WorldWideScience

Sample records for borocarbide superconductors rni2b2c

  1. Magnetic and structural features of RNi2B2C and RNiBC (R=Er, Ho, Dy, Tb, Gd) superconducting compounds

    OpenAIRE

    Baggio-Saitovitch, E. M.; Sánchez, D. R.; Micklitz, H.

    2002-01-01

    Temperature dependent Mössbauer spectroscopy on 57Fe doped (1 at % of Ni) RNi2B2C and RNiBC provided clear evidence of a pair-breaking field at the Ni site for non-superconducting compounds. This field is not present in the superconducting collinear AF DyNi2B2C, however it appears when this compound is diluted with non-magnetic Lu (Dy1-xLu xNi2B2C). Important local information on the spin structure of the R magnetic moments is obtained for both systems. The local symmetries of RNi2B2C and RNi...

  2. Neutron and resonant x-ray scattering studies of RNi2B2C (R = rare earth) single crystals

    International Nuclear Information System (INIS)

    Stassis, C.; Goldman, A.I.; Iowa State Univ., Ames, IA

    1996-01-01

    This family of intermetallic compounds is ideal for the study of the interplay between superconductivity and magnetism since, in several of these compounds (Ho, Er, Tm, Dy), superconductivity coexists with magnetic ordering. The most important findings of the scattering studies are (a) in the Ho-compound, a complex magnetic structure characterized by two incommensurate wave vectors, rvec k a = 0.585 rvec a* and rvec k c = 0.915 rvec c*, exists in the vicinity of 5 K, where the almost reentrant behavior of this compound occurs; (b) an incommensurate magnetic structure with wave vector along rvec a*, close to the zone boundary, is observed in several of these compounds; and (c) pronounced soft-phonon behavior was observed for both the acoustic and first optical Δ 4 [ξ00] branches in the superconducting Lu and Ho compounds, a behavior characteristic of strongly coupled conventional superconductors. Furthermore, these phonon anomalies occur at wave vectors close to those of the incommensurate magnetically ordered structures observed in the magnetic compounds of this family. This observation suggests that both the magnetic ordering and phonon softening originate from common nesting features of the Fermi surfaces of these compounds. Band theoretical calculations are in qualitative agreement with these results

  3. Flux line lattice symmetries in the borocarbide superconductor ...

    Indian Academy of Sciences (India)

    obtained in the borocarbide superconductor LuNi2B2C with the applied field along the c- and a- axes. For Hc the temperature dependence of the FLL structural phase transition from square to hexagonal symmetry was investigated. Above 10 K the transition onset field, H2(T), rises sharply, bending away from Hc2(T) in ...

  4. Flux line lattice symmetries in the borocarbide superconductor ...

    Indian Academy of Sciences (India)

    FLL) obtained in the borocarbide superconductor LuNi2B2C with the applied field along the c- and a- axes. For Hc the temperature dependence of the FLL structural phase transition from square to hexagonal symmetry was investigated.

  5. Rare earth magnetism in high-temperature and borocarbide superconductors

    International Nuclear Information System (INIS)

    Allenspach, P.; Gasser, U.

    2000-01-01

    High-temperature superconductors possess - besides their superconductivity - other fascinating features such as a rich magnetic phase diagram. While it is normally believed that superconductivity and rare-earth magnetism is decoupled in these systems a closer investigation clearly proves that both effects in a very similar manner depend on the doping of charge carriers. An inhomogeneous charge distribution results in inhomogeneous superconductivity and a loss of long-range magnetic order. Magnetic borocarbides are ideal model systems for an investigation into the interaction of superconductivity and (collective) magnetism due to their similar values for the critical temperature of superconductivity and the magnetic ordering temperature. Both lie typically below 15 K and are hence in a comfortable temperature regime for measurements. We will present for both classes of the above substances an analysis based on a wide variety of different measurements (susceptibility, specific heat, neutron diffraction and spectroscopy). This analysis provides an almost universal, phenomenological picture of their magnetic properties. (orig.)

  6. Flux line lattice symmetries in the borocarbide superconductor LuNi ...

    Indian Academy of Sciences (India)

    FLL) obtained in the borocarbide superconductor LuNi2B2C with the applied field along the - and -axes. For H | | c the temperature dependence of the FLL structural phase transition from square to hexagonal symmetry was investigated.

  7. Polarization-dependent X-ray-absorption spectroscopy of $RNi_{2} B_{2}$ C (R=Er $\\to$ Lu) Reduced Ni-3d occupancy in $YbNi_{2} B_{2} C$

    CERN Document Server

    Mazumdar, C; Von Lips, H; Golden, M S; Fink, J; Canfield, P C; Kaindl, G

    2001-01-01

    We present here the results of polarization-dependent X-ray- absorption near-edge structure (XANES) studies at the B-K, C-K, and Ni-L/sub 3/ thresholds of single-crystalline borocarbide compounds RNi/sub 2/B/sub 2/C (with R=Er to Lu) using bulk-sensitive fluorescence yield technique. The Ni-L/sub 3/ XANES spectrum for YbNi /sub 2/B/sub 2/C with photon polarization parallel to the ab plane is significantly more intense than in analogous spectra of other members of this series. This indicates a reduced Ni-3d occupancy in the Ni /sub 2/B/sub 2/ layer in YbNi/sub 2/B/sub 2/C, a fact that might be responsible for the absence of superconductivity in this material. (26 refs).

  8. Effect of hydrostatic and chemical pressure on the exchange interaction in magnetic borocarbide superconductors

    Science.gov (United States)

    Michor, H.; El-Hagary, M.; Naber, L.; Bauer, E.; Hilscher, G.

    2000-03-01

    The investigation of pair-breaking effects in magnetic rare-earth nickel borocarbide superconductors reveals a considerable increase of the magnetic exchange integral Jsf by hydrostatic as well as chemical pressure. In both, Jsf is governed by the R-C distance (or lattice constant a) and is described quantitatively by a simple phenomenological model. Thereby, just two parameters Jsf0=31 meV and ΔJsf/Δa=165 meV/Å explain well the influence of chemical pressure upon the initial depression rates of Tc in solid solutions R'1-xRxNi2B2C with R=Gd, Tb, Dy, Ho and R'=Y and Lu.

  9. Non-locality and the flux line lattice square to hexagonal symmetry transition in the borocarbide superconductors

    DEFF Research Database (Denmark)

    Eskildsen, M.R.; Fisher, I.R.; Gammel, P.L.

    2000-01-01

    Using small angle neutron scattering we have studied the square to hexagonal flux line lattice symmetry transition in different members of the borocarbide superconductors. The studies were performed using samples of ErNi2B2C, Lu(Ni1-xCox)(2)B2C with cobalt doping levels x = 1.5-9% and Y0.64Lu0.36Ni...

  10. Chemical bonding topology superconductors: III. Layered quaternary lanthanide nickel borocarbides and boronitrides

    International Nuclear Information System (INIS)

    King, R.B.

    1996-01-01

    The concept of porous delocalization has been extended to the conducting skeletons of quaternary lanthanide nickel borocarbide and boronitride superconductors and related nonsuperconducting materials. Such materials exhibit layered structures of the general type (LnX) n (Ni 2 B 2 )(Ln = lanthanide, particularly the nonmagnetic La III or Lu III ; X = C or N; n 1, 2, or 3) containing planar square Ni nets bonded to BCB 2- ligands in the superconducting LnNi 2 B 2 C, BC 3- ligands in the nonsuperconducting LnNiBC and Ln 2 NiBC 2 , and BN 2- ligands in the superconducting La 3 Ni 2 B 2 N 3 . The linear BCB 2- bridges linking adjacent Ni layers in LnNi 2 B 2 C lead to a porous conducting skeleton in LnNi 2 B 2 C. The BC 3- ligands in the nonsuperconducting LuNiBC and the closely related Ln 2 NiBC 2 = Ln 2 C 2 ·2LnNiBC do not link adjacent Ni layers in LuNiBC so that LuNiBC has only a two-dimensional conducting skeleton, which is not necessarily porous in these two dimensions. The superconducting La 3 Ni 2 B 2 N 3 = LaN·2LaNiBN has a similar local Ni environment as LuNiBC but with BN 2- rather than the isolelectronic BC 3- ligands above and below each Ni layer. However, in La 3 Ni 2 B 2 N 3 unlike LuNiBC the LaNiBN units are linked electronically by the La atoms in the intermediate LaN layer leading to a three-dimensional conducting skeleton in La 3 Ni 2 B 2 N 3 rather than the two-dimensional conducting skeleton of LuNiBC. The linear BNLaNB units linking the Ni layers in La 3 Ni 2 N 3 lead to a porous conducting skeleton similar to that in the LnNi 2 B 2 C superconductors

  11. Angular-dependent I-V characteristics in borocarbide superconductor YNi2B2C

    International Nuclear Information System (INIS)

    Chu, R M; Chen, Q Y; Chu, W K

    2006-01-01

    We present angular-dependent current-voltage (I-V) measurements in borocarbide YNi 2 B 2 C single crystals near the vortex-glass irreversible line. External magnetic fields are applied along the angle θ with respect to the c-axis. The nonlinear I-V curves reveal scaling behaviour near the transition. Using the scaling analysis, the relevant critical exponents and vortex transition temperatures are determined for all orientations. The data agrees well with the vortex-glass (VG) model. No evidence was found that supports the existence of a Bose-glass (BG) type of transition

  12. Possible coexistence of superconductivity and magnetic order in ...

    Indian Academy of Sciences (India)

    Abstract. Coexistence of superconductivity and magnetic order has been one of the exciting as- pects of the quaternary borocarbide superconductors. So far, RNi2B2C (R= Tm, Er, Ho and Dy) are the only known magnetic superconductors in this family. Here, we present our resistivity, mag- netization and heat capacity ...

  13. Pinning in nonmagnetic borocarbides

    International Nuclear Information System (INIS)

    Zholobenko, A.N.; Mikitik, G.P.; Fil, V.D.; Kim, J.D.; Lee, S.I.

    2005-01-01

    The field dependences of the Labush parameter in nonmagnetic borocarbides are measured by the method which does not require the free flux flow regime. The anticipated critical current densities are estimated. These values are by two orders of magnitude higher than those measured 'directly' in transport (magnetic) experiments. The giant peak-effect in the field dependences of the Labush parameter is revealed in the Y-based borocarbides. Its behavior is well approximated by the collective pinning theory

  14. 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.

  15. Fermi surfaces of rare-earth nickel borocarbides

    Energy Technology Data Exchange (ETDEWEB)

    Dugdale, S B; Utfeld, C; Wilkinson, I; Laverock, J; Major, Zs; Alam, M A [H H Wills Physics Laboratory, University of Bristol, Tyndall Avenue, Bristol BS8 1TL (United Kingdom); Canfield, P C [Ames Laboratory and Department of Physics and Astronomy, Iowa State University, Ames, IA 50011 (United States)], E-mail: s.b.dugdale@bristol.ac.uk

    2009-01-15

    A full three-dimensional study of the Fermi surface of LuNi{sub 2}B{sub 2}C is presented, using positron annihilation. The previously identified nesting feature, part of a complex multiply connected Fermi surface sheet, is clearly revealed and observed to extend across approximately 20% of the Brillouin zone. A cuboidal Fermi surface sheet is also found, in agreement with de Haas-van Alphen observations. The Fermi surface topology of the rare-earth nickel borocarbides is shown to vary little for rare-earth elements such as Er, Tm and Yb, suggesting that this topology is broadly common.

  16. 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.

  17. Superconductivity in the intermetallic borocarbides YPd2B2C, YPt2B2C and LaPt2B2C

    Science.gov (United States)

    Durajski, A. P.; Paliwoda, M. K.; Szczȩśniak, R.

    2016-11-01

    We report a detailed study of the thermodynamic properties of the conventional phonon-mediated superconductors YPd2B2C, YPt2B2C and LaPt2B2C. Our calculations conducted within the framework of the Migdal-Eliashberg formalism show that the experimental values of the critical temperature cannot be properly reproduced using commonly accepted value of Coulomb pseudopotential. Moreover, we proved that the values of universal ratios of conventional superconductivity appearing in the Bardeen-Copper-Schrieffer (BCS) theory are inconsistent with our results obtained from the investigated borocarbides. The observed differences are connected with the strong/medium-coupling and retardation effects existing in the studied systems.

  18. Nodal Structure of Unconventional Superconductors Determined by Thermal Conductivity

    International Nuclear Information System (INIS)

    Matsuda, Y.; Izawa, K.

    2003-01-01

    The superconducting gap structure, especially the direction of the nodes, is an unresolved issue in most of unconventional superconductors. Recently it has been demonstrated that the thermal conductivity κ is a powerful tool for probing the nodal structure. Here measuring κ in H rotating within the basal plane, we discuss the nodal structure of the unconventional superconductors, spin-triplet Sr 2 RuO 4 , heavy fermion CeCoIn 5 , organic κ -(BEDT-TTF) 2 Cu(NCS) 2 , and borocarbide YNi 2 B 2 C. (author)

  19. Determination of the directions of gap nodes in exotic superconductors

    Science.gov (United States)

    Matsuda, Y.; Izawa, K.

    2003-05-01

    The superconducting gap structure, especially the direction of the nodes, is an unresolved issue in most unconventional superconductors. Recently it has been demonstrated that the thermal conductivity κ is a powerful tool for probing the nodal structure. Here measuring κ in H rotating within the basal plane, we discuss the nodal structure of the unconventional superconductors, 2D spin-triplet Sr2RuO4, 2D heavy fermion CeCoIn5, 2D organic κ-(BEDT-TTF)2Cu(NCS)2, and 3D borocarbide YNi2B2C.

  20. Thermal expansion of superconducting fulleride and borocarbide compounds

    International Nuclear Information System (INIS)

    Burkhart, G.J.

    1995-08-01

    In order to detact and analyze thermodynamic phase transitions, the investigation of the thermal expansion via capacitance dilatometry is a powerful experimental technique, due to the extremely high resolution (ΔL/L∝10 -8 -10 -10 ). With respect to the air sensitivity of the fullerides a dilatometer operating under inert atmosphere was designed and the thermal expansion of polycrystalline fulleride (Rb 3 C 60 , K 3 C 60 ) and borocarbide (YNi 2 B 2 C, LuNi 2 B 2 C) compounds was determined in the temperature range 5-320 K. Most effort was focused on a quantitative evaluation of the discontinuity in the thermal expansivity α at the superconducting transition. The results are discussed in the context of the Ehrenfest relation, which connects the jump in the thermal expansivity Δα with the pressure dependence of the superconducting transition temperature dT c /dp and the jump in the specific heat Δc p /T c at the superconducting transition. For Rb 3 C 60 and K 3 C 60 the jump in the specific heat can be derived via the Ehrenfest relation using the results of the thermal expansion measurements and the well-known pressure dependence of the superconducting transition temperature. The derived values for Rb 3 C 60 and K 3 Cu 60 are Δc p /T c ∝75mJ/molK 2 and Δc p /T c ∝64 mJ.molK 2 , respectively. The directly measured specific heat jump of K 3 C 60 gives approximately the same value of Δc p /T c , and, therefore, the use of the Ehrenfest relation on fullerides is justified. The specific heat jumps Δc p /T c , determined from theoretically derived values of the density of states at the Fermi level N(E F ) and the McMillan-parameter λ, exceed the experimental results by a factor of 1.5-2. This finding reflects the uncertainty concerning the superconducting parameters N(E F ) and λ. (orig.)

  1. Nonlinear Elasticity of Borocarbide Superconductor YNi2B2C: A First-Principles Study

    Directory of Open Access Journals (Sweden)

    Lili Liu

    2017-01-01

    Full Text Available First-principles calculations combined with homogeneous deformation methods are used to investigate the second- and third-order elastic constants of YNi2B2C with tetragonal structure. The predicted lattice constants and second-order elastic constants of YNi2B2C agree well with the available data. The effective second-order elastic constants are obtained from the second- and third-order elastic constants for YNi2B2C. Based on the effective second-order elastic constants, Pugh’s modulus ratio, Poisson’s ratio, and Vickers hardness of YNi2B2C under high pressure are further investigated. It is shown that the ductility of YNi2B2C increases with increasing pressure.

  2. Flux line lattice symmetries in the borocarbide superconductor LuNi ...

    Indian Academy of Sciences (India)

    Home; Journals; Pramana – Journal of Physics; Volume 58; Issue 5-6 ... DK-4000 Roskilde, Denmark; Agere Systems, 700 Mountain Avenue, New Jersey 07974, USA; Bell Laboratories, Lucent Technologies, 700 Mountain Avenue, New Jersey 07974, USA; Ames Laboratory and Iowa State University, Iowa 50011, USA ...

  3. Probing electronic phase transitions with phonons via inelastic neutron scattering: superconductivity in borocarbides, charge and magnetic order in manganites

    International Nuclear Information System (INIS)

    Weber, F.

    2007-01-01

    The present thesis concentrates on the signatures of strong electron-phonon coupling in phonon properties measured by inelastic neutron scattering. The inelastic neutron scattering experiments were performed on the triple-axis spectrometers 1T and DAS PUMA at the research reactors in Saclay (France) and Munich (Germany), respectively. The work is subdivided into two separate chapters: In the first part, we report measurements of the lattice dynamical properties, i.e. phonon frequency, linewidth and intensity, of the conventional, i.e. phonon-mediated, superconductor YNi 2 B 2 C of the rare-earth-borocarbide family. The detailed check of theoretical predictions for these properties, which were calculated in the theory group of our institute, was one major goal of this work. We measured phonons in the normal state, i.e. T>T c , for several high symmetry directions up to 70 meV. We were able to extract the full temperature dependence of the superconducting energy gap 2Δ(T) from our phonon scans with such accuracy that even deviations from the weak coupling BCS behaviour could be clearly observed. By measuring phonons at different wave vectors we demonstrated that phonons are sensitive to the gap anisotropy under the precondition, that different phonons get their coupling strength from different parts of the Fermi surface. In the second part, we investigated the properties of Mn-O bond-stretching phonons in the bilayer manganite La 2-2x Sr 1+2x Mn 2 O 7 . At the doping level x=0.38 this compound has an ferromagnetic groundstate and exhibits the so-called colossal magnetoresistance effect in the vicinity of the Curie temperature T C . The atomic displacement patterns of the investigated phonons closely resemble possible Jahn-Teller distortions of the MnO 6 octahedra, which are introduced in this compound by the Jahn-Teller active Mn 3+ ions. We observed strong renormalizations of the phonon frequencies and clear peaks of the intrinsic phonon linewidth near the order

  4. Probing electronic phase transitions with phonons via inelastic neutron scattering: superconductivity in borocarbides, charge and magnetic order in manganites

    Energy Technology Data Exchange (ETDEWEB)

    Weber, F.

