eliashberg theory in the coupling region where some fundamental qualitative deviations from the conventional BCS- like behavior begin to appear. These deviations are identified as the onset of a cross-over from BCS superconductivity to Bose condensation. We point out that the beginning of this cross-over occurs when the gap Δ g becomes comparable to the boson energies Ω ph . This condition traduces the physical constraint that the distance the paired electron covers during the absorption of the virtual boson, cannot be larger than the coherence length. The frontier region of couplings is of the order of λ∼3, and high-T c , materials are concerned. A clear qualitative indication of the occurrence of a cross-over regime should be a dip structure above the gap in the density of states of excitations, and this is one of the most robust characteristics of the high-T c , superconducting state. Comparing our results with tunneling and photoemission experiments we conclude that high-T c materials (cuprates and fullerides) are indeed at the beginning of a cross-over from BCS superconductivity to Bose condensation, even though the fermionic nature still prevails. If the Uemura plot is relevant, then the dip should also be present in the other materials that are close to the cross-over regime like heavy Fermion and organic superconductors. In all these materials Ginzburg Landau equations are irrelevant. (orig.)

  5. Thermodynamics of many-band superconductors

    International Nuclear Information System (INIS)

    Waelte, A.

    2006-01-01

    In the present thesis the microscopical properties of the superconducting state of MgCNi 3 , MgB 2 , and some rare earth-transition metal borocarbides are studied by means of measurements of the specific heat. Furthermore the frequency spectrum of the lattice vibrations is estimated. The energy gap of the superconducting state can be determined from the specific heat of the superconducting state, which yields as like as the upper critical mafnetic field H c2 (0) hints on the electron-phonon coupling. From the analysis of these results and the comparison with results from transport measurements as well as the tunnel and point-contact spectroscopy can be concluded, how far the BCS model of superconductivity must be modified in order to be able to describe the superconducting state of the studied compounds. Studies on MgCNi 3 , which lies near a magnetic instability, show that occurring magnetic fluctuations have a bisection of the superconducting transition temperature T C as consequence. The under this aspect relatively high value of T C =7 K is a consequence of strong electron-phonon coupling, which is essentailly carried by nickel vibrations stabilized by carbon. A for the first time observed distinct anomaly in the specific heat of the classical many-band superconductor MgB 2 (here with pure 10 B) at about T c /4=10 K can be understood by means of a two-band model for the case of especially weak coupling between both bands. The analysis of the specific heat of the superconducting phase of the non-magnetic rare earth-nickel borocarbide YNi 2 B 2 C and LuNi 2 B 2 C leads to the conclusion thet visible effects of the many-band electron system are dependent on the mass on the position both of the rare earth and the transition metal. The signal of the superconducting phase transformation visible in the specific heat of the antiferromagnetic HoNi 2 B 2 C is smaller than expected

  6. Studies on ceramic superconductors

    International Nuclear Information System (INIS)

    Chaklader, A.C.D.; Roemer, G.; Hardy, W.N.; Brewer, J.H.; Carolan, J.F.; Parsons, R.R.

    1987-01-01

    The superconducting properties of both bulk specimens and sputtered thin films of the YBa 2 Cu 3 O x compound have been studied. The bulk specimens were fabricated by cold pressing and sintering, and also by hot-pressing (subsequent reheating). The dc resistivity measurements showed a sharp drop in the temperature range 92-87K in this material. Muon spin relaxation (μSR) measurements of sintered discs in 3.4 kOe revealed the formation of a mixed state with an effective magnetic penetration depth λ ∼ 1365 angstrom at 6K, implying an effective charge carrier density of 6 x 10 21 cm -3 . The temperature dependence λ(T) is that of an ordinary s-wave superconductor. The resistivity of the thin film prepared from the compound by dc planar magnetron sputtering, showed a sharp drop to a very low value near 80K. The compound YBa 2 Cu 3 O x loses its superconducting properties, when either hot-pressed (in air) or oxidized at 500 degree C in high O 2 pressure, but this property can be restored when reheated in one atmosphere of O 2 above 900 degree C

  7. Experimental comparison of simultaneous transmission of LTE-A multi-band and gigabit/s 4-PAM signals up to 50 m of large-core graded-index POF

    NARCIS (Netherlands)

    Forni, F.; Shi, Y.; Van Den Boom, H.P.A.; Tangdiongga, E.; Koonen, A.M.J.

    2016-01-01

    This paper reports the experimental results of the co-transmission of a multi-band LTE-A and gigabit/s baseband 4-PAM signals over 35 m and over 50 m of 1 mm core diameter PMMA GI-POF, using low-cost components. Both links used a red light 650nm laser diode and p-i-n photodiode with transimpedance

  8. Enhancement of crystallinity of cellulose produced by Escherichia coli through heterologous expression of bcsD gene from Gluconacetobacter xylinus.

    Science.gov (United States)

    Sajadi, Elaheh; Babaipour, Valiollah; Deldar, Ali Asghar; Yakhchali, Bagher; Fatemi, Seyed Safa-Ali

    2017-09-01

    To evaluate the crystallinity index of the cellulose produced by Escherichia coli Nissle 1917 after heterologous expression of the cellulose synthase subunit D (bcsD) gene of Gluconacetobacter xylinus BPR2001. The bcsD gene of G. xylinus BPR2001 was expressed in E. coli and its protein product was visualized using SDS-PAGE. FTIR analysis showed that the crystallinity index of the cellulose produced by the recombinants was 0.84, which is 17% more than that of the wild type strain. The increased crystallinity index was also confirmed by X-ray diffraction analysis. The cellulose content was not changed significantly after over-expressing the bcsD. The bcsD gene can improve the crystalline structure of the bacterial cellulose but there is not any significant difference between the amounts of cellulose produced by the recombinant and wild type E. coli Nissle 1917.

  9. Edge instabilities of topological superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Hofmann, Johannes S. [Institut fuer Theoretische Physik und Astrophysik, Universitaet Wuerzburg (Germany); Max-Planck-Institut fuer Festkoerperforschung, Stuttgart (Germany); Assaad, Fakher F. [Institut fuer Theoretische Physik und Astrophysik, Universitaet Wuerzburg (Germany); Schnyder, Andreas P. [Max-Planck-Institut fuer Festkoerperforschung, Stuttgart (Germany)

    2016-07-01

    Nodal topological superconductors display zero-energy Majorana flat bands at generic edges. The flatness of these edge bands, which is protected by time-reversal and translation symmetry, gives rise to an extensive ground state degeneracy and a diverging density of states. Therefore, even arbitrarily weak interactions lead to an instability of the flat-band edge states towards time-reversal and translation-symmetry broken phases, which lift the ground-state degeneracy. Here, we employ Monte Carlo simulations combined with mean-field considerations to examine the instabilities of the flat-band edge states of d{sub xy}-wave superconductors. We find that attractive interactions induce a complex s-wave pairing instability together with a density wave instability. Repulsive interactions, on the other hand, lead to ferromagnetism mixed with spin-triplet pairing at the edge. We discuss the implications of our findings for experiments on cuprate high-temperature superconductors.

  10. Superconductor stability, 1983: a review

    International Nuclear Information System (INIS)

    Dresner, L.

    1983-01-01

    Three main topics have been discussed in this paper, namely, internally cooled superconductors, cooling by superfluid helium, and metastable magnets. The discussion of each has centered around a dominant idea, and it is fitting to highlight these ideas by way of conclusion. With regard to internally cooled superconductors, most of what we have learned in the last few years centers on the strong motion caused by the thermal expansion of helium. How naive were our early calculations that treated the helium as though it were incompressible. Our discussion of He-II was organized around the Gorter-Mellink relation and the solutions of the nonlinear diffusion equation it gives rise to. And our discussion of metastable magnets revolved around the fruitful concept of the MPZ. These three ideas are sturdy trunks that support much of the thought about superconductor stability that has flowered in the past several years

  11. Topological insulators and topological superconductors

    CERN Document Server

    Bernevig, Andrei B

    2013-01-01

    This graduate-level textbook is the first pedagogical synthesis of the field of topological insulators and superconductors, one of the most exciting areas of research in condensed matter physics. Presenting the latest developments, while providing all the calculations necessary for a self-contained and complete description of the discipline, it is ideal for graduate students and researchers preparing to work in this area, and it will be an essential reference both within and outside the classroom. The book begins with simple concepts such as Berry phases, Dirac fermions, Hall conductance and its link to topology, and the Hofstadter problem of lattice electrons in a magnetic field. It moves on to explain topological phases of matter such as Chern insulators, two- and three-dimensional topological insulators, and Majorana p-wave wires. Additionally, the book covers zero modes on vortices in topological superconductors, time-reversal topological superconductors, and topological responses/field theory and topolo...

  12. Topological surface states in nodal superconductors.

    Science.gov (United States)

    Schnyder, Andreas P; Brydon, Philip M R

    2015-06-24

    Topological superconductors have become a subject of intense research due to their potential use for technical applications in device fabrication and quantum information. Besides fully gapped superconductors, unconventional superconductors with point or line nodes in their order parameter can also exhibit nontrivial topological characteristics. This article reviews recent progress in the theoretical understanding of nodal topological superconductors, with a focus on Weyl and noncentrosymmetric superconductors and their protected surface states. Using selected examples, we review the bulk topological properties of these systems, study different types of topological surface states, and examine their unusual properties. Furthermore, we survey some candidate materials for topological superconductivity and discuss different experimental signatures of topological surface states.

  13. Oxygen diffusion in cuprate superconductors

    International Nuclear Information System (INIS)

    Routbort, J.L.; Rothman, S.J.

    1995-01-01

    Superconducting properties of the cuprate superconductors depend on the oxygen content of the material; the diffusion of oxygen is thus an important process in the fabrication and application of these materials. This article reviews studies of the diffusion of oxygen in La 2-x Sr x CuO 4 , YBa 2 Cu 3 O 7- δ, YBa 2 Cu 4 O 8 , and the Bi 2 Sr 2 Ca n-1 Cu n O 2+4 (n = 1, and 2) superconductors, and attempt to elucidate the atomic mechanisms responsible

  14. Method of fabricating composite superconductors

    International Nuclear Information System (INIS)

    Koike, Y.; Shiraki, H.; Suzuki, E.; Yoshida, M.

    1977-01-01

    A method of making stabilized superconductors of a composition such as Nb 3 Sn is disclosed. The method includes forming a stock product comprising a tin base alloy as a core with a copper jacket and having a niobium tube clad thereon. The stock product is then embedded in a good thermally and electrically conducting matrix which is then coreduced until the desired size is obtained. This cold worked product is then submitted to a heat treatment to form superconductors of Nb 3 Sn

  15. Renormalization effects and phonon density of states in high temperature superconductors

    Directory of Open Access Journals (Sweden)

    Vinod Ashokan

    2013-02-01

    Full Text Available Using the versatile double time thermodynamic Green's function approach based on many body theory the renormalized frequencies, phonon energy line widths, shifts and phonon density of states (PDOS are investigated via a newly formulated Hamiltonian (does not include BCS type Hamiltonian that includes the effects of electron-phonon, anharmonicities and that of isotopic impurities. The automatic appearance of pairons, temperature, impurity and electron-phonon coupling of renormalized frequencies, widths, shifts and PDOS emerges as a characteristic feature of present theory. The numerical investigations on PDOS for the YBa2Cu3O7 − δ crystal predicts several new feature of high temperature superconductors (HTS and agreements with experimental observations.

  16. The Hall effect: An acid test for the Luttinger liquid theory of high Tc superconductors

    International Nuclear Information System (INIS)

    Anderson, P.W.

    1992-01-01

    The temperature dependence of the Hall effect has been one of the most intriguing puzzles of the 'normal' metallic state in cuprate superconductors. It is shown that the Luttinger liquid theory provides a quantitative picture of the data, in particular showing that relaxation time τ perpendicular defined by the Hall angle tan θ H ω c τ perpendicular is the relaxation rate of the spinon elementary excitations and that θ H has a simple and characteristic temperature dependence (A+BT 2 ) -1 . Observed magnitudes of θ H are incompatible with Fermi liquid theory. A discussion is added of the interlayer mechanism for superconductivity and the new form of BCS gap equation which results from it. (author). 12 refs.; 4 figs

  17. Effect of normal impurities on anisotropic superconductors with variable density of states

    Science.gov (United States)

    Whitmore, M. D.; Carbotte, J. P.

    1982-06-01

    We develop a generalized BCS theory of impure superconductors with an anisotropic electron-electron interaction represented by the factorizable model introduced by Markowitz and Kadanoff, and a variable electronic density of states N(ɛ), assumed to peak at the Fermi energy, which is modeled by a Lorentzian superimposed on a uniform background. As the impurity scattering is increased, the enhancement of T c by both the anisotropy and the peak in N(ɛ) is washed out. The reduction is investigated for different values of the anisotropy and different peak heights and widths. It is concluded that the effects of anisotropy and the peak are reduced together in such a way that any effect due to anisotropy is not easily distinguishable from that due to the peak.

  18. Effect of normal impurities on anisotropic superconductors with variable density of states

    International Nuclear Information System (INIS)

    Whitmore, M.D.; Carbotte, J.P.

    1982-01-01

    We develop a generalized BCS theory of impure superconductors with an anisotropic electron--electron interaction represented by the factorizable model introduced by Markowitz and Kadanoff, and a variable electronic density of states N(epsilon-c), assumed to peak at the Fermi energy, which is modeled by a Lorentzian superimposed on a uniform background. As the impurity scattering is increased, the enhancement of T/sub c/ by both the anisotropy and the peak in N(epsilon-c) is washed out. The reduction is investigated for different values of the anisotropy and different peak heights and widths. It is concluded that the effects of anisotropy and the peak are reduced together in such a way that any effect due to anisotropy is not easily distinguishable from that due to the peak

  19. Stability of superconductor

    International Nuclear Information System (INIS)

    Wada, Hitoshi; Takeuchi, Takao; Kuroda, Tsuneo

    2000-01-01

    To evaluate the stability of superconductors, we constructed a measurement system of the critical current density Jr property as function of temperature, magnetic strength, azimuth of magnetic field and distortion. LabView program automatically controlled the magnetic field, temperature, rotational displacement, load, multimeter and sample source in the system. The superconducting critical surface of Nb 3 Al wire was prepared by two methods: a low temperature diffusion method and a phase transformation method. Nb 3 Al prepared by two methods proved the temperature scaling law of magnetic pinning force density and parameters for fitting the pinning model were introduced. The tailing of Jc-T curve at the high temperature side was generated by pinning property of magnetic flux line. On measurement of AC magnetic susceptibility, a primary stack (JR filament) of RIT Nb 3 Al wire prepared by phase transformation connected electrically and the size corresponded to the effective core size, so that, large n value was shown in spite of high temperature treatment and it showed good distortion resistance. Nb 3 Al wire prepared by low temperature diffusion method indicated large anisotropy of Bc 2 and Jc in the rectangular wire. On V 3 Ga, the temperature scaling law of magnetic field was not established and it was observed the effective grain boundary pinning at the low magnetic field and the other pinning mechanism of which magnetic flux line synchronized in the high temperature field. The specific magnetic azimuth dependency showed in the neighborhood of the parallel magnetic field. Jc indicated the positive dependence of temperature in the peak magnetic field. Jc of Bi oxides tape conductor was measured and the results showed the magnetic field was governed by magnetic field dependence on the c axis direction. (S.Y.)

  20. Anisotropy and Strong-Coupling Effects on the Collective Mode Spectrum of Chiral Superconductors: Application to Sr2RuO4

    Directory of Open Access Journals (Sweden)

    James Avery Sauls

    2015-06-01

    Full Text Available Recent theories of Sr2RuO4 based on the interplay of strong interactions, spin-orbit coupling and multi-band anisotropy predict chiral or helical ground states with strong anisotropy of the pairing states, with deep minima in the excitation gap, as well as strong phase anisotropy for the chiral ground state. We develop time-dependent mean field theory to calculate the Bosonic spectrum for the class of 2D chiral superconductors spanning 3He-A to chiral superconductors with strong anisotropy. Chiral superconductors support a pair of massive Bosonic excitations of the time-reversed pairs labeled by their parity under charge conjugation. These modes are degenerate for 2D 3He-A. Crystal field anisotropy lifts the degeneracy. Strong anisotropy also leads to low-lying Fermions, and thus to channels for the decay of the Bosonic modes. Selection rules and phase space considerations lead to large asymmetries in the lifetimes and hybridization of the Bosonic modes with the continuum of un-bound Fermion pairs. We also highlight results for the excitation of the Bosonic modes by microwave radiation that provide clear signatures of the Bosonic modes of an anisotropic chiral ground state.

  1. WE-G-18C-07: Accelerated Water/fat Separation in MRI for Radiotherapy Planning Using Multi-Band Imaging Techniques

    Energy Technology Data Exchange (ETDEWEB)

    Crijns, S; Stemkens, B; Sbrizzi, A; Lagendijk, J; Berg, C van den; Andreychenko, A [UMC Utrecht, Utrecht, Utrecht (Netherlands)

    2014-06-15

    Purpose: Dixon sequences are used to characterize disease processes, obtain good fat or water separation in cases where fat suppression fails and to obtain pseudo-CT datasets. Dixon's method uses at least two images acquired with different echo times and thus requires prolonged acquisition times. To overcome associated problems (e.g., for DCE/cine-MRI), we propose to use a method for water/fat separation based on spectrally selective RF pulses. Methods: Two alternating RF pulses were used, that imposes a fat selective phase cycling over the phase encoding lines, which results in a spatial shift for fat in the reconstructed image, identical to that in CAIPIRINHA. Associated aliasing artefacts were resolved using the encoding power of a multi-element receiver array, analogous to SENSE. In vivo measurements were performed on a 1.5T clinical MR-scanner in a healthy volunteer's legs, using a four channel receiver coil. Gradient echo images were acquired with TE/TR = 2.3/4.7ms, flip angle 20°, FOV 45×22.5cm{sup 2}, matrix 480×216, slice thickness 5mm. Dixon images were acquired with TE,1/TE,2/TR=2.2/4.6/7ms. All image reconstructions were done in Matlab using the ReconFrame toolbox (Gyrotools, Zurich, CH). Results: RF pulse alternation yields a fat image offset from the water image. Hence the water and fat images fold over, which is resolved using in-plane SENSE reconstruction. Using the proposed technique, we achieved excellent water/fat separation comparable to Dixon images, while acquiring images at only one echo time. Conclusion: The proposed technique yields both inphase water and fat images at arbitrary echo times and requires only one measurement, thereby shortening the acquisition time by a factor 2. In future work the technique may be extended to a multi-band water/fat separation sequence that is able to achieve single point water/fat separation in multiple slices at once and hence yields higher speed-up factors.

  2. SELECTION OF BURST-LIKE TRANSIENTS AND STOCHASTIC VARIABLES USING MULTI-BAND IMAGE DIFFERENCING IN THE PAN-STARRS1 MEDIUM-DEEP SURVEY

    International Nuclear Information System (INIS)

    Kumar, S.; Gezari, S.; Heinis, S.; Chornock, R.; Berger, E.; Soderberg, A.; Stubbs, C. W.; Kirshner, R. P.; Rest, A.; Huber, M. E.; Narayan, G.; Marion, G. H.; Burgett, W. S.; Foley, R. J.; Scolnic, D.; Riess, A. G.; Lawrence, A.; Smartt, S. J.; Smith, K.; Wood-Vasey, W. M.

    2015-01-01

    We present a novel method for the light-curve characterization of Pan-STARRS1 Medium Deep Survey (PS1 MDS) extragalactic sources into stochastic variables (SVs) and burst-like (BL) transients, using multi-band image-differencing time-series data. We select detections in difference images associated with galaxy hosts using a star/galaxy catalog extracted from the deep PS1 MDS stacked images, and adopt a maximum a posteriori formulation to model their difference-flux time-series in four Pan-STARRS1 photometric bands g P1 , r P1 , i P1 , and z P1 . We use three deterministic light-curve models to fit BL transients; a Gaussian, a Gamma distribution, and an analytic supernova (SN) model, and one stochastic light-curve model, the Ornstein-Uhlenbeck process, in order to fit variability that is characteristic of active galactic nuclei (AGNs). We assess the quality of fit of the models band-wise and source-wise, using their estimated leave-out-one cross-validation likelihoods and corrected Akaike information criteria. We then apply a K-means clustering algorithm on these statistics, to determine the source classification in each band. The final source classification is derived as a combination of the individual filter classifications, resulting in two measures of classification quality, from the averages across the photometric filters of (1) the classifications determined from the closest K-means cluster centers, and (2) the square distances from the clustering centers in the K-means clustering spaces. For a verification set of AGNs and SNe, we show that SV and BL occupy distinct regions in the plane constituted by these measures. We use our clustering method to characterize 4361 extragalactic image difference detected sources, in the first 2.5 yr of the PS1 MDS, into 1529 BL, and 2262 SV, with a purity of 95.00% for AGNs, and 90.97% for SN based on our verification sets. We combine our light-curve classifications with their nuclear or off-nuclear host galaxy offsets, to

  3. SELECTION OF BURST-LIKE TRANSIENTS AND STOCHASTIC VARIABLES USING MULTI-BAND IMAGE DIFFERENCING IN THE PAN-STARRS1 MEDIUM-DEEP SURVEY

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, S.; Gezari, S.; Heinis, S. [Department of Astronomy, University of Maryland, Stadium Drive, College Park, MD 21224 (United States); Chornock, R.; Berger, E.; Soderberg, A.; Stubbs, C. W.; Kirshner, R. P. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Rest, A. [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Huber, M. E.; Narayan, G.; Marion, G. H.; Burgett, W. S. [Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States); Foley, R. J. [Astronomy Department, University of Illinois at Urbana-Champaign, 1002 West Green Street, Urbana, IL 61801 (United States); Scolnic, D.; Riess, A. G. [Department of Physics and Astronomy, Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21218 (United States); Lawrence, A. [Institute for Astronomy, University of Edinburgh Scottish Universities Physics Alliance, Royal Observatory, Blackford Hill, Edinburgh EH9 3HJ (United Kingdom); Smartt, S. J.; Smith, K. [Astrophysics Research Centre, School of Mathematics and Physics, Queen' s University Belfast, Belfast BT7 1NN (United Kingdom); Wood-Vasey, W. M. [Pittsburgh Particle Physics, Astrophysics, and Cosmology Center, Department of Physics and Astronomy, University of Pittsburgh, 3941 O' Hara Street, Pittsburgh, PA 15260 (United States); and others

    2015-03-20

    We present a novel method for the light-curve characterization of Pan-STARRS1 Medium Deep Survey (PS1 MDS) extragalactic sources into stochastic variables (SVs) and burst-like (BL) transients, using multi-band image-differencing time-series data. We select detections in difference images associated with galaxy hosts using a star/galaxy catalog extracted from the deep PS1 MDS stacked images, and adopt a maximum a posteriori formulation to model their difference-flux time-series in four Pan-STARRS1 photometric bands g {sub P1}, r {sub P1}, i {sub P1}, and z {sub P1}. We use three deterministic light-curve models to fit BL transients; a Gaussian, a Gamma distribution, and an analytic supernova (SN) model, and one stochastic light-curve model, the Ornstein-Uhlenbeck process, in order to fit variability that is characteristic of active galactic nuclei (AGNs). We assess the quality of fit of the models band-wise and source-wise, using their estimated leave-out-one cross-validation likelihoods and corrected Akaike information criteria. We then apply a K-means clustering algorithm on these statistics, to determine the source classification in each band. The final source classification is derived as a combination of the individual filter classifications, resulting in two measures of classification quality, from the averages across the photometric filters of (1) the classifications determined from the closest K-means cluster centers, and (2) the square distances from the clustering centers in the K-means clustering spaces. For a verification set of AGNs and SNe, we show that SV and BL occupy distinct regions in the plane constituted by these measures. We use our clustering method to characterize 4361 extragalactic image difference detected sources, in the first 2.5 yr of the PS1 MDS, into 1529 BL, and 2262 SV, with a purity of 95.00% for AGNs, and 90.97% for SN based on our verification sets. We combine our light-curve classifications with their nuclear or off-nuclear host

  4. Effect of quasiparticles on interlayer transport in highly anisotropic layered superconductors

    International Nuclear Information System (INIS)

    Artemenko, S.N.; Bulaevskii, L.N.; Maley, M.P.; Vinokur, V.M.

    1999-01-01

    We have performed a microscopic calculation of the dielectric response function in highly anisotropic layered superconductors and used the developed approach to obtain the frequency-dependent London penetration length and conductivity in the case of d-wave pairing for currents perpendicular to the layers. We consider a BCS model with coherent interlayer tunneling of electrons and take into account contributions from both superconducting electrons and quasiparticles to the dielectric response. We show that quasiparticles change the low-temperature behavior of the penetration length in the intermediate frequency range where the frequency is smaller than the superconducting order parameter but larger than the inverse quasiparticle scattering time. The obtained results are used to describe the low-temperature behavior of the Josephson plasma resonance, in particular the temperature dependence of the resonance frequency and the resonance linewidth in zero external magnetic field. We compare our results with the available experimental data for Tl 2 Ba 2 CuO 6 and Bi 2 Sr 2 CaCu 2 O 8+δ (Bi-2212) and show that results of a BCS model with coherent interlayer tunneling for the dc c-axis resistivity in the superconducting state are inconsistent with experimental data for underdoped and optimally doped Bi-2212 crystals. copyright 1999 The American Physical Society

  5. Development of superconductor application technology

    Energy Technology Data Exchange (ETDEWEB)

    Hong, G W; Kim, C J; Lee, H G; Lee, H J; Kim, K B; Won, D Y; Jang, K I; Kwon, S C; Kim, W J; Ji, Y A; Yang, S W; Kim, W K; Park, S D; Lee, M H; Lee, D M; Park, H W; Yu, J K; Lee, I S; Kim, J J; Choi, H S; Chu, Y; Kim, Y S; Kim, D H

    1997-09-01

    Fabrication of high Tc bulk superconductor and its application, fabrication of superconducting wire for electric power device and analysis for cryogenic system were carried out for developing superconductor application technologies for electric power system. High quality YBaCuO bulk superconductor was fabricated by controlling initial powder preparation process and prototype flywheel energy storage device was designed basically. The superconducting levitation force measuring device was made to examine the property of prepared superconductor specimen. Systematic studies onthe method of starting powder preparation, mechanical fabrication process, heat treatment condition and analysis of plastic deformation were carried out to increase the stability and reproducibility of superconducting wire. A starting power with good reactivity and fine particle size was obtained by mechanical grinding, control of phase assemblage, and emulsion drying method. Ag/BSCCO tape with good cross sectional shape and Jc of 20,000 A/cm{sup 2} was fabricated by applying CIP packing procedure. Multifilamentary wire with Jc of 10,000 A/cm{sup 2} was fabricated by rolling method using square billet as starting shape. The joining of the multifilamentary wire was done by etching and pressing process and showed 50% of joining efficiency. Analysis on the heat loss in cryostat for high Tc superconducting device was carried out for optimum design of the future cryogenic system. (author). 66 refs., 104 figs.

  6. Superconductor with improved persistence characteristics

    International Nuclear Information System (INIS)

    Stekly, Z. J. J.; Strauss, B. P.

    1984-01-01

    In a multifilamentary superconductor, plural filaments are separated from one another by a ductile nonsuperconducting copper matrix. The niobium titanium filaments are arrayed through the copper, with one filament being substantially larger than the others, and preferably, centrally located in the wire. Preferably also, the other filaments are arrayed in an annular configuration about the periphery of the wire

  7. Ceramic high-temperature superconductors

    International Nuclear Information System (INIS)

    Marquart, R.

    1989-01-01

    The contribution presents an overview treatment of the structure of the new superconductors (YBa 2 Cu 3 O 7-x ). Methods of powder production and processing technology are described, with current development projects by Dornier being taken into consideration. (orig.) [de

  8. Testing Superconductor Logic Integrated Circuits

    NARCIS (Netherlands)

    Arun, A.J.; Kerkhoff, Hans G.

    2005-01-01

    Superconductor logic has the potential of extremely low-power consumption and ultra-fast digital signal processing. Unfortunately, the obtained yield of the present processes is low and specific faults occur. This paper deals with fault-modelling, Design-for-Test structures, and ATPG for these

  9. High Temperature Superconductor Machine Prototype

    DEFF Research Database (Denmark)

    Mijatovic, Nenad; Jensen, Bogi Bech; Træholt, Chresten

    2011-01-01

    A versatile testing platform for a High Temperature Superconductor (HTS) machine has been constructed. The stationary HTS field winding can carry up to 10 coils and it is operated at a temperature of 77K. The rotating armature is at room temperature. Test results and performance for the HTS field...