    2007-11-02

    The present thesis concentrates on the signatures of strong electron-phonon coupling in phonon properties measured by inelastic neutron scattering. The inelastic neutron scattering experiments were performed on the triple-axis spectrometers 1T and DAS PUMA at the research reactors in Saclay (France) and Munich (Germany), respectively. The work is subdivided into two separate chapters: In the first part, we report measurements of the lattice dynamical properties, i.e. phonon frequency, linewidth and intensity, of the conventional, i.e. phonon-mediated, superconductor YNi{sub 2}B{sub 2}C of the rare-earth-borocarbide family. The detailed check of theoretical predictions for these properties, which were calculated in the theory group of our institute, was one major goal of this work. We measured phonons in the normal state, i.e. T>T{sub c}, for several high symmetry directions up to 70 meV. We were able to extract the full temperature dependence of the superconducting energy gap 2{delta}(T) from our phonon scans with such accuracy that even deviations from the weak coupling BCS behaviour could be clearly observed. By measuring phonons at different wave vectors we demonstrated that phonons are sensitive to the gap anisotropy under the precondition, that different phonons get their coupling strength from different parts of the Fermi surface. In the second part, we investigated the properties of Mn-O bond-stretching phonons in the bilayer manganite La{sub 2-2x}Sr{sub 1+2x}Mn{sub 2}O{sub 7}. At the doping level x=0.38 this compound has an ferromagnetic groundstate and exhibits the so-called colossal magnetoresistance effect in the vicinity of the Curie temperature T{sub C}. The atomic displacement patterns of the investigated phonons closely resemble possible Jahn-Teller distortions of the MnO{sub 6} octahedra, which are introduced in this compound by the Jahn-Teller active Mn{sup 3+} ions. We observed strong renormalizations of the phonon frequencies and clear peaks of

  5. Flux line lattice reorientation in the borocarbide superconductors with ¤H¤ parallel to ¤a¤

    DEFF Research Database (Denmark)

    Eskildsen, M.R.; Abrahamsen, A.B.; Lopez, D.

    2001-01-01

    Small angle neutron scattering studies of the flux line lattice in LuNi2B2C and ErNi2B2C induced by a held parallel to the a axis reveal a first order flux Line lattice reorientation transition. Below the transition the Bur line lattice nearest neighbor direction is parallel to the b axis...

  6. 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

  7. 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

  8. Topology and symmetry analysis of rare earth borocarbides structural family, analogy to hexaferrites and relation to properties

    International Nuclear Information System (INIS)

    Belokoneva, E.L.; Mori, Takao

    2009-01-01

    The topology and symmetry analysis was applied to a series of rare earth borocarbide compounds, which have been gaining increasing interest due to their magnetic and thermoelectric properties. Using principles of OD theory, the crystal structures were deconvoluted into L(1) (B 12 icosahedra and C-B-C chain) layers and L(2) (rare earth and B 6 octahedral) layers. The arrangement of B 12 icosahedra in the L(1) layer is equal to close packed spheres, however, symmetry of the B 12 block lowers symmetry of the resulting layer from P 6/mmm to P 3m1. Both layers, L(1) and L(2) possess symmetry P 3m1 and the conjugation of L(1) with L(2) layers occurs in accordance with the symmetry elements. No disorder may appear here because of equal symmetry of single layers and layer pairs and it is not a classical OD family. Only the increasing of the amount of one type of layers, namely L(1), provides the structural variations. Close analogy to the hexagonal ferrites family has been found. Topology and symmetry analysis reveals principles in the building up of the structural family, gives an insight into the particular order-disorder formation mechanism/criteria of these homologous borocarbide compounds and as the result relation to the properties (copyright 2009 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  9. Superconductor Dynamics

    CERN Document Server

    Gömöry, F.

    2014-07-17

    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 ...

  10. 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

  11. Superconductor cable

    Science.gov (United States)

    Smith, Jr., Darrell F.; Lake, Bill L.; Ballinger, Ronald G.

    1988-01-01

    A superconducting cable comprising an in-situ-formed type II superconductor, e.g. Nb.sub.3 Sn, in association with a stabilizing conductor both in heat transfer relationship with at least one passage adapted to carry liquified gaseous refrigerant. The conductor and said at least one passage are enclosed by a sheath comprising an alloy consisting essentially of about 49% nickel, about 4% chromium, about 3% niobium, about 1.4% titanium, about 1% aluminum, balance essentially iron.

  12. Superconductor electronic device applications

    International Nuclear Information System (INIS)

    VanDuzer, T.

    1989-01-01

    Superconductors are becoming important in many applications where high sensitivity or speed is required. In this paper the authors give brief introduction to superconductive device physics and some comments on the role of high-temperature superconductors. They then present the basic principles of a number of applications in metrology, electromagnetic sensing, and analog and digital circuits. They conclude with the prospects for hybrid semiconductor-superconductor devices, circuits, and systems

  13. Superconductor rotor cooling system

    Science.gov (United States)

    Gamble, Bruce B.; Sidi-Yekhlef, Ahmed; Schwall, Robert E.; Driscoll, David I.; Shoykhet, Boris A.

    2002-01-01

    A system for cooling a superconductor device includes a cryocooler located in a stationary reference frame and a closed circulation system external to the cryocooler. The closed circulation system interfaces the stationary reference frame with a rotating reference frame in which the superconductor device is located. A method of cooling a superconductor device includes locating a cryocooler in a stationary reference frame, and transferring heat from a superconductor device located in a rotating reference frame to the cryocooler through a closed circulation system external to the cryocooler. The closed circulation system interfaces the stationary reference frame with the rotating reference frame.

  14. Main applications of superconductors

    International Nuclear Information System (INIS)

    Tixador, P.; Brunet, Y.

    2007-01-01

    In 2004, the world market of superconductivity reached 3.65 billion euros and was mainly concerning the NbTi-type superconductors. The high critical temperature superconductors (HCTS) have not reached the industrial maturity yet, both in terms of efficiency and cost, but this situation may change at medium term. Superconductors are mainly used in the industry today to create moderated to high inductions (1.5 to more than 20 T) inside volumes up to several hundreds of m 3 . This article treats of the present day industrial applications of NbTi and Nb 3 Sn superconductors: 1 - specificities of superconductors: persisting mode, AC losses, protection of a superconducting magnet, dimensioning of a superconducting coil; 2 -industrial magnets: NMR imaging, spectroscopy, proton cyclotron; 3 - magnets for research: high energy physics (accelerators-colliders, detectors), fusion facilities (reaction, magnetic confinement, tokamak, ITER), laboratory magnets; 4 - magnets for specific applications: magnetic separation, magnetic levitated train, MHD. (J.S.)

  15. 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.

  16. Electrodynamics of Metallic Superconductors

    Directory of Open Access Journals (Sweden)

    M. Dressel

    2013-01-01

    Full Text Available The theoretical and experimental aspects of the microwave, terahertz, and infrared properties of superconductors are discussed. Electrodynamics can provide information about the superconducting condensate as well as about the quasiparticles. The aim is to understand the frequency dependence of the complex conductivity, the change with temperature and time, and its dependence on material parameters. We confine ourselves to conventional metallic superconductors, in particular, Nb and related nitrides and review the seminal papers but also highlight latest developments and recent experimental achievements. The possibility to produce well-defined thin films of metallic superconductors that can be tuned in their properties allows the exploration of fundamental issues, such as the superconductor-insulator transition; furthermore it provides the basis for the development of novel and advanced applications, for instance, superconducting single-photon detectors.

  17. Superconductor terahertz metamaterial

    OpenAIRE

    Gu, Jianqiang; Singh, Ranjan; Tian, Zhen; Cao, Wei; Xing, Qirong; Han, Jiaguang; Zhang, Weili

    2010-01-01

    We characterize the behaviour of split ring resonators made up of high-transition temperature YBCO superconductor using terahertz time domain spectroscopy. The superconductor metamaterial shows sharp change in the transmission spectrum at the fundamental inductive-capacitive resonance and the dipole resonance as the temperature dips below the transition temperature. Our results reveal that the high performance of such a metamaterial is limited by material imperfections and defects such as cra...

  18. Thermodynamics of many-band superconductors; Thermodynamik von Mehrband-Supraleitern

    Energy Technology Data Exchange (ETDEWEB)

    Waelte, A.

    2006-07-01

    In the present thesis the microscopical properties of the superconducting state of MgCNi{sub 3}, MgB{sub 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{sub 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{sub 3}, which lies near a magnetic instability, show that occurring magnetic fluctuations have a bisection of the superconducting transition temperature T{sub C} as consequence. The under this aspect relatively high value of T{sub 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{sub 2} (here with pure {sup 10}B) at about T{sub 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{sub 2}B{sub 2}C and LuNi{sub 2}B{sub 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{sub 2}B{sub 2}C is smaller than expected.

  19. 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

  20. Coupled superconductors and beyond

    International Nuclear Information System (INIS)

    Josephson, Brian D.

    2012-01-01

    This paper describes the events leading to the discovery of coupled superconductors, the author move in the 1970s to a perspective where mind plays a role comparable to matter, and the remarkable hostility sometimes encountered by those who venture into unconventional areas.

  1. 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

  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. Ambient-pressure organic superconductor

    Science.gov (United States)

    Williams, Jack M.; Wang, Hsien-Hau; Beno, Mark A.

    1986-01-01

    A new class of organic superconductors having the formula (ET).sub.2 MX.sub.2 wherein ET represents bis(ethylenedithio)-tetrathiafulvalene, M is a metal such as Au, Ag, In, Tl, Rb, Pd and the like and X is a halide. The superconductor (ET).sub.2 AuI.sub.2 exhibits a transition temperature of 5 K which is high for organic superconductors.

  4. 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...

  5. 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...

  6. 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...

  7. 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

  8. Excitations in exotic superconductors

    International Nuclear Information System (INIS)

    Hayden, S.

    1999-01-01

    Neutron scattering has played an important role in unravelling the mysteries of superconductivity. Studies of ordinary or conventional superconductors - materials such as aluminium and lead that lose their electrical resistance when cooled below a certain temperature - have focused on vibrations in the lattice structure of the crystal. In these cases magnetic excitations due to the collective motion of electron spins in the crystal are not particularly important and, moreover, are difficult to see. In contrast, magnetic excitations are thought to be important in the newer, exotic or unconventional superconductors such as heavy fermions and cuprates. Two independent groups working at the Institut Laue-Langevin (ILL) in Grenoble, France, and at the Japan Atomic Energy Research Institute (JAERI) in Tokai have recently observed a new magnetic excitation in the superconducting state of the heavy fermion compound uranium-palladium-aluminium, UPd 2 Al 3 , (Phys. Rev. Lett.1998 81 4244; 1998 80 5417). A similar excitation has been observed in yttrium barium copper oxide (YBa 2 Cu 3 O 6.93 ), a high-temperature superconductor. The results may hold clues about the nature of certain types of unconventional superconductivity. In this article the author describes these latest results. (UK)

  9. Superconductors for superconducting magnets

    Science.gov (United States)

    Larbalestier, David

    2011-03-01

    Even in 1913 Kamerlingh Onnes envisioned the use of superconductors to create powerful magnetic fields well beyond the capability provided by cooling normal metals with liquid helium. Only some ``bad places'' in his Hg and Pb wires seemed to impede his first attempts at this dream, one that he imagined would be resolved in a few weeks of effort. In fact, of course, resolution required another 50 years and development of both a true understanding of the difference between type I and type II superconductors and the discovery of compounds such as Nb 3 Sn that could remain superconducting to fields as high as 30 T. And then indeed, starting in the 1960s, Onnes's dreams were comfortably surpassed. In the last 45 years virtually all superconducting magnets have been made from just two Nb-base materials, Nb-Ti and Nb 3 Sn. Now it seems that a new generation of magnets based on cuprate high temperature superconductors with fields well above 30 T are possible using Bi-Sr-Ca-Cu-O and the RE-Ba-Cu-O compounds. We hope that a first demonstration of this possibility will be an all-superconducting 32 T magnet with RE-Ba-Cu-O insert that we are building for NHMFL users. The magnet application potential of this new generation of superconducting conductors will be discussed.

  10. Processing of Superconductor-Normal-Superconductor Josephson Edge Junctions

    Science.gov (United States)

    Kleinsasser, A. W.; Barner, J. B.

    1997-01-01

    The electrical behavior of epitaxial superconductor-normal-superconductor (SNS) Josephson edge junctions is strongly affected by processing conditions. Ex-situ processes, utilizing photoresist and polyimide/photoresist mask layers, are employed for ion milling edges for junctions with Yttrium-Barium-Copper-Oxide (YBCO) electrodes and primarily Co-doped YBCO interlayers.

  11. Testability issues in Superconductor Electronics

    NARCIS (Netherlands)

    Kerkhoff, Hans G.; Arun, A.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

  12. 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

  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. Hybrid superconductor magnet bearings

    Science.gov (United States)

    Chu, Wei-Kan

    1995-01-01

    Hybrid superconductor magnet bearings (HSMB's) utilize high temperature superconductors (HTS's) together with permanent magnets to form a frictionless interface between relatively rotating parts. They are low mass, stable, and do not incur expenditure of energy during normal operation. There is no direct physical contact between rotor and stator, and hence there is no wear and tear. However, just as any other applications of HTS's, it requires a very cold temperature to function. Whereas this might be perceived as a disadvantage on earth, it is of no great concern in space or on the moon. To astronomers, the moon is an excellent site for an observatory, but the cold and dusty vacuum environment on the moon precludes the use of mechanical bearings on the telescope mounts. Furthermore, drive mechanisms with very fine steps, and hence bearings with extremely low friction are needed to track a star from the moon, because the moon rotates very slowly. All aspects considered, the HSMB is about the only candidate that fits in naturally. Here, we present a design for one such bearing, capable of supporting a telescope that weighs about 3 lbs on Earth.

  15. 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.

  16. 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.

  17. Energy storage system using superconductor

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Chan Joong; Kim, Ki Baek; Park, Hae Woong; Hong, Kye Won [Korea Atomic Energy Research Institute, Taejon (Korea, Republic of)

    1995-03-01

    As a result of continuous efforts, high critical current density exceeding 104 A/cm{sup 2} at 77K and strong levitation capacity has been achieved in Y-Ba-Cu-O superconductor which is fabricated by melting technique. Various applications using the levitation properties of high-Tc superconductor is expected to come true in near future. Especially, by utilizing the levitation force between a permanent magnet and the superconductor, a flywheel system which store electrical energy as mechanical energy can be designed. (Author) 11 refs., 7 figs., 5 tabs.

  18. Manipulating nonequilibrium magnetism through superconductors.

    Science.gov (United States)

    Giazotto, Francesco; Taddei, Fabio; Fazio, Rosario; Beltram, Fabio

    2005-08-05

    Electrostatic control of the magnetization of a normal mesoscopic conductor is analyzed in a hybrid superconductor-normal-conductor-superconductor system. This effect stems from the interplay between the nonequilibrium condition in the normal region and the Zeeman splitting of the quasi-particle density of states of the superconductor subjected to a static in-plane magnetic field. Unexpected spin-dependent effects such as magnetization suppression, diamagnetic-like response of the susceptibility, as well as spin-polarized current generation are the most remarkable features presented. The impact of scattering events is evaluated and lets us show that this effect is compatible with realistic material properties and fabrication techniques.

  19. Manufacturing a Superconductor in School.

    Science.gov (United States)

    Barrow, John

    1989-01-01

    Described is the manufacture of a superconductor from a commercially available kit using equipment usually available in schools or easily obtainable. The construction is described in detail including equipment, materials, safety procedures, tolerances, and manufacture. (Author/CW)

  20. Manufacturing of Superconductors

    DEFF Research Database (Denmark)

    Bech, Jakob Ilsted; Bay, Niels

    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......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...... of the superconducting ceramic powder Bi2Sr2CaCu2O by a three-point test procedure implying die compaction, diametrical compression and uniaxial compression. · Application of plastic parameters to the constitutive model Drucker/Prager-cap. This model features mean pressure dependent flow stress and volumetric strains...

  1. 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

  2. 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)

  3. Modelling of bulk superconductor magnetization

    Science.gov (United States)

    Ainslie, M. D.; Fujishiro, H.

    2015-05-01

    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 MgB2 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.

  4. Process for fabricating continuous lengths of superconductor

    Science.gov (United States)

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

    1998-01-01

    A process for manufacturing a superconductor. The process is accomplished by depositing a superconductor precursor powder on a continuous length of a first substrate ribbon, overlaying a continuous length of a second substrate ribbon on said first substrate ribbon, and applying sufficient pressure to form a bound layered superconductor precursor between said first substrate ribbon and said second substrates ribbon. The layered superconductor precursor is then heat treated to form a super conductor layer.

  5. 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

  6. Multistrand superconductor cable

    Science.gov (United States)

    Borden, Albert R.

    1985-01-01

    Improved multistrand Rutherford-type superconductor cable is produced by using strands which are preformed, prior to being wound into the cable, so that each strand has a variable cross section, with successive portions having a substantially round cross section, a transitional oval cross section, a rectangular cross section, a transitional oval cross section, a round cross section and so forth, in repetitive cycles along the length of the strand. The cable is wound and flattened so that the portions of rectangular cross section extend across the two flat sides of the cable at the strand angle. The portions of round cross section are bent at the edges of the flattened cable, so as to extend between the two flat sides. The rectangular portions of the strands slide easily over one another, so as to facilitate flexing and bending of the cable, while also minimizing the possibility of causing damage to the strands by such flexing or bending. Moreover, the improved cable substantially maintains its compactness and cross-sectional shape when the cable is flexed or bent.

  7. 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...

  8. Thin film superconductor magnetic bearings

    Science.gov (United States)

    Weinberger, Bernard R.

    1995-12-26

    A superconductor magnetic bearing includes a shaft (10) that is subject to a load (L) and rotatable around an axis of rotation, a magnet (12) mounted to the shaft, and a stator (14) in proximity to the shaft. The stator (14) has a superconductor thin film assembly (16) positioned to interact with the magnet (12) to produce a levitation force on the shaft (10) that supports the load (L). The thin film assembly (16) includes at least two superconductor thin films (18) and at least one substrate (20). Each thin film (18) is positioned on a substrate (20) and all the thin films are positioned such that an applied magnetic field from the magnet (12) passes through all the thin films. A similar bearing in which the thin film assembly (16) is mounted on the shaft (10) and the magnet (12) is part of the stator (14) also can be constructed.

  9. Apparatus for fabricating continuous lengths of superconductor

    Science.gov (United States)

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

    2001-01-01

    A process and apparatus for manufacturing a superconductor. The process is accomplished by depositing a superconductor precursor powder on a continuous length of a first substrate ribbon, overlaying a continuous length of a second substrate ribbon on said first substrate ribbon, and applying sufficient pressure to form a bound layered superconductor comprising a layer of said superconducting precursor powder between said first substrate ribbon and said second substrates ribbon. The layered superconductor is then heat treated to establish the superconducting phase of said superconductor precursor powder.

  10. 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

  11. High temperature superconductor current leads

    Science.gov (United States)

    Hull, John R.; Poeppel, Roger B.

    1995-01-01

    An electrical lead having one end for connection to an apparatus in a cryogenic environment and the other end for connection to an apparatus outside the cryogenic environment. The electrical lead includes a high temperature superconductor wire and an electrically conductive material distributed therein, where the conductive material is present at the one end of the lead at a concentration in the range of from 0 to about 3% by volume, and at the other end of the lead at a concentration of less than about 20% by volume. Various embodiments are shown for groups of high temperature superconductor wires and sheaths.

  12. Terahertz Spectroscopy of Novel Superconductors

    OpenAIRE

    Lupi, Stefano

    2011-01-01

    Through the coupling of Synchrotron Radiation and Michelson interferometry, one may obtain in the terahertz (THz) range transmittance and reflectivity spectra with a signal-to-noise ratio (S/N) up to 103. In this paper we review the application of this spectroscopic technique to novel superconductors with an increasing degree of complexity: the single-gap boron-doped diamond; the isotropic multiband V3Si, where superconductivity opens two gaps at the Fermi energy; the CaAlSi superconductor, i...

  13. Terahertz Spectroscopy of Novel Superconductors

    Directory of Open Access Journals (Sweden)

    Stefano Lupi

    2011-01-01

    Full Text Available Through the coupling of Synchrotron Radiation and Michelson interferometry, one may obtain in the terahertz (THz range transmittance and reflectivity spectra with a signal-to-noise ratio (S/N up to 103. In this paper we review the application of this spectroscopic technique to novel superconductors with an increasing degree of complexity: the single-gap boron-doped diamond; the isotropic multiband V3Si, where superconductivity opens two gaps at the Fermi energy; the CaAlSi superconductor, isostructural to MgB2, with a single gap in the hexagonal ab plane and two gaps along the orthogonal c axis.

  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. Ultrasonic attenuation in cuprate superconductors

    Indian Academy of Sciences (India)

    Ultrasonic attenuation in cuprate superconductors. T GUPTA1,∗ and D M GAITONDE1,2. 1Harish-Chandra Research Institute, Allahabad 211 019, India. 2High Pressure Physics Division, Bhabha Atomic Research Centre, Mumbai 400 085, India. ∗. Email: gupta@mri.ernet.in. Abstract. We calculate the longitudinal ...

  16. 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

  17. Preparation of superconductor precursor powders

    Science.gov (United States)

    Bhattacharya, Raghunath; Blaugher, Richard D.

    1995-01-01

    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, such as nitrate salts of thallium, barium, calcium, and copper, which are capable of exhibiting superconductor properties upon subsequent appropriate treatment. The bath is continually energized to cause the metallic 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 thallium 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.

  18. 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

  19. 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.

  20. 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...

  1. 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

  2. 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.

  3. 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

  4. Ultrasonic attenuation in cuprate superconductors

    Indian Academy of Sciences (India)

    Introduction. The calculation of the UAR in d-wave superconductors has been considered earlier, both within the clean limit [1,2] and in the opposite hydrodynamic limit [3]. There exists evi- dence [4] that the superconducting state has well-defined quasiparticles corresponding to a d-wave BCS state. In the Meissner phase, ...

  5. In-gap bound states and tunneling conductance of multiband superconductors through a normal/superconductor/superconductor junction

    OpenAIRE

    Feng, Xiao-Yong; Ng, Tai-Kai

    2008-01-01

    The tunneling conductance between a metal and a multiband s-wave superconductor with a thin layer of single-band s-wave superconductor sandwiched in between is examined in this paper. We show that an in-gap peak in conductance curve is found as a result of the formation of in-gap bound state between the single-band and multiband superconductor junctions if the phases of the superconducting order parameters of the multiband superconductor are frustrated. The implication of this result in deter...

  6. Axion topological field theory of topological superconductors

    Science.gov (United States)

    Qi, Xiao-Liang; Witten, Edward; Zhang, Shou-Cheng

    2013-04-01

    Topological superconductors are gapped superconductors with gapless and topologically robust quasiparticles propagating on the boundary. In this paper, we present a topological field theory description of three-dimensional time-reversal invariant topological superconductors. In our theory the topological superconductor is characterized by a topological coupling between the electromagnetic field and the superconducting phase fluctuation, which has the same form as the coupling of “axions” with an Abelian gauge field. As a physical consequence of our theory, we predict the level crossing induced by the crossing of special “chiral” vortex lines, which can be realized by considering s-wave superconductors in proximity with the topological superconductor. Our theory can also be generalized to the coupling with a gravitational field.

  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. 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

  9. 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.

  10. 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

  11. 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

  12. 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.

  13. 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

  14. Phonon-induced quadrupolar ordering of the magnetic superconductor TmNi2B2C

    DEFF Research Database (Denmark)

    Andersen, N.H.; Jensen, J.; Jensen, T.B.S.

    2006-01-01

    We present synchrotron x-ray diffraction studies revealing that the lattice of thulium borocarbide is distorted below T(Q)similar or equal to 13.5 K at zero field. T-Q increases and the amplitude of the displacements is drastically enhanced by a factor of 10 at 60 kOe when a magnetic field is app...

  15. Theory of spin inelastic tunneling spectroscopy for superconductor-superconductor and superconductor-metal junctions

    Science.gov (United States)

    Berggren, P.; Fransson, J.

    2015-05-01

    We address the tunneling conductance and spin inelastic tunneling spectroscopy of localized paramagnetic moments in a superconducting environment, pertaining to recent measurements on Fe-octaethylporphyrin-chloride using superconducting scanning tunneling microscopy. We demonstrate that the Cooper pair correlations in the tip and substrate generate a finite uniaxial anisotropy field acting on the local spin moment, and we argue that this field may be a source for the observed changes in the conductance spectrum for decreasing distance between the scanning tunneling tip and the local magnetic moment. We make a side-by-side comparison between the superconductor-superconductor junction and normal-metal-superconductor junction, and find qualitative agreement between the two setups while quantitative differences become explicit. When simulating the effects of electron pumping, we obtain additional peaks in the conductance spectrum that can be attributed to excitations between higher-energy spin states. The transverse anisotropy field couples basis states of the local spin which opens for transitions between spin states that are otherwise forbidden by conservation of angular momentum. Finally, we explore the influences of temperature, which tend to enable in-gap transitions, and an external magnetic field, which enables deeper studies of the spin excitation spectrum. We especially notice the appearance of a low and high excitation peak on each side of the main coherence peak as an imprint of transitions between the Zeeman split ground states.

  16. Some Comments on London Theory for Superconductors

    OpenAIRE

    M. A. Grado Caffaro; M. Grado Caffaro

    1994-01-01

    The basic formulae of London theory for superconductors are reviewed. Moreover, an expression for the spatial charge density in a type-II superconductor is obtained; this equation is associated with sinusoidal oscillations. Considerations on both penetration depth and coherence length are exposed.

  17. 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…

  18. 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

  19. High temperature superconductors: A technological revolution

    Science.gov (United States)

    1990-01-01

    The objectives are to demonstrate the Meissner effect through magnetic levitation, to demonstrate one application of the Meissner effect, the low friction magnetic rotation bearing, and to demonstrate magnetic flux penetration and the Type II nature of ceramic superconductors via the stacking of the superconductor disks. Experimental equipment and procedures are described.

  20. 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

  1. Superconductor lunar telescopes --Abstract only

    Science.gov (United States)

    Chen, P. C.; Pitts, R.; Shore, S.; Oliversen, R.; Stolarik, J.; Segal, K.; Hojaji, H.

    1994-01-01

    We propose a new type of telescope designed specifically for the lunar environment of high vacuum and low temperature. Large area UV-Visible-IR telescope arrays can be built with ultra-light-weight replica optics. High T(sub c) superconductors provide support, steering, and positioning. Advantages of this approach are light-weight payload compatible with existing launch vehicles, configurable large area optical arrays, no excavation or heavy construction, and frictionless electronically controlled mechanisms. We have built a prototype and will be demonstarting some of its working characteristics.

  2. 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.

  3. 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.

  4. 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

  5. Method to improve superconductor cable

    Science.gov (United States)

    Borden, A.R.

    1984-03-08

    A method is disclosed of making a stranded superconductor cable having improved flexing and bending characteristics. In such method, a plurality of superconductor strands are helically wound around a cylindrical portion of a mandrel which tapers along a transitional portion to a flat end portion. The helically wound strands form a multistrand hollow cable which is partially flattened by pressure rollers as the cable travels along the transitional portion. The partially flattened cable is impacted with repeated hammer blows as the hollow cable travels along the flat end portion. The hammer blows flatten both the internal and the external surfaces of the strands. The cable is fully flattened and compacted by two sets of pressure rollers which engage the flat sides and the edges of the cable after it has traveled away from the flat end portion of the mandrel. The flattened internal surfaces slide easily over one another when the cable is flexed or bent so that there is very little possibility that the cable will be damaged by the necessary flexing and bending required to wind the cable into magnet coils.

  6. 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...

  7. Superconductor bearings, flywheels and transportation

    Science.gov (United States)

    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 LN2. More than 30 vacuum cryostats containing multi-seeded YBCO blocks are fabricated and are tested now in Germany, China and Brazil.

  8. 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

  9. 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.

  10. Aeronautical applications of high-temperature superconductors

    Science.gov (United States)

    Turney, George E.; Luidens, Roger W.; Uherka, Kenneth; Hull, John

    1989-01-01

    The successful development of high-temperature superconductors (HTS) could have a major impact on future aeronautical propulsion and aeronautical flight vehicle systems. A preliminary examination of the potential application of HTS for aeronautics indicates that significant benefits may be realized through the development and implementation of these newly discovered materials. Applications of high-temperature superconductors (currently substantiated at 95 k) were envisioned for several classes of aeronautical systems, including subsonic and supersonic transports, hypersonic aircraft, V/STOL aircraft, rotorcraft, and solar, microwave and laser powered aircraft. Introduced and described are the particular applications and potential benefits of high-temperature superconductors as related to aeronautics and/or aeronautical systems.

  11. 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.)

  12. Superconductors in the high school classroom

    Science.gov (United States)

    Lincoln, James

    2017-11-01

    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 to include first-year physics students in the world of modern physics, a topic as engaging as superconductivity should not be missed. It is an opportunity to inspire students to study physics through the myriad of possible applications that high temperature superconductors hold for the future.

  13. Effect of hybridization and dispersion of quasiparticles on the ...

    Indian Academy of Sciences (India)

    B K Sahoo and B N Panda. RNi2B2C (R = Tm, Er, Ho, Dy) show the coexistence of superconductivity and mag- netism [1–3] with high magnetic ordering temperatures. It is indeed remarkable that. RNi2B2C have all the three combinations, i.e. TC > TN, TC ≈ TN, TN > TC. It has already been observed experimentally that ...

  14. Structural studies of ceramic superconductors

    International Nuclear Information System (INIS)

    Hessel Andersen, N.

    1993-12-01

    The structural and superconducting properties of high temperature superconductors have been studied experimentally and by computer simulation technique. The oxygen ordering in the CuO x basal plane of the high temperature superconductor YBa 2 Cu 3 O 6+x has been studied by Monte Carlo computer simulation based on the socalled ASYNNNI model (Asymmetric Next Nearest Neighbor Interaction model), and the formation of specific domains of the two orthorhombic ordered oxygen phases, Ortho-I and Ortho-II, as function of the oxygen stoichiometry, x, has been related to the superconducting transition temperature, T c (x), via a Minimal Model. A similar relation has been established between the temporal variation of T c (t) and structural oxygen ordering during relaxation following a quench from high temperatures. By neutron diffraction studies on single crystalline YBa 2 Cu 3 O 6.4 the presence of short range domains of the Ortho-II type structure has been established, and the degree of ordering has been found to scale with the observed T c according to the expectations from the established Minimal Model. From neutron diffraction studies on Pb 2 Sr 2 Re 1-x Cu 3 O 8 (RE=Y and Ho) the transition from non-superconducting to superconducting samples with increasing Ca-stoichiometry has been related to the change in the Cu bond valence in the superconducting CuO 2 -planes. X-ray diffraction with Euler four-circle technique and TEM (Transmission Electron Microscopy) have been used to identify structural defects in epitaxial YBa 2 Cu 3 O 6+x thin films produced on MgO (1 0 0) and SrTiO 3 (1 0 0) substrates by laser ablation. The results supply an explanation for the differences in the observed critical current densities, and may be used for optimizing the film production process. A computer-controlled gasvolumetric and a gas-mixing flow system for sample preparation of high temperature superconductors, and studies of oxygen equilibrium pressure and bulk oxygen diffusion have been

  15. 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...

  16. 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.

  17. 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.

  18. Josephson spin current in triplet superconductor junctions

    OpenAIRE

    Asano, Yasuhiro

    2006-01-01

    This paper theoretically discusses the spin current in spin-triplet superconductor / insulator / spin-triplet superconductor junctions. At low temperatures, a midgap Andreev resonant state anomalously enhances not only the charge current but also the spin current. The coupling between the Cooper pairs and the electromagnetic fields leads to the Frounhofer pattern in the direct current spin flow in magnetic fields and the alternative spin current under applied bias-voltages.

  19. 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

  20. Double Helix Nodal Line Superconductor

    Science.gov (United States)

    Sun, Xiao-Qi; Lian, Biao; Zhang, Shou-Cheng

    2017-10-01

    Time-reversal invariant superconductors in three dimensions may contain nodal lines in the Brillouin zone, which behave as Wilson loops of 3D momentum-space Chern-Simons theory of the Berry connection. Here we study the conditions of realizing linked nodal lines (Wilson loops), which yield a topological contribution to the thermal magnetoelectric coefficient that is given by the Chern-Simons action. We find the essential conditions are the existence of torus or higher genus Fermi surfaces and spiral spin textures. We construct such a model with two torus Fermi surfaces, where a generic spin-dependent interaction leads to double-helix-like linked nodal lines as the superconductivity is developed.

  1. 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).

  2. 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).

  3. 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

  4. 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-Sm inte...

  5. Niobium titanium nitride-based superconductor-insulator-superconductor mixers for low-noise terahertz receivers

    NARCIS (Netherlands)

    Jackson, B.D.; De Lange, G.; Zijlstra, T.; Kroug, M.; Klapwijk, T.M.; Stern, J.A.

    2005-01-01

    Integrating NbTiN-based microstrip tuning circuits with traditional Nb superconductor-insulator-superconductor (SIS) junctions enables the low-noise operation regime of SIS mixers to be extended from below 0.7?to?1.15?THz. In particular, mixers incorporating a NbTiN/SiO2/NbTiN microstrip tuning

  6. Direct current heating in superconductor-insulator-superconductor tunnel devices for THz mixing applications

    NARCIS (Netherlands)

    Dieleman, P; Klapwijk, T.M; Kovtonyuk, S.; van de Stadt, H.

    1996-01-01

    DC heating effects in superconductor-insulator-superconductor (SIS) tunnel junctions are studied by comparing junctions sandwiched between niobium or aluminum layers. With niobium a temperature rise of several Kelvin is observed, which is reduced by an order of magnitude by using aluminum. A simple

  7. 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

  8. Possible alterations of the gravitational field in a superconductor

    OpenAIRE

    Ummarino, G. A.

    2000-01-01

    In this paper I calculate the possible alteration of the gravitational field in a superconductor by using the time-dependent Ginzburg-Landau equations (TDGL). I compare the behaviour of a high-Tc superconductor (HTCS) like YBa_2Cu_3O_7 (YBCO) with a classical low-Tc superconductor (LTCS) like Pb. Finally, I discuss what values of the parameters characterizing a superconductor can enhance the reduction of gravitational field.

  9. Search for New Superconductors for Energy and Power Applications

    Science.gov (United States)

    2014-10-21

    AFRL-OSR-VA-TR-2014-0271 (MURI 09) SEARCH FOR NEW SUPERCONDUCTORS FOR ENERGY AND POWER APPLICATIONS Ivan Schuller UNIVERSITY OF CALIFORNIA SAN DIEGO... Superconductors for Energy and Power Applications Organization/Institution name: University of California, San Diego Grant #: AFOSR MURI # FA9550-09-1...superconductivity, relied mostly on the almost accidental discoveries of new superconductors . The SuperSearch for New Superconductors MURI project departs from this

  10. Rotating superconductor magnet for producing rotating lobed magnetic field lines

    Science.gov (United States)

    Hilal, Sadek K.; Sampson, William B.; Leonard, Edward F.

    1978-01-01

    This invention provides a rotating superconductor magnet for producing a rotating lobed magnetic field, comprising a cryostat; a superconducting magnet in the cryostat having a collar for producing a lobed magnetic field having oppositely directed adjacent field lines; rotatable support means for selectively rotating the superconductor magnet; and means for energizing the superconductor magnet.

  11. Inhomogeneous magnetic field in AdS/CFT superconductor

    OpenAIRE

    Wen, Wen-Yu

    2008-01-01

    We study the holographically dual description of superconductor in (2+1)-dimensions in the presence of inhomogeneous magnetic field and observe that there exists type I and type II superconductor. A new feature of type changing is observed for type I superconductor near critical temperature.

  12. Quantum interference in an interfacial superconductor.

    Science.gov (United States)

    Goswami, Srijit; Mulazimoglu, Emre; Monteiro, Ana M R V L; Wölbing, Roman; Koelle, Dieter; Kleiner, Reinhold; Blanter, Ya M; Vandersypen, Lieven M K; Caviglia, Andrea D

    2016-10-01

    The two-dimensional superconductor that forms at the interface between the complex oxides lanthanum aluminate (LAO) and strontium titanate (STO) has several intriguing properties that set it apart from conventional superconductors. Most notably, an electric field can be used to tune its critical temperature (T c ; ref. 7), revealing a dome-shaped phase diagram reminiscent of high-T c superconductors. So far, experiments with oxide interfaces have measured quantities that probe only the magnitude of the superconducting order parameter and are not sensitive to its phase. Here, we perform phase-sensitive measurements by realizing the first superconducting quantum interference devices (SQUIDs) at the LAO/STO interface. Furthermore, we develop a new paradigm for the creation of superconducting circuit elements, where local gates enable the in situ creation and control of Josephson junctions. These gate-defined SQUIDs are unique in that the entire device is made from a single superconductor with purely electrostatic interfaces between the superconducting reservoir and the weak link. We complement our experiments with numerical simulations and show that the low superfluid density of this interfacial superconductor results in a large, gate-controllable kinetic inductance of the SQUID. Our observation of robust quantum interference opens up a new pathway to understanding the nature of superconductivity at oxide interfaces.

  13. Superconductors beyond 1-2-3

    International Nuclear Information System (INIS)

    Cava, R.J.