  10. Vortex lattices in layered superconductors

    International Nuclear Information System (INIS)

    Prokic, V.; Davidovic, D.; Dobrosavljevic-Grujic, L.

    1995-01-01

    We study vortex lattices in a superconductor--normal-metal superlattice in a parallel magnetic field. Distorted lattices, resulting from the shear deformations along the layers, are found to be unstable. Under field variation, nonequilibrium configurations undergo an infinite sequence of continuous transitions, typical for soft lattices. The equilibrium vortex arrangement is always a lattice of isocell triangles, without shear

  11. Superconductors by powder metallurgy techniques

    International Nuclear Information System (INIS)

    Pickus, M.R.; Wang, J.L.F.

    1976-05-01

    Fabrication methods for Nb 3 Sn type compounds are described. Information is included on the Bell Telephone process, the General Electric tape process, superconductor stability, the bronze process, powder metallurgy multifilamentary tapes and wires, and current assessment of powder metallurgy superconducting wire

  12. Dynamics of vortices in superconductors

    International Nuclear Information System (INIS)

    Weinan, E.

    1992-01-01

    We study the dynamics of vortices in type-II superconductors from the point of view of time-dependent Ginzburg-Landau equations. We outline a proof of existence, uniqueness and regularity of strong solutions for these equations. We then derive reduced systems of ODEs governing the motion of the vortices in the asymptotic limit of large Ginzburg-Landau parameter

  13. Development of superconductor application technology

    International Nuclear Information System (INIS)

    Hong, G. W.; Kim, C. J.; Lee, H. G.; Lee, H. J.; Kim, K. B.; Won, D. Y.; Jang, K. I.; Kwon, S. C.; Kim, W. J.; Ji, Y. A.; Yang, S. W.; Kim, W. K.; Park, S. D.; Lee, M. H.; Lee, D. M.; Park, H. W.; Yu, J. K.; Lee, I. S.; Kim, J. J.; Choi, H. S.; Chu, Y.; Kim, Y. S.; Kim, D. H.

    1997-09-01

    Fabrication of high Tc bulk superconductor and its application, fabrication of superconducting wire for electric power device and analysis for cryogenic system were carried out for developing superconductor application technologies for electric power system. High quality YBaCuO bulk superconductor was fabricated by controlling initial powder preparation process and prototype flywheel energy storage device was designed basically. The superconducting levitation force measuring device was made to examine the property of prepared superconductor specimen. Systematic studies onthe method of starting powder preparation, mechanical fabrication process, heat treatment condition and analysis of plastic deformation were carried out to increase the stability and reproducibility of superconducting wire. A starting power with good reactivity and fine particle size was obtained by mechanical grinding, control of phase assemblage, and emulsion drying method. Ag/BSCCO tape with good cross sectional shape and Jc of 20,000 A/cm 2 was fabricated by applying CIP packing procedure. Multifilamentary wire with Jc of 10,000 A/cm 2 was fabricated by rolling method using square billet as starting shape. The joining of the multifilamentary wire was done by etching and pressing process and showed 50% of joining efficiency. Analysis on the heat loss in cryostat for high Tc superconducting device was carried out for optimum design of the future cryogenic system. (author). 66 refs., 104 figs

  14. Chemistry of high temperature superconductors

    CERN Document Server

    1991-01-01

    This review volume contains the most up-to-date articles on the chemical aspects of high temperature oxide superconductors. These articles are written by some of the leading scientists in the field and includes a comprehensive list of references. This is an essential volume for researchers working in the fields of ceramics, materials science and chemistry.

  15. Strain effects in oxide superconductors

    International Nuclear Information System (INIS)

    Wada, H.; Kuroda, T.; Sekine, H.; Yuyama, M.; Itoh, K.

    1991-01-01

    Strain sensitivities of superconducting properties are critical to high magnetic field applications of superconductors, since critical temperature, T c , upper critical field, H c2 , and critical current (density), I c (J c ), are all degraded under strains. Oxide superconductors so far known are all very fragile, thus requiring to be fabricated in the form of composite. In the case of practical metallic superconductors, such as Nb 3 Sn and V 3 Ga, the so-called bronze method has been developed where these superconducting intermetallics are enveloped in a ductile metallic sheath. Recently, a fabrication method similar to the bronze method has been developed for the Bi 2 Sr 2 Ca 2 Cu 3 O x superconductors using Ag tubes as sheath. In the present study mono- and multicore BiPbSrCaCuO tape conductors were prepared by means of this Ag-sheath composite method, and examined in terms of strain sensitivity by measuring their T c and I c (J c ) under bending or tensile strains. (orig.)

  16. Role of superconducting energy gap in extended BCS-Bose crossover theory

    Science.gov (United States)

    Chávez, I.; García, L. A.; de Llano, M.; Grether, M.

    2017-10-01

    The generalized Bose-Einstein condensation (GBEC) theory of superconductivity (SC) is briefly surveyed. It hinges on three distinct new ingredients: (i) Treatment of Cooper pairs (CPs) as actual bosons since they obey Bose statistics, in contrast to BCS pairs which do not obey Bose commutation relations; (ii) inclusion of two-hole Cooper pairs (2hCPs) on an equal footing with two-electron Cooper pairs (2eCPs), thus making this a complete boson-fermion (BF) model; and (iii) inclusion in the resulting ternary ideal BF gas with particular BF vertex interactions that drive boson formation/disintegration processes. GBEC subsumes as special cases both BCS (having its 50-50 symmetry of both kinds of CPs) and ordinary BEC theories (having no 2hCPs), as well as the now familiar BCS-Bose crossover theory. We extended the crossover theory with the explicit inclusion of 2hCPs and construct a phase diagram of Tc/TF versus n/nf, where Tc and TF are the critical and Fermi temperatures, n is the total number density and nf that of unbound electrons at T = 0. Also, with this extended crossover one can construct the energy gap Δ(T)/Δ(0) versus T/Tc for some elemental SCs by solving at least two equations numerically: a gap-like and a number equation. In 50-50 symmetry, the energy gap curve agrees quite well with experimental data. But ignoring 2hCPs altogether leads to the gap curve falling substantially below that with 50-50 symmetry which already fits the data quite well, showing that 2hCPs are indispensable to describe SCs.

  17. Turismo y Sustentabilidad en Pequeñas Localidades Localidades Costeras de Baja California Sur (BCS

    Directory of Open Access Journals (Sweden)

    Reyna Ibañez Pérez

    2014-01-01

    Full Text Available El fomento del turismo se realiza en sitios que, aunque pequeños, cuentan con atractivos naturales y culturales, tal es el caso de las zonas costeras. Tan solo en México, se estima que existen más de 1,100 comunidades que dependen directamente de dicha actividad, esta te ndencia se refleja, de igual manera, en pequeñas localidades costeras de Baja California Sur (BCS. En este sentido, el objetivo de este trabajo fue realizar un an álisis exploratorio que permitió detectar a las comunidades costeras de BCS, donde el turismo genera un aporte importante a su economía local, además , se buscó identificar la problemática general que éstas enfrentan. Para realizar dicho estudio se revisó literatura, se organizó información estadística y se elaboró un análisis Fortalezas, Oportunidades, Debilidades y Amenazas (FODA. Los resultad os apuntan a que, en BCS, existen más de 35 localidades ru rales vinculadas con dicha actividad que comparten como problemática la escasa in fraestructura y la carencia de medidas de control de la afluencia turística. La principal recomendación es desarrollar líneas de investigación que permitan aportar elementos para medir la sustentabilidad turística a nivel local y, co n base en ello, diseñar medidas para la adecuada conducción de tan importante actividad.

  18. Fluctuoscopy of Superconductors

    Science.gov (United States)

    Varlamov, Andrey

    2012-02-01

    The study of superconducting fluctuations (SF) is a subject of fundamental and practical importance. Since the moment of discovery SF became a noticeable part of research in the field of superconductivity (SC) and a variety of fluctuation effects have been detected. The interest to SF in SC was regenerated by the discovery of HTS, where, due to extremely short coherence length and low effective dimensionality of the electron system, SF manifest themselves in a wide range of temperatures. The characteristic feature of SF is their strong dependence on temperature and magnetic field. This allows to separate SFs from other contributions and to use them as a tool for characterization of SC systems (``fluctuoscopy'') for example to extract the values of Tc, Hc2(T) and phase-breaking time from experimental data. We present the complete results for fluctuation magneto-conductivity (FMC) and Nernst signal (FNS) of impure 2D superconductor in the whole phase diagram above the transition line Hc2(T), including the domain of quantum fluctuations. Along some line H0(T), in agreement with experimental findings, FMC becomes zero and beyond it remains small and negative. The corresponding surface in coordinates (T,H) becomes in particular non-trivial at low temperatures and close to Hc2(0), where it is trough-shaped. The observation of large FNS in HTS and conventional SC above Tc(H), has attracted much attention recently. The idea to attribute it to the entropy transport by analogy to vortices was proposed. On the other hand this giant effect, close to Tc(0), was explained in terms of SF. Our general results allow to successfully fit the available experimental data in a wide range of magnetic fields and temperatures, to extract the value of the ``ghost'' field and other parameters of SC. We offer also a qualitative consideration, which gives a natural explanation for the giant value of FNS attributing it to a strong dependence of the fluctuation Cooper pair (FCP) chemical

  19. Effects of density imbalance on the BCS-BEC crossover in semiconductor electron-hole bilayers

    International Nuclear Information System (INIS)

    Pieri, P.; Strinati, G. C.; Neilson, D.

    2007-01-01

    We study the occurrence of excitonic superfluidity in electron-hole bilayers at zero temperature. We not only identify the crossover in the phase diagram from the BCS limit of overlapping pairs to the BEC limit of nonoverlapping tightly bound pairs but also, by varying the electron and hole densities independently, we can analyze a number of phases that occur mainly in the crossover region. With different electron and hole effective masses, the phase diagram is asymmetric with respect to excess electron or hole densities. We propose, as the criterion for the onset of superfluidity, the jump of the electron and hole chemical potentials when their densities cross

  20. BCS-BEC crossover at finite temperature for superfluid trapped Fermi atoms

    International Nuclear Information System (INIS)

    Perali, A.; Pieri, P.; Pisani, L.; Strinati, G.C.

    2004-01-01

    We consider the BCS-BEC (Bose-Einstein-condensate) crossover for a system of trapped Fermi atoms at finite temperature, both below and above the superfluid critical temperature, by including fluctuations beyond mean field. We determine the superfluid critical temperature and the pair-breaking temperature as functions of the attractive interaction between Fermi atoms, from the weak- to the strong-coupling limit (where bosonic molecules form as bound-fermion pairs). Density profiles in the trap are also obtained for all temperatures and couplings

  1. Non-BCS superconductivity for underdoped cuprates by spin-vortex attraction

    OpenAIRE

    Marchetti, P. A.; Ye, F.; Su, Z. B.; Yu, L.

    2011-01-01

    Within a gauge approach to the t-J model, we propose a new, non-BCS mechanism of superconductivity for underdoped cuprates. The gluing force of the superconducting mechanism is an attraction between spin vortices on two different N\\'eel sublattices, centered around the empty sites described in terms of fermionic holons. The spin fluctuations are described by bosonic spinons with a gap generated by the spin vortices. Due to the no-double occupation constraint, there is a gauge attraction betwe...

  2. The Cauchy problem for the Bogolyubov hierarchy of equations. The BCS model

    International Nuclear Information System (INIS)

    Vidybida, A.K.

    1975-01-01

    A chain of Bogolyubov's kinetic equations for an infinite quantum system of particles distributed in space with the mean density 1/V and interacting with the BCS model operator is considered as a single abstract equation in some countable normalized space bsup(v) of sequences of integral operators. In this case an unique solution of the Cauchy problem has been obtained at arbitrary initial conditions from bsup(v), stationary solutions of the equation have been derived, and the class of the initial conditions which approach to stationary ones is indicated

  3. Analytic solution of the BCS gap equation with a logarithmic singularity in the density of states

    International Nuclear Information System (INIS)

    Bhardwaj, A.; Muthu, S.K.

    1999-01-01

    The Bardeen-Cooper-Schrieffer (BCS) gap equation is solved analytically for a density of states function with a logarithmic singularity. It is an extension of our earlier work where we had assumed a constant density of states. We continue to work in the weak-coupling limit and consider both phononic and non-phononic pairings. Expressions are obtained for T c , Δ 0 (the gap at T=0), and the jump in the electronic specific heat at T=T c . We also calculate the isotope exponent and show that it is possible to reproduce the broad features of the experimental results in this framework. (orig.)

  4. Importance of the single-particle continuum in BCS pairing with a pseudostate basis

    Directory of Open Access Journals (Sweden)

    Lay J. A.

    2016-01-01

    Full Text Available In a recent work [arXiv:1510.03185] the use of the Transformed Harmonic Oscillator (THO basis for the discretization of the singleparticle continuum into a Generalized Bardeen-Cooper-Schrieffer (BCS formalism was proposed for the description of weakly bound nuclei. We make use of the flexibility of this formalism to study the evolution of the pairing when the nucleus becomes more and more weakly bound. Specifically we focus on the evolution of the occupation of the different partial waves in 22O when the Fermi level approaches zero.

  5. BEC-BCS-laser crossover in Coulomb-correlated electron-hole-photon systems

    International Nuclear Information System (INIS)

    Yamaguchi, M; Kamide, K; Ogawa, T; Yamamoto, Y

    2012-01-01

    Many-body features caused by Coulomb correlations are of great importance for understanding phenomena pertaining to polariton systems in semiconductor microcavities, i.e. electron-hole-photon systems. Remarkable many-body effects are shown to exist in both thermal-equilibrium phases and non-equilibrium lasing states. We then show a unified framework for connecting the thermal-equilibrium and the non-equilibrium steady states based on a non-equilibrium Green's function approach. Bose-Einstein condensate (BEC)-Bardeen-Cooper-Schrieffer (BCS)-laser crossovers are investigated by using this approach. (paper)

  6. Crossover between the dense electron-hole phase and the BCS excitonic phase in quantum dots

    International Nuclear Information System (INIS)

    Rodriguez, B.A.; Gonzalez, A.; Quiroga, L.; Capote, R.; Rodriguez, F.J.

    1999-09-01

    Second order perturbation theory and a Lipkin-Nogami scheme combined with an exact Monte Carlo projection after variation are applied to compute the ground-state energy of 6 ≤ N ≤ 210 electron-hole pairs confined in a parabolic two-dimensional quantum dot. The energy shows nice scaling properties as N or the confinement strength is varied. A crossover from the high-density electron-hole phase to the BCS excitonic phase is found at a density which is roughly four times the close-packing density of excitons. (author)

  7. Iron-Based Superconductors as Odd-Parity Superconductors

    Directory of Open Access Journals (Sweden)

    Jiangping Hu

    2013-07-01

    Full Text Available Parity is a fundamental quantum number used to classify a state of matter. Materials rarely possess ground states with odd parity. We show that the superconducting state in iron-based superconductors is classified as an odd-parity s-wave spin-singlet pairing state in a single trilayer FeAs/Se, the building block of the materials. In a low-energy effective model constructed on the Fe square bipartite lattice, the superconducting order parameter in this state is a combination of an s-wave normal pairing between two sublattices and an s-wave η pairing within the sublattices. The state has a fingerprint with a real-space sign inversion between the top and bottom As/Se layers. The results suggest that iron-based superconductors are a new quantum state of matter, and the measurement of the odd parity can help to establish high-temperature superconducting mechanisms.

  8. Superfluidity and BCS-BEC crossover of ultracold atomic Fermi gases in mixed dimensions

    Science.gov (United States)

    Zhang, Leifeng; Chen, Qijin

    Atomic Fermi gases have been under active investigation in the past decade. Here we study the superfluid and pairing phenomena of a two-component ultracold atomic Fermi gas in the presence of mixed dimensionality, in which one component is confined on a 1D optical lattice whereas the other is free in the 3D continuum. We assume a short-range pairing interaction and determine the superfluid transition temperature Tc and the phase diagram for the entire BCS-BEC crossover, using a pairing fluctuation theory which includes self-consistently the contributions of finite momentum pairs. We find that, as the lattice depth increases and the lattice spacing decreases, the behavior of Tc becomes very similar to that of a population imbalance Fermi gas in a simple 3D continuum. There is no superfluidity even at T = 0 below certain threshold of pairing strength in the BCS regime. Nonmonotonic Tc behavior and intermediate temperature superfluidity emerge, and for deep enough lattice, the Tc curve will split into two parts. Implications for experiment will be discussed. References: 1. Q.J. Chen, Ioan Kosztin, B. Janko, and K. Levin, Phys. Rev. B 59, 7083 (1999). 2. Chih-Chun Chien, Qijin Chen, Yan He, and K. Levin, Phys. Rev. Lett. 97, 090402(2006). Work supported by NSF of China and the National Basic Research Program of China.

  9. Study of two-proton radioactivity within the relativistic mean-field plus BCS approach

    International Nuclear Information System (INIS)

    Singh, D.; Saxena, G.

    2012-01-01

    Inspired by recent experimental studies of two-proton radioactivity in the light-medium mass region, we have employed relativistic mean-field plus state-dependent BCS approach (RMF+BCS) to study the ground state properties of selected even-Z nuclei in the region 20 ≤ Z ≤ 40. It is found that the effective potential barrier provided by the Coulomb interaction and that due to centrifugal force may cause a long delay in the decay of some of the nuclei even with small negative proton separation energy. This may cause the existence of proton-rich nuclei beyond the proton drip-line. Nuclei 38 Ti, 42 Cr, 45 Fe, 48 Ni, 55 Zn, 60 Ge, 63, 64 Se, 68 Kr, 72 Sr and 76 Zr are found to be the potential candidates for exhibiting two-proton radioactivity in the region 20 ≤ Z ≤ 40. The reliability of these predictions is further strengthened by the agreement of the calculated results for the ground state properties such as binding energy, one- and two-proton separation energy, proton and neutron radii, and deformation with the available experimental data for the entire chain of the isotopes of the nuclei in the region 20 ≤ Z ≤ 40. (author)

  10. Cultura, identidad política y multiculturalidad en Todos Santos, BCS1

    Directory of Open Access Journals (Sweden)

    Rossana Almada

    2005-01-01

    Full Text Available Este ensayo tiene como objetivo hablar del desbordamiento institucional de la política y su desplazamiento hacia la sociedad civil. Desde luego, no es la intención negar la importancia de instituciones políticas tales como partidos, sino señalar cómo la morfología de la complejidad social desdibuja las fronteras de la representación y traslada las demandas a las calles, a las cantinas,a las casas de los interesados. El trabajo forma parte de una investigación mayor a la que he llamado Juntos, pero no revueltos. Multiculturalidad e identidad local en Todos Santos, BCS, es por eso que presento como ejemplo de este fenómeno el caso del conflicto latente en Todos Santos, Baja California Sur (BCS tanto por el uso de los espacios como por las formas que tendrá que adquirir la identidad local que construyen, a partir de sus convergencias y negociaciones, los tres grupos en lucha por la hegemonía social todosanteña: extranjeros, principalmente estadounidenses y canadienses, mexicanos no sudcalifornianos y todosanteños.

  11. Dipole modes of a superfluid Bose–Fermi mixture in the BCS-BEC crossover

    International Nuclear Information System (INIS)

    Wen, Wen; Chen, Bingyan; Zhang, Xuewu

    2017-01-01

    Motivated by the first experimental realization by the Ecole Normale Supérieure (ENS) group of a mixture of a Bose–Einstein condensate with a Fermi superfluid continuously changing from a Bardeen–Cooper–Schrieffer (BCS) superfluid to a Bose–Einstein condensate (BEC) (Ferrier-Barbut et al 2014 Science 345 1035), we analytically study the dipole modes of the superfluid Bose–Fermi mixture in the BCS-BEC crossover. The analytical approach can explicitly reveal relationships between the frequencies of the dipole modes and the microscopic properties of the novel system. We start from coupled hydrodynamic equations, where the equation of state for the Fermi superfluid in the crossover is an analytical fitting formula based on experimental data, and by using a scaling approach we analytically study eigenfrequencies of the dipole modes for the coupled system in the ENS experimental parameters. Without the boson–fermion interaction in the equilibrium density profiles, our theoretical results can be reduced to the mean-field model and is consistent with the experimental data. However, by further taking into account the boson–fermion interaction numerically and analytically, we find that the results disagree with the experiment, especially in the parameter regime where the boson interaction is smaller than the boson–fermion interaction. (paper)

  12. NSSEFF Designing New Higher Temperature Superconductors

    Science.gov (United States)

    2017-04-13

    AFRL-AFOSR-VA-TR-2017-0083 NSSEFF - DESIGINING NEW HIGHER TEMPERATURE SUPERCONDUCTORS Meigan Aronson THE RESEARCH FOUNDATION OF STATE UNIVERSITY OF...2015 4. TITLE AND SUBTITLE NSSEFF - DESIGINING NEW HIGHER TEMPERATURE SUPERCONDUCTORS 5a.  CONTRACT NUMBER 5b.  GRANT NUMBER FA9550-10-1-0191 5c...materials, identifying the most promising candidates. 15. SUBJECT TERMS TEMPERATURE, SUPERCONDUCTOR 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF

  13. Passivation Of High-Temperature Superconductors

    Science.gov (United States)

    Vasquez, Richard P.

    1991-01-01

    Surfaces of high-temperature superconductors passivated with native iodides, sulfides, or sulfates formed by chemical treatments after superconductors grown. Passivating compounds nearly insoluble in and unreactive with water and protect underlying superconductors from effects of moisture. Layers of cuprous iodide and of barium sulfate grown. Other candidate passivating surface films: iodides and sulfides of bismuth, strontium, and thallium. Other proposed techniques for formation of passivating layers include deposition and gas-phase reaction.

  14. Applications of superconductors to electric motors

    International Nuclear Information System (INIS)

    McConnell, B.W.

    1988-01-01

    This paper reviews previous experience in applying superconductors to electric motors and examines the difficulties encountered. While motors and generators have a common basis, several significant differences exist. The application of high temperature superconductors to the major electric motor types is discussed and expected difficulties are presented. The limitations imposed by various motor designs are reflected in a statement of the desired material properties for high temperature superconductor electric motor applications

  15. Holographic complexity in gauge/string superconductors

    Directory of Open Access Journals (Sweden)

    Davood Momeni

    2016-05-01

    Full Text Available Following a methodology similar to [1], we derive a holographic complexity for two dimensional holographic superconductors (gauge/string superconductors with backreactions. Applying a perturbation method proposed by Kanno in Ref. [2], we study behaviors of the complexity for a dual quantum system near critical points. We show that when a system moves from the normal phase (T>Tc to the superconductor phase (T

  16. Theoretical investigation of the vortex state in new superconductors: MgB2 and PrOs4Sb12

    International Nuclear Information System (INIS)

    Dao, V.H.

    2006-01-01

    As illustrated by the present thesis work, gap function anisotropy and crystal anisotropy are combined when influencing superconducting properties under a magnetic field. In order to study the mixed state of the recently discovered multiband superconductor MgB 2 , we first derive the Ginzburg-Landau functional for a two-gap superconductor from a weak coupling BCS model. The interaction between the two condensates is then described by a unique Josephson-type coupling. The two-gap theory then enables to explain the curvature and the anisotropy of the upper critical field, as well as the 30 degrees change of orientation for the vortex lattice which is observed when increasing the strength of the magnetic field applied along the c-tilde axis. Besides, we investigate the vortex lattice geometry in the superconducting heavy fermion PrOs 4 Sb 12 . When taking into account non local corrections for an s-wave T h -tetrahedral superconductor, we can explain the observed deformation of the lattice by the crystal symmetry of the compound. Ab initio results of the band structures confirm quantitatively our analysis. (author)

  17. Melt processed high-temperature superconductors

    CERN Document Server

    1993-01-01

    The achievement of large critical currents is critical to the applications of high-temperature superconductors. Recent developments have shown that melt processing is suitable for producing high J c oxide superconductors. Using magnetic forces between such high J c oxide superconductors and magnets, a person could be levitated.This book has grown largely out of research works on melt processing of high-temperature superconductors conducted at ISTEC Superconductivity Research Laboratory. The chapters build on melt processing, microstructural characterization, fundamentals of flux pinning, criti

  18. Recent status of superconductors for accelerator magnets

    International Nuclear Information System (INIS)

    Greene, A.F.

    1992-01-01

    A survey is given of superconductor wire and cable which has been or will be used for construction of dipole magnets for all of the large European and US superconducting accelerator rings. Included is a simplified view of the construction methods and operating requirements of an accelerator dipole magnet, with emphasis on required superconductor performance. The methods of fabricating Nb-Ti superconductors are described, including the critical parameters and materials requirements. The superconductor performance requirements are summarized in an effort to relate why these are important to accelerator designers. Some of the recently observed time dependent effects are covered briefly

  19. A possible approach from BCS through HTS to RTS with three examples

    International Nuclear Information System (INIS)

    Chu, C.W.

    2012-01-01

    This paper is based on my talk delivered at the superconductivity centennial conference in The Hague, the Netherlands, on September 23, 2011, to explore the possibility of room temperature superconductivity according to what we have learned from the past, especially in the last 25 years since the discovery of high temperature superconductivity. While the field of superconductivity is broad, I have chosen to focus on the advancement of T c , which has been a major driving force for sustaining research on superconductivity for the last 100 years, ever since its discovery by Heike Kamerlingh Onnes in Leiden. A holistic multidisciplinary enlightened empirical approach is proposed with some specific steps following a brief summary of the past history in the search for superconductors with higher T c . Before concluding, three specific examples of our effort toward superconductors of higher T c are given to demonstrate that the future in raising T c is vast and bright.

  20. Correlation effects in high-Tc superconductors and heavy fermion compounds

    International Nuclear Information System (INIS)

    Kuzemsky, A.L.

    1993-10-01

    This paper describes certain aspects of Highly Correlated Systems (HCS) such as high Tc superconductors (HTSC) and some new class of Heavy Fermion (HF) systems which have been studied recently. The problem is discussed on how the charge and spin degrees of freedom participate in the specific character of superconductivity in the copper oxides and competition of the magnetism and Kondo screening in heavy fermions. The electronic structure and possible superconducting mechanisms of HTSC compounds are discussed. The similarity and dissimilarity with HF compounds is pointed out. It is shown that the spins and carriers in the copper oxides are coupled in a very nontrivial way in order to introduce the discussion and the comparison of the Emery model, the t - J-model and the Kondo-Heisenberg model. It concerns attempts to derive from fundamental multi-band Hamiltonian the reduced effective Hamiltonians to extract and separate the relevant low-energy physics. A short review of the arguments which seem to support the spin-polaron pairing mechanism in HTSC are presented. Many other topics like the idea of mixed valence states in oxides, the role of charge transfer (CT) excitations, phase separation, self-consistent nonperturbative technique, etc. are also discussed. (author). 161 refs

  1. Visualizing pair formation on the atomic scale in high-Tc superconductors

    International Nuclear Information System (INIS)

    Pasupathy, A.

    2008-01-01

    Full text: Unlike traditional superconductors, the density of states (DOS) of the high-T c superconductor Bi-2212 shows large nanoscale variations that have been detected using scanning tunneling microscopy (STM). Such variations are seen in the low temperature superconducting gap and in features associated with the coupling of pairs to boson modes. In order to understand these variations in the spectra, we perform atomic resolution STM measurements of Bi-2212 as a function of temperature. Using newly developed experimental techniques, we measure the evolution of the DOS from low temperature (T c ) to temperatures where all gaps in the spectrum have disappeared (T>T*). Such measurements show that the pairing gap nucleates in nanoscale regions at temperatures between T c and T*. By normalizing the low temperature DOS (T c ) to the DOS at high temperature, we are able to fit the superconducting DOS to the d-wave BCS form. We find that the experimental spectrum deviations from a simple d-wave fit indicating a strong coupling between electrons and bosonic modes. We will discuss the temperature evolution of these as well as other features in the DOS and correlate such measurements with the inhomogeneity seen in the gap magnitude at low temperature

  2. Energy gap in MgB2 superconductor: Andreev reflection studies

    International Nuclear Information System (INIS)

    Aswal, D.K.