    1990-01-01

    In 1986 physicists K. Alex Mueller and J. Georg Bednorz of the IBM Zuerich Research Laboratory realized that La-Ba-Cu ceramics were the key to developing a new class of high-temperature superconductors that would revitalize superconductivity research and technology. Their discovery began one of the most startling revolutions in solid-state physics. In February, 1987, Maw-Kuen Wu of the University of Alabama, Ching-Wu (Paul) Chu of the University of Houston and their co-workers replaced lanthanum in the Bednorz-Mueller compound with yttrium--a smaller rare-earth element--to form a superconductor whose transition temperature was 90 kelvins. Soon after, R.Bruce van Dover, Bertram Batlogg and the author at AT ampersand T Bell Laboratories were the first to determine that the superconductor was the chemical compound now known as 1-2-3 because of the ratio of yttrium to barium to copper atoms. The 1-2-3 material was the first superconductor with a transition temperature above 77 kelvins and therefore could be cooled easily and inexpensively in a bath of liquid nitrogen. During the past four years the efforts of thousands of investigators around the world have produced about a dozen superconductors that have transition temperatures above 40 kelvins as well as a handful above 77 kelvins. So far the highest transition temperature--which was achieved in a compound composed of thallium, barium, calcium, copper and oxygen--is an astounding 125 kelvins

  14. 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

  15. 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

  16. Internal stability of technical superconductors

    International Nuclear Information System (INIS)

    Kastner, K.

    1985-09-01

    Electrical stability and longitudinal quench propagation velocity of technical NbTi superconductors having various matrix compositions was investigated experimentally and theoretically (numerically) for different cooling conditions. Copper, cupro-nickel and both combined were used as matrix materials of the conductors. The measurements were performed between 5 and 8 K in vacuum and at 4.2 K in helium both applying magnetic fields up to 7 T. The quantitative agreement between experiments and calculations was better than a factor of 2 regarding all 8 specimen at the investigated environmental conditions (cooling, temperature, and magnetic field). The remaining uncertainty is mainly conditioned by the accumulation of small inaccuracies in knowledge of the various conductor parameters, but far less to be found in the computer program itself. The accuracy of these parameters cannot be further improved with reasonable effort and expenditure. It is shown, that position and fraction of the cupro-nickel barriers inside the mixed matrix conductors affect strongly quench propagation velocity; stability also is sensible to these parameters. The strong effect on quench propagation velocity may be explained by a feedback mechanism. A way is given, how to change stability and quench propagation velocity of a mixed matrix conductor by constructional measures without implicating an enhancement of the coupling current losses. (orig.) [de

  17. 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.

  18. 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.

  19. 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

  20. Practical superconductor development for electrical power applications

    Energy Technology Data Exchange (ETDEWEB)

    Goretta, K.C. (comp.)

    1991-10-01

    Development of useful high-critical-temperature (high-{Tc}) 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-{Tc} 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.

  1. 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.

  2. 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.

  3. Surface texturing of superconductors by controlled oxygen pressure

    Science.gov (United States)

    Chen, N.; Goretta, K.C.; Dorris, S.E.

    1999-01-05

    A method of manufacture of a textured layer of a high temperature superconductor on a substrate is disclosed. The method involves providing an untextured high temperature superconductor material having a characteristic ambient pressure peritectic melting point, heating the superconductor to a temperature below the peritectic temperature, establishing a reduced pO{sub 2} atmosphere below ambient pressure causing reduction of the peritectic melting point to a reduced temperature which causes melting from an exposed surface of the superconductor and raising pressure of the reduced pO{sub 2} atmosphere to cause solidification of the molten superconductor in a textured surface layer. 8 figs.

  4. 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

  5. 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.

  6. 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

  7. Aluminum-stabilized NB3SN superconductor

    Science.gov (United States)

    Scanlan, Ronald M.

    1988-01-01

    An aluminum-stabilized Nb.sub.3 Sn superconductor and process for producing same, utilizing ultrapure aluminum. Ductile components are co-drawn with aluminum to produce a conductor suitable for winding magnets. After winding, the conductor is heated to convert it to the brittle Nb.sub.3 Sn superconductor phase, using a temperature high enough to perform the transformation but still below the melting point of the aluminum. This results in reaction of substantially all of the niobium, while providing stabilization and react-in-place features which are beneficial in the fabrication of magnets utilizing superconducting materials.

  8. Electrical connection structure for a superconductor element

    Science.gov (United States)

    Lallouet, Nicolas; Maguire, James

    2010-05-04

    The invention relates to an electrical connection structure for a superconductor element cooled by a cryogenic fluid and connected to an electrical bushing, which bushing passes successively through an enclosure at an intermediate temperature between ambient temperature and the temperature of the cryogenic fluid, and an enclosure at ambient temperature, said bushing projecting outside the ambient temperature enclosure. According to the invention, said intermediate enclosure is filled at least in part with a solid material of low thermal conductivity, such as a polyurethane foam or a cellular glass foam. The invention is applicable to connecting a superconductor cable at cryogenic temperature to a device for equipment at ambient temperature.

  9. 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

  10. 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.

  11. Radiation effects on iron-based superconductors

    Science.gov (United States)

    Eisterer, M.

    2018-01-01

    This article reviews the results of irradiation experiments on iron-based superconductors, with particular emphasis on neutron irradiation. These experiments were either done to foster the theoretical understanding of superconductivity in these compounds by investigating the influence of impurity scattering on the fundamental superconducting properties or to investigate vortex physics and to benchmark flux pinning in view of applications. Results on the most explored iron-based compounds are summarized and compared with data on metallic superconductors, cuprates, and MgB2. Similarities and differences are discussed as well as the influence of the type and energy of the particles used for the experiments.

  12. High temperature crystalline superconductors from crystallized glasses

    Science.gov (United States)

    Shi, Donglu

    1992-01-01

    A method of preparing a high temperature superconductor from an amorphous phase. The method involves preparing a starting material of a composition of Bi.sub.2 Sr.sub.2 Ca.sub.3 Cu.sub.4 Ox or Bi.sub.2 Sr.sub.2 Ca.sub.4 Cu.sub.5 Ox, forming an amorphous phase of the composition and heat treating the amorphous phase for particular time and temperature ranges to achieve a single phase high temperature superconductor.

  13. Magnetic refrigeration using flux compression in superconductors

    International Nuclear Information System (INIS)

    Israelsson, U.E.; Strayer, D.M.; Jackson, H.W.; Petrac, D.

    1990-01-01

    The feasibility of using flux compression in high-temperature superconductors to produce the large time-varying magnetic fields required in a field cycled magnetic refrigerator operating between 20 K and 4 K is presently investigated. This paper describes the refrigerator concept and lists limitations and advantages in comparison with conventional refrigeration techniques. The maximum fields obtainable by flux compression in high-temperature superconductor materials, as presently prepared, are too low to serve in such a refrigerator. However, reports exist of critical current values that are near usable levels for flux pumps in refrigerator applications. 9 refs

  14. Development of superconductors for fusion technology

    International Nuclear Information System (INIS)

    Walters, C.R.

    1977-11-01

    The subject is dealt with under the headings: introduction and summary; A.C. losses; stability (adiabatic and dynamic stability, experimental stability in sheet superconductor, cryostatic stability); mechanical considerations (conductor design, toroidal coil shape, winding techniques); comparison of construction techniques. (U.K.)

  15. Current density in radiation stimulated superconductors

    International Nuclear Information System (INIS)

    Wafelbakker, C.K.

    1977-01-01

    Eliashberg's theory of stimulated superconductivity is reviewed and discussed within the BCS-Mattis formalism for impure superconductors. Stimulation by microwaves as well as by acoustical fields is considered. Eliashberg's results are completed by obtaining the nonequilibrium current response to an applied transverse vector potential. The resulting expression may be used to obtain the critical current of small specimens. (Auth.)

  16. Relaxation in superconductors with large normal defects

    Czech Academy of Sciences Publication Activity Database

    Zablotskyy, Vitaliy A.; Jirsa, Miloš; Petrenko, Pavlo

    2005-01-01

    Roč. 18, - (2005), s. 200-205 ISSN 0953-2048 Institutional research plan: CEZ:AV0Z10100520 Keywords : bulk high-T c superconductor s * relaxation * mesoscopic particles * vortex pinning Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.896, year: 2005

  17. Conductivity of Holographic Superconductor within Ginzburg ...

    Indian Academy of Sciences (India)

    Abstract. The frequency-dependent conductivity is obtained for the holographic superconductor by using the Ginzburg–Landau theory with a |Ψ|4 term. Our results show that |Ψ|4 term plays a role in the low-temperature behaviour of the conductivity.

  18. 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

  19. 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

  20. 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 ...

  1. Excitations in Topological Superfluids and Superconductors

    Science.gov (United States)

    Wu, Hao

    In this thesis I present the theoretical work on Fermionic surface states, and %the bulk Bosonic collective excitations in topological superfluids and superconductors. Broken symmetries %Bulk-edge correspondence in topological condensed matter systems have implications for the spectrum of Fermionic excitations confined on surfaces or topological defects. (Abstract shortened by ProQuest.).

  2. 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

  3. 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.)

  4. Magnetic Ordering in Layered High Temperature Superconductors

    OpenAIRE

    Sergeeva, G. G.

    1999-01-01

    We discuss the scenario of two-step magnetic ordering in layered high temperature superconductors after charge ordering. As the temperature decreases, the transition from 3D Heisenberg spin behavior to 2D XY coupling of the Cu spins occurs at Berezinskii-Kosterlitz-Thouless temperature in dielectric stripes. Further temperature decreasing leads to the 3D spin glass transition.

  5. 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

  6. Optical magnetic flux generation in superconductor

    Indian Academy of Sciences (India)

    Abstract. The generation of the magnetic flux quanta inside the superconductors is studied as a new effect to destroy superconductivity using femtosecond (fs) laser. The vortices are successfully generated in the YBa2Cu3O7−δ thin film striplines by the fs laser. It is revealed that the vortex distribution in the strip reflects the fs ...

  7. Kinetic energy driven pairing in cuprate superconductors

    NARCIS (Netherlands)

    Maier, TA; Jarrell, M; Macridin, A; Slezak, C

    2004-01-01

    Pairing occurs in conventional superconductors through a reduction of the electronic potential energy accompanied by an increase in kinetic energy. In the underdoped cuprates, optical experiments show that pairing is driven by a reduction of the electronic kinetic energy. Using the dynamical cluster

  8. 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 ...

  9. Optical magnetic flux generation in superconductor

    Indian Academy of Sciences (India)

    Abstract. The generation of the magnetic flux quanta inside the superconductors is studied as a new effect to destroy ... Ultrafast phenomena; femtosecond laser; optical magnetic flux generation. PACS Nos 85.25. .... [8] M Tonouchi, M Tani, Z Wang, K Sakai, S Tomozawa, M Hangyo, Y Murakami and S. Nakashima, Jpn. J.

  10. 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 ...

  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. Neutron diffraction and reflection studies of superconductors

    International Nuclear Information System (INIS)

    Reynolds, J.M.

    1998-01-01

    I have studied two magnetic properties of superconductors using different neutron scattering techniques. Due to their magnetic moment and lack of electrical charge, neutrons can provide an extremely sensitive probe into magnetism on a small scale. Unusual magnetic structures have previously been observed in the non-superconducting PrBa 2 Cu 3 O 6+δ , in particular showing a coupling between the rare-earth and the Cu-O 2 planes. For comparison, I have used elastic neutron scattering to measure the temperature dependent magnetic structure of the high-T c superconductor NdBa 2 Cu 3 O 7 , and its nonsuperconducting reduced form NdBa 2 Cu 3 O 6 . The magnetic structures of both the Nd and Cu sub-lattices axe presented. Measurements axe shown for single crystals of both the oxygenated and reduced form, and also for a non-stoichiometric single crystal with Nd substituted on the Ba sites. I present a quantitative analysis of the magnetic moments, with account taken of the instrumental resolution including sample mosaicity and intrinsic peak shapes. No evidence was found for any coupling of the type seen in PrBa 2 Cu 3 O 6+δ . Many of the underlying properties of superconductors are evidenced in the way magnetic fields are excluded in the different states. I have used polarized neutron reflectometry to measure the magnetic field profile in thin film superconductors. I present measurements for pure niobium and preliminary measurements for YBa 2 Cu 3 O 7 . The samples studied are much thicker than those previously measured, to provide a closer match to the bulk superconductor properties and allow meaningful measurements of the higher field states. For niobium, the applied field dependence is measured for fields covering the Meissner and mixed states, and models are compared for these states and the surface superconductivity state. (author)

  13. 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

  14. 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.

  15. 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

  16. Nanoscale Investigation of New Fe-Based Superconductors

    Science.gov (United States)

    2012-10-15

    12-10-2012 4. TITLE AND SUBTITLE Nanoscale Investigation of New Iron - Based Superconductors 5a. CONTRACT NUMBER FA23861114054 5b. GRANT NUMBER 5c...Final Report for AOARD Grant 114054 “Nanoscale Investigation of New Fe- based Superconductors ” Date: October 15, 2012 Name of Principal...particles [5]. These results indicate that interesting phenomena may happen in iron chalcogenide superconductors when their size goes to nanometer

  17. 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.

  18. 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. .

  19. Noncommutative extension of AdS–CFT and holographic superconductors

    Directory of Open Access Journals (Sweden)

    Souvik Pramanik

    2015-03-01

    Full Text Available In this Letter, we consider a Non-Commutative (NC extension of AdS–CFT correspondence and its effects on holographic superconductors. NC corrections are incorporated via the NC generalization of Schwarzschild black hole metric in AdS with the probe limit. We study NC effects on the relations connecting the charge density and the critical temperature of the Holographic Superconductors. Furthermore, condensation operator of the superconductor has been analyzed. Our results suggest that generically, NC effects increase the critical temperature of the holographic superconductor.

  20. Noncommutative extension of AdS-CFT and holographic superconductors

    Science.gov (United States)

    Pramanik, Souvik; Das, Sudipta; Ghosh, Subir

    2015-03-01

    In this Letter, we consider a Non-Commutative (NC) extension of AdS-CFT correspondence and its effects on holographic superconductors. NC corrections are incorporated via the NC generalization of Schwarzschild black hole metric in AdS with the probe limit. We study NC effects on the relations connecting the charge density and the critical temperature of the Holographic Superconductors. Furthermore, condensation operator of the superconductor has been analyzed. Our results suggest that generically, NC effects increase the critical temperature of the holographic superconductor.

  1. Noncommutative extension of AdS–CFT and holographic superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Pramanik, Souvik, E-mail: souvick.in@gmail.com; Das, Sudipta, E-mail: sudipta_jumaths@yahoo.co.in; Ghosh, Subir, E-mail: subir_ghosh2@rediffmail.com

    2015-03-06

    In this Letter, we consider a Non-Commutative (NC) extension of AdS–CFT correspondence and its effects on holographic superconductors. NC corrections are incorporated via the NC generalization of Schwarzschild black hole metric in AdS with the probe limit. We study NC effects on the relations connecting the charge density and the critical temperature of the Holographic Superconductors. Furthermore, condensation operator of the superconductor has been analyzed. Our results suggest that generically, NC effects increase the critical temperature of the holographic superconductor.

  2. BCS superconductivity in mixed valence and heavy fermion superconductors

    Science.gov (United States)

    Gor'kov, Lev P.; Barzykin, Victor

    2005-03-01

    We consider competition of Kondo effect and s-wave superconductivity in heavy fermion and mixed valence superconductors, using the slave boson 1/N approach for the periodic Anderson model. Similar to the well known results for single-impurity Kondo effect in superconductors, we have found that re-entrant behavior of the superconducting transition temperature, Tc, should be observed in heavy fermion superconductors as a function of model parameters or concentration of impurities. Suppression of Tc in mixed valence superconductors is much weaker, without re-entrant behavior of Tc. Our results have most validity in the low-temperature regime.

  3. Voltage current characteristics of type III superconductors

    International Nuclear Information System (INIS)

    Dorofejev, G.L.; Imenitov, A.B.; Klimenko, E.Y.

    1980-01-01

    An adequate description of voltage-current characteristics is important in order to understand the nature of high critical current for the electrodynamic construction of type-III superconductors and for commercial superconductor specification. Homogeneous monofilament and multifilament Nb-Ti, Nb-Zr,Nb 3 Sn wires were investigated in different ranges of magnetic field, temperature and current. The shape of the voltage-current characteristics of multifilament wires, and the parameter's dependence on temperature and magnetic field may be explained qualitatively by the longitudinal heterogeneous nature of the filaments. A method of attaining the complete specification of the wire's electro-physical properties is proposed. It includes the traditional description of a critical surface (i.e. the surface corresponding to a certain conventional effective resistivity in T,B,J-space) and a description of any increasing parameter that depends on B and T. (author)

  4. Electrical bushing for a superconductor element

    Science.gov (United States)

    Mirebeau, Pierre; Lallouet, Nicolas; Delplace, Sebastien; Lapierre, Regis

    2010-05-04

    The invention relates to an electrical bushing serving to make a connection at ambient temperature to a superconductor element situated in an enclosure at cryogenic temperature. The electrical bushing passes successively through an enclosure at intermediate temperature between ambient temperature and cryogenic temperature, and an enclosure at ambient temperature, and it comprises a central electrical conductor surrounded by an electrically insulating sheath. According to the invention, an electrically conductive screen connected to ground potential surrounds the insulating sheath over a section that extends from the end of the bushing that is in contact with the enclosure at cryogenic temperature at least as far as the junction between the enclosure at intermediate temperature and the enclosure at ambient temperature. The invention is more particularly applicable to making a connection to a superconductor cable.

  5. High-pressure study on some superconductors

    CERN Document Server

    Li, K Q; Yao, Y S; Che, G C; Zhao, Z X

    2002-01-01

    High-pressure study has played an important role in the investigation of conventional superconductors. Since the discovery of cuprate superconductors, high-pressure study has become even more important, especially as regards high-pressure synthesis and the effect of pressure. In this report, the new materials Ca-doped Pr-123, (Fe, Cu)-1212, and MgB sub 2 - a very new and interesting system synthesized under high pressure with good quality - will be discussed. Chemical inner pressure has been thought to explain the high T sub c of Ca-doped Pr-123. As another possibility, the replacement of the physical pressure effect by a chemical effect will be discussed.

  6. Vortex-antivortex patterns in mesoscopic superconductors

    International Nuclear Information System (INIS)

    Teniers, Gerd; Moshchalkov, V.V.; Chibotaru, L.F.; Ceulemans, Arnout

    2003-01-01

    We have studied the nucleation of superconductivity in mesoscopic structures of different shape (triangle, square and rectangle). This was made possible by using an analytical gauge transformation for the vector potential A which gives A n =0 for the normal component along the boundary line of the rectangle. As a consequence the superconductor-vacuum boundary condition reduces to the Neumann boundary condition. By solving the linearized Ginzburg-Landau equation with this boundary condition we have determined the field-temperature superconducting phase boundary and the corresponding vortex patterns. The comparison of these patterns for different structures demonstrates that the critical parameters of a superconductor can be manipulated and fine-tuned through nanostructuring

  7. Conductive polymer/superconductor bilayer structures

    International Nuclear Information System (INIS)

    McDevitt, J.T.; Haupt, S.G.; Riley, D.R.; Zhao, J.; Grassi, J.; Lo, R.K.; Jones, C.

    1994-01-01

    The preparation of a hybrid conducting polymer/high-temperature superconductor device consisting of a polypyrrole-coated YBa 2 Cu 3 O 7-∂ microbridge is reported. Electrochemical techniques are exploited to alter the oxidation state of the polymer and, in doing so, it is found for the first time that superconductivity can be modulated in a controllable and reproducible fashion by a polymer layer. Whereas the neutral (insulating) polypyrrole only slightly influences the electrical properties of the underlying YBa 2 Cu 3 O 7-∂ film, the oxidized (conductive) polymer depresses Tc by up to 50K. In a similar fashion, the oxidation state of the polymer is found to modulate reversibly the magnitude of J c , the superconducting critical current. Thus, a new type of molecular switch for controlling superconductivity is demonstrated. Electrochemical, resistance vs. temperature, conact resistance, atomic force microscopy and scanning electron microscopy measurements are utilized to explore the polymer/superconductor interactions

  8. 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

  9. Anharmonic model for high-Tc superconductors

    International Nuclear Information System (INIS)

    Plakida, N.M.; Aksenov, V.L.; Drechsler, S.L.

    1987-01-01

    A considerable enhancement of the superconducting transition temperature T c in perovskite oxide compounds is explained in the framework of the anharmonic model for superconductors with structurally unstable lattices. It is shown that anharmonic local excitations with fluctuation amplitudes much greater than harmonic vibrations amplitudes lead to a considerable enhancement of the coupling constant λ. The obtained estimations for T c are in agreement with experimental data for La(Y)BaCuO systems

  10. Semiconductor/High-Tc-Superconductor Hybrid ICs

    Science.gov (United States)

    Burns, Michael J.

    1995-01-01

    Hybrid integrated circuits (ICs) containing both Si-based semiconducting and YBa(2)Cu(3)O(7-x) superconducting circuit elements on sapphire substrates developed. Help to prevent diffusion of Cu from superconductors into semiconductors. These hybrid ICs combine superconducting and semiconducting features unavailable in superconducting or semiconducting circuitry alone. For example, complementary metal oxide/semiconductor (CMOS) readout and memory devices integrated with fast-switching Josephson-junction super-conducting logic devices and zero-resistance interconnections.

  11. Flywheel energy storage with superconductor magnetic bearings

    Science.gov (United States)

    Weinberger, Bernard R.; Lynds, Jr., Lahmer; Hull, John R.

    1993-01-01

    A flywheel having superconductor bearings has a lower drag to lift ratio that translates to an improvement of a factor of ten in the rotational decay rate. The lower drag results from the lower dissipation of melt-processed YBCO, improved uniformity of the permanent magnet portion of the bearings, operation in a different range of vacuum pressure from that taught by the art, and greater separation distance from the rotating members of conductive materials.

  12. Spray-Deposited Superconductor/Polymer Coatings

    Science.gov (United States)

    Wise, Stephanie A.; Tran, Sang Q.; Hooker, Matthew W.

    1993-01-01

    Coatings that exhibit the Meissner effect formed at relatively low temperature. High-temperature-superconductor/polymer coatings that exhibit Meissner effect deposited onto components in variety of shapes and materials. Simple, readily available equipment needed in coating process, mean coatings produced economically. Coatings used to keep magnetic fields away from electronic circuits in such cryogenic applications as magnetic resonance imaging and detection of infrared, and in magnetic suspensions to provide levitation and/or damping of vibrations.

  13. Critical de Broglie wavelength in superconductors

    Science.gov (United States)

    Talantsev, E. F.

    2018-03-01

    There are growing numbers of experimental evidences that the self-field critical currents, Jc(sf,T), are a new instructive tool to investigate fundamental properties of superconductors ranging from atomically thin films [M. Liao et al., Nat. Phys. 6 (2018), https://doi.org/10.1038/s41567-017-0031-6; E. F. Talantsev et al., 2D Mater. 4 (2017) 025072; A. Fete et al., Appl. Phys. Lett. 109 (2016) 192601] to millimeter-scale samples [E. F. Talantsev et al., Sci. Rep. 7 (2017) 10010]. The basic empirical equation which quantitatively accurately described experimental Jc(sf,T) was proposed by Talantsev and Tallon [Nat. Commun. 6 (2015) 7820] and it was the relevant critical field (i.e. thermodynamic field, Bc, for type-I and lower critical field, Bc1, for type-II superconductors) divided by the London penetration depth, λL. In this paper, we report new findings relating to this empirical equation. It is that the critical wavelength of the de Broglie wave, λdB,c, of the superconducting charge carrier which within a numerical pre-factor is equal to the largest of two characteristic lengths of Ginzburg-Landau theory, i.e. the coherence length, ξ, for type-I superconductors or the London penetration depth, λL, for type-II superconductors. We also formulate a microscopic criterion for the onset of dissipative transport current flow: ps ṡ 2ṡλL ln(1+2ṡ(λL ξ )) ≥ 1 2 ṡ ( h 2π), where ps is the charge carrier momentum, h is Planck’s constant and the inequality sign “ <” is reserved for the dissipation-free flow.

  14. High temperature superconductors applications in telecommunications

    International Nuclear Information System (INIS)

    Kumar, A.A.; Li, J.; Zhang, M.F.

    1994-01-01

    The purpose of this paper is twofold: to discuss high temperature superconductors with specific reference to their employment in telecommunications applications; and to discuss a few of the limitations of the normally employed two-fluid model. While the debate on the actual usage of high temperature superconductors in the design of electronic and telecommunications devices-obvious advantages versus practical difficulties-needs to be settled in the near future, it is of great interest to investigate the parameters and the assumptions that will be employed in such designs. This paper deals with the issue of providing the microwave design engineer with performance data for such superconducting waveguides. The values of conductivity and surface resistance, which are the primary determining factors of a waveguide performance, are computed based on the two-fluid model. A comparison between two models-a theoretical one in terms of microscopic parameters (termed Model A) and an experimental fit in terms of macroscopic parameters (termed Model B)-shows the limitations and the resulting ambiguities of the two-fluid model at high frequencies and at temperatures close to the transition temperature. The validity of the two-fluid model is then discussed. Our preliminary results show that the electrical transport description in the normal and superconducting phases as they are formulated in the two-fluid model needs to be modified to incorporate the new and special features of high temperature superconductors. Parameters describing the waveguide performance-conductivity, surface resistance and attenuation constant-will be computed. Potential applications in communications networks and large scale integrated circuits will be discussed. Some of the ongoing work will be reported. In particular, a brief proposal is made to investigate of the effects of electromagnetic interference and the concomitant notion of electromagnetic compatibility (EMI/EMC) of high T c superconductors

  15. Neutron powder diffraction and high Tc superconductors

    International Nuclear Information System (INIS)

    Hewat, A.W.

    1988-01-01

    Neutron powder diffraction is a technique for determining the crystalline structure and texture of materials for which single crystals cannot be obtained. As such it has made important contributions to the characterisation and understanding of the new high temperature superconductors. As well, NPD has wide applications in materials science, ranging from the study of catalyst and zeolite structures, to the texture of railway lines and composite superconducting wires. (orig.)

  16. Conductivity of Holographic Superconductor within Ginzburg ...

    Indian Academy of Sciences (India)

    e-mail: newbayren@163.com. Abstract. The frequency-dependent conductivity is obtained for the holographic superconductor by using the Ginzburg–Landau theory with ... gravity sector is ds2 = −f (r)dt2 + dr2 f (r) + r2(dx2 + dy2) with f (r) = r2. L − M r . L is the AdS radius, and M is the mass of the black hole. The large r limit ...

  17. Magnetic properties of heavy-fermion superconductors

    International Nuclear Information System (INIS)

    Rauchschwalbe, U.

    1986-01-01

    In the present thesis the magnetic properties of heavy-fermion superconductors are investigated. The magnetoresistance and the critical magnetic fields show a variety of anomalous phenomena. The Kondo lattices CeCu 2 Si and CeAl 3 are analysed by magnetoresistance and the field dependence of the resistivitis of UBe 13 , UPt 3 , URu 2 Si 2 and CeRu 3 Si are measured for temperatures < or approx. 1 K. (BHO)

  18. Isotopic effect in high temperature superconductors

    International Nuclear Information System (INIS)

    Ohno, Takashi

    2000-01-01

    It is well-known that it essentially contributed to construct the BCB theory that a mechanism on formation of the Cooper pairs was dependent upon a lattice oscillation to change a critical temperature, T(sub c) of a superconductor with isotopic displacement. In this paper, here was, at first, described on an isotopic index actually measured to high temperature superconductors, and was introduced on a study on selective displacement of oxygen position. And then, a detailed measurement of 63-Cu(2) nuclear quadrupole resonance (NQR) at a plane position of YBa2Cu4O8 (Y1248) displaced with 18-O and 16-O, discussion of the isotopic effect on a base of 63-Cu(2) nuclear spin-lattice relaxation ratio, and consideration on the isotopic index according to the isotopic effect were described. As a result of the considerations, it could be concluded that the isotopic effect in a high temperature superconductor proved that antiferromagnetic spin fluctuation was an origin of Cooper pairs cohesive strength. (G.K.)

  19. Fabrication of high-quality superconductor-insulator-superconductor junctions on thin SiN membranes

    Science.gov (United States)

    Garcia, Edouard; Jacobson, Brian R.; Hu, Qing

    1993-01-01

    We have successfully fabricated high-quality and high-current density superconductor-insulator-superconductor (SIS) junctions on freestanding thin silicon nitride (SIN) membranes. These devices can be used in a novel millimeter-wave and THz receiver system which is made using micromachining. The SIS junctions with planar antennas were fabricated first on a silicon wafer covered with a SiN membrane, the Si wafer underneath was then etched away using an anisotropic KOH etchant. The current-voltage characteristics of the SIS junctions remained unchanged after the whole process, and the junctions and the membrane survived thermal cycling.

  20. Quasiparticle entropy in superconductor/normal metal/superconductor proximity junctions in the diffusive limit

    Science.gov (United States)

    Virtanen, P.; Vischi, F.; Strambini, E.; Carrega, M.; Giazotto, F.

    2017-12-01

    We discuss the quasiparticle entropy and heat capacity of a dirty superconductor/normal metal/superconductor junction. In the case of short junctions, the inverse proximity effect extending in the superconducting banks plays a crucial role in determining the thermodynamic quantities. In this case, commonly used approximations can violate thermodynamic relations between supercurrent and quasiparticle entropy. We provide analytical and numerical results as a function of different geometrical parameters. Quantitative estimates for the heat capacity can be relevant for the design of caloritronic devices or radiation sensor applications.

  1. A phenomenological approach to high Tc oxide superconductors

    International Nuclear Information System (INIS)

    Chela-Flores, J.; Das, M.P.; Saif, A.G.

    1987-06-01

    Oxide superconductors are described in terms of macroscopic wave functions Ψ and Φ corresponding, respectively, to electron pairs of the superconducting and insulating states. In terms of the total free energy of the system, including the effect of interaction, we discuss the electrodynamic responses of the oxide superconductors in relation with the experiments to data. (author). 10 refs

  2. Coherent Excited States in Superconductors due to a Microwave Field

    NARCIS (Netherlands)

    Semenov, A. V.; Devyatov, I. A.; de Visser, P.J.; Klapwijk, T.M.

    2016-01-01

    We describe theoretically the depairing effect of a microwave field on diffusive s-wave superconductors. The ground state of the superconductor is altered qualitatively in analogy to the depairing due to a dc current. In contrast to dc depairing, the density of states acquires, for microwaves

  3. Helical instability of charged vortices in layered superconductors

    OpenAIRE

    Gurevich, A.

    2010-01-01

    It is shown that the electric charge of vortices can result in a helical instability of straight vortex lines in layered superconductors, particularly Bi-based cuprates or organic superconductors. This instability may result in a phase transition to a uniformly twisted vortex state, which could be detected by torque magnetometry, neutron diffraction, electromagnetic or calorimetric measurements.

  4. Five-fold way to new high Tc superconductors

    Indian Academy of Sciences (India)

    In the process we abstract, using available phenomenology and RVB theory, that there are five directions to search for new high c superconductors. We call them five-fold way. As the paths are reasonably exclusive and well-defined, they provide more guided opportunities, than before, for discovering new superconductors ...

  5. High-temperature superconductors in application - fight for the top

    International Nuclear Information System (INIS)

    Anon.

    1990-01-01

    For the superconductor market two-digit growth rates are predicted until after the year 2000. The decrosslinking of the high temperature superconductors initiated a worldwide race for first applications. The report considers the situation of raw materials and the application potentials in the USA, Japan and Western Europe. (orig.) [de

  6. Status of high temperature superconductor development for accelerator magnets

    Science.gov (United States)

    Hirabayashi, H.

    1995-01-01

    High temperature superconductors are still under development for various applications. As far as conductors for magnets are concerned, the development has just been started. Small coils wound by silver sheathed Bi-2212 and Bi-2223 oxide conductors have been reported by a few authors. Essential properties of high T(sub c) superconductors like pinning force, coherent length, intergrain coupling, weak link, thermal property, AC loss and mechanical strength are still not sufficiently understandable. In this talk, a review is given with comparison between the present achievement and the final requirement for high T(sub c) superconductors, which could be particularly used in accelerator magnets. Discussions on how to develop high T(sub c) superconductors for accelerator magnets are included with key parameters of essential properties. A proposal of how to make a prototype accelerator magnet with high T(sub c) superconductors with prospect for future development is also given.

  7. System and method for quench protection of a superconductor

    Science.gov (United States)

    Huang, Xianrui; Sivasubramaniam, Kiruba Haran; Bray, James William; Ryan, David Thomas

    2008-03-11

    A system and method for protecting a superconductor from a quench condition. A quench protection system is provided to protect the superconductor from damage due to a quench condition. The quench protection system comprises a voltage detector operable to detect voltage across the superconductor. The system also comprises a frequency filter coupled to the voltage detector. The frequency filter is operable to couple voltage signals to a control circuit that are representative of a rise in superconductor voltage caused by a quench condition and to block voltage signals that are not. The system is operable to detect whether a quench condition exists in the superconductor based on the voltage signal received via the frequency filter and to initiate a protective action in response.

  8. Development of high temperature superconductors having high critical current density

    Energy Technology Data Exchange (ETDEWEB)

    Hong, Gye Wong; Kim, C. J.; Lee, H.G.; Kwon, S. C.; Lee, H. J.; Kim, K. B.; Park, J. Y.; Jung, C. H

    2000-08-01

    Fabrication of high T{sub c} superconductors and its applications for electric power device were carried out for developing superconductor application technologies. High quality YBCO superconductors was fabricated by melt texture growth, top-seeded melt growth process and multi-seeded melt growth process and the properties was compared. The critical current density of the melt processed YBCO superconductors was about few 10,000 A/cm{sup 2} and the levitation force was 50 N. The processing time needed for the growth of the 123 single grain was greatly reduced by applying multi-seeding without no significant degradation of the levitation force. The multi-seeded melt growth process was confirmed as a time-saving and cost-effective method for the fabrication of bulk superconductors with controlled crystallographic orientation.

  9. Precursor composites for oxygen dispersion hardened silver sheathed superconductor composites

    Science.gov (United States)

    Podtburg, Eric R.

    1999-01-01

    An oxide superconductor composite having improved texture and durability. The oxide superconductor composite includes an oxide superconductor phase substantially surrounded with/by a noble metal matrix, the noble metal matrix comprising a metal oxide in an amount effective to form metal oxide domains that increase hardness of the composite. The composite is characterized by a degree of texture at least 10% greater than a comparable oxide superconductor composite lacking metal oxide domains. An oxide superconducting composite may be prepared by oxidizing the precursor composite under conditions effective to form solute metal oxide domains within the silver matrix and to form a precursor oxide in the precursor alloy phase; subjecting the oxidized composite to a softening anneal under conditions effective to relieve stress within the noble metal phase; and converting the oxide precursor into an oxide superconductor.

  10. Effect of exciton pairing on the stationary Josephson current in superconductor-semimetal-superconductor junctions

    International Nuclear Information System (INIS)

    Itskovich, I.F.; Shekhter, R.I.

    1983-01-01

    The effect of exciton pairing of charge carriers in a semimetal on the stationary Josephson current in superconductor-semimetal-superconductor junctions is considered. It is shown that the phase transition of the semimetal interlayer into an exciton dielectric state for T/sub γ/< T/sub c/ (T/sub γ/, T/sub c/ are the superconducting and exciton transition temperatures, respectively) is accompanied by a kink on the critical current j/sub c/ versus temperature curve at the point T = T/sub γ/. A sharp nonmonotonic temperature dependence of the reduced current j/sub c//j/sub c/0 (j/sub c/0 is the critical current at T/sub γ/ = 0) is also possible in the range T< T/sub γ/. At low temperatures T<< v/sub 1,2//d<< T/sub γ/ (v/sub 1,2/ are the Fermi velocities of the carriers in the semimetal, d is the thickness of the interlayer) the critical current of the superconductor-semimetal-superconductor junction is exponentially smaller than the current in the absence of exciton pairing

  11. Disappearance of nodal gap across the insulator-superconductor transition in a copper-oxide superconductor.

    Science.gov (United States)

    Peng, Yingying; Meng, Jianqiao; Mou, Daixiang; He, Junfeng; Zhao, Lin; Wu, Yue; Liu, Guodong; Dong, Xiaoli; He, Shaolong; Zhang, Jun; Wang, Xiaoyang; Peng, Qinjun; Wang, Zhimin; Zhang, Shenjin; Yang, Feng; Chen, Chuangtian; Xu, Zuyan; Lee, T K; Zhou, X J

    2013-01-01

    The parent compound of the copper-oxide high-temperature superconductors is a Mott insulator. Superconductivity is realized by doping an appropriate amount of charge carriers. How a Mott insulator transforms into a superconductor is crucial in understanding the unusual physical properties of high-temperature superconductors and the superconductivity mechanism. Here we report high-resolution angle-resolved photoemission measurement on heavily underdoped Bi₂Sr₂-xLaxCuO(₆+δ) system. The electronic structure of the lightly doped samples exhibit a number of characteristics: existence of an energy gap along the nodal direction, d-wave-like anisotropic energy gap along the underlying Fermi surface, and coexistence of a coherence peak and a broad hump in the photoemission spectra. Our results reveal a clear insulator-superconductor transition at a critical doping level of ~0.10 where the nodal energy gap approaches zero, the three-dimensional antiferromagnetic order disappears, and superconductivity starts to emerge. These observations clearly signal a close connection between the nodal gap, antiferromagnetism and superconductivity.