    2003-01-01

    To investigate the nature of energy gap in MgB 2 superconductor, we have performed Andreev-reflection studies on MgB 2 / Ag planar junctions. The differential resistance (dV/dI) versus voltage (V) characteristics were recorded as a function of temperature, magnetic field and junction-type. The dV/dI vs V characteristic recorded at low temperature and zero-field for a clean MgB 2 / Ag planar junction exhibited several interesting features, such as, zero bias anomaly, a distinct double-minima, sharp resonance peaks near the energy gap etc. The data, however, could not be explained using Blonder-Tinkham-Klapwijk theory of isotropic superconductor, which indicated that energy gap in MgB 2 is not consistent with the weak-coupling BCS theory. This is further supported by unusual temperature and magnetic field dependence of the tunneling characteristics. The results indicate several possibilities for the energy gap in MgB 2 , such as, an anisotropic energy gap, two-energy or an unconventional gap scenario. (author)

  3. Departure from BCS response in photoexcited superconducting NbN films observed by terahertz spectroscopy

    Czech Academy of Sciences Publication Activity Database

    Šindler, Michal; Kadlec, Christelle; Kužel, Petr; Il'in, K.; Siegel, M.; Němec, Hynek

    2018-01-01

    Roč. 97, č. 5 (2018), s. 1-5, č. článku 054507. ISSN 2469-9950 R&D Projects: GA ČR GA17-04412S Institutional support: RVO:68378271 Keywords : terahertz spectroscopy * NbN thin films * superconductors Subject RIV: BM - Solid Matter Physics ; Magnetism OBOR OECD: Condensed matter physics (including formerly solid state physics, supercond.) Impact factor: 3.836, year: 2016

  4. Photographing magnetic fields in superconductors

    International Nuclear Information System (INIS)

    Harrison, R.B.; Wright, L.S.

    Magneto-optic techniques coupled with high-speed photography are being used to study the destruction of superconductivity by a magnetic field. The phenomenon of superconductivity will be introduced with emphasis placed on the properties of type I and type II superconductors in a magnetic field. The Faraday effect and its application to the study of the penetration of magnetic fields into these superconductors will be described; the relative effectiveness of some types of paramagnetic glass will be demonstrated. A number of cinefilms will be shown to illustrate the versatility of the magneto-optic method for observing flux motion and patterns. The analysis of data obtained from a high speed film (10,200 fps) of a flux jump in Nb-Zr will be presented and discussed

  5. Oxygen diffusion in cuprate superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Routbort, J.L.; Rothman, S.J.

    1995-01-01

    Superconducting properties of the cuprate superconductors depend on the oxygen content of the material; the diffusion of oxygen is thus an important process in the fabrication and application of these materials. This article reviews studies of the diffusion of oxygen in La{sub 2}{sub {minus}}{sub {times}}Sr{sub {times}}CuO{sub 4}, YBa{sub 2}Cu{sub 3}O{sub 7}{sub {minus}}{delta}, YBa{sub 2}Cu{sub 4}O{sub 8}, and the Bi{sub 2}Sr{sub 2}Ca{sub n}{sub {minus}}{sub 1}Cu{sub n}O{sub 2}{sub +}{sub 4} (n = 1, and 2) superconductors, and attempt to elucidate the atomic mechanisms responsible.

  6. QCD as a dual superconductor

    International Nuclear Information System (INIS)

    Zachariasen, F.

    1986-01-01

    The author describes the construction of an effective action describing long-range Yang-Mills theory. This action is motivated by a study of the system of Dyson equations and Ward identities, but cannot (yet) be derived from the underlying quantum theory. The effective action turns out to describe a medium very much like a dual relativistic superconductor; that is, with electric and magnetic fields interchanged. There is a dual Meissner effect, which serves to compress color electric fields into flux tubes, containing quantized units of color electric flux. This produces electric confinement. There is a magnetic condensate, resulting from a spontaneous symmetry breaking analogous to that in the relativistic superconductor, as in the Abelian Higgs model. He gives the motivation leading to the effective action, and describes the quantized electric flux tube solutions. Finally, he mentions briefly some other applications

  7. Theoretical studies of unconventional superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Groensleth, Martin Sigurd

    2008-07-01

    This thesis presents four research papers. In the first three papers we have derived analytical results for the transport properties in unconventional superconductors and ferromagnetic systems with multiple broken symmetries. In Paper I and parts of Paper II we have studied tunneling transport between two non-unitary ferromagnetic spin-triplet superconductors, and found a novel interplay between ferromagnetism and superconductivity manifested in the Josephson effect as a spin- and charge-current in the absence of an applied voltage across the junction. The critical amplitudes of these currents can be adjusted by the relative magnetization direction on each side of the junction. Furthermore, in Paper II, we have found a way of controlling a spin-current between two ferromagnets with spin-orbit coupling. Paper III considers a junction consisting of a ferromagnet and a non-unitary ferromagnetic superconductor, and we show that the conductance spectra contains detailed information about the superconducting gaps and pairing symmetry of the Cooper-pairs. In the last paper we present a Monte Carlo study of an effective Hamiltonian describing orbital currents in the CuO2 layers of high-temperature superconductive cuprates. The model features two intrinsically anisotropic Ising models, coupled through an anisotropic next-nearest neighbor interaction, and an Ashkin-Teller nearest neighbor fourth order coupling. We have studied the specific heat anomaly, as well as the anomaly in the staggered magnetization associated with the orbital currents and its susceptibility. We have found that in a limited parameter regime, the specific heat anomaly is substantially suppressed, while the susceptibility has a non-analytical peak across the order-disorder transition. The model is therefore a candidate for describing the breakup of hidden order when crossing the pseudo-gap line on the under-doped side in the phase diagram of high-temperature superconductors. (Author) 64 refs., figs

  8. Interaction between light and superconductors

    Science.gov (United States)

    Gilabert, Alain

    In the first part of this review article we resume briefly the fundamental aspect of the photon-superconductor interaction. The emphase is focused on the characteristic times and on the phenomenological models (the T*, the μ* models and the model of the kinetics equations) describing the out of equilibrium superconductivity. The experiments made on classical illuminated superconductors especially on tunnel junctions are then reported. In the second part we present the applied aspect of the photon-superconductor interaction. The interaction of the light with the high Tc superconductors is reviewed in the last part. Dans la première partie de cet article de revue, on résume brièvement 1'aspect fondamental de l'action des photons sur les supraconducteurs en s'attachant surtout à rappeler les différents temps caractéristiques de cette interaction et les modèles phénoménologiques (le modèle T*, le modèle μ*, le modèle des équations cinétiques) décrivant la supraconductivité hors équilibre. La seconde partie rappelle les expériences réalisées sur les supraconducteurs classiques illuminés et spécialement les jonctions tunnel ainsi que certaines applications de la supraconductivité hors équilibre comme les liens faibles controllables par des moyens optiques. La dernière partie est consacrée aux nouvelles expériences qui démarrent concernant l'action de la lumière sur les supraconducteurs à hautes températures critiques.

  9. Negative magnetic relaxation in superconductors

    Directory of Open Access Journals (Sweden)

    Krasnoperov E.P.

    2013-01-01

    Full Text Available It was observed that the trapped magnetic moment of HTS tablets or annuli increases in time (negative relaxation if they are not completely magnetized by a pulsed magnetic field. It is shown, in the framework of the Bean critical-state model, that the radial temperature gradient appearing in tablets or annuli during a pulsed field magnetization can explain the negative magnetic relaxation in the superconductor.

  10. The energetic state of mitochondria modulates complex III biogenesis through the ATP-dependent activity of Bcs1.

    Science.gov (United States)

    Ostojić, Jelena; Panozzo, Cristina; Lasserre, Jean-Paul; Nouet, Cécile; Courtin, Florence; Blancard, Corinne; di Rago, Jean-Paul; Dujardin, Geneviève

    2013-10-01

    Our understanding of the mechanisms involved in mitochondrial biogenesis has continuously expanded during the last decades, yet little is known about how they are modulated to optimize the functioning of mitochondria. Here, we show that mutations in the ATP binding domain of Bcs1, a chaperone involved in the assembly of complex III, can be rescued by mutations that decrease the ATP hydrolytic activity of the ATP synthase. Our results reveal a Bcs1-mediated control loop in which the biogenesis of complex III is modulated by the energy-transducing activity of mitochondria. Although ATP is well known as a regulator of a number of cellular activities, we show here that ATP can be also used to modulate the biogenesis of an enzyme by controlling a specific chaperone involved in its assembly. Our study further highlights the intramitochondrial adenine nucleotide pool as a potential target for the treatment of Bcs1-based disorders. Copyright © 2013 Elsevier Inc. All rights reserved.

  11. Emergent loop-nodal s(±)-wave superconductivity in CeCu(2)Si(2): similarities to the iron-based superconductors.

    Science.gov (United States)

    Ikeda, Hiroaki; Suzuki, Michi-To; Arita, Ryotaro

    2015-04-10

    Heavy-fermion superconductors are prime candidates for novel electron-pairing states due to the spin-orbital coupled degrees of freedom and electron correlations. Superconductivity in CeCu_{2}Si_{2} discovered in 1979, which is a prototype of unconventional (non-BCS) superconductors in strongly correlated electron systems, still remains unsolved. Here we provide the first report of superconductivity based on the advanced first-principles theoretical approach. We find that the promising candidate is an s_{±}-wave state with loop-shaped nodes on the Fermi surface, different from the widely expected line-nodal d-wave state. The dominant pairing glue is magnetic but high-rank octupole fluctuations. This system shares the importance of multiorbital degrees of freedom with the iron-based superconductors. Our findings reveal not only the long-standing puzzle in this material, but also urge us to reconsider the pairing states and mechanisms in all heavy-fermion superconductors.

  12. Theory of novel normal and superconducting states in doped oxide high-Tc superconductors

    International Nuclear Information System (INIS)

    Dzhumanov, S.

    2001-10-01

    A consistent and complete theory of the novel normal and superconducting (SC) states of doped high-T c superconductors (HTSC) is developed by combining the continuum model of carrier self-trapping, the tight-binding model and the novel Fermi-Bose-liquid (FBL) model. The ground-state energy of carriers in lightly doped HTSC is calculated within the continuum model and adiabatic approximation using the variational method. The destruction of the long-range antiferromagnetic (AF) order at low doping x≥ x cl ≅0.015, the formation of the in-gap states or bands and novel (bi)polaronic insulating phases at x c2 ≅0.06-0.08, and the new metal- insulator transition at x≅x c2 in HTSC are studied within the continuum model of impurity (defect) centers and large (bi)polarons by using the appropriate tight-binding approximations. It is found that the three-dimensional (3d) large (bi)polarons are formed at ε ∞ /ε 0 ≤0.1 and become itinerant when the (bi)polaronic insulator-to-(bi)polaronic metal transitions occur at x x c2 . We show that the novel pseudogapped metallic and SC states in HTSC are formed at x c2 ≤x≤x p ≅0.20-0.24. We demonstrate that the large polaronic and small BCS-like pairing pseudogaps opening in the excitation spectrum of underdoped (x c2 BCS =0.125), optimally doped (x BCS o ≅0.20) and overdoped (x>x o ) HTSC above T c are unrelated to superconductivity and they are responsible for the observed anomalous optical, transport, magnetic and other properties of these HTSC. We develop the original two-stage FBL model of novel superconductivity describing the combined novel BCS-like pairing scenario of fermions and true superfluid (SF) condensation scenario of composite bosons (i.e. bipolarons and cooperons) in any Fermi-systems, where the SF condensate gap Δ B and the BCS-like pairing pseudogap Δ F have different origins. The pair and single particle condensations of attracting 3d and two- dimensional (2d) composite bosons are responsible for

  13. BEC-BCS crossover in a (p+ip)-wave pairing Hamiltonian coupled to bosonic molecular pairs

    International Nuclear Information System (INIS)

    Dunning, Clare; Isaac, Phillip S.; Links, Jon; Zhao, Shao-You

    2011-01-01

    We analyse a (p+ip)-wave pairing BCS Hamiltonian, coupled to a single bosonic degree of freedom representing a molecular condensate, and investigate the nature of the BEC-BCS crossover for this system. For a suitable restriction on the coupling parameters, we show that the model is integrable and we derive the exact solution by the algebraic Bethe ansatz. In this manner we also obtain explicit formulae for correlation functions and compute these for several cases. We find that the crossover between the BEC state and the strong pairing p+ip phase is smooth for this model, with no intermediate quantum phase transition.

  14. Fifteen years of seismic monitoring at the Las Tres Virgenes, BCS, geothermal field; Quince anos de monitoreo sismico en el campo geotermico de Las Tres Virgenes, BCS

    Energy Technology Data Exchange (ETDEWEB)

    Ortiz Prieto, Irais; Lorenzo Pulido, Cecilia [Comision Federal de Electricidad, Gerencia de Proyectos Geotermoelectricos, Morelia, Michoacan (Mexico)]. E-mail: cecilia.lorenzo@cfe.gob.mx

    2009-07-15

    Seismic monitoring at the Las Tres Virgenes, BCS, geothermal field started in 1992 with an analog station of vertical components detecting a large number of earthquakes of varying magnitudes. In February 1993, a seismic network was installed, composed of six digital stations DR-2000-with S-6000 and S-5000 sensors and three registration channels (N-S, E-W and vertical). This was the basis for the development of a program to correct arrival-time data for P and S waves due to instrument drift. From January to April 1994 and May to August 1995, based on the 170 seismic events recorded, a velocity model was proposed. From December 1995 to July 1996, seismic data were processed and interpreted, and zones of occurrence were determined for events according to magnitude and the predominant noise in the field. From September 2003 to December 2004, 10 seismic stations (permanent and temporary) were installed and monitored and it was concluded the most active fault system was El Volcan. From September to December 2004, production wells LV-4 and LV-13 were acid-stimulated and seismic monitoring during this period allowed for the definition of two important seismic zones, both related to the El Volcan fault system and to injection well LV-8. After reopening these production wells, it was concluded an increase in seismic activity had occurred. From May to August 2006, information was compiled from the seismic network and it was concluded El Partido had became the most active fault system. Presently the seismic network in this field is composed of one SARA station and four K2 units. The SARA station is telemetrically connected to the base station. [Spanish] En el campo geotermico de Las Tres Virgenes, BCS, el monitoreo sismico empezo a partir de 1992 con una sola estacion analogica de registro vertical, la cual detecto una gran cantidad de temblores de distintas magnitudes. En febrero de 1993 se instalo una red sismica con seis estaciones digitales DR-2000 con sensores S-6000 y S

  15. Interplay between superconductivity and magnetism in iron-based superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Chubukov, Andrey V [University of Wisconsin

    2015-06-10

    This proposal is for theoretical work on strongly correlated electron systems, which are at the center of experimental and theoretical activities in condensed-matter physics. The interest to this field is driven fascinating variety of observed effects, universality of underlying theoretical ideas, and practical applications. I propose to do research on Iron-based superconductors (FeSCs), which currently attract high attention in the physics community. My goal is to understand superconductivity and magnetism in these materials at various dopings, the interplay between the two, and the physics in the phase in which magnetism and superconductivity co-exist. A related goal is to understand the origin of the observed pseudogap-like behavior in the normal state. My research explores the idea that superconductivity is of electronic origin and is caused by the exchange of spin-fluctuations, enhanced due to close proximity to antiferromagnetism. The multi-orbital/multi-band nature of FeSCs opens routes for qualitatively new superconducting states, particularly the ones which break time-reversal symmetry. By all accounts, the coupling in pnictdes is below the threshold for Mott physics and I intend to analyze these systems within the itinerant approach. My plan is to do research in two stages. I first plan to address several problems within weak-coupling approach. Among them: (i) what sets stripe magnetic order at small doping, (ii) is there a preemptive instability into a spin-nematic state, and how stripe order affects fermions; (iii) is there a co-existence between magnetism and superconductivity and what are the system properties in the co-existence state; (iv) how superconductivity emerges despite strong Coulomb repulsion and can the gap be s-wave but with nodes along electron FSs, (v) are there complex superconducting states, like s+id, which break time reversal symmetry. My second goal is to go beyond weak coupling and derive spin-mediated, dynamic interaction between

  16. Hartree-Fock+BCS approach to unstable nuclei with the Skyrme force

    International Nuclear Information System (INIS)

    Tajima, Naoki

    2001-01-01

    We reanalyze the results of our extensive Hartree-Fock+BCS calculation from new points of view paying attention to the properties of unstable nuclei. The calculation has been done with the Skyrme SIII force for the ground and shape isomeric states of 1029 even-even nuclei ranging 2≤Z≤114. We also discuss the advantages of the employed three-dimensional Cartesian-mesh representation, especially on its remarkably high precision with apparently coarse meshes when applied to atomic nuclei. In Appendices we give the coefficients of finite-point numerical differentiation and integration formulae suitable for Cartesian mesh representation and elucidate the features of each formula and the differences from a method based on the Fourier transformation. (author)

  17. Purely in silico BCS classification: science based quality standards for the world's drugs.

    Science.gov (United States)

    Dahan, Arik; Wolk, Omri; Kim, Young Hoon; Ramachandran, Chandrasekharan; Crippen, Gordon M; Takagi, Toshihide; Bermejo, Marival; Amidon, Gordon L

    2013-11-04

    BCS classification is a vital tool in the development of both generic and innovative drug products. The purpose of this work was to provisionally classify the world's top selling oral drugs according to the BCS, using in silico methods. Three different in silico methods were examined: the well-established group contribution (CLogP) and atom contribution (ALogP) methods, and a new method based solely on the molecular formula and element contribution (KLogP). Metoprolol was used as the benchmark for the low/high permeability class boundary. Solubility was estimated in silico using a thermodynamic equation that relies on the partition coefficient and melting point. The validity of each method was affirmed by comparison to reference data and literature. We then used each method to provisionally classify the orally administered, IR drug products found in the WHO Model list of Essential Medicines, and the top-selling oral drug products in the United States (US), Great Britain (GB), Spain (ES), Israel (IL), Japan (JP), and South Korea (KR). A combined list of 363 drugs was compiled from the various lists, and 257 drugs were classified using the different in silico permeability methods and literature solubility data, as well as BDDCS classification. Lastly, we calculated the solubility values for 185 drugs from the combined set using in silico approach. Permeability classification with the different in silico methods was correct for 69-72.4% of the 29 reference drugs with known human jejunal permeability, and for 84.6-92.9% of the 14 FDA reference drugs in the set. The correlations (r(2)) between experimental log P values of 154 drugs and their CLogP, ALogP and KLogP were 0.97, 0.82 and 0.71, respectively. The different in silico permeability methods produced comparable results: 30-34% of the US, GB, ES and IL top selling drugs were class 1, 27-36.4% were class 2, 22-25.5% were class 3, and 5.46-14% were class 4 drugs, while ∼8% could not be classified. The WHO list

  18. Enhancement of mechanical properties of 123 superconductors

    Science.gov (United States)

    Balachandran, U.

    1995-04-25

    A composition and method are disclosed of preparing YBa{sub 2}Cu{sub 3}O{sub 7{minus}x} superconductor. Addition of tin oxide containing compounds to YBCO superconductors results in substantial improvement of fracture toughness and other mechanical properties without affect on T{sub c}. About 5-20% additions give rise to substantially improved mechanical properties.

  19. Electrodynamics of spin currents in superconductors

    International Nuclear Information System (INIS)

    Hirsch, J.E.

    2008-01-01

    In recent work we formulated a new set of electrodynamic equations for superconductors as an alternative to the conventional London equations, compatible with the prediction of the theory of hole superconductivity that superconductors expel negative charge from the interior towards the surface. Charge expulsion results in a macroscopically inhomogeneous charge distribution and an electric field in the interior, and because of this a spin current is expected to exist. Furthermore, we have recently shown that a dynamical explanation of the Meissner effect in superconductors leads to the prediction that a spontaneous spin current exists near the surface of superconductors (spin Meissner effect). In this paper we extend the electrodynamic equations proposed earlier for the charge density and charge current to describe also the space and time dependence of the spin density and spin current. This allows us to determine the magnitude of the expelled negative charge and interior electric field as well as of the spin current in terms of other measurable properties of superconductors. We also provide a 'geometric' interpretation of the difference between type I and type II superconductors, discuss how superconductors manage to conserve angular momentum, discuss the relationship between our model and Slater's seminal work on superconductivity, and discuss the magnitude of the expected novel effects for elemental and other superconductors. (Abstract Copyright [2008], Wiley Periodicals, Inc.)

  20. Enhancement of mechanical properties of 123 superconductors

    Science.gov (United States)

    Balachandran, Uthamalingam

    1995-01-01

    A composition and method of preparing YBa.sub.2 Cu.sub.3 O.sub.7-x superconductor. Addition of tin oxide containing compounds to YBCO superconductors results in substantial improvement of fracture toughness and other mechanical properties without affect on T.sub.c. About 5-20% additions give rise to substantially improved mechanical properties.

  1. Superconductors in the High School Classroom

    Science.gov (United States)

    Lincoln, James

    2017-01-01

    In this article, we discuss the behavior of high-temperature superconductors and how to demonstrate them safely and effectively in the high school or introductory physics classroom. Included here is a discussion of the most relevant physics topics that can be demonstrated, some safety tips, and a bit of the history of superconductors. In an effort…

  2. Hexatic vortex glass in disordered superconductors

    International Nuclear Information System (INIS)

    Chudnovsky, E.M.

    1989-01-01

    It is shown that interaction of the flux-line lattice with randomly arranged pinning centers should destroy the long-range positional order in the lattice, but not the long-range orientational order. A new phase: hexatic vortex glass, is suggested for the mixed state of disordered, type-II superconductors. Relevance to amorphous and high-T c superconductors is discussed

  3. Method of production multifilamentary intermetallic superconductors

    International Nuclear Information System (INIS)

    Marancik, W.G.; Young, M.S.

    1980-01-01

    A method of making A-15 type intermetallic superconductors is disclosed which features elimination of numerous annealing steps. Nb or V filaments are embedded in Cu matrices; annular layers of Sn or Ga, respectively, separated from each other by Cu layers, provide the other component of the intermetallic superconductors Nb3Sn and V3Ga

  4. Neutron-scattering studies of magnetic superconductors

    International Nuclear Information System (INIS)

    Sinha, S.K.; Crabtree, G.W.; Hinks, D.G.; Mook, H.A.; Pringle, O.A.

    1982-01-01

    Results obtained in the last few years obtained by neutron diffraction on the nature of the magnetic ordering in magnetic superconductors are reviewed. Emphasis is given to studies of the complex intermediate phase in ferromagnetic superconductors where both superconductivity and ferromagnetism appear to coexist

  5. The critical current of granular superconductor

    International Nuclear Information System (INIS)

    Ignat'ev, V.K.

    1998-01-01

    A mechanism of hyper vortex pinning in granular superconductors is proposed to describe the field dependence of the critical current density and pinning potential. The results are in a good agreement with the experiment. The model represents the peak effect and the percolation mechanism of conductivity in ceramic superconductors

  6. Provisional in-silico biopharmaceutics classification (BCS) to guide oral drug product development.

    Science.gov (United States)

    Wolk, Omri; Agbaria, Riad; Dahan, Arik

    2014-01-01

    The main objective of this work was to investigate in-silico predictions of physicochemical properties, in order to guide oral drug development by provisional biopharmaceutics classification system (BCS). Four in-silico methods were used to estimate LogP: group contribution (CLogP) using two different software programs, atom contribution (ALogP), and element contribution (KLogP). The correlations (r(2)) of CLogP, ALogP and KLogP versus measured LogP data were 0.97, 0.82, and 0.71, respectively. The classification of drugs with reported intestinal permeability in humans was correct for 64.3%-72.4% of the 29 drugs on the dataset, and for 81.82%-90.91% of the 22 drugs that are passively absorbed using the different in-silico algorithms. Similar permeability classification was obtained with the various in-silico methods. The in-silico calculations, along with experimental melting points, were then incorporated into a thermodynamic equation for solubility estimations that largely matched the reference solubility values. It was revealed that the effect of melting point on the solubility is minor compared to the partition coefficient, and an average melting point (162.7 °C) could replace the experimental values, with similar results. The in-silico methods classified 20.76% (± 3.07%) as Class 1, 41.51% (± 3.32%) as Class 2, 30.49% (± 4.47%) as Class 3, and 6.27% (± 4.39%) as Class 4. In conclusion, in-silico methods can be used for BCS classification of drugs in early development, from merely their molecular formula and without foreknowledge of their chemical structure, which will allow for the improved selection, engineering, and developability of candidates. These in-silico methods could enhance success rates, reduce costs, and accelerate oral drug products development.

  7. Topological surface states in nodal superconductors

    International Nuclear Information System (INIS)

    Schnyder, Andreas P; Brydon, Philip M R

    2015-01-01

    Topological superconductors have become a subject of intense research due to their potential use for technical applications in device fabrication and quantum information. Besides fully gapped superconductors, unconventional superconductors with point or line nodes in their order parameter can also exhibit nontrivial topological characteristics. This article reviews recent progress in the theoretical understanding of nodal topological superconductors, with a focus on Weyl and noncentrosymmetric superconductors and their protected surface states. Using selected examples, we review the bulk topological properties of these systems, study different types of topological surface states, and examine their unusual properties. Furthermore, we survey some candidate materials for topological superconductivity and discuss different experimental signatures of topological surface states. (topical review)

  8. Future applications of superconductors for industrial use

    International Nuclear Information System (INIS)

    Reddy, S.P.

    1988-01-01

    Superconductors have been in existence for many years. Recent developments in superconductivity at higher temperatures are directed towards the potential use of superconductors at ambient temperatures. The diligent efforts of the scientific, engineering, and political agencies in researching and developing superconducting materials have resulted in encouraging accomplishments. Although superconductors could be used in every branch of electrical engineering, the authors focuses on a few areas in this paper. The power distribution and utilization in a typical industry is compared to that of a system using superconductors. Brief discussions of various machines with superconductors at ambient temperatures, based on developments made so far on large superconducting machines, for potential industrial applications are included in this paper

  9. Quantifying the Chasm: Exploring the Impact of the BCS on Total Football Revenues for Division One Football Programs from 2002-2012

    Science.gov (United States)

    Caro, Cary A.

    2014-01-01

    The Bowl Championship Series served as a collection of bowl games that were designed to crown the national champion in Division One football. The BCS created two classifications of institutions in Division football, those that were granted automatic access (AQ) to the post-season games, and those that were not (non-AQ). The BCS also generated…

  10. The Combination of GIS and Biphasic to Better Predict In Vivo Dissolution of BCS Class IIb Drugs, Ketoconazole and Raloxifene.

    Science.gov (United States)

    Tsume, Yasuhiro; Igawa, Naoto; Drelich, Adam J; Amidon, Gregory E; Amidon, Gordon L

    2018-01-01

    The formulation developments and the in vivo assessment of Biopharmaceutical Classification System (BCS) class II drugs are challenging due to their low solubility and high permeability in the human gastrointestinal (GI) tract. Since the GI environment influences the drug dissolution of BCS class II drugs, the human GI characteristics should be incorporated into the in vitro dissolution system to predict bioperformance of BCS class II drugs. An absorptive compartment may be important in dissolution apparatus for BCS class II drugs, especially for bases (BCS IIb) because of high permeability, precipitation, and supersaturation. Thus, the in vitro dissolution system with an absorptive compartment may help predicting the in vivo phenomena of BCS class II drugs better than compendial dissolution apparatuses. In this study, an absorptive compartment (a biphasic device) was introduced to a gastrointestinal simulator. This addition was evaluated if this in vitro system could improve the prediction of in vivo dissolution for BCS class IIb drugs, ketoconazole and raloxifene, and subsequent absorption. The gastrointestinal simulator is a practical in vivo predictive tool and exhibited an improved in vivo prediction utilizing the biphasic format and thus a better tool for evaluating the bioperformance of BCS class IIb drugs than compendial apparatuses. Copyright © 2018. Published by Elsevier Inc.

  11. Simultaneous projection of particle-number and angular momentum BCS wave-functions in the rare-earth nuclei

    International Nuclear Information System (INIS)

    Oudih, M.R.; Benhamouda, N.; Fellah, M.; Allal, N.H.