  12. The improved damping of superconductor bearings for 35 kWh superconductor flywheel energy storage system

    International Nuclear Information System (INIS)

    Han, Y.H.; Park, B.J.; Jung, S.Y.; Han, S.C.; Lee, W.R.; Bae, Y.C.

    2013-01-01

    Highlights: ► We made a 35 kWh superconductor flywheel energy storage system. ► The damping coefficient of the superconductor bearing was increased over 3000 N s/m. ► The source of damping was discussed. -- Abstract: A 35 kWh Superconductor Flywheel Energy Storage system (SFES) using hybrid bearing sets, which is composed of a high temperature superconductor (HTS) bearing and an active magnet damper (AMD), has been developed at KEPCO Research Institute (KEPRI). Damping is a source of energy loss but necessary for the stability of the flywheel system. We found that the damping of HTS bearings can be improved by thermal insulating bolts, which play a role of passive type external damper. To investigate the source of the increased damping, damping coefficients were measured with HTS bearings using insulating bolts made of three kinds of polymer materials. The damping coefficient was raised over 3000 N s/m in the case of PEEK bolts. The value was almost a quarter of the AMD. In this study, thermoelastic and Coulomb friction damping mechanisms are discussed. The main damping mechanism was the thermoelastic damping of the bolts themselves. And interfacial gap between the insulating bolt and metal chamber, which increased during the cooling process, was considered to be the cause of the anisotropic damping coefficients. Finally, the effects of the HTS bearings on the first critical speed are shown

  13. Interaction of gravitational waves with superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Inan, N.A.; Thompson, J.J. [University of California, Schools of Natural Sciences, Merced, CA (United States); Chiao, R.Y. [University of California, Schools of Natural Sciences and Engineering, Merced, CA (United States)

    2017-06-15

    Applying the Helmholtz Decomposition theorem to linearized General Relativity leads to a gauge-invariant formulation where the transverse-traceless part of the metric perturbation describes gravitational waves in matter. Gravitational waves incident on a superconductor can be described by a linear London-like constituent equation characterized by a ''gravitational shear modulus'' and a corresponding plasma frequency and penetration depth. Electric-like and magnetic-like gravitational tensor fields are defined in terms of the strain field of a gravitational wave. It is shown that in the DC limit, the magnetic-like tensor field is expelled from the superconductor in a gravitational Meissner-like effect. The Cooper pair density is described by the Ginzburg-Landau theory embedded in curved space-time. The ionic lattice is modeled by quantum harmonic oscillators coupled to gravitational waves and characterized by quasi-energy eigenvalues for the phonon modes. The formulation predicts the possibility of a dynamical Casimir effect since the zero-point energy of the ionic lattice phonons is found to be modulated by the gravitational wave, in a quantum analog of a ''Weber-bar effect.'' Applying periodic thermodynamics and the Debye model in the low-temperature limit leads to a free energy density for the ionic lattice. Lastly, we relate the gravitational strain of space to the strain of matter to show that the response to a gravitational wave is far less for the Cooper pair density than for the ionic lattice. This predicts a charge separation effect in the superconductor as a result of the gravitational wave. (copyright 2016 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  14. Zeeman effects in heavy electron superconductors

    International Nuclear Information System (INIS)

    Michal, Vincent

    2012-01-01

    Understanding the properties of newly discovered strongly correlated electron compounds is a considerable challenge for both fundamental matters and long-term industrial impact. Experimental activity on heavy electron metals and superconductors has lead to highlighting effects that depart from current knowledge. The thesis is aimed at modelling effects that have been observed in response to magnetic field in the heavy electron superconductor CeCoIn 5 . This consists of two parts. In the first time we deal with the vortex lattice state anomalous local magnetic field space variations as highlighted by small angle neutron scattering and muon spin rotation experiment. On the basis of the Ginzburg-Landau theory with account of spin effect, we analyse the local field inhomogeneity in the vortex lattice and derive expressions for the neutron scattering form factors and muon spin rotation static linewidth. The anomalous experimental data are shown to be result of spin driven supercurrents which circulate around the vortex cores and lead to an increase with external field in the internal field inhomogeneity on a distance of the order of the superconducting coherence length from the vortex axis. The importance of the effect is controlled by a single quantity (the Maki parameter). The second part is on nearly commensurate spin density wave transition in a quasi two-dimensional superconductor. It is motivated by observation of the confinement of spin density wave ordering inside the superconducting state of CeCoIn 5 in magnetic field. In the frame of the spin-fermion formulation we propose a mechanism for the ground state transition consisting in the field-induced slowing down of a collective spin density fluctuation mode (spin-exciton) to static ordering. This represents a scenario by which the transition to spin ordering is intrinsically related to superconductivity. (author) [fr

  15. Iron-based superconductors via soft chemistry

    International Nuclear Information System (INIS)

    Friederichs, Gina Maya

    2015-01-01

    This thesis provides new soft chemistry approaches to Fe-based superconductors. Mild syntheses were demonstrated to be able to overcome difficulties, occurring in conventional synthesis and to enable the access to new metastable phases. A solvent-based metathesis reaction led to β-FeSe exclusively. Contrary to solid state syntheses, the formation of hexagonal α-FeSe could be avoided under mild conditions. The deintercalation of interstitial Fe (by formation of Fe 3 O 4 ) could be proven by low temperature O 2 -annealing of Fe 1+x Te 1-y Se y . By using redox (de)intercalations K 1-x Fe 2-y Se 2 , metastable Na 1-x Fe 2-y As 2 and Na 1-x ((Fe 1-y Co y ) 1-z As) 2 could successfully be obtained at room temperature. The mild synthesis conditions led to compounds like FeSe and K 1-x Fe 2-y Se 2 which exhibited different physical properties than found by conventional high temperature methods. In general, the developed (de)intercalation reactions represent a new, universally applicable tool in order to manipulate the structure along with the properties of Fe-based superconductors. The basic structural features of the characteristic FeX 4/4 tetrahedral layers, however, are preserved. Soft chemistry syntheses have been shown to allow the formation of a variety of phases, like Na 1-x Fe 2-y As 2 , Na 1-x ((Fe 1-y Co y ) 1-z As) 2 and K 1-x Fe 2-y Se 2 . Hence, especially low temperature approaches may enable the realization of complex stacking sequences, potentially leading to the fulfillment of the greatest goal in the research of superconductors - room temperature superconductivity.

  16. Diverse Neutron Scattering Measurements in Unconventional Superconductors

    Science.gov (United States)

    Carr, Scott

    Superconductivity is an amazing phenomena. Beyond the eye-popping demos and promises of floating trains, it is a macroscopic manifestation of pure quantum physics. Where most quantum effects are smothered by thermal energy even at the lowest of temperatures, superconductivity brings the strangeness of quantum mechanics to reasonably accessible temperatures. An while it does have applications in terms of efficient charge transfer and the production of powerful magnetic fields, this is not why we study it. The mystery of its origin, oddness of its effects, and beauty of its consequences drives us to delve into the richness of this amazing phenomena. One key player in the physics of these exotic superconductors appears to be magnetism. Magnetism is a constant presence in the phase diagrams of exotic superconductors and appears to couple to the superconducting transition in some interesting ways. The details of the connection remain unknown, but it is clear that magnetism, either through static order, fluctuations, or both, is an important aspect of the crystalline environments which foster superconductivity. Through the tool of neutron scattering I investigate this connection across an array or different compounds using a variety of techniques. In this thesis, I conclude on the role of phase separation in superconducting K yFe1.6+xSe2 using neutron diffraction, perform a survey of magnetic excitations across the superconducting phase diagram in NaFe1-xCoxAs with neutron time-of-flight spectroscopy, and reveal new magnetic properties of the old heavy fermion superconductor UPt3 via more traditional neutron measurements.

  17. Condensation energy density in Bi-2212 superconductors

    International Nuclear Information System (INIS)

    Matsushita, Teruo; Kiuchi, Masaru; Haraguchi, Teruhisa; Imada, Takeki; Okamura, Kazunori; Okayasu, Satoru; Uchida, Satoshi; Shimoyama, Jun-ichi; Kishio, Kohji

    2006-01-01

    The relationship between the condensation energy density and the anisotropy parameter, γ a , has been derived for Bi-2212 superconductors in various anisotropic states by analysing the critical current density due to columnar defects introduced by heavy ion irradiation. The critical current density depended on the size of the defects, determined by the kind and irradiation energy of the ions. A significantly large critical current density of 17.0 MA cm -2 was obtained at 5 K and 0.1 T even for the defect density of a matching field of 1 T in a specimen irradiated with iodine ions. The dependence of the critical current density on the size of the defects agreed well with the prediction from the summation theory of pinning forces, and the condensation energy density could be obtained consistently from specimens irradiated with different ions. The condensation energy density obtained increased with decreasing γ a over the entire range of measurement temperature, and reached about 60% of the value for the most three-dimensional Y-123 observed by Civale et al at 5 K. This gives the reason for the very strong pinning in Bi-2212 superconductors at low temperatures. The thermodynamic critical field obtained decreased linearly with increasing temperature and extrapolated to zero at a certain characteristic temperature, T * , lower than the critical temperature, T c . T * , which seems to be associated with the superconductivity in the block layers, was highest for the optimally doped specimen. This shows that the superconductivity becomes more inhomogeneous as the doped state of a superconductor deviates from the optimum condition

  18. Collective excitations in unconventional superconductors and superfluids

    CERN Document Server

    Brusov, Peter

    2009-01-01

    This is the first monograph that strives to give a complete and detailed description of the collective modes (CMs) in unconventional superfluids and superconductors (UCSF&SC). Using the most powerful method of modern theoretical physics - the path (functional) integral technique - authors build the three- and two-dimensional models for s -, p - and d -wave pairing in neutral as well as in charged Fermi-systems, models of superfluid Bose-systems and Fermi-Bose-mixtures. Within these models they study the collective properties of such systems as superfluid 3 He, superfluid 4 He, superfluid 3 He-

  19. Infrared properties of high Tc superconductors

    International Nuclear Information System (INIS)

    Schlesinger, Z.; Rotter, L.D.; Collins, R.T.; Holtzberg, F.; Feild, C.

    1991-01-01

    Over the past several years a coherent phenomenology of the high T c cuprate superconductors has begun to emerge. Infrared measurements have contributed several important ingredients to this picture including: (1) the inference of a scattering rate that is linear in frequency for ω>T, and of order ω, (2) a characteristic energy scale in the superconducting state of 500 cm -1 (60 meV), which can be interpreted as a superconducting pair excitation threshold or energy gap, and (3) evidence for very unusual temperature dependence in the vicinity of T c . An attempt to describe these aspects of the data is presented here

  20. Proximity effects in ferromagnet/superconductor structures

    International Nuclear Information System (INIS)

    Yu, H.L.; Sun, G.Y.; Yang, L.Y.; Xing, D.Y.

    2004-01-01

    The Nambu spinor Green's function approach is applied to study proximity effects in ferromagnet/superconductor (FM/SC) structures. They include the induced superconducting order parameter and density of states (DOS) with superconducting feature on the FM side, and spin-dependent DOS within the energy gap on the SC side. The latter indicates an appearance of gapless superconductivity and a coexistence of ferromagnetism and superconductivity in a small regime near the interface. The influence of exchange energy in FM and barrier strength at interface on the proximity effects is discussed

  1. Quench properties of high current superconductors

    International Nuclear Information System (INIS)

    Garber, M.; Sampson, W.B.

    1980-01-01

    A technique has been developed which allows the simultaneous determination of most of the important parameters of a high current superconductor. The critical current, propagation velocity, normal state resistivity, magnetoresistance, and enthalpy are determined as a function of current and applied field. The measurements are made on non-inductive samples which simulate conditions in full scale magnets. For wide, braided conductors the propagation velocity was found to vary approximately quadratically with current in the 2 to 5 kA region. A number of conductors have been tested including some Nb 3 Sn braids which have critical currents in excess of 10 kA at 5 T, 4.2 K

  2. An infrared view of high Tc superconductors

    International Nuclear Information System (INIS)

    Tanner, D.B.; Timusk, T.; McMaster Univ., Hamilton, ON

    1989-01-01

    Studies of the infrared properties of the high T c superconductors are reviewed, with particular emphasis on attempts to determine the energy gap by far infrared spectroscopy and on the properties of the strong absorption that occurs in the mid infrared. The authors argue that this mid-infrared absorption is a direct particle-hole excitation rather than a Holstein emission process. In addition, they conclude that although the energy gap is not easily observed, several recent experiments place it in the weak to moderate strong coupling range

  3. Discovery of a superhard iron tetraboride superconductor.

    Science.gov (United States)

    Gou, Huiyang; Dubrovinskaia, Natalia; Bykova, Elena; Tsirlin, Alexander A; Kasinathan, Deepa; Schnelle, Walter; Richter, Asta; Merlini, Marco; Hanfland, Michael; Abakumov, Artem M; Batuk, Dmitry; Van Tendeloo, Gustaaf; Nakajima, Yoichi; Kolmogorov, Aleksey N; Dubrovinsky, Leonid

    2013-10-11

    Single crystals of novel orthorhombic (space group Pnnm) iron tetraboride FeB4 were synthesized at pressures above 8 GPa and high temperatures. Magnetic susceptibility and heat capacity measurements demonstrate bulk superconductivity below 2.9 K. The putative isotope effect on the superconducting critical temperature and the analysis of specific heat data indicate that the superconductivity in FeB4 is likely phonon mediated, which is rare for Fe-based superconductors. The discovered iron tetraboride is highly incompressible and has the nanoindentation hardness of 62(5) GPa; thus, it opens a new class of highly desirable materials combining advanced mechanical properties and superconductivity.

  4. Potential aerospace applications of high temperature superconductors

    Science.gov (United States)

    Selim, Raouf

    1994-12-01

    The recent discovery of High Temperature Superconductors (HTS) with superconducting transition temperature, T(sub c), above the boiling point of liquid nitrogen has opened the door for using these materials in new and practical applications. These materials have zero resistance to electric current, have the capability of carrying large currents and as such have the potential to be used in high magnetic field applications. One of the space applications that can use superconductors is electromagnetic launch of payloads to low-earth-orbit. An electromagnetic gun-type launcher can be used in small payload systems that are launched at very high velocity, while sled-type magnetically levitated launcher can be used to launch larger payloads at smaller velocities. Both types of launchers are being studied by NASA and the aerospace industry. The use of superconductors will be essential in any of these types of launchers in order to produce the large magnetic fields required to obtain large thrust forces. Low Temperature Superconductor (LTS) technology is mature enough and can be easily integrated in such systems. As for the HTS, many leading companies are currently producing HTS coils and magnets that potentially can be mass-produced for these launchers. It seems that designing and building a small-scale electromagnetic launcher is the next logical step toward seriously considering this method for launching payloads into low-earth-orbit. A second potential application is the use of HTS to build sensitive portable devices for the use in Non Destructive Evaluation (NDE). Superconducting Quantum Interference Devices (SQUID's) are the most sensitive instruments for measuring changes in magnetic flux. By using HTS in SQUID's, one will be able to design a portable unit that uses liquid nitrogen or a cryocooler pump to explore the use of gradiometers or magnetometers to detect deep cracks or corrosion in structures. A third use is the replacement of Infra-Red (IR) sensor leads on

  5. Guided design of copper oxysulfide superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Yee, Chuck-Hou; Birol, Turan; Kotliar, Gabriel

    2015-07-01

    We describe a framework for designing novel materials, combining modern first-principles electronic-structure tools, materials databases, and evolutionary algorithms capable of exploring large configurational spaces. Guided by the chemical principles introduced by Antipov et al., for the design and synthesis of the Hg-based high-temperature superconductors, we apply our framework to screen 333 proposed compositions to design a new layered copper oxysulfide, Hg(CaS)2CuO2. We evaluate the prospects of superconductivity in this oxysulfide using theories based on charge-transfer energies, orbital distillation and uniaxial strain.

  6. Tunneling effect in superconductors with magnetic impurities

    International Nuclear Information System (INIS)

    Ahmed, M.

    1985-07-01

    We investigate the influence of transition metal impurities on the amplitude of the Josephson tunneling current. We consider a junction made up of two identical superconductors containing transition metal impurities and define a parameter K which is the normalised difference of the derivative of Josephson currents for superconducting pairs with and without magnetic impurities. We find K=0 for U/πGAMMA >1 in the Abrikosov-Gorkov theory, as well as large deviations of K from this value for 1< U/πGAMMA<3, where U/πGAMMA is the parameter of the Anderson theory. (author)

  7. Magnetic pinning in superconductor-ferromagnet multilayers

    International Nuclear Information System (INIS)

    Bulaevskii, L. N.; Chudnovsky, E. M.; Maley, M. P.

    2000-01-01

    We argue that superconductor/ferromagnet multilayers of nanoscale period should exhibit strong pinning of vortices by the magnetic domain structure in magnetic fields below the coercive field when ferromagnetic layers exhibit strong perpendicular magnetic anisotropy. The estimated maximum magnetic pinning energy for single vortex in such a system is about 100 times larger than the pinning energy by columnar defects. This pinning energy may provide critical currents as high as 10 6 -10 7 A/cm 2 at high temperatures (but not very close to T c ) at least in magnetic fields below 0.1 T. (c) 2000 American Institute of Physics

  8. Magnetic pinning in superconductor-ferromagnet multilayers

    Energy Technology Data Exchange (ETDEWEB)

    Bulaevskii, L. N. [Department of Physics and Astronomy, CUNY Lehman College 250 Bedford Park Boulevard West, Bronx, New York 10468-1589 (United States); Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Chudnovsky, E. M. [Department of Physics and Astronomy, CUNY Lehman College, 250 Bedford Park Boulevard West, Bronx, New York 10468-1589 (United States); Maley, M. P. [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)

    2000-05-01

    We argue that superconductor/ferromagnet multilayers of nanoscale period should exhibit strong pinning of vortices by the magnetic domain structure in magnetic fields below the coercive field when ferromagnetic layers exhibit strong perpendicular magnetic anisotropy. The estimated maximum magnetic pinning energy for single vortex in such a system is about 100 times larger than the pinning energy by columnar defects. This pinning energy may provide critical currents as high as 10{sup 6}-10{sup 7} A/cm{sup 2} at high temperatures (but not very close to T{sub c}) at least in magnetic fields below 0.1 T. (c) 2000 American Institute of Physics.

  9. Quench in high temperature superconductor magnets

    CERN Document Server

    Schwartz, J.