    2000-01-01

    A method of simultaneous particle-number and angular-momentum projection of the BCS wave-function is presented. The particle number projection method is of FBCS type. In the frame work of the adiabatic approximation, the rotational energies of the axially symmetric even-even nuclei are established and numerically calculated for the rare-earth region. (author)

  12. Common phase diagram for low-dimensional superconductors

    International Nuclear Information System (INIS)

    Michalak, Rudi

    2003-01-01

    A phenomenological phase diagram which has been derived for high-temperature superconductors from NMR Knight-shift measurements of the pseudogap is compared to the phase diagram that is obtained for organic superconductors and spin-ladder superconductors, both low-dimensional systems. This is contrasted to the phase diagram of some Heavy Fermion superconductors, i.e. superconductors not constrained to a low dimensionality

  13. Passivation of high temperature superconductors

    Science.gov (United States)

    Vasquez, Richard P. (Inventor)

    1991-01-01

    The surface of high temperature superconductors such as YBa2Cu3O(7-x) are passivated by reacting the native Y, Ba and Cu metal ions with an anion such as sulfate or oxalate to form a surface film that is impervious to water and has a solubility in water of no more than 10(exp -3) M. The passivating treatment is preferably conducted by immersing the surface in dilute aqueous acid solution since more soluble species dissolve into the solution. The treatment does not degrade the superconducting properties of the bulk material.

  14. Microgravity Processing of Oxide Superconductors

    Science.gov (United States)

    Hofmeister, William H.; Bayuzick, Robert J.; Vlasse, Marcus; McCallum, William; Peters, Palmer (Technical Monitor)

    2000-01-01

    The primary goal is to understand the microstructures which develop under the nonequilibrium solidification conditions achieved by melt processing in copper oxide superconductor systems. More specifically, to define the liquidus at the Y- 1:2:3 composition, the Nd-1:2:3 composition, and several intermediate partial substitution points between pure Y-1:2:3 and Nd-1:2:3. A secondary goal has been to understand resultant solidification morphologies and pathways under a variety of experimental conditions and to use this knowledge to better characterize solidification phenomena in these systems.

  15. Intrinsic stability of technical superconductors

    International Nuclear Information System (INIS)

    Veringa, H.J.

    1981-10-01

    For the operation of technical superconductors under high current density conditions, the superconducting wires composing high current cables should be intrinsically stabilized. In this report the various important stability criteria are derived and investigated on their validity. An experimental set up is made to check the occurrence of magnetic instabilities if the different applicable criteria are violated. It is found that the observed instabilities can be predicted on the basis of the model given in this report. Production of high current cables based upon composites made by the ECN technique seems to be possible. (Auth.)

  16. Vortex ice in nanostructured superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Reichhardt, Charles [Los Alamos National Laboratory; Reichhardt, Cynthia J [Los Alamos National Laboratory; Libal, Andras J [Los Alamos National Laboratory

    2008-01-01

    We demonstrate using numerical simulations of nanostructured superconductors that it is possible to realize vortex ice states that are analogous to square and kagome ice. The system can be brought into a state that obeys either global or local ice rules by applying an external current according to an annealing protocol. We explore the breakdown of the ice rules due to disorder in the nanostructure array and show that in square ice, topological defects appear along grain boundaries, while in kagome ice, individual defects appear. We argue that the vortex system offers significant advantages over other artificial ice systems.

  17. Peak effect in twinned superconductors

    International Nuclear Information System (INIS)

    Larkin, A.I.; Marchetti, M.C.; Vinokur, V.M.

    1995-01-01

    A sharp maximum in the critical current J c as a function of temperature just below the melting point of the Abrikosov flux lattice has recently been observed in both low- and high-temperature superconductors. This peak effect is strongest in twinned crystals for fields aligned with the twin planes. We propose that this peak signals the breakdown of the collective pinning regime and the crossover to strong pinning of single vortices on the twin boundaries. This crossover is very sharp and can account for the steep drop of the differential resistivity observed in experiments. copyright 1995 The American Physical Society

  18. Electron-phonon interaction in the binary superconductor lutetium carbide LuC2 via first-principles calculations

    Science.gov (United States)

    Dilmi, S.; Saib, S.; Bouarissa, N.

    2018-06-01

    Structural, electronic, electron-phonon coupling and superconducting properties of the intermetallic compound LuC2 are investigated by means of ab initio pseudopotential plane wave method within the generalized gradient approximation. The calculated equilibrium lattice parameters yielded a very good accord with experiment. There is no imaginary phonon frequency in the whole Brillouin zone supporting thus the dynamical stability in the material of interest. The average electron-phonon coupling parameter is found to be 0.59 indicating thus a weak-coupling BCS superconductor. Using a reasonable value of μ* = 0.12 for the effective Coulomb repulsion parameter, the superconducting critical temperature Tc is found to be 3.324 which is in excellent agreement with the experimental value of 3.33 K. The effect of the spin-orbit coupling on the superconducting properties of the material of interest has been examined and found to be weak.

  19. Two-band superconductor magnesium diboride

    International Nuclear Information System (INIS)

    Xi, X X

    2008-01-01

    This review focuses on the most important features of the 40 K superconductor MgB 2 -the weakly interacting multiple bands (the σ and π bands) and the distinct multiple superconducting energy gaps (the σ and π gaps). Even though the pairing mechanism of superconductor MgB 2 is the conventional electron-phonon coupling, the prominent influence of the two bands and two gaps on its properties sets it apart from other superconductors. It leads to markedly different behaviors in upper critical field, vortex structure, magnetoresistance and many other superconducting and normal-state properties in MgB 2 from single-band superconductors. Further, it gives rise to new physics that does not exist in single-band superconductors, such as the internal Josephson effects between the two order parameters. These unique phenomena depend sensitively on scattering inside and between the two bands, and the intraband and interband scattering can be modified by chemical substitution and irradiation. MgB 2 has brought unprecedented attention to two-band superconductivity, which has been found to exist in other old and new superconductors. The legacy of MgB 2 will be long lasting because of this, as well as the lessons it teaches in terms of the search for new phonon-mediated higher T c superconductors

  20. Studies of high temperature superconductors

    International Nuclear Information System (INIS)

    Narlikar, A.

    1989-01-01

    The high temperature superconductors (HTSCs) discovered are from the family of ceramic oxides. Their large scale utilization in electrical utilities and in microelectronic devices are the frontal challenges which can perhaps be effectively met only through consolidated efforts and expertise of a multidisciplinary nature. During the last two years the growth of the new field has occurred on an international scale and perhaps has been more rapid than in most other fields. There has been an extraordinary rush of data and results which are continually being published as short texts dispersed in many excellent journals, some of which were started to ensure rapid publication exclusively in this field. As a result, the literature on HTSCs has indeed become so massive and so diffuse that it is becoming increasingly difficult to keep abreast with the important and reliable facets of this fast-growing field. This provided the motivation to evolve a process whereby both professional investigators and students can have ready access to up-to- date in-depth accounts of major technical advances happening in this field. The present series Studies of High Temperature Superconductors has been launched to, at least in part, fulfill this need

  1. Superconductors made of niobium germanide

    International Nuclear Information System (INIS)

    Newkirk, L.R.; Valencia, F.A.

    1976-01-01

    This invention concerns the superconductors and particularly the mass coatings of niobium germanide (Nb 3 Ge) exhibiting superconductor properties, as well as the compositions enabling them to be obtained, having transition temperatures of around 20 0 K or more. The invention proposes a composition of a material of the general formula Nb 3 Ge, containing from around 1 to around 10 at. % oxygen. Preferably, the material contains around 5 at. % of oxygen. The invention also proposes fabricated articles in which the compositions described above are associated with and joined to a metallic substrate. Hence, for instance, the present studies involving a superconducting power transmission line for direct current make it possible to envisage the use of conductors placed in a double envelope, enabling the superconducting element transmitting the current to be carried, whilst containing the cryogenic coolant. In this type of design, the coat of superconducting material surrounds a tube containing liquid helium or possibly liquid hydrogen if a sufficiently high superconduction transition temperature can be reached. The tube must be a good heat and electricity conductor in order to achieve good stability of the superconducting coating [fr

  2. High-Tc superconductor applications

    International Nuclear Information System (INIS)

    Anon.

    1988-01-01

    There has been much speculation about new products and business opportunities which high-Tc superconductors might make possible. However, with the exception of one Japanese survey, there have not been any recognized forecasts suggesting a timeframe and relative economic impact for proposed high-Tc products. The purpose of this survey is to provide definitive projections of the timetable for high-Tc product development, based on the combined forecasts of the leading U.S. superconductivity experts. The FTS panel of experts on high-Tc superconductor applications, representing both business and research, forecast the commercialization and economic impact for 28 classes of electronic, magnetic, communications, instrumentation, transportation, industrial, and power generation products. In most cases, forecasts predict the occurrence of developments within a 90% statistical confidence limit of 2-to-3 years. The report provides background information on the 28 application areas, as well as other information useful for strategic planners. The panel also forecast high-Tc research spending, markets, and international competitiveness, and provide insight into how the industry will evolve

  3. Superconductor bearings, flywheels and transportation

    International Nuclear Information System (INIS)

    Werfel, F N; Floegel-Delor, U; Rothfeld, R; Riedel, T; Goebel, B; Wippich, D; Schirrmeister, P

    2012-01-01

    This paper describes the present status of high temperature superconductors (HTS) and of bulk superconducting magnet devices, their use in bearings, in flywheel energy storage systems (FESS) and linear transport magnetic levitation (Maglev) systems. We report and review the concepts of multi-seeded REBCO bulk superconductor fabrication. The multi-grain bulks increase the averaged trapped magnetic flux density up to 40% compared to single-grain assembly in large-scale applications. HTS magnetic bearings with permanent magnet (PM) excitation were studied and scaled up to maximum forces of 10 kN axially and 4.5 kN radially. We examine the technology of the high-gradient magnetic bearing concept and verify it experimentally. A large HTS bearing is tested for stabilizing a 600 kg rotor of a 5 kWh/250 kW flywheel system. The flywheel rotor tests show the requirement for additional damping. Our compact flywheel system is compared with similar HTS–FESS projects. A small-scale compact YBCO bearing with in situ Stirling cryocooler is constructed and investigated for mobile applications. Next we show a successfully developed modular linear Maglev system for magnetic train operation. Each module levitates 0.25t at 10 mm distance during one-day operation without refilling LN 2 . More than 30 vacuum cryostats containing multi-seeded YBCO blocks are fabricated and are tested now in Germany, China and Brazil.

  4. Raman spectra of SDW superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Rout, G.C. [Condensed Matter Physics Group, Department of Physics, Government Science College, Chatrapur, Orissa 761 020 (India)]. E-mail: gcr@iopb.res.in; Bishoyi, K.C. [P.G. Department of Physics, F.M. College (Autonomous), Balasore, Orissa 756 001 (India); Behera, S.N. [Institute of Physics, Bhubaneswar 751 005 (India)

    2005-03-15

    We report the calculation of the phonon response of the coexistent spin density wave (SDW) and superconducting (SC) state and predict the observation of SC gap in the Raman spectra of rare-earth nickel borocarbide superconductors. The SDW state normally does not couple to the lattice and hence, the phonons in the system are not expected to be affected by the SDW state. But there is a possibility of observing SC gap mode in the Raman spectra of a SDW superconductor due to the coupling of the SC gap excitation to the Raman active phonons in the system via the electron-phonon (e-p) interaction. A theoretical model is used for the coexistent phase and electron-phonon interaction. Phonon Green's function is calculated by Zubarev's technique and the phonon self-energy due to e-p interaction which is given by electron density response function in the coexistent state corresponding to the SDW wave vector q = Q is evaluated. The results so obtained exhibit agreement with the experimental observations.

  5. Raman spectra of SDW superconductors

    International Nuclear Information System (INIS)

    Rout, G.C.; Bishoyi, K.C.; Behera, S.N.

    2005-01-01

    We report the calculation of the phonon response of the coexistent spin density wave (SDW) and superconducting (SC) state and predict the observation of SC gap in the Raman spectra of rare-earth nickel borocarbide superconductors. The SDW state normally does not couple to the lattice and hence, the phonons in the system are not expected to be affected by the SDW state. But there is a possibility of observing SC gap mode in the Raman spectra of a SDW superconductor due to the coupling of the SC gap excitation to the Raman active phonons in the system via the electron-phonon (e-p) interaction. A theoretical model is used for the coexistent phase and electron-phonon interaction. Phonon Green's function is calculated by Zubarev's technique and the phonon self-energy due to e-p interaction which is given by electron density response function in the coexistent state corresponding to the SDW wave vector q = Q is evaluated. The results so obtained exhibit agreement with the experimental observations

  6. Modified entropic gravitation in superconductors

    International Nuclear Information System (INIS)

    Matos, Clovis Jacinto de

    2012-01-01

    Verlinde recently developed a theoretical account of gravitation in terms of an entropic force. The central element in Verlinde’s derivation is information and its relation with entropy through the holographic principle. The application of this approach to the case of superconductors requires to take into account that information associated with superconductor’s quantum vacuum energy is not stored on Planck size surface elements, but in four volume cells with Planck-Einstein size. This has profound consequences on the type of gravitational force generated by the quantum vacuum condensate in superconductors, which is closely related with the cosmological repulsive acceleration responsible for the accelerated expansion of the Universe. Remarkably this new gravitational type force depends on the level of breaking of the weak equivalence principle for cooper pairs in a given superconducting material, which was previously derived by the author starting from similar principles. It is also shown that this new gravitational force can be interpreted as a surface force. The experimental detection of this new repulsive gravitational-type force appears to be challenging.

  7. High Temperature Superconductor Accelerator Magnets

    CERN Document Server

    AUTHOR|(CDS)2079328; de Rijk, Gijs; Dhalle, Marc

    2016-11-10

    For future particle accelerators bending dipoles are considered with magnetic fields exceeding $20T$. This can only be achieved using high temperature superconductors (HTS). These exhibit different properties from classical low temperature superconductors and still require significant research and development before they can be applied in a practical accelerator magnet. In order to study HTS in detail, a five tesla demonstrator magnet named Feather-M2 is designed and constructed. The magnet is based on ReBCO coated conductor, which is assembled into a $10kA$ class Roebel cable. A new and optimized Aligned Block layout is used, which takes advantage of the anisotropy of the conductor. This is achieved by providing local alignment of the Roebel cable in the coil windings with the magnetic field lines. A new Network Model capable of analyzing transient electro-magnetic and thermal phenomena in coated conductor cables and coils is developed. This model is necessary to solve critical issues in coated conductor ac...

  8. Position-sensitive superconductor detectors

    International Nuclear Information System (INIS)

    Kurakado, M.; Taniguchi, K.

    2016-01-01

    Superconducting tunnel junction (STJ) detectors and superconducting transition- edge sensors (TESs) are representative superconductor detectors having energy resolutions much higher than those of semiconductor detectors. STJ detectors are thin, thereby making it suitable for detecting low-energy X rays. The signals of STJ detectors are more than 100 times faster than those of TESs. By contrast, TESs are microcalorimeters that measure the radiation energy from the change in the temperature. Therefore, signals are slow and their time constants are typically several hundreds of μs. However, TESs possess excellent energy resolutions. For example, TESs have a resolution of 1.6 eV for 5.9-keV X rays. An array of STJs or TESs can be used as a pixel detector. Superconducting series-junction detectors (SSJDs) comprise multiple STJs and a single-crystal substrate that acts as a radiation absorber. SSJDs are also position sensitive, and their energy resolutions are higher than those of semiconductor detectors. In this paper, we give an overview of position-sensitive superconductor detectors.

  9. S-I-N tunneling spectroscopy of MgB2 superconductor: evidence of two superconducting energy gaps

    International Nuclear Information System (INIS)

    Sen, Shashwati; Aswal, D.K.; Singh, Ajay; Gadkari, S.C.; Shah, K.; Gupta, S.K.; Sahni, V.C.

    2002-01-01

    The tunneling spectra of polycrystalline MgB 2 , have been recorded, at different temperatures between 29 K and T c , using planar superconductor- insulating-normal (S-I-N) tunneling spectroscopy. The planar S-I-N tunnel junctions have been fabricated by thermally evaporating Ag electrodes on MgB 2 surface. The naive layer, which forms at the surface of MgB 2 , due to atmospheric degradation, was employed as an insulating layer between Ag electrodes and MgB 2 . We have found presence of two clear superconducting energy gaps in MgB 2 . The magnitudes of these gaps at 29.5 K are 1.8 and 5.9 MeV, respectively. In the vicinity of T c , while larger energy gap obeyed BCS temperature dependence, the smaller energy gap deviated from BCS dependence. All the spectra exhibited zero-bias conductance, which decreased linearly with temperature and vanished at T c . (author)

  10. Electronic structure of transition metal dichalcogenides PdTe2 and Cu0.05PdTe2 superconductors obtained by angle-resolved photoemission spectroscopy

    International Nuclear Information System (INIS)

    Liu Yan; Zhao Jian-Zhou; Yu Li; Hu Cheng; Liu De-Fa; Peng Ying-Ying; Xie Zhuo-Jin; He Jun-Feng; Chen Chao-Yu; Feng Ya; Yi He-Mian; Liu Xu; Zhao Lin; He Shao-Long; Liu Guo-Dong; Dong Xiao-Li; Zhang Jun; Lin Cheng-Tian; Chen Chuang-Tian; Xu Zu-Yan

    2015-01-01

    The layered transition metal chalcogenides have been a fertile land in solid state physics for many decades. Various MX 2 -type transition metal dichalcogenides, such as WTe 2 , IrTe 2 , and MoS 2 , have triggered great attention recently, either for the discovery of novel phenomena or some extreme or exotic physical properties, or for their potential applications. PdTe 2 is a superconductor in the class of transition metal dichalcogenides, and superconductivity is enhanced in its Cu-intercalated form, Cu 0.05 PdTe 2 . It is important to study the electronic structures of PdTe 2 and its intercalated form in order to explore for new phenomena and physical properties and understand the related superconductivity enhancement mechanism. Here we report systematic high resolution angle-resolved photoemission (ARPES) studies on PdTe 2 and Cu 0.05 PdTe 2 single crystals, combined with the band structure calculations. We present in detail for the first time the complex multi-band Fermi surface topology and densely-arranged band structure of these compounds. By carefully examining the electronic structures of the two systems, we find that Cu-intercalation in PdTe 2 results in electron-doping, which causes the band structure to shift downwards by nearly 16 meV in Cu 0.05 PdTe 2 . Our results lay a foundation for further exploration and investigation on PdTe 2 and related superconductors. (rapid communication)

  11. Synthesis of highly phase pure BSCCO superconductors

    Science.gov (United States)

    Dorris, S.E.; Poeppel, R.B.; Prorok, B.C.; Lanagan, M.T.; Maroni, V.A.

    1995-11-21

    An article and method of manufacture (Bi, Pb)-Sr-Ca-Cu-O superconductor are disclosed. The superconductor is manufactured by preparing a first powdered mixture of bismuth oxide, lead oxide, strontium carbonate, calcium carbonate and copper oxide. A second powdered mixture is then prepared of strontium carbonate, calcium carbonate and copper oxide. The mixtures are calcined separately with the two mixtures then combined. The resulting combined mixture is then subjected to a powder in tube deformation and thermal processing to produce a substantially phase pure (Bi, Pb)-Sr-Ca-Cu-O superconductor. 5 figs.

  12. Superconductor in a weak static gravitational field

    Energy Technology Data Exchange (ETDEWEB)

    Ummarino, Giovanni Alberto [Dipartimento DISAT, Politecnico di Torino, Turin (Italy); National Research Nuclear University MEPhI-Moscow Engineering Physics Institute, Moscow (Russian Federation); Gallerati, Antonio [Dipartimento DISAT, Politecnico di Torino, Turin (Italy)

    2017-08-15

    We provide the detailed calculation of a general form for Maxwell and London equations that takes into account gravitational corrections in linear approximation. We determine the possible alteration of a static gravitational field in a superconductor making use of the time-dependent Ginzburg-Landau equations, providing also an analytic solution in the weak field condition. Finally, we compare the behavior of a high-T{sub c} superconductor with a classical low-T{sub c} superconductor, analyzing the values of the parameters that can enhance the reduction of the gravitational field. (orig.)

  13. Two-dimensional Semiconductor-Superconductor Hybrids

    DEFF Research Database (Denmark)

    Suominen, Henri Juhani

    This thesis investigates hybrid two-dimensional semiconductor-superconductor (Sm-S) devices and presents a new material platform exhibiting intimate Sm-S coupling straight out of the box. Starting with the conventional approach, we investigate coupling superconductors to buried quantum well....... To overcome these issues we integrate the superconductor directly into the semiconducting material growth stack, depositing it in-situ in a molecular beam epitaxy system under high vacuum. We present a number of experiments on these hybrid heterostructures, demonstrating near unity interface transparency...

  14. Electromagnetic properties of metals and superconductors

    International Nuclear Information System (INIS)

    Sinha, K.P.

    1977-01-01

    Part 1: Metals. 1. Introduction. 1.1. Normal and anomalous skin effects. 2. Helicons and magneto-plasma waves. 3. Helicon-phonon interaction. 3.1. Magneto-plasma (Alfven) waves. 4. Cyclotron waves. 5. Spin waves in electron system. Part 2: Superconductors. 6. Introduction. 6.1. Response to weak electromagnetic fields. 7. Effect of strong radiation field on superconductors. 8. Laser-induced non-equilibrium state in superconductors. 9. Possibility of photon-induced electron pairing - one-boson processes. 10. Possibility of photon-induced electron pairing -two-boson processes. (author)

  15. Solar flare hard and soft x ray relationship determined from SMM HXRBS and BCS data

    Science.gov (United States)

    Toot, G. David

    1989-01-01

    The exact nature of the solar flare process is still somewhat a mystery. A key element to understanding flares if the relationship between the hard x rays emitted by the most energetic portions of the flare and the soft x rays from other areas and times. This relationship was studied by comparing hard x ray light curved from the Hard X-Ray Burst Spectrometer (HXRBS) with the soft x ray light curve and its derivation from the Bent Crystal Spectrometer (BCS) which is part of the X-Ray Polychrometer (XRP), these instruments being on the Solar Maximum Mission spacecraft (SMM). Data sample was taken from flares observed with the above instruments during 1980, the peak of the previous maximum of solar activity. Flares were chosen based on complete coverage of the event by several instruments. The HXRBS data covers the x ray spectrum from about 25 keV to about 440 keV in 15 spectral channels, while the BCS data used covers a region of the Spectrum around 3 angstroms including emission from the Ca XIX ion. Both sets of data were summed over their spectral ranges and plotted against time at a maximum time resolution of around 3 seconds. The most popular theory of flares holds that a beam of electrons produces the hard x rays by bremsstrahlung while the soft x rays are the thermal response to this energy deposition. The question is whether the rate of change of soft x ray emission might reflect the variability of the electron beam and hence the variability of the hard x rays. To address this, we took the time derivative of the soft x ray light curve and compared it to the hard flares, 12 of them showed very closed agreement between the soft x ray derivative and the hard x ray light curve. The other five did not show this behavior but were similar to each other in general soft x ray behavior. Efforts to determine basic differences between the two kinds of flares continue. In addition the behavior of soft x ray temperature of flares was examined.

  16. The low/high BCS permeability class boundary: physicochemical comparison of metoprolol and labetalol.

    Science.gov (United States)

    Zur, Moran; Gasparini, Marisa; Wolk, Omri; Amidon, Gordon L; Dahan, Arik

    2014-05-05

    Although recognized as overly conservative, metoprolol is currently the common low/high BCS permeability class boundary reference compound, while labetalol was suggested as a potential alternative. The purpose of this study was to identify the various characteristics that the optimal marker should exhibit, and to investigate the suitability of labetalol as the permeability class reference drug. Labetalol's BCS solubility class was determined, and its physicochemical properties and intestinal permeability were thoroughly investigated, both in vitro and in vivo in rats, considering the complexity of the whole of the small intestine. Labetalol was found to be unequivocally a high-solubility compound. In the pH range throughout the small intestine (6.5-7.5), labetalol exhibited pH-dependent permeability, with higher permeability at higher pH values. While in vitro octanol-buffer partitioning (Log D) values of labetalol were significantly higher than those of metoprolol, the opposite was evident in the in vitro PAMPA permeability assay. The results of the in vivo perfusion studies in rats lay between the two contradictory in vitro studies; metoprolol was shown to have moderately higher rat intestinal permeability than labetalol. Theoretical distribution of the ionic species of the drugs was in corroboration with the experimental in vitro and the in vivo data. We propose three characteristics that the optimal permeability class reference drug should exhibit: (1) fraction dose absorbed in the range of 90%; (2) the optimal marker drug should be absorbed largely via passive transcellular permeability, with no/negligible carrier-mediated active intestinal transport (influx or efflux); and (3) the optimal marker drug should preferably be nonionizable. The data presented in this paper demonstrate that neither metoprolol nor labetalol can be regarded as optimal low/high-permeability class boundary standard. While metoprolol is too conservative due to its complete absorption

  17. Two classes of superconductors discovered in our material research: Iron-based high temperature superconductor and electride superconductor

    International Nuclear Information System (INIS)

    Hosono, Hideo

    2009-01-01

    We discovered two new classes of superconductors in the course of material exploration for electronic-active oxides. One is 12CaO . 7Al 2 O 3 crystal in which electrons accomodate in the crystallographic sub-nanometer-sized cavities. This material exhibiting metal-superconductor transition at 0.2 K is the first electride superconductor. The other is iron oxypnicitides with a layered structure. This superconductor is rather different from high T c cuprates in several respects. The high T c is emerged by doping carriers to the metallic parent phases which undergo crystallographic transition (tetra to ortho) and Pauli para to antiferromagnetic transition at ∼150 K. The T c is robust to impurity doping to the Fe sites or is induced by partial substitution of the Fe 2+ sites with Co 2+ or Ni 2+ . This article gives a brief summary of these discoveries and recent advances.

  18. Competing pseudogap and impurity effects on the normal-state specific heat properties of cuprate superconductors

    Science.gov (United States)

    Dzhumanov, S.; Karimboev, E. X.

    2014-07-01

    In this paper, we show that the pseudogap in the excitation spectra of high-Tc cuprates together with the impurity phase and charge inhomogeneity plays key roles in determining the essential features of their anomalous specific heat properties observed above Tc. We consider the doped cuprate superconductor as a multi-carrier model system (which consists of intrinsic and extrinsic polarons and pre-formed bosonic Cooper pairs) and study the competing pseudogap and impurity effects on the normal-state electronic specific heat of high-Tc cuprates taking into account charge inhomogeneities. We argue that unconventional electron-phonon interactions are responsible for the precursor Cooper pairing in the polaronic band below a mean-field temperature T∗ and the existence of a pseudogap above Tc in the cuprates. The electronic specific heat Ce(T) of doped cuprates below T∗ is calculated taking into account three contributions coming from the excited components of Cooper pairs, the ideal Bose-gas of incoherent Cooper pairs and the unpaired carriers in the impurity band. Above T∗, two contributions to Ce(T) coming from the unpaired intrinsic and extrinsic polarons are calculated within the two-component degenerate Fermi-gas model. By comparing our results with the experimental Ce(T) data obtained for La- and Y-based cuprates, we find that the observed behaviors of Ce(T) (below and above T∗) are similar to the calculated results for Ce(T) and the BCS-type jumps of Ce(T) at T∗ may be depressed by the impurity effects and may become more or less pronounced BCS-type anomalies in Ce(T) .

  19. San Juanico, BCS, Mexico, hybrid electric plant renewable energies in the rural communities development; Planta electrica hibrida San Juanico, B.C.S., Mexico, las energias renovables en el desarrollo de las comunidades rurales

    Energy Technology Data Exchange (ETDEWEB)

    Lopez Rios, Serafin [Gerencia de Proyectos Geotermoelectricos, Comision Federal de Electricidad (Mexico)

    1999-08-01

    The hybrid electric plant of San Juanico, B.C.S., Mexico, is described in terms of its environmental goals, operating process and contribution to the development of that rural community of the Baja California Peninsula. San Juanico hybrid electric plant is organized in three electrical generation systems that work in parallel: one uses solar energy, another wind energy and a third one uses diesel fuel. [Spanish] Se describe la planta hibrida de San Juanico, BCS, Mexico, en terminos de los objetivos ambientales que condujeron a su realizacion, asi como de su proceso operativo y de la participacion que tiene en el desarrollo de esa comunidad rural de la peninsula de Baja California, Mexico. La planta hibrida de San Juanico esta constituida por tres sistemas de generacion de electrcicidad que operan en paralelo: uno utiliza energia radiante del sol, otro energia del viento y un tercero utiliza diesel.

  20. Pairing in the BCS and LN approximations using continuum single particle level density

    International Nuclear Information System (INIS)

    Id Betan, R.M.; Repetto, C.E.

    2017-01-01

    Understanding the properties of drip line nuclei requires to take into account the correlations with the continuum spectrum of energy of the system. This paper has the purpose to show that the continuum single particle level density is a convenient way to consider the pairing correlation in the continuum. Isospin mean-field and isospin pairing strength are used to find the Bardeen–Cooper–Schrieffer (BCS) and Lipkin–Nogami (LN) approximate solutions of the pairing Hamiltonian. Several physical properties of the whole chain of the Tin isotope, as gap parameter, Fermi level, binding energy, and one- and two-neutron separation energies, were calculated and compared with other methods and with experimental data when they exist. It is shown that the use of the continuum single particle level density is an economical way to include explicitly the correlations with the continuum spectrum of energy in large scale mass calculation. It is also shown that the computed properties are in good agreement with experimental data and with more sophisticated treatment of the pairing interaction.

  1. Effects of cluster-shell competition and BCS-like pairing in 12C

    Science.gov (United States)

    Matsuno, H.; Itagaki, N.

    2017-12-01

    The antisymmetrized quasi-cluster model (AQCM) was proposed to describe α-cluster and jj-coupling shell models on the same footing. In this model, the cluster-shell transition is characterized by two parameters, R representing the distance between α clusters and Λ describing the breaking of α clusters, and the contribution of the spin-orbit interaction, very important in the jj-coupling shell model, can be taken into account starting with the α-cluster model wave function. Not only the closure configurations of the major shells but also the subclosure configurations of the jj-coupling shell model can be described starting with the α-cluster model wave functions; however, the particle-hole excitations of single particles have not been fully established yet. In this study we show that the framework of AQCM can be extended even to the states with the character of single-particle excitations. For ^{12}C, two-particle-two-hole (2p2h) excitations from the subclosure configuration of 0p_{3/2} corresponding to a BCS-like pairing are described, and these shell model states are coupled with the three α-cluster model wave functions. The correlation energy from the optimal configuration can be estimated not only in the cluster part but also in the shell model part. We try to pave the way to establish a generalized description of the nuclear structure.

  2. Generalized Heine–Stieltjes and Van Vleck polynomials associated with two-level, integrable BCS models

    International Nuclear Information System (INIS)

    Marquette, Ian; Links, Jon

    2012-01-01

    We study the Bethe ansatz/ordinary differential equation (BA/ODE) correspondence for Bethe ansatz equations that belong to a certain class of coupled, nonlinear, algebraic equations. Through this approach we numerically obtain the generalized Heine–Stieltjes and Van Vleck polynomials in the degenerate, two-level limit for four cases of integrable Bardeen–Cooper–Schrieffer (BCS) pairing models. These are the s-wave pairing model, the p + ip-wave pairing model, the p + ip pairing model coupled to a bosonic molecular pair degree of freedom, and a newly introduced extended d + id-wave pairing model with additional interactions. The zeros of the generalized Heine–Stieltjes polynomials provide solutions of the corresponding Bethe ansatz equations. We compare the roots of the ground states with curves obtained from the solution of a singular integral equation approximation, which allows for a characterization of ground-state phases in these systems. Our techniques also permit the computation of the roots of the excited states. These results illustrate how the BA/ODE correspondence can be used to provide new numerical methods to study a variety of integrable systems. (paper)

  3. Lipid Based Formulations of Biopharmaceutics Classification System (BCS Class II Drugs: Strategy, Formulations, Methods and Saturation

    Directory of Open Access Journals (Sweden)

    Šoltýsová I.

    2016-12-01

    Full Text Available Active ingredients in pharmaceuticals differ by their physico-chemical properties and their bioavailability therefore varies. The most frequently used and most convenient way of administration of medicines is oral, however many drugs are little soluble in water. Thus they are not sufficiently effective and suitable for such administration. For this reason a system of lipid based formulations (LBF was developed. Series of formulations were prepared and tested in water and biorelevant media. On the basis of selection criteria, there were selected formulations with the best emulsification potential, good dispersion in the environment and physical stability. Samples of structurally different drugs included in the Class II of the Biopharmaceutics classification system (BCS were obtained, namely Griseofulvin, Glibenclamide, Carbamazepine, Haloperidol, Itraconazol, Triclosan, Praziquantel and Rifaximin, for testing of maximal saturation in formulations prepared from commercially available excipients. Methods were developed for preparation of formulations, observation of emulsification and its description, determination of maximum solubility of drug samples in the respective formulation and subsequent analysis. Saturation of formulations with drugs showed that formulations 80 % XA and 20 % Xh, 35 % XF and 65 % Xh were best able to dissolve the drugs which supports the hypothesis that it is desirable to identify limited series of formulations which could be generally applied for this purpose.

  4. Trends in Energy Management Technology: BCS Integration Technologies - Open Communications Networking

    Energy Technology Data Exchange (ETDEWEB)

    Webster, Tom

    2002-09-18

    Our overall purpose in writing this series of articles is to provide Federal energy managers some basic informational tools to assist their decision making process relative to energy management systems design, specification, procurement, and energy savings potential. Since Federal buildings rely on energy management systems more than their commercial counterparts, it is important for energy practitioners to have a high level of knowledge and understanding of these complex systems. This is the second article in a series and will focus on building control system (BCS) networking fundamentals and an assessment of current approaches to open communications protocols. This is important because networking is a complex subject and the networks form the basic infrastructure for energy management functions and for integrating a wide variety of OEM equipment into a complete EMCIS. The first article [1] covered enabling technologies for emerging energy management systems. Future topics will concentrate on more practical aspects including applications software, product offerings, networking strategies, and case studies of actual installations. Please refer to the first article for a more complete overview of the purpose and background for this series.

  5. Unconventional superconductors. Anisotropy and multiband effects

    Energy Technology Data Exchange (ETDEWEB)

    Askerzade, Iman [Ankara Univ. (Turkey). Center of Excellence of Superconductivity Research of Turkey; Azerbaijan National Academy of Sciences (Azerbaijan). Inst. of Physics

    2012-07-01

    This book deals with the new class of materials unconventional superconductors, cuprate compounds, borocarbides, magnesium-diboride and oxypnictides. It gives a systematical review of physical properties of novel superconductors. There is an increasing number of fundamental properties of these compounds which are relevant to future applications, opening new possibilities. The theoretical explanation is presented as generalization of Ginzburg-Landau phenomenology and microscopical Eliashberg theory for multiband and anisotropic superconductors. Various applications of this approaches and time dependent version of two-band Ginzburg-Landau theory are considered. An important topic are fluctuations in two-band and anisotropic superconductors. Significant new results on current problems are presented to stimulate further research. Numerous illustrations, diagrams and tables make this book useful as a reference for students and researchers. (orig.)

  6. Performance boundaries in Nb3Sn superconductors

    NARCIS (Netherlands)

    Godeke, A.

    2005-01-01

    Superconducting magnets for High Energy Physics, Fusion, Magnetic Resonance Imaging (NMR) and Nuclear Magnetic Resonance, benefit from the extremely high current densities that can be achieved in superconductors compared to normal conducting materials. These magnets are usually constructed starting

  7. Unconventional superconductors anisotropy and multiband effects

    CERN Document Server

    Askerzade, Iman

    2012-01-01

    This book deals with the new class of materials unconventional superconductors, cuprate compounds, borocarbides, magnesium-diboride and oxypnictides. It gives a systematical review of physical properties of novel  superconductors. There is an increasing number of fundamental properties of these compounds which are relevant to future applications, opening new possibilities. The theoretical explanation is presented as generalization of Ginzburg-Landau phenomenology and microscopical Eliashberg theory for multiband and anisotropic superconductors. Various applications of this approachs and time dependent version of two-band Ginzburg-Landau theory are considered. An important topic are fluctuations in two-band and anisotropic superconductors. Significant  new results on current problems are presented to stimulate further research. Numerous illustrations, diagrams and tables make this book useful as a reference for students and researchers.

  8. High Temperature Superconductor Bolometers for Planetary Science

    Data.gov (United States)

    National Aeronautics and Space Administration — This work is a design study of an instrument optimized for JPL's novel high temperature superconductor bolometers. The work involves designing an imaging...

  9. Progress of metallic superconductors in Japan

    Energy Technology Data Exchange (ETDEWEB)

    Tachikawa, Kyoji, E-mail: tacsuper@keyaki.cc.u-tokai.ac.jp [Faculty of Engineering, Tokai University, 4-1-1, Kitakaname, Hiratsuka, Kanagawa 259-1292 (Japan)

    2013-01-15

    Highlights: ► Japanese contributions on the R and D of different metallic superconductors are summarized. ► Nb–Ti wires have been developed for MRI, accelerator, MAGLEV train and other applications. ► Multifilamentary Nb{sub 3}Sn wires with excellent performance have been developed for high-field use. ► Long-length Nb{sub 3}Al wires with promising strain tolerance have been fabricated by a new process. -- Abstract: This article overviews the development of metallic superconductors in Japan covering different kinds of alloys and intermetallic compounds. Metallic superconductors have opened many new application areas in science and technology. Japan has been one of the leading countries in the world, both in the research and development and in large-scale manufacturing of metallic superconductors.

  10. Neutron irradiation effects in advanced superconductors

    International Nuclear Information System (INIS)

    Yoshida, H.; Kodaka, H.; Miyata, K.; Hayashi, Y.; Atobe, K.

    1988-01-01

    This paper reports the effects of neutron irradiation on superconducting transitions studied by susceptibility and resistivity measurements for A15 type compounds, Laves-phase compounds and oxide superconductors. For A15 superconductors, the transition temperature (T c ) decreased with increasing neutron fluence and showed large drop started at about 5 x 10 18 n/cm 2 (E > 0.1 MeV). Post-irradiation annealing gave recovery of T c , but the behaviors were different for the materials with different composition and microstructure. The Laves-phase compounds showed less degradation than the A15 superconductors. For oxide superconductors very sensitive transition change was observed, including the radiation-induced superconductivity

  11. High temperature superconductors and other superfluids

    CERN Document Server

    Alexandrov, A S

    2017-01-01

    Written by eminent researchers in the field, this text describes the theory of superconductivity and superfluidity starting from liquid helium and a charged Bose-gas. It also discusses the modern bipolaron theory of strongly coupled superconductors, which explains the basic physical properties of high-temperature superconductors. This book will be of interest to fourth year graduate and postgraduate students, specialist libraries, information centres and chemists working in high-temperature superconductivity.

  12. Force measurements for levitated bulk superconductors

    International Nuclear Information System (INIS)

    Tachi, Y.; Sawa, K.; Iwasa, Y.; Nagashima, K.; Otani, T.; Miyamoto, T.; Tomita, M.; Murakami, M.

    2000-01-01

    We have developed a force measurement system which enables us to directly measure the levitation force of levitated bulk superconductors. Experimental data of the levitation forces were compared with the results of numerical simulation based on the levitation model that we deduced in our previous paper. They were in fairly good agreement, which confirms that our levitation model can be applied to the force analyses for levitated bulk superconductors. (author)

  13. Force measurements for levitated bulk superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Tachi, Y. [Department of Electrical Engineering, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama (Japan); ISTEC, Superconductivity Research Laboratory, 1-16-25 Shibaura, Minato-ku, Tokyo (Japan). E-mail: tachi at istec.or.jp; Uemura, N. [Department of Electrical Engineering, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama (Japan); ISTEC, Superconductivity Research Laboratory, 1-16-25 Shibaura, Minato-ku, Tokyo (Japan); Sawa, K. [Department of Electrical Engineering, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama (Japan); Iwasa, Y. [Francis Bitter Magnet Laboratory, Massachusetts Institute of Technology, Cambridge, MA (United States); Nagashima, K. [Railway Technical Research Institute, Hikari-cho, Kokubunji-shi, Tokyo (Japan); Otani, T.; Miyamoto, T.; Tomita, M.; Murakami, M. [ISTEC, Superconductivity Research Laboratory, 1-16-25 Shibaura, Minato-ku, Tokyo (Japan)

    2000-06-01

    We have developed a force measurement system which enables us to directly measure the levitation force of levitated bulk superconductors. Experimental data of the levitation forces were compared with the results of numerical simulation based on the levitation model that we deduced in our previous paper. They were in fairly good agreement, which confirms that our levitation model can be applied to the force analyses for levitated bulk superconductors. (author)

  14. Superconductors in the power grid materials and applications

    CERN Document Server

    2015-01-01

    Superconductors offer high throughput with low electric losses and have the potential to transform the electric power grid. Transmission networks incorporating cables of this type could, for example, deliver more power and enable substantial energy savings. Superconductors in the Power Grid: Materials and Applications provides an overview of superconductors and their applications in power grids. Sections address the design and engineering of cable systems and fault current limiters and other emerging applications for superconductors in the power grid, as well as case studies of industrial applications of superconductors in the power grid. Expert editor from highly respected US government-funded research centre Unique focus on superconductors in the power grid Comprehensive coverage

  15. Superconductors for pulsed rf accelerators

    International Nuclear Information System (INIS)

    Campisi, I.E.; Farkas, Z.D.

    1985-04-01

    The choice of superconducting materials for accelerator rf cavities has been determined in the past only in part by basic properties of the superconductors, such as the critical field, and to a larger extent by criteria which include fabrication processes, surface conditions, heat transfer capabilities and so on. For cw operated cavities the trend has been toward choosing materials with higher critical temperatures and lower surface resistance, from Lead to Niobium, from Niobium to Nb 3 Sn. This trend has been dictated by the specific needs of storage ring cw system and by the relatively low fields which could be reached without breakdown. The work performed at SLAC on superconducting cavities using microsecond long high power rf pulses has shown that in Pb, Nb, and Nb 3 Sn fields close to the critical magnetic fields can be reached without magnetic breakdown

  16. Electromagnetic theory for filamentary superconductors

    International Nuclear Information System (INIS)

    Carr, W.J. Jr.

    1975-01-01

    It is shown that a multifilament superconductor, made up of a bundle of twisted filaments embedded in a normal matrix, can be treated as a new state of matter with anisotropic electrical and magnetic properties. Macroscopic electromagnetic field vectors, which satisfy Maxwell's equations, are defined in terms of averages over the ''microscopic'' fields. However, the sources for the field, i.e., the current and charge densities and the magnetization and polarization, differ in some respects from those for ordinary matter. In particular, since the elementary magnetic dipole moments are distributed along lines rather than located at fixed points, the definition of the magnetization transverse to the filaments differs by a factor of 2 from that for ordinary matter, and the definition of the macroscopic current density is also slightly modified. Constitutive relationships among the field vectors in terms of permeabilities, dielectric constants, and conductivities are examined in the limits of strong and weak fields

  17. New possibilities for superconductor electronics

    International Nuclear Information System (INIS)

    Likharev, K.K.; Semenov, V.K.; Zorin, A.B.

    1989-01-01

    Situation in the superconducting electronics, the field being developed since mid '60s has changed drastically recently as a result of not only discovery of the high-T c superconductivity, but also of the nearly simultaneous invention of several novel electronic devices. A detailed analysis of the new situation and prospects of this important field was carried out recently by the present authors of this paper. A complete report on our analysis is being published elsewhere, while in this paper we are presenting a brief summary of its results. The analysis has shown that the virtually only advantage which can arise from applications of the high-T c superconductors in electronics is a drastic reduction of the refrigeration costs, rather than an improvement of the device performance

  18. Plutonium helps probe protein, superconductor

    International Nuclear Information System (INIS)

    Anon.

    1990-01-01

    Scientists are finding that plutonium can be a useful research tool that may help them answer important questions in fields as diverse as biochemistry and solid-state physics. This paper reports that U.S. research involving plutonium is confined to the Department of Energy's national laboratories and centers around nuclear weapons technology, waste cleanup and disposal, and health effects. But at Los Alamos National Laboratory, scientists also are using plutonium to probe the biochemical behavior of calmodulin, a key calcium-binding protein that mediates calcium-regulated processes in biological systems. At Argonne National Laboratory, another team is trying to learn how a superconductor's properties are affected by the 5f electrons of an actinide like plutonium

  19. Search for Majorana fermions in topological superconductors.

    Energy Technology Data Exchange (ETDEWEB)

    Pan, Wei [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Shi, Xiaoyan [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Hawkins, Samuel D. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Klem, John Frederick [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2014-10-01

    The goal of this project is to search for Majorana fermions (a new quantum particle) in a topological superconductor (a new quantum matter achieved in a topological insulator proximitized by an s-wave superconductor). Majorana fermions (MFs) are electron-like particles that are their own anti-particles. MFs are shown to obey non-Abelian statistics and, thus, can be harnessed to make a fault-resistant topological quantum computer. With the arrival of topological insulators, novel schemes to create MFs have been proposed in hybrid systems by combining a topological insulator with a conventional superconductor. In this LDRD project, we will follow the theoretical proposals to search for MFs in one-dimensional (1D) topological superconductors. 1D topological superconductor will be created inside of a quantum point contact (with the metal pinch-off gates made of conventional s-wave superconductors such as niobium) in a two-dimensional topological insulator (such as inverted type-II InAs/GaSb heterostructure).

  20. Topological insulators and superconductors from string theory

    International Nuclear Information System (INIS)

    Ryu, Shinsei; Takayanagi, Tadashi

    2010-01-01

    Topological insulators and superconductors in different spatial dimensions and with different discrete symmetries have been fully classified recently, revealing a periodic structure for the pattern of possible types of topological insulators and superconductors, both in terms of spatial dimensions and in terms of symmetry classes. It was proposed that K theory is behind the periodicity. On the other hand, D-branes, a solitonic object in string theory, are also known to be classified by K theory. In this paper, by inspecting low-energy effective field theories realized by two parallel D-branes, we establish a one-to-one correspondence between the K-theory classification of topological insulators/superconductors and D-brane charges. In addition, the string theory realization of topological insulators and superconductors comes naturally with gauge interactions, and the Wess-Zumino term of the D-branes gives rise to a gauge field theory of topological nature, such as ones with the Chern-Simons term or the θ term in various dimensions. This sheds light on topological insulators and superconductors beyond noninteracting systems, and the underlying topological field theory description thereof. In particular, our string theory realization includes the honeycomb lattice Kitaev model in two spatial dimensions, and its higher-dimensional extensions. Increasing the number of D-branes naturally leads to a realization of topological insulators and superconductors in terms of holography (AdS/CFT).

  1. Magnetic properties of layered superconductors

    International Nuclear Information System (INIS)

    Mansky, P.A.

    1993-01-01

    The organic superconductors (BEDT-TTF) 2 Cu(SNC) 2 and (TMTSF) 2 ClO 4 , with T c = 10K and 1.2K, have layered and highly anisotropic crystal structures. This thesis describes AC magnetic susceptibility measurements on these materials which illustrate the consequences of the discrete layered structure for the magnetic properties of the superconducting state. A DC magnetic field applied parallel to the layers of either material causes the rapid suppression of the AC screening response, and this indicates that the pinning restoring force for vortex motion parallel to the layers is anomalously weak in this orientation. This is believed to be due to the small size of the interlayer coherence length relative to the layer spacing. A simple estimate based on the energy and length scales relevant to Josephson coupled layers gives the correct order of magnitude for the pinning force. Pinning for vortices oriented perpendicular to the layers is larger by a factor of 500 for BEDT and 25 for TMTSF. When the DC field is applied at an angle to the layers, the initial suppression of the susceptibility is identical to that for a field parallel to the layers; when the field component normal to the layers exceeds a threshold, a sharp recovery of screening occurs. These observations indicate that the field initially enters the sample only in the direction parallel to the layers. The recovery of screening signals field penetration in the perpendicular direction at higher field strength, and is due to the onset of pinning by in-plane vortex cores. This magnetic open-quotes lock-inclose quotes effect is a qualitatively new behavior and is a direct consequence of weak interlayer coupling. The London penetration depth associated with interlayer currents is found to be on the order of hundreds of microns, comparable to that of a Josephson junction, and two to three orders of magnitude larger than for conventional superconductors

  2. Systematic study of even-even nuclei with Hartree-Fock+BCS method using Skyrme SIII force

    Energy Technology Data Exchange (ETDEWEB)

    Tajima, Naoki; Takahara, Satoshi; Onishi, Naoki [Tokyo Univ. (Japan). Coll. of Arts and Sciences

    1997-03-01

    We have applied the Hartree-Fock+BCS method with Skyrme SIII force formulated in a three-dimensional Cartesian-mesh representation to even-even nuclei with 2 {<=} Z {<=} 114. We discuss the results concerning the atomic masses, the quadrupole (m=0, 2) and hexadecapole (m=0, 2, 4) deformations, the skin thicknesses, and the halo radii. We also discuss the energy difference between oblate and prolate solutions and the shape difference between protons and neutrons. (author)

  3. Mechanistic investigation of food effect on disintegration and dissolution of BCS class III compound solid formulations: the importance of viscosity.

    Science.gov (United States)

    Radwan, Asma; Amidon, Gordon L; Langguth, Peter

    2012-10-01

    A negative food effect, i.e. a decrease in bioavailability upon the co-administration of compounds together with food, has been attributed particularly with high solubility/low permeability compounds (BCS class III). Different mechanisms have been proposed including intestinal dilution leading to a lower concentration gradient across the intestinal wall as well as binding of the active pharmaceutical ingredient to food components in the intestine and thereby decreasing the fraction of the dose available for absorption. These mechanisms refer primarily to the compound and not to the dosage form. An increase in viscosity of the dissolution fluid will in particular affect the absorption of BCS type III compounds with preferential absorption in the upper small intestine if the API release is delayed from the dosage form. The present study demonstrated that the increase in viscosity of the dissolution medium, following ingestion of a solid meal, may drastically reduce disintegration and dissolution. For that purpose the viscosity of the standard FDA meal was determined and simulated by solutions of HPMC in buffer. As model formulations, three commercially available tablets containing trospium chloride, a BCS class III m-cholinoreceptor antagonist was used. Trospium chloride drug products have been described to undergo a negative food effect of more than 80% following ingestion with food. The tablets showed prolonged disintegration times and reduced dissolution rates in viscous media, which could be attributed to changes in the liquid penetration rates. The effect was particularly significant for film-coated tablets relative to uncoated dosage forms. The results show the necessity of considering media viscosity when designing in vitro models of drug release for BCS type III drug formulations. Copyright © 2012 John Wiley & Sons, Ltd.

  4. Regional-Dependent Intestinal Permeability and BCS Classification: Elucidation of pH-Related Complexity in Rats Using Pseudoephedrine

    OpenAIRE

    Fairstein, Moran; Swissa, Rotem; Dahan, Arik

    2013-01-01

    Based on its lower Log P value relative to metoprolol, a marker for the low/high-permeability (Peff) class boundary, pseudoephedrine was provisionally classified as BCS low-permeability compound. On the other hand, following oral administration, pseudoephedrine fraction dose absorbed (Fabs) and systemic bioavailability approaches 100%. This represents a challenge to the generally recognized Peff–Fabs correlation. The purpose of this study was to elucidate the underlying mechanisms behind the ...

  5. Regional-dependent intestinal permeability and BCS classification: elucidation of pH-related complexity in rats using pseudoephedrine.

    Science.gov (United States)

    Fairstein, Moran; Swissa, Rotem; Dahan, Arik

    2013-04-01

    Based on its lower Log P value relative to metoprolol, a marker for the low/high-permeability (P(eff)) class boundary, pseudoephedrine was provisionally classified as BCS low-permeability compound. On the other hand, following oral administration, pseudoephedrine fraction dose absorbed (F(abs)) and systemic bioavailability approaches 100%. This represents a challenge to the generally recognized P(eff)-F(abs) correlation. The purpose of this study was to elucidate the underlying mechanisms behind the confusion in pseudoephedrine's BCS classification. Pseudoephedrine's BCS solubility class was determined, and its physicochemical properties and intestinal permeability were thoroughly investigated, both in vitro and in vivo in rats, considering the complexity of the whole of the small intestine. Pseudoephedrine was found to be unequivocally a high-solubility compound. All of the permeability studies revealed similar phenomenon; at any given intestinal segment/pH, the permeability of metoprolol was higher than that of pseudoephedrine, however, as the intestinal region becomes progressively distal, and the pH gradually increases, pseudoephedrine's permeability rises above that of metoprolol in the former segment. This unique permeability pattern likely explains pseudoephedrine's complete absorption. In conclusion, pseudoephedrine is a BCS Class I compound; no discrepancy between P(eff) and F(abs) is involved in its absorption. Rather, it reflects the complexity behind P(eff) when considering the whole of the intestine. We propose to allow high-permeability classification to drugs with P(eff) that matches/exceeds the low/high class benchmark anywhere throughout the intestinal tract and not restricted necessarily to the jejunum.

  6. Strong nonequilibrium coherent states in mesoscopic superconductor-semiconductor-superconductor junctions

    DEFF Research Database (Denmark)

    Kutchinsky, Jonatan; Wildt, Morten; Taboryski, Rafael Jozef

    1999-01-01

    A biased superconductor-normal metal-superconductor junction is known to be a strong nonequilibrium system, where Andreev scattering at the interfaces creates a quasiparticle distribution function far from equilibrium, a manifestation of this is the well-known subgap structure in the I...

  7. Superconductor-semiconductor-superconductor planar junctions of aluminium on DELTA-doped gallium arsenide

    DEFF Research Database (Denmark)

    Taboryski, Rafael Jozef; Clausen, Thomas; Kutchinsky, jonatan

    1997-01-01

    We have fabricated and characterized planar superconductor-semiconductor-superconductor (S-Sm-S) junctions with a high quality (i.e. low barrier) interface between an n++ modulation doped conduction layer in MBE grown GaAs and in situ deposited Al electrodes. The Schottky barrier at the S...

  8. Superconductors

    International Nuclear Information System (INIS)

    Newkirk, L.R.; Valencia, F.A.

    1977-01-01

    The structural quality of niobium germanide as a high-transition-temperature superconducting material is substantially improved by the presence of about 5 at. percent oxygen. Niobium germanide having this oxygen content may readily be prepared as a bulk coating bonded to a metallic substrate by chemical vapor deposition techniques. 2 figures, 1 table

  9. Superconductors

    Science.gov (United States)

    Newkirk, Lawrence R.; Valencia, Flavio A.

    1977-02-01

    The structural quality of niobium germanide as a high-transition-temperature superconducting material is substantially improved by the presence of about 5 at. % oxygen. Niobium germanide having this oxygen content may readily be prepared as a bulk coating bonded to a metallic substrate by chemical vapor deposition techniques.

  10. Breast cancer screening (BCS) chart: a basic and preliminary model for making screening mammography more productive and efficient.

    Science.gov (United States)

    Poorolajal, Jalal; Akbari, Mohammad Esmaeil; Ziaee, Fatane; Karami, Manoochehr; Ghoncheh, Mahshid

    2017-05-15

    The breast cancer screening (BCS) chart is suggested as a basic and preliminary tool to improve efficiency of screening mammography. We conducted this case-control study in 2016 and enrolled 1422 women aged 30-75 years, including 506 women with breast cancer (cases) and 916 women without breast cancer (controls). We developed the BCS chart using a multiple logistic regression analysis. We combined the risks of breast cancer to predict the individual risk of breast cancer. Then, we stratified and colored the predicted risk probabilities as follows: green), 05-09% (yellow), 10-14% (orange), 15-19% (red), 20-24% (brown) and ≥25% (black). The BCS chart provides the risk probability of breast cancer, based on age, body mass index, late menopause, having a benign breast disease and a positive family history of breast cancer among the first-degree or the second/third-degree relatives. According to this chart, an individual can be classified in a category of low risk (green), medium risk (yellow and orange), high risk (red and brown) and very high risk (black) for breast cancer. This chart is a flexible and easy to use tool that can detect high-risk subjects and make the screening program more efficient and productive. © The Author 2017. Published by Oxford University Press on behalf of Faculty of Public Health. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com

  11. Intradot spin-flip Andreev reflection tunneling through a ferromagnet-quantum dot-superconductor system with ac field

    International Nuclear Information System (INIS)

    Song Hongyan; Zhou Shiping

    2008-01-01

    We investigate Andreev reflection (AR) tunneling through a ferromagnet-quantum dot-superconductor (F-QD-S) system in the presence of an external ac field. The intradot spin-flip scattering in the QD is involved. Using the nonequilibrium Green function and BCS quasiparticle spectrum for superconductor, time-averaged AR conductance is formulated. The competition between the intradot spin-flip scattering and photon-assisted tunneling dominates the resonant behaviors of the time-averaged AR conductance. For weak intradot spin-flip scattering strengths, the AR conductance shows a series of equal interval resonant levels. However, the single-peak at main resonant level develops into a well-resolved double-peak resonance at a strong intradot spin-flip scattering strength. Remarkable, multiple-photon-assisted tunneling that generates photonic sideband peaks with a variable interval has been found. In addition, the AR conductance-bias voltage characteristic shows a transition between the single-peak to double-peak resonance as the ratio of the two tunneling strengths varies

  12. Study of bubble structure in N = 20 isotones within relativistic mean-field plus BCS approach

    International Nuclear Information System (INIS)

    Kumawat, M.; Singh, U.K.; Jain, S.K.; Saxena, G.; Aggarwal, Mamta; Singh, S. Somorendro; Kaushik, M.