    2013-01-01

    High field superconducting magnets using high temperature superconductors are being developed for high energy physics, nuclear magnetic resonance and energy storage applications. Although the conductor technology has progressed to the point where such large magnets can be readily envisioned, quench protection remains a key challenge. It is well-established that quench propagation in HTS magnets is very slow and this brings new challenges that must be addressed. In this paper, these challenges are discussed and potential solutions, driven by new technologies such as optical fiber based sensors and thermally conducting electrical insulators, are reviewed.

  10. GaN/NbN epitaxial semiconductor/superconductor heterostructures

    Science.gov (United States)

    Yan, Rusen; Khalsa, Guru; Vishwanath, Suresh; Han, Yimo; Wright, John; Rouvimov, Sergei; Katzer, D. Scott; Nepal, Neeraj; Downey, Brian P.; Muller, David A.; Xing, Huili G.; Meyer, David J.; Jena, Debdeep

    2018-03-01

    Epitaxy is a process by which a thin layer of one crystal is deposited in an ordered fashion onto a substrate crystal. The direct epitaxial growth of semiconductor heterostructures on top of crystalline superconductors has proved challenging. Here, however, we report the successful use of molecular beam epitaxy to grow and integrate niobium nitride (NbN)-based superconductors with the wide-bandgap family of semiconductors—silicon carbide, gallium nitride (GaN) and aluminium gallium nitride (AlGaN). We apply molecular beam epitaxy to grow an AlGaN/GaN quantum-well heterostructure directly on top of an ultrathin crystalline NbN superconductor. The resulting high-mobility, two-dimensional electron gas in the semiconductor exhibits quantum oscillations, and thus enables a semiconductor transistor—an electronic gain element—to be grown and fabricated directly on a crystalline superconductor. Using the epitaxial superconductor as the source load of the transistor, we observe in the transistor output characteristics a negative differential resistance—a feature often used in amplifiers and oscillators. Our demonstration of the direct epitaxial growth of high-quality semiconductor heterostructures and devices on crystalline nitride superconductors opens up the possibility of combining the macroscopic quantum effects of superconductors with the electronic, photonic and piezoelectric properties of the group III/nitride semiconductor family.

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

    Science.gov (United States)

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

    2015-05-13

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

  12. American superconductor technology to help CERN to explore the mysteries of matter company's high temperature superconductor wire to be used in CERN's Large Hadron Collider

    CERN Multimedia

    2003-01-01

    American Superconductor Corporation has been selected by CERN, to provide 14,000 meters of high temperature superconductor (HTS) wire for current lead devices that will be used in CERN's Large Hadron Collider (1 page).

  13. Strong Correlation Physics in Aromatic Hydrocarbon Superconductors

    Science.gov (United States)

    Capone, Massimo; Giovannetti, Gianluca

    2012-02-01

    We show, by means of ab-initio calculations, that electron-electron correlations play an important role in doped aromatic hydrocarbon superconductors, including potassium doped picene with Tc= 18K [1], coronene and phenanthrene [2]. For the case of picene the inclusion of exchange interactions by means of hybrid functionals reproduces the correct gap for the undoped compound and predicts an antiferromagnetic state for x=3, where superconductivity has been observed [3]. The latter finding is compatible with a sizable value of the correlation strength. The differences between the different compounds are analyzed and results of Dynamical Mean-Field Theory including both correlation effects and electron-phonon interactions are presented. Finally we discuss the consequences of strong correlations in an organic superconductor in relation to the properties of Cs3C60, in which electron correlations drive an antiferromagnetic state [4] but also lead to an enhancement of superconductivity [5]. 1. R. Mitsuhashi et al. Nature 464, 76 (2010)2. X.F. Wang et al, Nat. Comm. 2, 507 (2011)3. G. Giovannetti and M. Capone, Phys. Rev. B 83, 134508 (2011)4. Y. Takabayashi et al., Science 323, 1585 (2009)5. M. Capone et al. Rev. Mod. Phys. 81, 943 (2009

  14. Optical conductivity of iron-based superconductors.

    Science.gov (United States)

    Charnukha, A

    2014-06-25

    The new family of unconventional iron-based superconductors discovered in 2006 immediately relieved their copper-based high-temperature predecessors as the most actively studied superconducting compounds in the world. The experimental and theoretical effort made in order to unravel the mechanism of superconductivity in these materials has been overwhelming. Although our understanding of their microscopic properties has been improving steadily, the pairing mechanism giving rise to superconducting transition temperatures up to 55 K remains elusive. And yet the hope is strong that these materials, which possess a drastically different electronic structure but similarly high transition temperatures compared to the copper-based compounds, will shed essential new light onto the several-decade-old problem of unconventional superconductivity. In this work we review the current understanding of the itinerant-charge-carrier dynamics in the iron-based superconductors and parent compounds largely based on the optical conductivity data the community has gleaned over the past seven years using such experimental techniques as reflectivity, ellipsometry, and terahertz transmission measurements and analyze the implications of these studies for the microscopic properties of the iron-based materials as well as the mechanism of superconductivity therein.

  15. High-temperature superconductors make major progress

    CERN Multimedia

    CERN Bulletin

    2014-01-01

    This month's Nature Materials featured an important breakthrough for high-temperature superconductors. A new method has been found for processing Bi-2212 high-temperature superconducting round wire in order to drastically increase its critical current density. The result confirms that this conductor is a serious candidate for future very-high-field magnets.   This image shows the cross-section of two Bi-2212 wires. The bottom wire has less leakage and void porosity due to a heat treatment done at an overpressure of 100 bar - about 100 times the pressure used to produce the top wire (image from [Nature Materials, Vol. 13 (2014), 10.1038/nmat3887]). The workhorse for building superconducting accelerator magnets has been, so far, the Niobium-Titanium (Nb-Ti) alloy superconductor. But with Nb-Ti having reached its full potential, other conductors must be used to operate in higher magnetic fields beyond those reached with the LHC magnets. Today, the intermetallic Niobium-Tin (Nb3Sn) is th...

  16. Dual superconductor models of color confinement

    CERN Document Server

    Ripka, Georges

    2004-01-01

    The lectures, delivered at ECT (European Centre for Theoretical Studies in Nuclear Physics and Related Areas) in Trento (Italy) in 2002 and 2003, are addressed to physicists who wish to acquire a minimal background to understand present day attempts to model the confinement of quantum chromo-dynamics (QCD) in terms of dual superconductors. The lectures focus more on the models than on attempts to derive them from QCD. They discuss the Dirac theory of magnetic monopoles, the world sheet swept out by Dirac strings, deformations of Dirac strings and charge quantization, gauge fields associated to the field tensor and to the dual field tensor, the Landau-Ginzburg (Abelian Higgs) model of a dual superconductor, the flux tube joining two equal and opposite color-electric charges, the Abrikosov-Nielsen-Olesen vortex, the divergencies of the London limit, the comparison of the calculated flux tube and string tension with lattice data, duality transformations and the use of Kalb-Ramond fields, the two-potential Zwanzi...

  17. Percolation effect in thick film superconductors

    International Nuclear Information System (INIS)

    Sali, R.; Harsanyi, G.

    1994-01-01

    A thick film superconductor paste has been developed to study the properties of granulated superconductor materials, to observe the percolation effect and to confirm the theory of the conducting mechanism in the superconducting thick films. This paste was also applied to make a superconducting planar transformer. Due to high T c and advantageous current density properties the base of the paste was chosen to be of Bi(Pb)SrCaCuO system. For contacts a conventional Ag/Pt paste was used. The critical temperature of the samples were between 110 K and 115 K depending on the printed layer thickness. The critical current density at the boiling temperature of the liquid He- was between 200-300 A/cm 2 . The R(T) and V(I) functions were measured with different parameters. The results of the measurements have confirmed the theory of conducting mechanism in the material. The percolation structure model has been built and described. As an application, a superconducting planar thick film transformer was planned and produced. Ten windings of the transformer were printed on one side of the alumina substrate and one winding was printed on the other side. The coupling between the two sides was possible through the substrate. The samples did not need special drying and firing parameters. After the preparation, the properties of the transformer were measured. The efficiency and the losses were determined. Finally, some fundamental advantages and problems of the process were discussed

  18. Microwave response of thin-film superconductors

    International Nuclear Information System (INIS)

    Sridhar, S.

    1988-01-01

    The interaction of microwaves with superconductors was explored via extensive measurements of the surface resistance R/sub s/ and reactance X/sub s/ at 10 GHz of superconducting Sn. The measurements were carried out as functions of thickness d and temperature T for Sn films ranging in thickness from 190 A to bulk. By varying the thickness with accompanied variation of mean free path, we were able to examine the wave-vector dependence of the microwave-superconductor interaction. An analysis, based on the Bardeen--Cooper--Schrieffer electrodynamical kernel, was developed for calculating R/sub s/ and X/sub s/ as functions of d, T, and frequency. Details of the measurement techniques and analysis are presented. Experiment and theory agree excellently, with no adjustable parameters. For films with d<800 A we find that the electrodynamics is local because of impurity scattering, while for thicker films nonlocal effects are important. The results imply that superconducting films with microwave response that agrees with theoretical expectations can be fabricated for potential applications in a variety of superconducting structures

  19. Electronic phase separation and high temperature superconductors

    International Nuclear Information System (INIS)

    Kivelson, S.A.

    1994-01-01

    The authors review the extensive evidence from model calculations that neutral holes in an antiferromagnet separate into hole-rich and hole-poor phases. All known solvable limits of models of holes in a Heisenberg antiferromagnet exhibit this behavior. The authors show that when the phase separation is frustrated by the introduction of long-range Coulomb interactions, the typical consequence is either a modulated (charge density wave) state or a superconducting phase. The authors then review some of the strong experimental evidence supporting an electronically-driven phase separation of the holes in the cuprate superconductors and the related Ni oxides. Finally, the authors argue that frustrated phase separation in these materials can account for many of the anomalous normal state properties of the high temperature superconductors and provide the mechanism of superconductivity. In particular, it is shown that the T-linear resistivity of the normal state is a paraconductivity associated with a novel composite pairing, although the ordered superconducting state is more conventional

  20. Advantageous grain boundaries in iron pnictide superconductors.

    Science.gov (United States)

    Katase, Takayoshi; Ishimaru, Yoshihiro; Tsukamoto, Akira; Hiramatsu, Hidenori; Kamiya, Toshio; Tanabe, Keiichi; Hosono, Hideo

    2011-08-02

    High critical temperature superconductors have zero power consumption and could be used to produce ideal electric power lines. The principal obstacle in fabricating superconducting wires and tapes is grain boundaries-the misalignment of crystalline orientations at grain boundaries, which is unavoidable for polycrystals, largely deteriorates critical current density. Here we report that high critical temperature iron pnictide superconductors have advantages over cuprates with respect to these grain boundary issues. The transport properties through well-defined bicrystal grain boundary junctions with various misorientation angles (θ(GB)) were systematically investigated for cobalt-doped BaFe(2)As(2) (BaFe(2)As(2):Co) epitaxial films fabricated on bicrystal substrates. The critical current density through bicrystal grain boundary (J(c)(BGB)) remained high (>1 MA cm(-2)) and nearly constant up to a critical angle θ(c) of ∼9°, which is substantially larger than the θ(c) of ∼5° for YBa(2)Cu(3)O(7-δ). Even at θ(GB)>θ(c), the decay of J(c)(BGB) was much slower than that of YBa(2)Cu(3)O(7-δ).

  1. Optical conductivity of iron-based superconductors

    International Nuclear Information System (INIS)

    Charnukha, A

    2014-01-01

    The new family of unconventional iron-based superconductors discovered in 2006 immediately relieved their copper-based high-temperature predecessors as the most actively studied superconducting compounds in the world. The experimental and theoretical effort made in order to unravel the mechanism of superconductivity in these materials has been overwhelming. Although our understanding of their microscopic properties has been improving steadily, the pairing mechanism giving rise to superconducting transition temperatures up to 55 K remains elusive. And yet the hope is strong that these materials, which possess a drastically different electronic structure but similarly high transition temperatures compared to the copper-based compounds, will shed essential new light onto the several-decade-old problem of unconventional superconductivity. In this work we review the current understanding of the itinerant-charge-carrier dynamics in the iron-based superconductors and parent compounds largely based on the optical-conductivity data the community has gleaned over the past seven years using such experimental techniques as reflectivity, ellipsometry, and terahertz transmission measurements and analyze the implications of these studies for the microscopic properties of the iron-based materials as well as the mechanism of superconductivity therein. (topical review)

  2. Rotordynamic Characterization of a Hybrid Superconductor Magnet Bearing

    Science.gov (United States)

    Ma, Ki B.; Xia, Zule H.; Cooley, Rodger; Fowler, Clay; Chu, Wei-Kan

    1996-01-01

    A hybrid superconductor magnet bearing uses magnetic forces between permanent magnets to provide lift and the flux pinning force between permanent magnets and superconductors to stabilize against instabilities intrinsic to the magnetic force between magnets. We have constructed a prototype kinetic energy storage system, using a hybrid superconductor magnet bearing to support a 42 lb. flywheel at the center. With five sensors on the periphery of the flywheel, we have monitored the position and attitude of the flywheel during its spin down. The results indicate low values of stiffnesses for the bearing. The implications of this and other consequences will be discussed.

  3. Fine-Filament MgB2 Superconductor Wire

    Science.gov (United States)

    Cantu, Sherrie

    2015-01-01

    Hyper Tech Research, Inc., has developed fine-filament magnesium diboride (MgB2) superconductor wire for motors and generators used in turboelectric aircraft propulsion systems. In Phase I of the project, Hyper Tech demonstrated that MgB2 multifilament wires (superconductor and engineering current density and AC losses. Hyper Tech also fabricated MgB2 rotor coil packs for a superconducting generator. The ultimate goal is to enable low-cost, round, lightweight, low-AC-loss superconductors for motor and generator stator coils operating at 25 K in next-generation turboelectric aircraft propulsion systems.

  4. Flux-flow resistivity of three high-temperature superconductors

    International Nuclear Information System (INIS)

    Cha, Y.S.; Evans, D.J.; Hull, J.R.; Seol, S.Y.

    1996-01-01

    Results of experiments on flux-flow resistivity (the relationship of voltage to current) of three high-temperature superconductors are described. The superconductors are a melt-cast BSCCO 2212 rod, a single filament BSCCO powder-in-tube (PIT) tape, and a multifilament PIT tape. The flux-flow resistivity of these superconductors was measured at three temperatures: 77 K (saturated liquid nitrogen), 87 K (saturated liquid argon), and 67 K (subcooled liquid nitrogen). Implications of the present results for practical applications are discussed

  5. Behavior of magnetic superconductors in a magnetic field

    International Nuclear Information System (INIS)

    Buzdin, A.I.

    1984-01-01

    We investigate the behavior in a magnetic field of magnetic superconductors in which the ferromagnetic and superconducting transition temperatures are close together. It is shown that as the temperature is lowered the order of the superconducting transition changes from second to first. The corresponding critical fields and the field and temperature dependences of the magnetization are determined. Attention is focused on a discontinuity in the magnetization in the vortex core in magnetic superconductors. This feature plus the relatively large scattering cross section make magnetic superconductors convenient objects for the study of the superconducting vortex lattice by neutron diffraction

  6. THz detectors using surface Josephson plasma waves in layered superconductors

    International Nuclear Information System (INIS)

    Savel'ev, Sergey; Yampol'skii, Valery; Nori, Franco

    2006-01-01

    We describe a proposal for THz detectors based on the excitation of surface waves, in layered superconductors, at frequencies lower than the Josephson plasma frequency ω J . These waves propagate along the vacuum-superconductor interface and are attenuated in both transverse directions out of the surface (i.e., towards the superconductor and towards the vacuum). The surface Josephson plasma waves are also important for the complete suppression of the specular reflection from a sample (Wood's anomalies, used for gratings) and produce a huge enhancement of the wave absorption, which can be used for the detection of THz waves

  7. Holographic superconductor in the analytic hairy black hole

    International Nuclear Information System (INIS)

    Myung, Yun Soo; Park, Chanyong

    2011-01-01

    We study the charged black hole of hyperbolic horizon with scalar hair (charged Martinez-Troncoso-Zanelli: CMTZ black hole) as a model of analytic hairy black hole for holographic superconductor. For this purpose, we investigate the second order phase transition between CMTZ and hyperbolic Reissner-Nordstroem-AdS (HRNAdS) black holes. However, this transition unlikely occurs. As an analytic treatment for holographic superconductor, we develop superconductor in the bulk and superfluidity on the boundary using the CMTZ black hole below the critical temperature. The presence of charge destroys the condensates around the zero temperature, which is in accord with the thermodynamic analysis of the CMTZ black hole.

  8. Density of states and tunneling characteristics of layered superconductors

    International Nuclear Information System (INIS)

    Liu, S.H.; Klemm, R.A.

    1993-04-01

    We have studied the structure of the density-of-states (DOS) curves and tunneling characteristics of layered superconductors with two distinct layers in a unit cell. In general, the peaks of the DOS curves do not correspond to energy gaps of each layer, but depend on the gaps and the interlayer hopping strengths in a complex manner. This makes the interpretation of tunneling data of layered superconductors much less straightforward than isotropic superconductors. Our simulated tunneling characteristics bear certain resemblance to experimental results

  9. Compact terahertz passive spectrometer with wideband superconductor-insulator-superconductor mixer.

    Science.gov (United States)

    Kikuchi, K; Kohjiro, S; Yamada, T; Shimizu, N; Wakatsuki, A

    2012-02-01

    We developed a compact terahertz (THz) spectrometer with a superconductor-insulator-superconductor (SIS) mixer, aiming to realize a portable and highly sensitive spectrometer to detect dangerous gases at disaster sites. The receiver cryostat which incorporates the SIS mixer and a small cryocooler except for a helium compressor has a weight of 27 kg and dimensions of 200 mm × 270 mm × 690 mm. In spite of the small cooling capacity of the cryocooler, the SIS mixer is successfully cooled lower than 4 K, and the temperature variation is suppressed for the sensitive measurement. By adopting a frequency sweeping system using photonic local oscillator, we demonstrated a spectroscopic measurement of CH(3)CN gas in 0.2-0.5 THz range.

  10. Transport measurements in superconductors: critical current of granular high TC ceramic superconductor samples

    International Nuclear Information System (INIS)

    Passos, W.A.C.

    2016-01-01

    This work presents a method to obtain critical current of granular superconductors. We have carried out transport measurements (ρxT curves and VxI curves) in a YBa 2 Cu 3 O 7-δ sample to determine critical current density of it. Some specimens reveal a 'semiconductor-like' behavior (electrical resistivity decreases with increasing temperatures above critical temperature T c of material) competing with superconductor behavior. Due to high granular fraction of the sample, these competition is clearly noted in ρxT curves. Measurements carried out from 0 to 8500 Oe of applied field show the same behavior, and the critical current density of the samples is shown. (author)

  11. Static Properties of Superconductor Journal Bearing Substator for Superconductor Flywheel Energy Storage System

    International Nuclear Information System (INIS)

    Park, B. J.; Jung, S. Y.; Lee, J. P.; Park, B. C.; Jeong, N. H.; Sung, T. H.; Han, Y. H.