    2017-01-01

    Guided by various theoretical studies and encouraged with recent first experimental evidence of proton density depletion in "3"4Si, we have applied relativistic mean field plus BCS approach for systematic study of bubble structure in magic nuclei with N = 20 isotones. Our present investigations include single particle energies, deformations, separation energies as well as neutron and proton densities etc. It is found that proton sd shells (1d_5_/_2,2s_1_/_2,1d_3_/_2) in N = 20 isotones play very important role in the formation of bubble structure. The unoccupied 2s_1_/_2 state gives rise to bubble since this 2s_1_/_2 state does not have any centrifugal barrier, therefore for Z = 8 - 14 in the isotonic chain radial distributions of such state is found with peak in the interior of the nucleus with corresponding wave functions extending into the surface region. Consequently, in these nuclei with unoccupied s-state the central density found depleted as compared to the nucleus wherein this state is fully occupied. It is important to note here that in these nuclei depletion in proton density for "3"4Si is found with most significance which is in accord with the recent experiment. Moving further for higher Z value, Z = 16 and Z = 18 the 2s_1_/_2 state remains semi-occupied and contributing partially in the depletion of central density resulting semi-bubble structure for Z = 16 and 18. For Z≥20, 2s_1_/_2 state get fully occupied and no sign of bubble structures are seen for higher isotones

  13. pH-Dependent solubility and permeability criteria for provisional biopharmaceutics classification (BCS and BDDCS) in early drug discovery.

    Science.gov (United States)

    Varma, Manthena V; Gardner, Iain; Steyn, Stefanus J; Nkansah, Paul; Rotter, Charles J; Whitney-Pickett, Carrie; Zhang, Hui; Di, Li; Cram, Michael; Fenner, Katherine S; El-Kattan, Ayman F

    2012-05-07

    The Biopharmaceutics Classification System (BCS) is a scientific framework that provides a basis for predicting the oral absorption of drugs. These concepts have been extended in the Biopharmaceutics Drug Disposition Classification System (BDDCS) to explain the potential mechanism of drug clearance and understand the effects of uptake and efflux transporters on absorption, distribution, metabolism, and elimination. The objective of present work is to establish criteria for provisional biopharmaceutics classification using pH-dependent passive permeability and aqueous solubility data generated from high throughput screening methodologies in drug discovery settings. The apparent permeability across monolayers of clonal cell line of Madin-Darby canine kidney cells, selected for low endogenous efflux transporter expression, was measured for a set of 105 drugs, with known BCS and BDDCS class. The permeability at apical pH 6.5 for acidic drugs and at pH 7.4 for nonacidic drugs showed a good correlation with the fraction absorbed in human (Fa). Receiver operating characteristic (ROC) curve analysis was utilized to define the permeability class boundary. At permeability ≥ 5 × 10(-6) cm/s, the accuracy of predicting Fa of ≥ 0.90 was 87%. Also, this cutoff showed more than 80% sensitivity and specificity in predicting the literature permeability classes (BCS), and the metabolism classes (BDDCS). The equilibrium solubility of a subset of 49 drugs was measured in pH 1.2 medium, pH 6.5 phosphate buffer, and in FaSSIF medium (pH 6.5). Although dose was not considered, good concordance of the measured solubility with BCS and BDDCS solubility class was achieved, when solubility at pH 1.2 was used for acidic compounds and FaSSIF solubility was used for basic, neutral, and zwitterionic compounds. Using a cutoff of 200 μg/mL, the data set suggested a 93% sensitivity and 86% specificity in predicting both the BCS and BDDCS solubility classes. In conclusion, this study identified

  14. Entanglement between pairing and screening in the Gorkov-Melik-Barkhudarov correction to the critical temperature throughout the BCS-BEC crossover

    Science.gov (United States)

    Pisani, L.; Perali, A.; Pieri, P.; Strinati, G. Calvanese

    2018-01-01

    The problem of the theoretical description of the critical temperature Tc of a Fermi superfluid dates back to the work by Gorkov and Melik-Barkhudarov (GMB), who addressed it for a weakly coupled (dilute) superfluid in what would today be referred to as the (extreme) BCS (weak-coupling) limit of the BCS-BEC crossover. The point made in this context by GMB was that particle-particle (pairing) excitations, which are responsible for superfluidity to occur below Tc, and particle-hole excitations, which give rise to screening also in a normal system, get effectively disentangled from each other in the BCS limit, thus yielding a reduction by a factor of 2.2 of the value of Tc obtained when neglecting screening effects. Subsequent work on this topic, that was aimed at extending the original GMB argument away from the BCS limit with diagrammatic methods, has tout court kept this disentangling between pairing and screening throughout the BCS-BEC crossover, without realizing that the conditions for it to be valid are soon violated away from the BCS limit. Here, we reconsider this problem from a more general perspective and argue that pairing and screening are intrinsically entangled with each other along the whole BCS-BEC crossover but for the BCS limit considered by GMB, with the particle-hole excitations soon transmuting into particle-particle excitations away from this limit. We substantiate our argument by performing a detailed numerical calculation of the GMB diagrammatic contribution suitably extended to the whole BCS-BEC crossover, where the full wave-vector and frequency dependence occurring in the repeated in-medium two-particle scattering is duly taken into account. Our numerical calculations are tested against analytic results available in both the BCS and BEC limits, and the contribution of the GMB diagrammatic term to the scattering length of composite bosons in the BEC limit is highlighted. We calculate Tc throughout the BCS-BEC crossover and find that it

  15. Design study of SMES system using high temperature superconductors

    International Nuclear Information System (INIS)

    Yoshihara, T.; Masuda, M.; Shintomi, T.; Hasegawa, J.

    1988-01-01

    Various studies of high Tc superconductors are being energetically pursued all over the world, since IBM Zurich Research Laboratory reported on the superconducting oxide. A new design using a high Tc superconductor is under study for 5000 MWh, on the assumption that it is available like conventional superconductors. Problems related to the Tc SMES system, mainly thermal insulation, refrigeration system, stability of superconductors, etc., are considered. Some design examples of high Tc SMES system are proposed

  16. Sealed glass coating of high temperature ceramic superconductors

    Science.gov (United States)

    Wu, Weite; Chu, Cha Y.; Goretta, Kenneth C.; Routbort, Jules L.

    1995-01-01

    A method and article of manufacture of a lead oxide based glass coating on a high temperature superconductor. The method includes preparing a dispersion of glass powders in a solution, applying the dispersion to the superconductor, drying the dispersion before applying another coating and heating the glass powder dispersion at temperatures below oxygen diffusion onset and above the glass melting point to form a continuous glass coating on the superconductor to establish compressive stresses which enhance the fracture strength of the superconductor.

  17. Dynamics of superconductor bearings in a cryogenic failure

    Energy Technology Data Exchange (ETDEWEB)

    Rastogi, Amit [Department of Engineering, Cambridge University, Cambridge CB2 1PZ (United Kingdom)]. E-mail: Amit.Rastogi@avizatechnology.com; Campbell, A.M. [Department of Engineering, Cambridge University, Cambridge CB2 1PZ (United Kingdom); Coombs, T.A. [Department of Engineering, Cambridge University, Cambridge CB2 1PZ (United Kingdom)

    2006-08-01

    The dynamics of superconductor bearings in a cryogenic failure scenario have been analyzed. As the superconductor warms up, the rotor goes through multiple resonance frequencies, begins to slow down and finally touches down when the superconductor goes through its transition temperature. The bearing can be modelled as a system of springs with axial, radial and cross stiffness. These springs go through various resonant modes as the temperature of the superconductor begins to rise. We have presented possible explanations for such behaviour.

  18. In silico prediction of drug dissolution and absorption with variation in intestinal pH for BCS class II weak acid drugs: ibuprofen and ketoprofen.

    Science.gov (United States)

    Tsume, Yasuhiro; Langguth, Peter; Garcia-Arieta, Alfredo; Amidon, Gordon L

    2012-10-01

    The FDA Biopharmaceutical Classification System guidance allows waivers for in vivo bioavailability and bioequivalence studies for immediate-release solid oral dosage forms only for BCS class I. Extensions of the in vivo biowaiver for a number of drugs in BCS class III and BCS class II have been proposed, in particular, BCS class II weak acids. However, a discrepancy between the in vivo BE results and in vitro dissolution results for BCS class II acids was recently observed. The objectives of this study were to determine the oral absorption of BCS class II weak acids via simulation software and to determine if the in vitro dissolution test with various dissolution media could be sufficient for in vitro bioequivalence studies of ibuprofen and ketoprofen as models of carboxylic acid drugs. The oral absorption of these BCS class II acids from the gastrointestinal tract was predicted by GastroPlus™. Ibuprofen did not satisfy the bioequivalence criteria at lower settings of intestinal pH of 6.0. Further the experimental dissolution of ibuprofen tablets in a low concentration phosphate buffer at pH 6.0 (the average buffer capacity 2.2 mmol l (-1) /pH) was dramatically reduced compared with the dissolution in SIF (the average buffer capacity 12.6 mmol l (-1) /pH). Thus these predictions for the oral absorption of BCS class II acids indicate that the absorption patterns depend largely on the intestinal pH and buffer strength and must be considered carefully for a bioequivalence test. Simulation software may be a very useful tool to aid the selection of dissolution media that may be useful in setting an in vitro bioequivalence dissolution standard. Copyright © 2012 John Wiley & Sons, Ltd.

  19. In Silico Prediction of Drug Dissolution and Absorption with variation in Intestinal pH for BCS Class II Weak Acid Drugs: Ibuprofen and Ketoprofen§

    Science.gov (United States)

    Tsume, Yasuhiro; Langguth, Peter; Garcia-Arieta, Alfredo; Amidon, Gordon L.

    2012-01-01

    The FDA Biopharmaceutical Classification System guidance allows waivers for in vivo bioavailability and bioequivalence studies for immediate-release solid oral dosage forms only for BCS class I. Extensions of the in vivo biowaiver for a number of drugs in BCS Class III and BCS class II have been proposed, particularly, BCS class II weak acids. However, a discrepancy between the in vivo- BE results and in vitro- dissolution results for a BCS class II acids was recently observed. The objectives of this study were to determine the oral absorption of BCS class II weak acids via simulation software and to determine if the in vitro dissolution test with various dissolution media could be sufficient for in vitro bioequivalence studies of ibuprofen and ketoprofen as models of carboxylic acid drugs. The oral absorption of these BCS class II acids from the gastrointestinal tract was predicted by GastroPlus™. Ibuprofen did not satisfy the bioequivalence criteria at lower settings of intestinal pH=6.0. Further the experimental dissolution of ibuprofen tablets in the low concentration phosphate buffer at pH 6.0 (the average buffer capacity 2.2 mmol L-1/pH) was dramatically reduced compared to the dissolution in SIF (the average buffer capacity 12.6 mmol L -1/pH). Thus these predictions for oral absorption of BCS class II acids indicate that the absorption patterns largely depend on the intestinal pH and buffer strength and must be carefully considered for a bioequivalence test. Simulation software may be very useful tool to aid the selection of dissolution media that may be useful in setting an in vitro bioequivalence dissolution standard. PMID:22815122

  20. Optimizing solubility and permeability of a biopharmaceutics classification system (BCS) class 4 antibiotic drug using lipophilic fragments disturbing the crystal lattice.

    Science.gov (United States)

    Tehler, Ulrika; Fagerberg, Jonas H; Svensson, Richard; Larhed, Mats; Artursson, Per; Bergström, Christel A S

    2013-03-28

    Esterification was used to simultaneously increase solubility and permeability of ciprofloxacin, a biopharmaceutics classification system (BCS) class 4 drug (low solubility/low permeability) with solid-state limited solubility. Molecular flexibility was increased to disturb the crystal lattice, lower the melting point, and thereby improve the solubility, whereas lipophilicity was increased to enhance the intestinal permeability. These structural changes resulted in BCS class 1 analogues (high solubility/high permeability) emphasizing that simple medicinal chemistry may improve both these properties.

  1. Pinning and creep in high-Tc superconductors

    International Nuclear Information System (INIS)

    Ovchinnikov, Yu.N.; Ivlev, B.I.

    1992-01-01

    The angular and magnetic field dependence of a critical current parallel to the layers in the layered superconductors is studied. The critical current value is found for a superconductor with strong pinning centers. Quantum flux creep in sufficiently perfect layered high-Tc superconductors is discussed. The cross-over temperature between activated and quantum creep is found. (orig.)

  2. The color of polarization in cuprate superconductors

    International Nuclear Information System (INIS)

    Hoff, H.A.; Osofsky, M.S.; Lechter, W.L.; Pande, C.S.

    1991-01-01

    A technique for the identification of individual anisotropic grains in a heterogeneous and opaque material involves the observation of grain color in reflected light through crossed polarizers (color of polarization). Such colors are generally characteristic of particular phases. When grains of many members of the class of hole carrier cuprate superconductors are so viewed at room temperature with a 'daylight' source, a characteristic color of polarization is observed. This color was studied in many of these cuprate superconductors and a strong correlation was found between color and the existence of superconductivity. Two members were also examined of the electron cuprate superconductors and it was found that they possess the same color of polarization as the hole carrier cuprate superconductors so far examined. The commonality of the characteristic color regardless of charge carrier indicates that the presence of this color is independent of carrier type. The correlation of this color with the existence of superconductivity in the cuprate superconductors suggests that the origin of the color relates to the origin of superconductivity. Photometric techniques are also discussed

  3. Doped Tl-1212 and Tl-1223 superconductors

    International Nuclear Information System (INIS)

    Eder, M.H.

    2001-09-01

    This work describes the preparation and characterization of thallium-lead-strontium-barium-calcium-(uranium)-copperoxide (Tl-1212, Tl-1223) high-temperature superconductors. The precursors were prepared via nitrate method. After calcination the oxidic powders were mixed with stoichiometric amounts of an Tl 2 O 3 , PbO, Er 2 O 3 and Gd 2 O 3 by milling and afterwards uniaxial compressed. Sintering was carried out in silver foils. X-ray diffractometry and high-resolution microscopy in combination with scanning electron microscopy (including EDAX) were used to study the influence of varying thallium/lead-, strontium/barium-, calcium/rare earth element ratios and the effect of uranium on the phase composition and microstructure of bulk superconductors. Furthermore the influence of the composition on the electrical and magnetical properties was studied. On phase pure Tl-1212 and Tl-1223 superconductors NMR-measurements were done. Small amounts of gadolinium and erbium instead of calcium and excess-uranium have a positive impact on the electrical and magnetical properties of the Tl-1223 superconductors. Higher amounts of these doping elements favor the Tl-1212 phase. Tl-1212 superconductors with varying thallium/lead- strontium/barium- and calcium/gadolinium ratios were prepared phasepure in wide range of doping. Transition temperatures up to 96 K were achieved. It was shown that lead has an oxidation number of +4 and thallium of +3. (author)

  4. The study of some physical properties of high temperature superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Ismail, Atif Mahmoud

    2008-07-01

    The phenomenon of superconductivity, the discovery of high temperature superconductivity in the Cuprates and the properties of these materials is described in the introductory chapter. It also includes a discussion of the pseudogap, which has remained a mystery as has the high transition temperature. Possible applications of high temperature superconductivity are reviewed before the theories by Bardeen, Cooper, and Schrieffer (BCS) and Ginzburg and Landau are briefly sketched. The last section gives excerpts of the by now vast literature on this subject, focussing on the role impurities play in this context. The second chapter develops the mathematical tools and the theoretical background for the description of many-body systems. Various Green's functions are introduced which are then used to describe scattering of quasiparticles off defects of arbitrary strength. They are also required to calculate the a.c. conductivity, for which an expression is derived using linear response theory. The convergence problems one encounters when actually calculating the conductivity are briefly discussed. Detailed calculations for the normal state are presented in the third chapter and in the appendix. The third Chapter begins with a detailed presentation of the tight binding model for the energy dispersion because this model appears to give a more accurate description of the electronic properties of high temperature superconductors than the nearly free electron model. The shape of the two-dimensional Fermi surface is calculated and displayed as function of band filling and the next-nearest neighbor hopping integral B, assuming a rigid band. B plays an important role in the formation of so-called hot spots. The quasiparticle density of states and its Hilbert transform F({omega}) are solved by means of complete elliptic integrals formalism. These results are used to obtain impurity bound states. A simple model for the superconductivity in the cuprate materials is developed on the

  5. The study of some physical properties of high temperature superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Ismail, Atif Mahmoud

    2008-07-01

    The phenomenon of superconductivity, the discovery of high temperature superconductivity in the Cuprates and the properties of these materials is described in the introductory chapter. It also includes a discussion of the pseudogap, which has remained a mystery as has the high transition temperature. Possible applications of high temperature superconductivity are reviewed before the theories by Bardeen, Cooper, and Schrieffer (BCS) and Ginzburg and Landau are briefly sketched. The last section gives excerpts of the by now vast literature on this subject, focussing on the role impurities play in this context. The second chapter develops the mathematical tools and the theoretical background for the description of many-body systems. Various Green's functions are introduced which are then used to describe scattering of quasiparticles off defects of arbitrary strength. They are also required to calculate the a.c. conductivity, for which an expression is derived using linear response theory. The convergence problems one encounters when actually calculating the conductivity are briefly discussed. Detailed calculations for the normal state are presented in the third chapter and in the appendix. The third Chapter begins with a detailed presentation of the tight binding model for the energy dispersion because this model appears to give a more accurate description of the electronic properties of high temperature superconductors than the nearly free electron model. The shape of the two-dimensional Fermi surface is calculated and displayed as function of band filling and the next-nearest neighbor hopping integral B, assuming a rigid band. B plays an important role in the formation of so-called hot spots. The quasiparticle density of states and its Hilbert transform F({omega}) are solved by means of complete elliptic integrals formalism. These results are used to obtain impurity bound states. A simple model for the superconductivity in the cuprate materials is developed on

  6. The study of some physical properties of high temperature superconductors

    International Nuclear Information System (INIS)

    Ismail, Atif Mahmoud

    2008-01-01

    The phenomenon of superconductivity, the discovery of high temperature superconductivity in the Cuprates and the properties of these materials is described in the introductory chapter. It also includes a discussion of the pseudogap, which has remained a mystery as has the high transition temperature. Possible applications of high temperature superconductivity are reviewed before the theories by Bardeen, Cooper, and Schrieffer (BCS) and Ginzburg and Landau are briefly sketched. The last section gives excerpts of the by now vast literature on this subject, focussing on the role impurities play in this context. The second chapter develops the mathematical tools and the theoretical background for the description of many-body systems. Various Green's functions are introduced which are then used to describe scattering of quasiparticles off defects of arbitrary strength. They are also required to calculate the a.c. conductivity, for which an expression is derived using linear response theory. The convergence problems one encounters when actually calculating the conductivity are briefly discussed. Detailed calculations for the normal state are presented in the third chapter and in the appendix. The third Chapter begins with a detailed presentation of the tight binding model for the energy dispersion because this model appears to give a more accurate description of the electronic properties of high temperature superconductors than the nearly free electron model. The shape of the two-dimensional Fermi surface is calculated and displayed as function of band filling and the next-nearest neighbor hopping integral B, assuming a rigid band. B plays an important role in the formation of so-called hot spots. The quasiparticle density of states and its Hilbert transform F(ω) are solved by means of complete elliptic integrals formalism. These results are used to obtain impurity bound states. A simple model for the superconductivity in the cuprate materials is developed on the basis

  7. Bulk Superconductors in Mobile Application

    Science.gov (United States)

    Werfel, F. N.; Delor, U. Floegel-; Rothfeld, R.; Riedel, T.; Wippich, D.; Goebel, B.; Schirrmeister, P.

    We investigate and review concepts of multi - seeded REBCO bulk superconductors in mobile application. ATZ's compact HTS bulk magnets can trap routinely 1 T@77 K. Except of magnetization, flux creep and hysteresis, industrial - like properties as compactness, power density, and robustness are of major device interest if mobility and light-weight construction is in focus. For mobile application in levitated trains or demonstrator magnets we examine the performance of on-board cryogenics either by LN2 or cryo-cooler application. The mechanical, electric and thermodynamical requirements of compact vacuum cryostats for Maglev train operation were studied systematically. More than 30 units are manufactured and tested. The attractive load to weight ratio is more than 10 and favours group module device constructions up to 5 t load on permanent magnet (PM) track. A transportable and compact YBCO bulk magnet cooled with in-situ 4 Watt Stirling cryo-cooler for 50 - 80 K operation is investigated. Low cooling power and effective HTS cold mass drives the system construction to a minimum - thermal loss and light-weight design.

  8. Structural behavior of cable superconductors

    International Nuclear Information System (INIS)

    Becker, H.; Marston, P.

    1983-01-01

    The structural properties of cable superconductor coils, for particle accelerators such as the Tevatron and the CBA (Colliding Beam Accelerator), depend upon direction of loading. For compression perpendicular to the ''flat faces'' of the conductor, the coils exhibit nonlinear, inelastic and time dependent behavior. The same is true for ''inplane'' compression loading perpendicular to the conductor edges. In the lengthwise direction, the coils display tension and compression stress-strain curves typical of structural metals. The loading of primary concern is compression perpendicular to the conductor faces since deformations in that direction can have a major influence on magnetic field quality. However, the coil behavior under that condition is uncertain because of the nonlinear stress strain curve complicated by creep and relaxation at the stress levels induced by preloading and Lorentz forces. Furthermore, the stiffness of the loading fixture appears to influence the data as shown by results from tests run under different conditions at Berkeley, Brookhaven and MIT. The paper displays test data on stress-strain curves for all three loading directions. Results are presented for RT, 77 K and 4 K behavior. Data of various investigators are compared. The applicability of a relatively simple power law between stress and strain is depicted

  9. Theory of Josephson effect in d-wave superconductor/diffusive ferromagnet/d-wave superconductor junctions

    NARCIS (Netherlands)

    Yokoyama, T.; Tanaka, Y.; Golubov, Alexandre Avraamovitch

    2007-01-01

    We study Josephson effect in d-wave superconductor/diffusive ferromagnet/d-wave superconductor junctions, changing the exchange field and the angles between the normal to the interfaces and the crystal axes of d-wave superconductors. We find a 0–π transition at a certain value of the exchange field.

  10. Fracture toughness for copper oxide superconductors

    Science.gov (United States)

    Goretta, K.C.; Kullberg, M.L.

    1993-04-13

    An oxide-based strengthening and toughening agent, such as tetragonal ZrO[sub 2] particles, has been added to copper oxide superconductors, such as superconducting YBa[sub 2]Cu[sub 3]O[sub x] (123) to improve its fracture toughness (K[sub IC]). A sol-gel coating which is non-reactive with the superconductor, such as Y[sub 2]BaCuO[sub 5] (211) on the ZrO[sub 2] particles minimized the deleterious reactions between the superconductor and the toughening agent dispersed therethrough. Addition of 20 mole percent ZrO[sub 2] coated with 211 yielded a 123 composite with a K[sub IC] of 4.5 MPa(m)[sup 0.5].

  11. Fracture toughness for copper oxide superconductors

    Science.gov (United States)

    Goretta, Kenneth C.; Kullberg, Marc L.

    1993-01-01

    An oxide-based strengthening and toughening agent, such as tetragonal Zro.sub.2 particles, has been added to copper oxide superconductors, such as superconducting YBa.sub.2 Cu.sub.3 O.sub.x (123) to improve its fracture toughness (K.sub.IC). A sol-gel coating which is non-reactive with the superconductor, such as Y.sub.2 BaCuO.sub.5 (211) on the ZrO.sub.2 particles minimized the deleterious reactions between the superconductor and the toughening agent dispersed therethrough. Addition of 20 mole percent ZrO.sub.2 coated with 211 yielded a 123 composite with a K.sub.IC of 4.5 MPa(m).sup.0.5.

  12. Practical superconductor development for electrical power applications

    International Nuclear Information System (INIS)

    Goretta, K.C.

    1991-10-01

    Development of useful high-critical-temperature (high-T c ) superconductors requires synthesis of superconducting compounds; fabrication of wires, tapes, and films from these compounds; production of composite structures that incorporate stabilizers or insulators; and design and testing of efficient components. This report describes technical progress of research and development efforts aimed at producing superconducting components based on the Y-Ba-Cu, Bi-Sr-Ca-Cu, Bi-Pb-Sr-Ca-Cu, and Tl-Ba-Ca-Cu oxides systems. Topics discussed are synthesis and heat treatment of high-T c superconductors, formation of monolithic and composite wires and tapes, superconductor/metal connectors, characterization of structures and superconducting and mechanical properties, and fabrication and properties of thin films. Collaborations with industry and academia are also documented. 10 figs

  13. Stability of magnets levitated above superconductors

    International Nuclear Information System (INIS)

    Davis, L.C.; Logothetis, E.M.; Soltis, R.E.

    1988-01-01

    The stability of a permanent magnet levitated above a slab of hard superconductor is considered. The force on a dipole magnet over a perfectly diamagnetic disk is calculated. It is found that the radial component of the force is directed outward and is 10%--20% of the image (vertical) force near the edge. Estimates of the magnetic friction force due to flux motion in a hard superconductor are made using Bean's model. The magnitude of the magnetic friction is large enough to stabilize the magnet over most of the disk for typical values of the critical current in ceramic superconductors (∼10 3 A/cm 2 ), but too small for the highest values reported (>10 6 A/cm 2 ). It is conjectured that flux trapping due to inhomogeneities gives rise to transient restoring forces

  14. A nonquasiclassical description of inhomogeneous superconductors

    International Nuclear Information System (INIS)

    Zaikin, A.D.; Panyukov, S.V.

    1988-01-01

    Exact microscopic equations are derived that make it possible to describe inhomogeneous superconductors when the quasi-classical approach is not suitable. These equations are simpler than the Gorkov equations. The authors generalize the derived equations for describing the nonequilibrium states of inhomogeneous superconductors. It is demonstrated that the derived equations (including the case of a nonequilibrium quasi particle distribution function) may be written in the form of linear differential equations for the simultaneous wave function μ, ν. The quasi-classical limit of such equations is examined. Effective boundary conditions are derived for the μ, ν functions that allow description of superconductors with a sharp change in parameters within the scope of the quasi-classical approach

  15. Charge and spin transport in mesoscopic superconductors

    Directory of Open Access Journals (Sweden)

    M. J. Wolf

    2014-02-01

    Full Text Available Background: Non-equilibrium charge transport in superconductors has been investigated intensely in the 1970s and 1980s, mostly in the vicinity of the critical temperature. Much less attention has been paid to low temperatures and the role of the quasiparticle spin.Results: We report here on nonlocal transport in superconductor hybrid structures at very low temperatures. By comparing the nonlocal conductance obtained by using ferromagnetic and normal-metal detectors, we discriminate charge and spin degrees of freedom. We observe spin injection and long-range transport of pure, chargeless spin currents in the regime of large Zeeman splitting. We elucidate charge and spin transport by comparison to theoretical models.Conclusion: The observed long-range chargeless spin transport opens a new path to manipulate and utilize the quasiparticle spin in superconductor nanostructures.

  16. Processing Y- and Bi-based superconductors

    International Nuclear Information System (INIS)

    Balachandran, U.; Dos Santos, D.I.; von Stumberg, A.W.; Graham, S.W.; Singh, J.P.; Youngdahl, C.A.; Goretta, K.C.; Shi, D.; Poeppel, R.B.

    1989-01-01

    This paper reports on bulk specimens of YBa 2 Cu 3 O x and Bi 2 Sr 2 CaCu 2 O y formed and then processed by sintering in the solid state, in the presence of a liquid phase, or by sinter forging. Both Y- and Bi-based superconductors are difficult to densify by solid-state sintering but easy to densify in the presence of a liquid phase. Effects of sintering conditions on superconducting properties are, however, different between the two materials. These differences will be discussed. Attempts to texture microstructures and increase J c by sinter-forging techniques have been successful for Y-based superconductors, but unsuccessful for Bi-based superconductors

  17. Energy gap of ferromagnet-superconductor bilayers

    Energy Technology Data Exchange (ETDEWEB)

    Halterman, Klaus; Valls, Oriol T

    2003-10-15

    The excitation spectrum of clean ferromagnet-superconductor bilayers is calculated within the framework of the self-consistent Bogoliubov-de Gennes theory. Because of the proximity effect, the superconductor induces a gap in the ferromagnet spectrum, for thin ferromagnetic layers. The effect depends strongly on the exchange field in the ferromagnet. We find that as the thickness of the ferromagnetic layer increases, the gap disappears, and that its destruction arises from those quasiparticle excitations with wave vectors mainly along the interface. We discuss the influence that the interface quality and Fermi energy mismatch between the ferromagnet and superconductor have on the calculated energy gap. We also evaluate the density of states in the ferromagnet, and we find it in all cases consistent with the gap results.

  18. Transport Properties of an Electron-Hole Bilayer in Contact with a Superconductor Hybrid Junction

    Science.gov (United States)

    Bercioux, D.; Klapwijk, T. M.; Bergeret, F. S.

    2017-08-01

    We investigate the transport properties of a junction consisting of an electron-hole bilayer in contact with normal and superconducting leads. The electron-hole bilayer is considered as a semimetal with two electronic bands. We assume that in the region between the contacts the system hosts an exciton condensate described by a BCS-like model with a gap Γ in the quasiparticle density of states. We first discuss how the subgap electronic transport through the junction is mainly governed by the interplay between two kinds of reflection processes at the interfaces: the standard Andreev reflection at the interface between the superconductor and the exciton condensate, and a coherent crossed reflection at the semimetal-exciton-condensate interface that converts electrons from one layer into the other. We show that the differential conductance of the junction shows a minimum at voltages of the order of Γ /e . Such a minimum can be seen as a direct hallmark of the existence of the gapped excitonic state.

  19. Raman scattering in cuprate superconductors : an analysis in the spin bag model

    International Nuclear Information System (INIS)

    Behera, S.N.; Gaitonde, D.M.

    1992-01-01

    The spin bag model for the high temperature superconductivity (SC) in the cuprates is reformulated, so that the spin density wave (SDW) collective mode mediated pairing interaction between the doped charge carriers, has a formal similarity to the usual phonon mediated BCS mechanism. The collective modes of the spin bag superconductor are calculated and the spectral density function for the amplitude mode is plotted. The self energy and the spectral density function of an optic phonon are calculated in the spin bag superconducting state. The spectral density function does not couple to the SDW-amplitude mode. A low frequency is shown to harden while the high frequency (greater than the SC-gap) one softens; which are features in qualitative agreement with the behaviour seen in the Raman data. When the phonon frequency is larger than the SC-gap, its spectral function shows a low frequency weak peak, attributed to the SC-gap excitation which is not observed experimentally. (author). 21 refs., 3 figs

  20. The superconductor revolutions and the (slow) applications evolution

    International Nuclear Information System (INIS)

    Foner, S.

    1990-01-01

    The discovery in the 1960's of type 2 superconductors with high critical current densities in high magnetic fields (and the development of NbTi in particular) led to the first revolution. The discovery of high temperature superconductors (HTS) started the second revolution. At this stage ceramists became involved with superconductors. I will assess the status of various superconductor applications, progress of HTS and their possible applications at 4.2K, and near-term needs for superconducting materials operating at 30T in specialized facilities. Reasons for the slow growth of superconductor applications will be reviewed

  1. Iron chalcogenide superconductors at high magnetic fields

    Science.gov (United States)

    Lei, Hechang; Wang, Kefeng; Hu, Rongwei; Ryu, Hyejin; Abeykoon, Milinda; Bozin, Emil S; Petrovic, Cedomir

    2012-01-01

    Iron chalcogenide superconductors have become one of the most investigated superconducting materials in recent years due to high upper critical fields, competing interactions and complex electronic and magnetic phase diagrams. The structural complexity, defects and atomic site occupancies significantly affect the normal and superconducting states in these compounds. In this work we review the vortex behavior, critical current density and high magnetic field pair-breaking mechanism in iron chalcogenide superconductors. We also point to relevant structural features and normal-state properties. PMID:27877518

  2. Workshop on accelerator magnet superconductors. Proceedings

    International Nuclear Information System (INIS)

    2004-01-01

    The workshop on accelerator magnet superconductors has gathered 102 registered participants from research laboratories, universities and industry. 8 European companies, active in superconducting materials and cables were present. This workshop has been organized to deal with the status of the world research and development on superconducting materials and cables for high field magnets (B > 10 T). The workshop has also reviewed the status of high temperature superconductors and transmission line cables for potential use in low field superconducting magnets for injectors and beam transfer lines, as well as cables for pulsed magnets that might be used in future hadron colliders or injectors

  3. Aluminium stabilized Nb$-3$/Sn superconductors

    International Nuclear Information System (INIS)

    Thoener, M.; Krauth, H.; Rudolph, J.; Szulczyk, A.

    1988-01-01

    Composite superconductors made of reacted Nb 3 Sn stabilized with high purity Al were produced. Two methods were tested. The first involved soft soldering a Cu clad aluminum tape to the Nb 3 Sn conductor. In the second method the conductor, cable or monolith, was coextruded with the aluminum. Results obtained from using both methods indicated that mechanically reinforcing materials can be easily introduced into superconductors. Tests were conducted to determine magnetoresistance, electric contact resistance, yield strength, Young modulus, critical current, and other properties of the composites. Strengthening with Duratherm during coextrusion was also evaluated

  4. London limit for lattice model of superconductor

    International Nuclear Information System (INIS)

    Ktitorov, S.A.

    2004-01-01

    The phenomenological approach to the strong-bond superconductor, which is based on the Ginzburg-Landau equation in the London limit, is considered. The effect of the crystalline lattice discreteness on the superconductors electromagnetic properties is studied. The classic problems on the critical current and magnetic field penetration are studied within the frames of the lattice model for thin superconducting films. The dependence of the superconducting current on the thin film order parameter is obtained. The critical current dependence on the degree of deviation from the continual approximation is calculated [ru

  5. Workshop on accelerator magnet superconductors. Proceedings

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2004-07-01

    The workshop on accelerator magnet superconductors has gathered 102 registered participants from research laboratories, universities and industry. 8 European companies, active in superconducting materials and cables were present. This workshop has been organized to deal with the status of the world research and development on superconducting materials and cables for high field magnets (B > 10 T). The workshop has also reviewed the status of high temperature superconductors and transmission line cables for potential use in low field superconducting magnets for injectors and beam transfer lines, as well as cables for pulsed magnets that might be used in future hadron colliders or injectors.

  6. A multi-mode multi-band RF receiver front-end for a TD-SCDMA/LTE/LTE-advanced in 0.18-μm CMOS process

    International Nuclear Information System (INIS)

    Guo Rui; Zhang Haiying

    2012-01-01

    A fully integrated multi-mode multi-band directed-conversion radio frequency (RF) receiver front-end for a TD-SCDMA/LTE/LTE-advanced is presented. The front-end employs direct-conversion design, and consists of two differential tunable low noise amplifiers (LNA), a quadrature mixer, and two intermediate frequency (IF) amplifiers. The two independent tunable LNAs are used to cover all the four frequency bands, achieving sufficient low noise and high gain performance with low power consumption. Switched capacitor arrays perform a resonant frequency point calibration for the LNAs. The two LNAs are combined at the driver stage of the mixer, which employs a folded double balanced Gilbert structure, and utilizes PMOS transistors as local oscillator (LO) switches to reduce flicker noise. The front-end has three gain modes to obtain a higher dynamic range. Frequency band selection and mode of configuration is realized by an on-chip serial peripheral interface (SPI) module. The front-end is fabricated in a TSMC 0.18-μm RF CMOS process and occupies an area of 1.3 mm 2 . The measured double-sideband (DSB) noise figure is below 3.5 dB and the conversion gain is over 43 dB at all of the frequency bands. The total current consumption is 31 mA from a 1.8-V supply. (semiconductor integrated circuits)

  7. Coupling between magnetic and superconducting order parameters and evidence for the spin excitation gap in the superconducting state of a heavy fermion superconductor UPd2Al3

    International Nuclear Information System (INIS)

    Metoki, Naoto; Haga, Yoshinori; Koike, Yoshihiro; Aso, Naofumi; Onuki, Yoshichika

    1997-01-01

    Neutron scattering experiments have been carried out in order to study the interplay between magnetism and superconductivity in a heavy fermion superconductor, UPd 2 Al 3 . We have observed 1% suppression of the (0 0 0.5) magnetic peak intensity below the superconducting transition temperature T c . This is direct evidence for the coupling of the magnetic order parameter with the superconducting one. Furthermore, we have observed a spin excitation gap associated with superconductivity. The gap energy ΔE g increases continuously from ΔE g =0 to 0.4 meV with decreasing temperature from T c to 0.4 K. This gap energy corresponds to 2k B T c , which is smaller than the superconducting gap expected from the BCS theory (3.5k B T c ). These results are indicative of the strong interplay between magnetism and superconductivity. (author)

  8. Higgs Mode in the d -Wave Superconductor Bi2Sr2CaCu2O8 +x Driven by an Intense Terahertz Pulse

    Science.gov (United States)

    Katsumi, Kota; Tsuji, Naoto; Hamada, Yuki I.; Matsunaga, Ryusuke; Schneeloch, John; Zhong, Ruidan D.; Gu, Genda D.; Aoki, Hideo; Gallais, Yann; Shimano, Ryo

    2018-03-01

    We investigate the terahertz (THz)-pulse-driven nonlinear response in the d -wave cuprate superconductor Bi2Sr2CaCu2O8 +x (Bi2212) using a THz pump near-infrared probe scheme in the time domain. We observe an oscillatory behavior of the optical reflectivity that follows the THz electric field squared and is markedly enhanced below Tc . The corresponding third-order nonlinear effect exhibits both A1 g and B1 g symmetry components, which are decomposed from polarization-resolved measurements. A comparison with a BCS calculation of the nonlinear susceptibility indicates that the A1 g component is associated with the Higgs mode of the d -wave order parameter.

  9. Paramagnetic limiting of the upper critical field of the layered organic superconductor κ-(BEDT-TTF)2Cu(SCN)2

    International Nuclear Information System (INIS)

    Zuo, F.; Brooks, J.S.; McKenzie, R.H.; Schlueter, J.A.; Williams, J.M.

    2000-01-01

    We report detailed measurements of the interlayer magnetoresistance of the layered organic superconductor κ-(BEDT-TTF) 2 Cu(SCN) 2 for temperatures down to 0.5 K and fields up to 30 T. The upper critical field is determined from the resistive transition for a wide range of temperatures and field directions. For magnetic fields parallel to the layers, the upper critical field increases approximately linearly with decreasing temperature. The upper critical field at low temperatures is compared to the Pauli paramagnetic limit, at which singlet superconductivity should be destroyed by the Zeeman splitting of the electron spins. The measured value is comparable to a value for the paramagnetic limit calculated from thermodynamic quantities but exceeds the limit calculated from BCS theory. The angular dependence of the upper critical field shows a cusplike feature for fields close to the layers, consistent with decoupled layers.

  10. Microgravity Processing of Oxide Superconductors

    Science.gov (United States)

    Olive, James R.; Hofmeister, William H.; Bayuzick, Robert J.; Vlasse, Marcus

    1999-01-01

    Considerable effort has been concentrated on the synthesis and characterization of high T(sub c) oxide superconducting materials. The YBaCuO system has received the most intense study, as this material has shown promise for the application of both thin film and bulk materials. There are many problems with the application of bulk materials- weak links, poor connectivity, small coherence length, oxygen content and control, environmental reactivity, phase stability, incongruent melting behavior, grain boundary contamination, brittle mechanical behavior, and flux creep. The extent to which these problems are intrinsic or associated with processing is the subject of controversy. This study seeks to understand solidification processing of these materials, and to use this knowledge for alternative processing strategies, which, at the very least, will improve the understanding of bulk material properties and deficiencies. In general, the phase diagram studies of the YBaCuO system have concentrated on solid state reactions and on the Y2BaCuO(x) + liquid yields YBa2Cu3O(7-delta) peritectic reaction. Little information is available on the complete melting relations, undercooling, and solidification behavior of these materials. In addition, rare earth substitutions such as Nd and Gd affect the liquidus and phase relations. These materials have promising applications, but lack of information on the high temperature phase relations has hampered research. In general, the understanding of undercooling and solidification of high temperature oxide systems lags behind the science of these phenomena in metallic systems. Therefore, this research investigates the fundamental melting relations, undercooling, and solidification behavior of oxide superconductors with an emphasis on improving ground based synthesis of these materials.

  11. Ultracold lithium-6 atoms in the BEC-BCS crossover: experiments and the construction of a new apparatus; Atomes de lithium-6 ultra froids dans la transition BEC-BCS: experiences et construction d'un montage experimental

    Energy Technology Data Exchange (ETDEWEB)

    Teichmann, M

    2007-09-15

    We use a fermionic gas of Lithium-6 as a model system to study superfluidity. The limiting cases of superfluidity are Bose-Einstein condensation (BEC) and superconductivity, described by the theory by Bardeen, Cooper and Schrieffer (BCS). In Lithium-6 gases, we can explore the whole range between the two cases, known as the BEC-BCS crossover, using a Feshbach resonance. We study the change of the momentum distribution of the gas in this cross-over and compare to theoretical models. We also investigate the hydrodynamic expansion, characteristic for a superfluid gas. We observe a sudden change of the ellipticity of the gas close to the transition to the superfluid phase. Moreover, we localized heteronuclear Feshbach resonances between {sup 6}Li and {sup 7}Li. We are currently constructing a second generation of the experimental setup. An new laser system, based on high power laser diodes, was developed. Changes in the vacuum chamber, including a complete reconstruction of the Zeeman slower, have increased the atomic flux, allowing us to increase the repetition rate of our experiment. Modifications of the geometry of the magnetic traps lead to a higher number of trapped atoms. (author)

  12. Ultracold lithium-6 atoms in the BEC-BCS crossover: experiments and the construction of a new apparatus; Atomes de lithium-6 ultra froids dans la transition BEC-BCS: experiences et construction d'un montage experimental

    Energy Technology Data Exchange (ETDEWEB)

    Teichmann, M

    2007-09-15

    We use a fermionic gas of Lithium-6 as a model system to study superfluidity. The limiting cases of superfluidity are Bose-Einstein condensation (BEC) and superconductivity, described by the theory by Bardeen, Cooper and Schrieffer (BCS). In Lithium-6 gases, we can explore the whole range between the two cases, known as the BEC-BCS crossover, using a Feshbach resonance. We study the change of the momentum distribution of the gas in this cross-over and compare to theoretical models. We also investigate the hydrodynamic expansion, characteristic for a superfluid gas. We observe a sudden change of the ellipticity of the gas close to the transition to the superfluid phase. Moreover, we localized heteronuclear Feshbach resonances between {sup 6}Li and {sup 7}Li. We are currently constructing a second generation of the experimental setup. An new laser system, based on high power laser diodes, was developed. Changes in the vacuum chamber, including a complete reconstruction of the Zeeman slower, have increased the atomic flux, allowing us to increase the repetition rate of our experiment. Modifications of the geometry of the magnetic traps lead to a higher number of trapped atoms. (author)

  13. Enhancing critical current density of cuprate superconductors

    Science.gov (United States)

    Chaudhari, Praveen

    2015-06-16

    The present invention concerns the enhancement of critical current densities in cuprate superconductors. Such enhancement of critical current densities include using wave function symmetry and restricting movement of Abrikosov (A) vortices, Josephson (J) vortices, or Abrikosov-Josephson (A-J) vortices by using the half integer vortices associated with d-wave symmetry present in the grain boundary.

  14. Electronic structure of Fe-based superconductors

    Indian Academy of Sciences (India)

    Abstract. Fe-based superconductors have drawn much attention during the last decade due to the presence of superconductivity in materials containing the magnetic element, Fe, and the coexistence of superconductivity and magnetism. Extensive study of the electronic structure of these systems suggested the dominant ...

  15. Development of superconductors for fusion technology

    International Nuclear Information System (INIS)

    Wilson, M.N.; Walters, C.R.

    1976-04-01

    A report is presented on the development of a 10 4 Amp NbTi cryogenically stabilized superconductor. The long term objective was the construction of a superconducting toroidal field magnet for a post JET Tokamak experiment. The report is in sections entitled: magnet reference parameters; specific conductor designs; theoretical studies; experimental measurements; fabrication techniques; discussion, summary, conclusions and recommendations. (U.K.)

  16. Anomalous infrared absorption in granular superconductors

    International Nuclear Information System (INIS)

    Carr, G.L.; Garland, J.C.; Tanner, D.B.

    1983-01-01

    Granular superconductors are shown to have a far-infrared absorption that is larger when the samples are superconducting than when they are normal. By constrast, theoretical models for these materials predict that when the samples become superconducting, the absorption should decrease

  17. Electronic structure of Fe-based superconductors

    Indian Academy of Sciences (India)

    2015-05-29

    May 29, 2015 ... Fe-based superconductors have drawn much attention during the last decade due to the presence of superconductivity in materials containing the magnetic element, Fe, and the coexistence of superconductivity and magnetism. Extensive study of the electronic structure of these systems suggested the ...

  18. Quantum Dots Coupled to a Superconductor

    DEFF Research Database (Denmark)

    Jellinggaard, Anders Robert

    are tuned electrostatically. This includes tuning the odd occupation of the dot through a quantum phase transition, where it forms a singlet with excitations in the superconductor. We detail the fabrication of these bottom gated devices, which additionally feature ancillary sensor dots connected...

  19. Epitaxy of semiconductor-superconductor nanowires

    DEFF Research Database (Denmark)

    Krogstrup, P.; Ziino, N.L.B.; Chang, W.

    2015-01-01

    Controlling the properties of semiconductor/metal interfaces is a powerful method for designing functionality and improving the performance of electrical devices. Recently semiconductor/superconductor hybrids have appeared as an important example where the atomic scale uniformity of the interface...

  20. The Effective Coherence Length in Anisotropic Superconductors

    International Nuclear Information System (INIS)

    Polturak, E.; Koren, G.; Nesher, O

    1999-01-01

    If electrons are transmitted from a normal conductor(N) into a superconductor(S), common wisdom has it that the electrons are converted into Cooper pairs within a coherence length from the interface. This is true in conventional superconductors with an isotropic order parameter. We have established experimentally that the situation is rather different in high Tc superconductors having an anisotropic order parameter. We used epitaxial thin film S/N bilayers having different interface orientations in order to inject carriers from S into N along different directions. The distance to which these carriers penetrate were determined through their effect on the Tc of the bilayers. We found that the effective coherence length is 20A only along the a or b directions, while in other directions we find a length of 250dr20A out of plane, and an even larger value for in-plane, off high symmetry directions. These observations can be explained using the Blonder-Tinkham-Klapwijk model adapted to anisotropic superconductivity. Several implications of our results on outstanding problems with high Tc junctions will be discussed

  1. Deformation of high-temperature superconductors

    International Nuclear Information System (INIS)

    Goretta, K.C.; Routbort, J.L.; Miller, D.J.; Chen, N.; Dominguez-Rodriguez, A.; Jimenez-Melendo, M.; De Arellano-Lopez, A.R.

    1994-08-01

    Of the many families of high-temperature superconductors, only the properties of those discovered prior to 1989 - Y-Ba-Cu-O, Tl-Ba(Sr)-Ca-Cu-O, and Bi(Pb)-Sr-Ca-Cu-O - have been studied extensively. Deformation tests have been performed on YBa 2 Cu 3 O x (Y-123), YBa 2 Cu 4 O x (Y-124), TlBa 2 Ca 2 Cu 3 O x (Bi-2223). The tests have revealed that plasticity is generally limited in these compounds and that the rate-controlling diffusional kinetics for creep are very slow. Nevertheless, hot forming has proved to be quite successful for fabrication of bulk high-temperature superconductors, so long as deformation rates are low or large hydrostatic stresses are applied. Steady-state creep data have proved to be useful in designing optimal heat treatments for superconductors and in support of more-fundamental diffusion experiments. The high-temperature superconductors are highly complex oxides, and it is a challenge to understand their deformation responses. In this paper, results of interest and operant creep mechanisms will be reviewed

  2. Nonmonotonic critical temperature in superconductor ferromagnet bilayers

    NARCIS (Netherlands)

    Fominov, Ya. V.; Fominov, I.V.; Chtchelkatchev, N.M.; Golubov, Alexandre Avraamovitch

    2002-01-01

    The critical temperature Tc of a superconductor/ferromagnet (SF) bilayer can exhibit nonmonotonic dependence on the thickness df of the F layer. SF systems have been studied for a long time; according to the experimental situation, a ¿dirty¿ limit is often considered which implies that the mean free

  3. Scalar Condensation of Holographic Superconductors using ...

    Indian Academy of Sciences (India)

    Abstract. We study holographic superconductors analytically by using the Ginzburg–Landau action with the γ-quartic term | |4. Our results show that γ-term plays a role in the scalar condensation. It is found that the system displays two kinds of critical temperatures. One is independent of γ. But the other increases with ...

  4. Gastrointestinal Behavior of Weakly Acidic BCS Class II Drugs in Man--Case Study of Diclofenac Potassium.

    Science.gov (United States)

    Van Den Abeele, Jens; Brouwers, Joachim; Mattheus, Ruben; Tack, Jan; Augustijns, Patrick

    2016-02-01

    This study aimed to investigate the gastrointestinal supersaturation and precipitation behavior of a weakly acidic Biopharmaceutics Classification System (BCS) Class II drug in healthy volunteers. For this purpose, a tablet containing 50 mg diclofenac potassium (Cataflam(®)) was predissolved in 240 mL of water and this solution was subsequently orally administered to five healthy volunteers under fasted and fed state conditions with or without concomitant use of a proton-pump inhibitor (PPI) (40 mg esomeprazole, Nexiam(®)). Subsequently, total diclofenac content and dissolved intraluminal drug concentrations as well as drug thermodynamic solubility were determined in gastrointestinal aspirates. In all volunteers, gastric supersaturation resulted in precipitation of diclofenac in the stomach. The extent of precipitation correlated well with gastric pH (r = - 0.78). pH dependency of precipitation was corroborated by the absence of precipitate in the stomach after coadministration of a meal and/or a PPI. Diclofenac was found to be fully dissolved in the duodenum in all test conditions. It can be concluded that substantial pH-dependent gastric precipitation of a weakly acidic BCS Class II drug administered as a solution occurs in humans. With regard to its implications for intestinal absorption, results suggest the instantaneous redissolution of gastric drug precipitate upon transfer to the duodenum. Copyright © 2016. Published by Elsevier Inc.

  5. Ultracold lithium-6 atoms in the BEC-BCS crossover: experiments and the construction of a new apparatus

    International Nuclear Information System (INIS)

    Teichmann, M.

    2007-09-01

    We use a fermionic gas of Lithium-6 as a model system to study superfluidity. The limiting cases of superfluidity are Bose-Einstein condensation (BEC) and superconductivity, described by the theory by Bardeen, Cooper and Schrieffer (BCS). In Lithium-6 gases, we can explore the whole range between the two cases, known as the BEC-BCS crossover, using a Feshbach resonance. We study the change of the momentum distribution of the gas in this cross-over and compare to theoretical models. We also investigate the hydrodynamic expansion, characteristic for a superfluid gas. We observe a sudden change of the ellipticity of the gas close to the transition to the superfluid phase. Moreover, we localized heteronuclear Feshbach resonances between 6 Li and 7 Li. We are currently constructing a second generation of the experimental setup. An new laser system, based on high power laser diodes, was developed. Changes in the vacuum chamber, including a complete reconstruction of the Zeeman slower, have increased the atomic flux, allowing us to increase the repetition rate of our experiment. Modifications of the geometry of the magnetic traps lead to a higher number of trapped atoms. (author)

  6. Snake instability of dark solitons across the BEC-BCS crossover: An effective-field-theory perspective

    Science.gov (United States)

    Lombardi, G.; Van Alphen, W.; Klimin, S. N.; Tempere, J.

    2017-09-01

    In the present article the snake instability mechanism for dark solitons in superfluid Fermi gases is studied in the context of a recently developed effective field theory [S. N. Klimin et al., Eur. Phys. J. B 88, 122 (2015), 10.1140/epjb/e2015-60213-4]. This theoretical treatment has proven to be suitable to study stable dark solitons in quasi-one-dimensional setups across the BEC-BCS crossover. In this paper the nodal plane of the stable soliton solution is perturbed by adding a transverse modulation. The numerical solution of the system of coupled nonlinear differential equations describing the amplitude of the perturbation leads to an estimate of the growth rate and characteristic length scale of the instability, which are calculated for a wide range of interaction regimes and compared to other theoretical predictions. The behavior of the maximum transverse size that the atomic cloud can have in order to preserve the stability is described across the BEC-BCS crossover. The analysis of the effects of spin imbalance on this critical length reveals a stabilization of the soliton with increasing imbalance and therefore provides the experimental community with a method to achieve the realization of stable solitons in real three-dimensional configurations, without reducing the system dimensionality.

  7. The new Fe-based superconductors

    International Nuclear Information System (INIS)

    Mao, Zhiqiang

    2011-01-01

    The discovery of unconventional superconductivity in doped iron pnictides has ushered in a new era of high temperature superconductivity. The superconductivity of these materials occurs in close proximity to magnetic instability; superconductivity is achieved by suppressing a long-range antiferromagnetic (AFM) order through charge carrier doping or pressure. In this talk, I will first give a brief overview of the phase diagrams of iron-based superconductors, and then talk about our recent research on iron chalcogenide Fe 1+y (Te 1-x Se x ) superconductors, which is structurally the simplest of the Fe-based superconductors. Although the Fermi surface of iron chalcogenides is similar to iron pnictides, the parent compound Fe 1+y Te exhibits AFM order with in-plane magnetic wave-vector (π, 0). This contrasts the pnictide parent compounds where the magnetic order has an in-plane magnetic wave-vector (π, π) that connects hole and electron parts of the Fermi surface. Despite these differences, both the pnictide and chalcogenide Fe-superconductors exhibit superconducting spin resonances around (π, π), suggesting a common symmetry for their superconducting order parameter. A central question in this burgeoning field is therefore how (π, π) superconductivity can emerge from a (π, 0) magnetic instability. I will address this issue in my talk. I will show the phase diagram of electronic and magnetic properties we recently established for this system and discuss the relationship between magnetic coupling and electronic properties. Our results reveal that the magnetic soft mode evolving from the (π, 0)-type magnetic long-range order is associated with weak charge carrier localization. Bulk superconductivity occurs only as magnetic correlations near (π, 0) are strongly suppressed and the magnetic mode at (π, π) becomes dominant; this suggests a common magnetic origin for superconductivity in iron chalcogenide and pnictide superconductors. (author)

  8. Weak links in high critical temperature superconductors

    Science.gov (United States)

    Tafuri, Francesco; Kirtley, John R.

    2005-11-01

    The traditional distinction between tunnel and highly transmissive barriers does not currently hold for high critical temperature superconducting Josephson junctions, both because of complicated materials issues and the intrinsic properties of high temperature superconductors (HTS). An intermediate regime, typical of both artificial superconductor-barrier-superconductor structures and of grain boundaries, spans several orders of magnitude in the critical current density and specific resistivity. The physics taking place at HTS surfaces and interfaces is rich, primarily because of phenomena associated with d-wave order parameter (OP) symmetry. These phenomena include Andreev bound states, the presence of the second harmonic in the critical current versus phase relation, a doubly degenerate state, time reversal symmetry breaking and the possible presence of an imaginary component of the OP. All these effects are regulated by a series of transport mechanisms, whose rules of interplay and relative activation are unknown. Some transport mechanisms probably have common roots, which are not completely clear and possibly related to the intrinsic nature of high-TC superconductivity. The d-wave OP symmetry gives unique properties to HTS weak links, which do not have any analogy with systems based on other superconductors. Even if the HTS structures are not optimal, compared with low critical temperature superconductor Josephson junctions, the state of the art allows the realization of weak links with unexpectedly high quality quantum properties, which open interesting perspectives for the future. The observation of macroscopic quantum tunnelling and the qubit proposals represent significant achievements in this direction. In this review we attempt to encompass all the above aspects, attached to a solid experimental basis of junction concepts and basic properties, along with a flexible phenomenological background, which collects ideas on the Josephson effect in the presence

  9. Weak links in high critical temperature superconductors

    International Nuclear Information System (INIS)

    Tafuri, Francesco; Kirtley, John R

    2005-01-01

    The traditional distinction between tunnel and highly transmissive barriers does not currently hold for high critical temperature superconducting Josephson junctions, both because of complicated materials issues and the intrinsic properties of high temperature superconductors (HTS). An intermediate regime, typical of both artificial superconductor-barrier-superconductor structures and of grain boundaries, spans several orders of magnitude in the critical current density and specific resistivity. The physics taking place at HTS surfaces and interfaces is rich, primarily because of phenomena associated with d-wave order parameter (OP) symmetry. These phenomena include Andreev bound states, the presence of the second harmonic in the critical current versus phase relation, a doubly degenerate state, time reversal symmetry breaking and the possible presence of an imaginary component of the OP. All these effects are regulated by a series of transport mechanisms, whose rules of interplay and relative activation are unknown. Some transport mechanisms probably have common roots, which are not completely clear and possibly related to the intrinsic nature of high-T C superconductivity. The d-wave OP symmetry gives unique properties to HTS weak links, which do not have any analogy with systems based on other superconductors. Even if the HTS structures are not optimal, compared with low critical temperature superconductor Josephson junctions, the state of the art allows the realization of weak links with unexpectedly high quality quantum properties, which open interesting perspectives for the future. The observation of macroscopic quantum tunnelling and the qubit proposals represent significant achievements in this direction. In this review we attempt to encompass all the above aspects, attached to a solid experimental basis of junction concepts and basic properties, along with a flexible phenomenological background, which collects ideas on the Josephson effect in the presence

  10. Normal zone soliton in large composite superconductors

    International Nuclear Information System (INIS)

    Kupferman, R.; Mints, R.G.; Ben-Jacob, E.

    1992-01-01

    The study of normal zone of finite size (normal domains) in superconductors, has been continuously a subject of interest in the field of applied superconductivity. It was shown that in homogeneous superconductors normal domains are always unstable, so that if a normal domain nucleates, it will either expand or shrink. While testing the stability of large cryostable composite superconductors, a new phenomena was found, the existence of stable propagating normal solitons. The formation of these propagating domains was shown to be a result of the high Joule power generated in the superconductor during the relatively long process of current redistribution between the superconductor and the stabilizer. Theoretical studies were performed in investigate the propagation of normal domains in large composite super conductors in the cryostable regime. Huang and Eyssa performed numerical calculations simulating the diffusion of heat and current redistribution in the conductor, and showed the existence of stable propagating normal domains. They compared the velocity of normal domain propagation with the experimental data, obtaining a reasonable agreement. Dresner presented an analytical method to solve this problem if the time dependence of the Joule power is given. He performed explicit calculations of normal domain velocity assuming that the Joule power decays exponentially during the process of current redistribution. In this paper, the authors propose a system of two one-dimensional diffusion equations describing the dynamics of the temperature and the current density distributions along the conductor. Numerical simulations of the equations reconfirm the existence of propagating domains in the cryostable regime, while an analytical investigation supplies an explicit formula for the velocity of the normal domain

  11. Recrystallization of high temperature superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Kouzoudis, Dimitris [Iowa State Univ., Ames, IA (United States)

    1996-05-09

    Currently one of the most widely used high Tc superconductors is the Bi-based compounds Bi2Sr2CaCu2Oz and Bi2Sr2Ca2Cu3Oz (known as BSCCO 2212 and 2223 compounds) with Tc values of about 85 K and 110 K respectively. Lengths of high performance conductors ranging from 100 to 1000 m long are routinely fabricated and some test magnets have been wound. An additional difficulty here is that although Bi-2212 and Bi-2223 phases exist over a wide range of stoichiometries, neither has been prepared in phase-pure form. So far the most successful method of constructing reliable and robust wires or tapes is the so called powder-in-tube (PIT) technique [1, 2, 3, 4, 5, 6, 7] in which oxide powder of the appropriate stoichiometry and phase content is placed inside a metal tube, deformed into the desired geometry (round wire or flat tape), and annealed to produce the desired superconducting properties. Intermediate anneals are often incorporated between successive deformation steps. Silver is the metal used in this process because it is the most compatible with the reacting phase. In all of the commercial processes for BSCCO, Ag seems to play a special catalytic role promoting the growth of high performance aligned grains that grow in the first few micrometers near the Ag/BSCCO interface. Adjacent to the Ag, the grain alignment is more perfect and the current density is higher than in the center of the tape. It is known that Ag lowers the melting point of several of the phases but the detailed mechanism for growth of these high performance grains is not clearly understood. The purpose of this work is to study the nucleation and growth of the high performance material at this interface.

  12. Multi-Band Frequency Selective Surfaces: Analysis

    Science.gov (United States)

    2008-08-01

    performed by a graduate student from the University of Turin (Italy) in the frame of a six-month internship at TNO, following these steps: la Study the IEMEN...antennas using EBG substrates", Ph.D. dissertation, Departamento de Comunicaciones , Universidad Politecnica de Valencia, Valencia, Spain, 2006. [21

  13. Multi-band Modelling of Appearance

    DEFF Research Database (Denmark)

    Stegmann, Mikkel Bille; Larsen, Rasmus

    2003-01-01

    the appearance of both derived feature bands and an intensity band. As a special case of feature-band augmented appearance modelling we propose a dedicated representation with applications to face segmentation. The representation addresses a major problem within face recognition by lowering the sensitivity...

  14. Multi-band Modelling of Appearance

    DEFF Research Database (Denmark)

    Stegmann, Mikkel Bille; Larsen, Rasmus

    2002-01-01

    the appearance of both derived feature bands and an intensity band. As a special case of feature-band augmented appearance modelling we propose a dedicated representation with applications to face segmentation. The representation addresses a major problem within face recognition by lowering the sensitivity...

  15. Bcs1p can rescue a large and productive cytochrome bc(1) complex assembly intermediate in the inner membrane of yeast mitochondria.

    Science.gov (United States)

    Conte, Laura; Trumpower, Bernard L; Zara, Vincenzo

    2011-01-01

    The yeast cytochrome bc(1) complex, a component of the mitochondrial respiratory chain, is composed of ten distinct protein subunits. In the assembly of the bc(1) complex, some ancillary proteins, such as the chaperone Bcs1p, are actively involved. The deletion of the nuclear gene encoding this chaperone caused the arrest of the bc(1) assembly and the formation of a functionally inactive bc(1) core structure of about 500-kDa. This immature bc(1) core structure could represent, on the one hand, a true assembly intermediate or, on the other hand, a degradation product and/or an incorrect product of assembly. The experiments here reported show that the gradual expression of Bcs1p in the yeast strain lacking this protein was progressively able to rescue the bc(1) core structure leading to the formation of the functional homodimeric bc(1) complex. Following Bcs1p expression, the mature bc(1) complex was also progressively converted into two supercomplexes with the cytochrome c oxidase complex. The capability of restoring the bc(1) complex and the supercomplexes was also possessed by the mutated yeast R81C Bcsp1. Notably, in the human ortholog BCS1L, the corresponding point mutation (R45C) was instead the cause of a severe bc(1) complex deficiency. Differently from the yeast R81C Bcs1p, two other mutated Bcs1p's (K192P and F401I) were unable to recover the bc(1) core structure in yeast. This study identifies for the first time a productive assembly intermediate of the yeast bc(1) complex and gives new insights into the molecular mechanisms involved in the last steps of bc(1) assembly. Copyright © 2010 Elsevier B.V. All rights reserved.

  16. Fabrication and study of hybrid molecule/superconductor assemblies

    International Nuclear Information System (INIS)

    McDevitt, J.T.; Haupt, S.G.; Jurbergs, D.; Riley, D.R.; Zhao, J.; Zhou, J.P.; Lo, K.; Grassi, J.; Jones, C.

    1994-01-01

    The fabrication of electronic devices from molecular materials has attracted much attention recently. Schottky diodes, molecular transistors, metal-insulator-semiconductor diodes, MIS field effect transistors and light emitting diodes have all been prepared utilizing such substances. The active elements in these devices have been constructed by depositing the molecular phase onto the surface of a metal, semiconductor or insulating substrate. With the recent discovery of high temperature superconductivity, new opportunities now exist for the study of molecule/superconductor interactions as well as for the construction of novel hybrid molecule/superconductor devices. In this paper, methods for preparing the first two classes of composite molecule/superconductor devices are reported. Consequently, light sensors based on organic dye-coated superconductor junctions as well as molecular switches fashioned from organic conductive polymer-coated superconductor microbridges are discussed. Moreover, the initial results related to the study of molecule/superconductor energy and electron transfer phenomena are reported

  17. Low resistivity contact to iron-pnictide superconductors

    Science.gov (United States)

    Tanatar, Makariy; Prozorov, Ruslan; Ni, Ni; Bud& #x27; ko, Sergey; Canfield, Paul

    2013-05-28

    Method of making a low resistivity electrical connection between an electrical conductor and an iron pnictide superconductor involves connecting the electrical conductor and superconductor using a tin or tin-based material therebetween, such as using a tin or tin-based solder. The superconductor can be based on doped AFe.sub.2As.sub.2, where A can be Ca, Sr, Ba, Eu or combinations thereof for purposes of illustration only.

  18. Functional development in density functional theory for superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Sanna, Antonio; Gross, E.K.U.; Essenberger, Frank [Max Planck Institute of Microstructure Physics, Halle (Saale) (Germany)

    2015-07-01

    Density functional theory for superconductors (SCDFT) is a fully parameter-free approach to superconductivity that allows for accurate predictions of critical temperature and properties of superconductors. We report on the most recent extensions of the method, in particular the development of new functionals to: (1) incorporate in a correct fashion Migdal's theorem; (2) compute the excitation spectrum; (3) include spin-fluctuation mediated pairing Applications and predictions are shown for a set of materials, including conventional and unconventional superconductors.

  19. High temperature superconductor cable concepts for fusion magnets

    CERN Document Server

    AUTHOR|(CDS)2078397

    2013-01-01

    Three concepts of high temperature superconductor cables carrying kA currents (RACC, CORC and TSTC) are investigated, optimized and evaluated in the scope of their applicability as conductor in fusion magnets. The magnetic field and temperature dependence of the cables is measured; the thermal expansion and conductivity of structure, insulation and filling materials are investigated. High temperature superconductor winding packs for fusion magnets are calculated and compared with corresponding low temperature superconductor cases.

  20. On the electronegativity of the high-Tc oxide superconductor

    International Nuclear Information System (INIS)

    Zhang Liyuan.

    1991-08-01

    We employ a very useful quantity, the electronegativity, to classify the superconductor. The value of the group average electronegativity to separate superconductor into two categories is 2. Each category has unique chemical bond features. The high-T c oxide superconductor belongs to the second category with group average electronegativity being larger than 2. Their unusual bond nature also gives new insight into some essential factors beneficial to enhance superconductivity. (author). 9 refs, 2 tabs

  1. The iron pnictide superconductors an introduction and overview

    CERN Document Server

    Citro, Roberta

    2017-01-01

    This book covers different aspects of the physics of iron-based superconductors ranging from the theoretical, the numerical and computational, to the experimental ones. It starts from the basic theory modeling many-body physics in Fe-superconductors and other multi-orbital materials and drreaches up to the magnetic and Cooper pair fluctuations and nematic order. Finally, it offers a comprehensive overview of the most recent advancements in the experimental investigations of iron based superconductors. .

  2. Filters for mobile radio from high Tc ceramic superconductors

    International Nuclear Information System (INIS)

    Peterson, G.E.; Wong, E.; Alford, N.McN.

    1990-01-01

    Mobile radio frequencies lie between 30 MHz and 1,000 MHz. This frequency range is ideal for ceramic high T c superconductors. We have designed Chebyshev, Butterworth and interdigital filters that can employ high T c superconductors in the form of rods, tubes and helices. In general, the performance of these filters at milliwatt power levels is excellent. We will describe fabrication of the superconductors and filter design

  3. Optimization of superconductor--normal-metal--superconductor Josephson junctions for high critical-current density

    International Nuclear Information System (INIS)

    Golub, A.; Horovitz, B.

    1994-01-01

    The application of superconducting Bi 2 Sr 2 CaCu 2 O 8 and YBa 2 Cu 3 O 7 wires or tapes to electronic devices requires the optimization of the transport properties in Ohmic contacts between the superconductor and the normal metal in the circuit. This paper presents results of tunneling theory in superconductor--normal-metal--superconductor (SNS) junctions, in both pure and dirty limits. We derive expressions for the critical-current density as a function of the normal-metal resistivity in the dirty limit or of the ratio of Fermi velocities and effective masses in the clean limit. In the latter case the critical current increases when the ratio γ of the Fermi velocity in the superconductor to that of the weak link becomes much less than 1 and it also has a local maximum if γ is close to 1. This local maximum is more pronounced if the ratio of effective masses is large. For temperatures well below the critical temperature of the superconductors the model with abrupt pair potential on the SN interfaces is considered and its applicability near the critical temperature is examined

  4. Tunneling in cuprate and bismuthate superconductors

    International Nuclear Information System (INIS)

    Zasadzinski, J.F.; Huang, Qiang; Tralshawala, N.

    1991-10-01

    Tunneling measurements using a point-contact technique are reported for the following high temperature superconducting oxides: Ba 1-x K x BiO 3 (BKBO), Nd 2-x Ce x CuO 4 (NCCO), Bi 2 Sr 2 CaCu 2 O 7 (BSCCO) and Tl 2 Ba 2 CaCu 2 O x (TBCCO). For the bismuthate, BKBO, ideal, S-I-N tunneling characteristics are observed using a Au tip. The normalized conductance is fitted to a BCS density of states and thermal smearing only proving there is no fundamental limitation in BKBO for device applications. For the cuprates, the normalized conductance displays BCS-like characteristics, but with a broadening larger than from thermal smearing. Energy gap values are presented for each material. For BKBO and NCCO the Eliashberg functions, α 2 F(ω), obtained from the tunneling are shown to be in good agreement with neutron scattering results. Proximity effect tunneling studies are reported for Au/BSCCO bilayers and show that the energy gap of BSCCO can be observed through Au layers up to 600 Angstrom thick

  5. Towards ferromagnet/superconductor junctions on graphene

    International Nuclear Information System (INIS)

    Pakkayil, Shijin Babu

    2015-01-01

    Ever since A. Aspect et al. performed the famous 1982 experiment to prove the violation of Bell's inequality, there have been suggestions to conduct the same experiment in a solid state system. Some of those proposals involve superconductors as the source of entangled electron pair and spin depended interfaces as the optical analogue of polariser/filter. Semiconductors can serve as the best medium for such an experiment due to their long relaxation lengths. So far there are no reports on a ferromagnet/superconductor junctions on a semiconductor even though such junctions has been successfully realised in metallic systems. This thesis reports the successful fabrication of ferromagnet/superconductor junction along with characterising measurements in a perfectly two dimensional zero-gap semiconductor known as graphene. Since it's discovery in 2004, graphene has attracted prodigious interest from both academia and industry due to it's inimitable physical properties: very high mobility, high thermal and electrical conductivity, a high Young's modulus and impermeability. Graphene is also expected to have very long spin relaxation length and high spin life time because of it's low spin orbit coupling. For this reason and since researchers are always looking for novel materials and devices to comply with the high demands for better and faster data storage devices, graphene has emanated as a brand new material system for spin based devices. The very first spin injection and detection in graphene was realised in 2007 and ever since, the focal point of the research has been to improve the spin transport properties. A part of this thesis discusses a new fabrication recipe which has a high yield for successfully contacting graphene with a ferromagnet. A high starting yield for ferromagnetic contacts is a irremissible condition for combining superconducting contacts to the device to fabricate ferromagnet/superconductor junctions. Any fabrication recipe

  6. Towards ferromagnet/superconductor junctions on graphene

    Energy Technology Data Exchange (ETDEWEB)

    Pakkayil, Shijin Babu

    2015-07-01

    Ever since A. Aspect et al. performed the famous 1982 experiment to prove the violation of Bell's inequality, there have been suggestions to conduct the same experiment in a solid state system. Some of those proposals involve superconductors as the source of entangled electron pair and spin depended interfaces as the optical analogue of polariser/filter. Semiconductors can serve as the best medium for such an experiment due to their long relaxation lengths. So far there are no reports on a ferromagnet/superconductor junctions on a semiconductor even though such junctions has been successfully realised in metallic systems. This thesis reports the successful fabrication of ferromagnet/superconductor junction along with characterising measurements in a perfectly two dimensional zero-gap semiconductor known as graphene. Since it's discovery in 2004, graphene has attracted prodigious interest from both academia and industry due to it's inimitable physical properties: very high mobility, high thermal and electrical conductivity, a high Young's modulus and impermeability. Graphene is also expected to have very long spin relaxation length and high spin life time because of it's low spin orbit coupling. For this reason and since researchers are always looking for novel materials and devices to comply with the high demands for better and faster data storage devices, graphene has emanated as a brand new material system for spin based devices. The very first spin injection and detection in graphene was realised in 2007 and ever since, the focal point of the research has been to improve the spin transport properties. A part of this thesis discusses a new fabrication recipe which has a high yield for successfully contacting graphene with a ferromagnet. A high starting yield for ferromagnetic contacts is a irremissible condition for combining superconducting contacts to the device to fabricate ferromagnet/superconductor junctions. Any fabrication recipe

  7. Impurities and conductivity in a D-wave superconductor

    International Nuclear Information System (INIS)

    Balatsky, A.V.

    1994-01-01

    Impurity scattering in the unitary limit produces low energy quasiparticles with anisotropic spectrum in a two-dimensional d-wave superconductor. The authors describe a new quasi-one-dimensional limit of the quasiparticle scattering, which might occur in a superconductor with short coherence length and with finite impurity potential range. The dc conductivity in a d-wave superconductor is predicted to be proportional to the normal state scattering rate and is impurity-dependent. They show that quasi-one-dimensional regime might occur in high-T c superconductors with Zn impurities at low temperatures T approx-lt 10 K

  8. Method and apparatus to trigger superconductors in current limiting devices

    Science.gov (United States)

    Yuan, Xing; Hazelton, Drew Willard; Walker, Michael Stephen

    2004-10-26

    A method and apparatus for magnetically triggering a superconductor in a superconducting fault current limiter to transition from a superconducting state to a resistive state. The triggering is achieved by employing current-carrying trigger coil or foil on either or both the inner diameter and outer diameter of a superconductor. The current-carrying coil or foil generates a magnetic field with sufficient strength and the superconductor is disposed within essentially uniform magnetic field region. For superconductor in a tubular-configured form, an additional magnetic field can be generated by placing current-carrying wire or foil inside the tube and along the center axial line.

  9. Surface electrostatic waves in bounded high temperature superconductors

    International Nuclear Information System (INIS)

    Averkov, Yu.O.; Yakovenko, V.M.

    2008-01-01

    The dispersion relations of surface electrostatic waves propagating along the surface of semi bounded layered superconductor and in the slab of layered superconductor are theoretically investigated. An arbitrary inclination of superconductor layers to the interface of a vacuum - crystal and an arbitrary direction of propagation of surface waves in the plane of the interface are taking into account. The possibility of initiation of an absolute instability during the propagation of a non-relativistic plasma stream above the surface of the layered superconductor is shown

  10. Non-centrosymmetric superconductors introduction and overview

    CERN Document Server

    Sigrist, Manfred

    2012-01-01

    Superconductivity in materials without inversion symmetry in the respective crystal structures occurs in the presence of antisymmetric spin-orbit coupling as a consequence of an emerging electric field gradient. The superconducting condensate is then a superposition of spin-singlet and spin-triplet Cooper pairs. This scenario accounts for various experimental findings such as nodes in the superconducting gap or extremely large upper critical magnetic fields. Spin-triplet pairing can occur in non-centrosymmetric superconductors in spite of Anderson’s theorem that spin-triplet pairing requires a crystal structure that exhibits inversion symmetry. This book, authored and edited by leading researchers in the field, is both an introduction to and overview on this exciting branch of novel superconductors. Its self-contained and tutorial style makes it particularly suitable for self-study and as source of teaching material for special seminars and courses. At the same time it constitutes an up-to-date and authorit...

  11. Method for fabrication of high temperature superconductors

    Science.gov (United States)

    Balachandran, Uthamalingam [Hinsdale, IL; Ma, Beihai [Naperville, IL; Miller, Dean [Darien, IL

    2009-07-14

    A layered article of manufacture and a method of manufacturing same is disclosed. A substrate has a biaxially textured MgO crystalline layer having the c-axes thereof inclined with respect to the plane of the substrate deposited thereon. A layer of one or more of YSZ or Y.sub.2O.sub.3 and then a layer of CeO.sub.2 is deposited on the MgO. A crystalline superconductor layer with the c-axes thereof normal to the plane of the substrate is deposited on the CeO.sub.2 layer. Deposition of the MgO layer on the substrate is by the inclined substrate deposition method developed at Argonne National Laboratory. Preferably, the MgO has the c-axes thereof inclined with respect to the normal to the substrate in the range of from about 10.degree. to about 40.degree. and YBCO superconductors are used.

  12. A Fifth Force: Generalized through Superconductors

    Science.gov (United States)

    Robertson, Glen A.

    1999-01-01

    The connection between the Biefield-Brown Effect, the recent repeat of the 1902 Trouton-Noble (TN) experiments, and the gravity shielding experiments was explored. This connection is visualized through high capacitive electron concentrations. From this connection, a theory is proposed that connects mass energy to gravity and a fifth force. The theory called the Gravi-Atomic Energy theory presents two new terms: Gravi-atomic energy and quantum vacuum pressure (QVP). Gravi-atomic energy is defined as the radiated mass energy, which acts on vacuum energy to create a QVP about a mass, resulting in gravity and the fifth force. The QVP emission from a superconductor was discussed followed by the description of a test for QVP from a superconductor using a Cavendish balance.

  13. Local electromagnetic waves in layered superconductors

    International Nuclear Information System (INIS)

    Gvozdikov, V.M.; Vega-Monroy, R.

    1999-01-01

    A dispersion equation for electromagnetic waves localized on a defect layer of a layered superconductor is obtained in the frame of a model which neglects electron hopping between layers but assumes an arbitrary current-current response function within the layers. The defect layer differs from the rest of the layers by density and mass of charge carriers. It is shown that near the critical temperature in the London limit the local mode lies within the superconducting gap and has a wave vector threshold depending on the layered crystal and defect layer parameters. In the case of highly anisotropic layered superconductors, like Bi- or Tl-based high-T c cuprates, the local mode exists within a narrow range of positive variations of the mass and charge carriers. (author)

  14. Propagation of normal zones in composite superconductors

    International Nuclear Information System (INIS)

    Dresner, L.

    1976-08-01

    This paper describes calculations of propagation velocities of normal zones in composite superconductors. Full accounting is made for (1) current sharing, (2) the variation with temperature of the thermal conductivity of the copper matrix, and the specific heats of the matrix and the superconductor, and (3) the variation with temperature of the steady-state heat transfer at a copper-helium interface in the nucleate-boiling, transition, and film-boiling ranges. The theory, which contains no adjustable parameters, is compared with experiments on bare (uninsulated) conductors. Agreement is not good. It is concluded that the effects of transient heat transfer may need to be included in the theory to improve agreement with experiment

  15. Critical current enhancement in high Tc superconductors

    International Nuclear Information System (INIS)

    Jin, S.; Graebner, J.E.; Tiefel, T.H.

    1990-01-01

    Progress toward major technological applications of the bulk, high T c superconductors has been hindered by two major barriers, i.e., the Josephson weak-links at grain boundaries and the lack of sufficient intragrain flux pinning. It has been demonstrated that the weak link problem can be overcome by extreme alignment of grains such as in melt-textured-growth (MTG) materials. Modified or improved processing by various laboratories has produced further increased critical currents. However, the insufficient flux pinning seems to limit the critical current density in high fields to about 10 4 --10 5 A/cm 2 at 77K, which is not satisfactory for many applications. In this paper, processing, microstructure, and critical current behavior of the MTG type superconductors are described, and various processing possibilities for flux pinning enhancement are discussed

  16. Application of High Temperature Superconductors to Accelerators

    CERN Document Server

    Ballarino, A

    2000-01-01

    Since the discovery of high temperature superconductivity, a large effort has been made by the scientific community to investigate this field towards a possible application of the new oxide superconductors to different devices like SMES, magnetic bearings, flywheels energy storage, magnetic shielding, transmission cables, fault current limiters, etc. However, all present day large scale applications using superconductivity in accelerator technology are based on conventional materials operating at liquid helium temperatures. Poor mechanical properties, low critical current density and sensitivity to the magnetic field at high temperature are the key parameters whose improvement is essential for a large scale application of high temperature superconductors to such devices. Current leads, used for transferring currents from the power converters, working at room temperature, into the liquid helium environment, where the magnets are operating, represent an immediate application of the emerging technology of high t...

  17. Flux Tube Dynamics in the Dual Superconductor

    International Nuclear Information System (INIS)

    Lampert, M.; Svetitsky, B.

    1999-01-01

    We have studied plasma oscillations in a flux tube created in a dual superconductor. The theory contains an Abelian gauge field coupled magnetically to a Higgs field that confines electric charge via the dual Meissner effect. Starting from a static flux tube configuration, with electric charges at either end, we release a fluid of electric charges in the system that accelerate and screen the electric field. The weakening of the electric field allows the flux tube to collapse, and the inertia of the charges forces it open again. We investigate both Type I and Type II superconductors, with plasma frequencies both above and below the threshold for radiation into the Higgs vacuum. (The parameters appropriate to QCD are in the Type II regime; the plasma frequency depends on the mass taken for the fluid constituents.) The coupling of the plasma oscillations to the Higgs field making up the flux tube is the main new feature in our work

  18. Positron annihilation studies on high temperature superconductors

    International Nuclear Information System (INIS)

    Sundar, C.S.; Bharathi, A.

    1996-01-01

    A survey of the positron annihilation studies on high temperature superconductors (HTSC), with results drawn mainly from our work, is presented. These include results of the studies on the temperature dependence of positron lifetime across T c , which have been carried out in the whole gamut of oxide superconductors. These experimental results are discussed in conjunction with the results of theoretically calculated positron density distribution, and it is shown that the observed temperature dependence of lifetime is intimately linked to the probing of the Cu-O network by the positrons. Results on the investigation of oxygen defects, which play a crucial role in HTSC, are presented. The most significant contribution of positrons to HTSC relates to the investigation of Fermi surface and the results of these studies, drawn from literature, are indicated. Some of our recent results in other novel superconducting materials, viz., the fullerenes and borocarbides are also presented. (author). 69 refs., 15 figs

  19. Superconductors for W VII-X coils

    International Nuclear Information System (INIS)

    Maurer, W.

    1987-01-01

    Superconductor concepts are discussed with respect to operational current, cooling and bending behavior, and ac losses. The encouraging results for NbTi superconducting technology are recalled. It is argued that the WVII-X stellarator modular superconducting coils can be built just as the modular Cu coils for WVII-AS. Special attention must be paid to the dB/dt allowed for the conductor. Shape and price depend on the means used to avoid ac losses. Formula to elucidate the main physical parameters influencing ac loss behavior of superconductors are given. Configurations investigated with respect to plasma behavior are compared. Masses to be cooled were estimated for two configurations. The estimated cooling power is of the order of 3kW

  20. High-Tc ferroelectrics and superconductors

    International Nuclear Information System (INIS)

    Muller, K.A.

    1990-01-01

    The meaning of the title refers to transition temperatures T c in ferroelectrics (FE) and superconductors (S). The highest T c 's in either field are observed in oxides: 1770 K in the ferroelectric La 2 TiO 7 and 125 K in the superconductor Tl 2 Ca 2 Cu 3 O 10 . Therefore, the question can be asked whether the observed high T c 's in oxide FE and S are a pure coincidence or whether there may be an underlying reason for it. This question is addressed first by recalling recent advances concerning anharmonic FE-properties and then by reviewing S-findings in the new compounds related to these properties