    2008-01-01

    A Superconductor Flywheel Energy Storage System(SFES) mainly consists of a pair of non-contacting High Temperature Superconductor(HTS) bearings that provide very low frictional losses, a composite flywheel with high energy storage density. The HTS bearings, which offer dynamic stability without active control, are the key technology that distinguishes the SFES from other flywheel energy storage devices, and great effort is being put into developing this technology. The Superconductor Journal Bearing(SJB) mainly consists of HTS bulks and a stator, which holds the HTS bulks and also acts as a cold head. Static properties of HTS bearings provide data to solve problems which may occur easily in a running system. Since stiffness to counter vibration is the main parameter in designing an HTS bearing system, we investigate SJB magnetic force through static properties between the Permanent Magnet(PM) and HTS. We measure stiffness in static condition and the results are used to determine the optimal number of HTS bulks for a 100kWh SFES.

  12. Static Properties of Superconductor Journal Bearing Substator for Superconductor Flywheel Energy Storage System

    Energy Technology Data Exchange (ETDEWEB)

    Park, B. J.; Jung, S. Y.; Lee, J. P.; Park, B. C.; Jeong, N. H.; Sung, T. H.; Han, Y. H. [Korea Electric Power Research Institute, Superconductivity and Application Group, Daejeon (Korea, Republic of)

    2008-10-15

    A Superconductor Flywheel Energy Storage System(SFES) mainly consists of a pair of non-contacting High Temperature Superconductor(HTS) bearings that provide very low frictional losses, a composite flywheel with high energy storage density. The HTS bearings, which offer dynamic stability without active control, are the key technology that distinguishes the SFES from other flywheel energy storage devices, and great effort is being put into developing this technology. The Superconductor Journal Bearing(SJB) mainly consists of HTS bulks and a stator, which holds the HTS bulks and also acts as a cold head. Static properties of HTS bearings provide data to solve problems which may occur easily in a running system. Since stiffness to counter vibration is the main parameter in designing an HTS bearing system, we investigate SJB magnetic force through static properties between the Permanent Magnet(PM) and HTS. We measure stiffness in static condition and the results are used to determine the optimal number of HTS bulks for a 100kWh SFES.

  13. Tunneling and transport properties of superconductors

    International Nuclear Information System (INIS)

    Tralshawala, N.

    1993-01-01

    We obtained the electron-phonon spectral function, α 2 F(ω), from our tunneling data on Ba 1-x K x BiO 3 (BKBO) and Nd 2-x Ce x CuO 4-y (NCCO). The analysis is novel in its utilization of tunneling α 2 F(ω) function to estimate the contribution to resistivity from the electron-phonon scattering. We tested this methodology for conventional superconductors Nb, V, and VN. We make a strong case for the phonon-mediated coupling in BKBO. We show that phono-mediated coupling plays a major role in the superconductivity of NCCO. Tunneling data on BKBO exhibit a BCS gap and this ratio 2Δ/k B T c (of about 3.9) corresponds to a moderately coupled superconductor. The tunneling α 2 F(ω) compares well with the phonon density of states obtained from the inelastic neutron scattering data; and the T c calculated from the tunneling α 2 F(ω) matches well with the measured value. We explain the resistivity of BKBO using the tunneling α 2 F(ω). The high-T c (about 27 K), the low λ value (about 1), and the fact that optical phonons contribute heavily to the higher T c suggests that a deeper physical understanding of BKBO is needed to understand the high-T c cuprates. NCCO is a moderate T c cuprate superconductor that also shares the presence of spin density wave instability with other cuprates. But NCCO is electron-doped. The gap region tunneling data is distinctly non-BCS-like, but nevertheless we can obtain α 2 F(ω), which compares well with the phonon density of states and can explain the measured T c . We show that NCCO is also moderately coupled with stronger coupling to the optical phonons. Our analysis allows the identification of a T 2 contribution to the resistivity of NCCO and establishes a connection between variations in the magnitude of this contribution and the plasma frequency ω p

  14. Superconductors. Applications to electronics and electro-technology

    International Nuclear Information System (INIS)

    Baixeras, J.

    1998-01-01

    This book replaces superconductivity in its historical background and gives the current and potential applications of superconductors. It is devoted to searchers, engineers and engineer students. (O.M.)

  15. Electron refrigeration in hybrid structures with spin-split superconductors

    Science.gov (United States)

    Rouco, M.; Heikkilä, T. T.; Bergeret, F. S.

    2018-01-01

    Electron tunneling between superconductors and normal metals has been used for an efficient refrigeration of electrons in the latter. Such cooling is a nonlinear effect and usually requires a large voltage. Here we study the electron cooling in heterostructures based on superconductors with a spin-splitting field coupled to normal metals via spin-filtering barriers. The cooling power shows a linear term in the applied voltage. This improves the coefficient of performance of electron refrigeration in the normal metal by shifting its optimum cooling to lower voltage, and also allows for cooling the spin-split superconductor by reverting the sign of the voltage. We also show how tunnel coupling spin-split superconductors with regular ones allows for a highly efficient refrigeration of the latter.

  16. Leaders in high temperature superconductivity commercialization win superconductor industry award

    CERN Multimedia

    2007-01-01

    CERN's Large Hadron Collider curretn leads project head Amalia Ballarino named superconductor industry person of the year 2006. Former high temperature superconductivity program manager at the US Department of energy James Daley wins lifetime achievement award. (1,5 page)

  17. Stress and strain effects on the properties of composite superconductors

    International Nuclear Information System (INIS)

    Welch, D.O.

    1982-01-01

    Practical superconductors for use in the production of high magnetic fields are generally in the form of composites of filaments of superconducting material embedded in a matrix of normally conducting material. Lorentz forces which arise during magnet operation are examples of sources of external stress, while internal stresses can arise during the fabrication of the composite superconductor, primarily due to differential thermal contraction between different materials in the composite. The properties of superconducting compounds are often sensitive functions of the elastic strain state in the compound; consequently there is a strong coupling between the mechanical and electrical properties of composite superconductors. The basic features of this phenomenon will be illustrated by a discussion of the properties of simple composite superconductors

  18. Some thermodynamical properties of normal (or ferromagnetic) metal / superconductor heterojunctions

    International Nuclear Information System (INIS)

    Cayssol, Jerome

    2003-01-01

    We have investigated the orbital magnetism of a ballistic hybrid normal-superconductor ring. We have obtained the flux dependent excitation spectrum for arbitrary normal and superconductor lengths. We have introduced a new method to evaluate the current harmonics. We have described the cross-over from the, 'h/eh/e-periodic persistent current to the', h/2e-periodic Josephson current. In a second study, we have calculated the effect of intrinsic ordinary reflexion on the Josephson current in a ballistic superconductor-ferromagnetic-superconductor. The spectrum is strongly modified by gap openings but the current and the 0-π transition are only slightly modified up to very high spin polarisation. In a third study, we analyse the contain of some solutions of Usadel equation. The standard perturbation theory dressed by cooperons enables us to interpret those solutions in terms of diffusive paths connecting Andreev reflexion events. (author) [fr

  19. High point for CERN and high-temperature superconductors

    CERN Multimedia

    2007-01-01

    Amalia Ballarino is named the Superconductor Industry Person of the year 2006. Amalia Ballarino showing a tape of high-superconducting material used for the LHC current leads.The CERN project leader for the high-temperature superconducting current leads for the LHC, Amalia Ballarino, has received the award for "Superconductor Industry Person of the Year". This award, the most prestigious international award in the development and commercialization of superconductors, is presented by the leading industry newsletter "Superconductor Week". Amalia Ballarino was selected from dozens of nominations from around the world by a panel of recognized leading experts in superconductivity. "It is a great honour for me," says Amalia Ballarino. "It has been many years of hard work, and it’s a great satisfaction to see that the work has been completed successfully." Amalia Ballarino has been working on high-temperature superconducting materials sin...

  20. Structural and electronic properties of ion-implanted superconductors

    International Nuclear Information System (INIS)

    Bernas, H.; Nedellec, P.

    1980-01-01

    Recent work on ion implanted superconductors is reviewed. In situ x-ray, channeling, resistivity, and electron tunneling experiments now approach the relation between lattice order (or disorder) and superconductivity

  1. Ceramic high temperature superconductor levitating motor with laser commutator

    International Nuclear Information System (INIS)

    Roslan Abd Shukor; Lee Keng Heong

    1996-01-01

    The design of a magnetically levitating motor using a ceramic high temperature superconductor with laser commutator is discussed. A YBa sub 2 Cu sub 3 O sub 7-δ high temperature superconductor with 25 mm diameter and 6 mm thickness is used to levitate a Nd-Fe-B magnet (19.0 mm diameter and 4.8 mm thickness) which is attached symmetrically to a 150 mm long graphite rod. A smaller magnet (5.5 mm diameter and 2.0 mm thickness) is attached at each end of the rod with the appropriate poles arrangements. A suitable laser beam chopper is used to optically drive a solenoid which repels the smaller magnets thus driving the motor. A simple and efficient liquid nitrogen supply system is designed to cool the superconductor. The stability of the bearing is provided by the flux pinning in this type-II superconductor. Some characteristics of the motor are discussed

  2. Spin, charge, and orbital orderings in iron-based superconductors

    International Nuclear Information System (INIS)

    Jiang Qing; Kang Yao-Tai; Yao Dao-Xin

    2013-01-01

    In this article, we briefly review spin, charge, and orbital orderings in iron-based superconductors, as well as the multi-orbital models. The interplay of spin, charge, and orbital orderings is a key to understand the high temperature superconductivity. As an illustration, we use the two-orbital model to show the spin and charge orderings in iron-based superconductors based on the mean-field approximation in real space. The typical spin and charge orderings are shown by choosing appropriate parameters, which are in good agreement with experiments. We also show the effect of Fe vacancies, which can introduce the nematic phase and interesting magnetic ground states. The orbital ordering is also discussed in iron-based superconductors. It is found that disorder may play a role to produce the superconductivity. (topical review - iron-based high temperature superconductors)

  3. Scanning tunneling spectroscopy on electron-boson interactions in superconductors

    CERN Document Server

    Schackert, Michael Peter

    2015-01-01

    This work describes the experimental study of electron-boson interactions in superconductors by means of inelastic electron tunneling spectroscopy performed with a scanning tunneling microscope (STM) at temperatures below 1 K. This new approach allows the direct measurement of the Eliashberg function of conventional superconductors as demonstrated on lead (Pb) and niobium (Nb). Preparative experiments on unconventional iron-pnictides are presented in the end.

  4. Magnetoelastic energy calculations for finite element analysis of superconductors

    International Nuclear Information System (INIS)

    Akin, J.E.; Stoddart, W.C.T.

    1977-01-01

    It has been shown that the high current density and magnetic flux density associated with superconductors can make the magnetoelastic energy a significant portion of the total energy in a structural system. The present work presents a procedure for evaluating this magnetoelastic energy for use in the finite element analysis of the structural dynamics and stability of the superconductor. A simple, special case of the element matrices is illustrated

  5. The critical current of superconductors: an historical review

    International Nuclear Information System (INIS)

    Dew-Hughes, D.

    2001-01-01

    The most important practical characteristic of a superconductor is its critical current density. This article traces the history, both of the experimental discoveries and of the development of the theoretical ideas that have lead to the understanding of those factors that control critical current densities. These include Silsbee's hypothesis, the Meissner effect, London, Ginsburg-Landau and Abrikosov theories, flux pinning and the critical state, and the control of texture in high temperature superconductors

  6. Magnetic flow dynamics in critical state in discrete superconductor

    International Nuclear Information System (INIS)

    Ginzburg, S.L.; Nakin, A.V.; Savitskaya, N.E.

    2005-01-01

    Theoretic description of avalanche-like magnetic flow dynamics in critical state in discrete second class superconductor is given using model of the 1-D discrete superconductor. In the investigated system self-organizing critical state in a generalized sense is incarnated. This means that critical state consists of a great number of metastatic conditions, transferring one into another by means of avalanches. At the same time leap density of system's total magnetic flux presents a power function

  7. 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.)

  8. Enhancement of critical temperature in fractal metamaterial superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Smolyaninov, Igor I., E-mail: smoly@umd.edu [Department of Electrical and Computer Engineering, University of Maryland, College Park, MD 20742 (United States); Smolyaninova, Vera N. [Department of Physics Astronomy and Geosciences, Towson University, 8000 York Road, Towson, MD 21252 (United States)

    2017-04-15

    Fractal metamaterial superconductor geometry has been suggested and analyzed based on the recently developed theoretical description of critical temperature increase in epsilon near zero (ENZ) metamaterial superconductors. Considerable enhancement of critical temperature has been predicted in such materials due to appearance of large number of additional poles in the inverse dielectric response function of the fractal. Our results agree with the recent observation (Fratini et al. Nature 466, 841 (2010)) that fractal defect structure promotes superconductivity.

  9. Characteristic features of the exotic superconductors: A summary

    International Nuclear Information System (INIS)

    Brandow, B.

    1997-09-01

    The authors summarize the results of a comprehensive examination of the characteristic features of the exotic superconductors, the superconductors so-labelled by Uemura and co-workers. In both the electronic and the crystal-chemistry properties, they find anomalous features which appear to be universal for these materials, as well as other features which are clearly not universal but common enough to be considered typical for these materials. Some implications of these anomalies are discussed

  10. Holographic superconductors in Einstein-æther gravity

    Science.gov (United States)

    Lin, Kai; Wu, Yumei

    2017-11-01

    In this paper, we apply Anti-de Sitter (AdS) black hole solution of the Einstein-æther theory to the study of the holographic superconductor and show that the AdS black hole solution can be rewritten in some very simple forms, from which it is easy to identify the locations of various killing horizons. Then, we investigate the different effects of these horizons on the holographic superconductor.

  11. Second harmonics and compensation effect in ceramic superconductors

    International Nuclear Information System (INIS)

    Mai Suan Li

    1998-09-01

    The nonlinear ac susceptibility and the compensation effect observed in ceramic superconductors which show the paramagnetic Meissner effect are studied by the Monte Carlo simulations on a three dimensional lattice model of the Josephson array with finite self-conductance. Our study is based on the possible existence of the chiral glass phase in these materials. In agreement with experiments, the compensation effect is demonstrated to be present in d-wave superconductors but not in the s-wave ones. (author)

  12. Electronic and optical properties of thin-film superconductors and superconductor-semiconductor interfaces

    Science.gov (United States)

    Roshchin, Igor Vladimirovich

    2000-06-01

    Recently, the interest in the properties of superconductor-normal metal and especially superconductor-semiconductor interfaces increased in the basic research area. The superconducting proximity effect, known for about four decades, still poses many unanswered questions. Use of a semiconductor instead of a metal broadens the possibilities: superconductor- semiconductor interfaces are tunable, and their parameters, can be varied in a wide range. This type of interfaces may also be used in future superconducting electronic device applications. Our studies of the interfaces between high-quality thin film Nb and NbN superconductors, and (100) n+-InAs (1019cm -3) are done by transport and optical measurements. For the first time, the proximity effect in superconductor-semiconductor interfaces is observed using Raman scattering. The InAs longitudinal optical phonon LO mode (237cm-1) and the plasmon- phonon coupled modes, L- (221cm-1) and L+ (position is carrier concentration dependent), are studied. The intensity ratio of the LO mode (associated with the near- surface charge accumulation region, CAR in InAs) to that of the L- mode (associated with bulk InAs) is observed to increase by up to 40%, when the temperature is decreased below the superconducting transition temperature Tc. Further experimental and theoretical studies are required to find the underlying mechanism. Effects of surface damage and surface passivation on the electronic properties of InAs are studied. Damage, produced by Ar-ion etching, reduces the surface band bending. Passivation of the InAs surface by application of alkanethiols is found to reduce the surface band bending and to preserve the surface of InAs from oxidation. In close collaboration with A. Shnirman, a theoretical model for the Andreev reflection contributions to the current at the SN interfaces is developed using the tunneling Hamiltonian method. Both, the interference due to multiple Andreev reflection, and the electron

  13. System and method for quench and over-current protection of superconductor

    Science.gov (United States)

    Huang, Xianrui; Laskaris, Evangelos Trifon; Sivasubramaniam, Kiruba Haran; Bray, James William; Ryan, David Thomas; Fogarty, James Michael; Steinbach, Albert Eugene

    2005-05-31

    A system and method for protecting a superconductor. The system may comprise a current sensor operable to detect a current flowing through the superconductor. The system may comprise a coolant temperature sensor operable to detect the temperature of a cryogenic coolant used to cool the superconductor to a superconductive state. The control circuit is operable to estimate the superconductor temperature based on the current flow and the coolant temperature. The system may also be operable to compare the estimated superconductor temperature to at least one threshold temperature and to initiate a corrective action when the superconductor temperature exceeds the at least one threshold temperature.

  14. Correction of magnetization sextupole and decapole in a 5 centimeter bore SSC dipole using passive superconductor

    International Nuclear Information System (INIS)

    Green, M.A.

    1991-05-01

    Higher multipoles due to magnetization of the superconductor in four and five centimeter bore Superconducting Super Collider (SSC) superconducting dipole magnets have been observed. The use of passive superconductor to correct out the magnetization sextupole has been demonstrated on two dipoles built by the Lawrence Berkeley Laboratory (LBL). This reports shows how passive correction can be applied to the five centimeter SSC dipoles to remove sextupole and decapole caused by magnetization of the dipole superconductor. Two passive superconductor corrector options will be presented. The change in magnetization sextupole and decapole due to flux creep decay of the superconductor during injection can be partially compensated for using the passive superconductor. 9 refs; 5 figs

  15. Generalized superconductors and holographic optics. Part II

    Energy Technology Data Exchange (ETDEWEB)

    Mahapatra, Subhash [Department of Physics, Indian Institute of Technology,Kanpur 208016 (India)

    2015-01-29

    Using linear response theory, we analyze the electromagnetic response functions of generalized holographic superconductors, in AdS-Schwarzschild and single R-charged black hole backgrounds in four dimensions. By introducing momentum dependent vector mode perturbations, the response functions for these systems are studied numerically, including the effects of backreaction. This complements and completes the probe limit analysis for these backgrounds initiated in our previous work (http://arxiv.org/abs/1305.6273). Our numerical analysis indicates a negative Depine-Lakhtakia index for both the backgrounds studied, at low enough frequencies. The dependence of the response functions on the backreaction parameter and the model parameters are established and analyzed with respect to similar backgrounds in five dimensions.

  16. 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...... plays a key role in determining the quality of the induced superconducting gap. Here we present epitaxial growth of semiconductor-metal core-shell nanowires by molecular beam epitaxy, a method that provides a conceptually new route to controlled electrical contacting of nanostructures and the design...... of devices for specialized applications such as topological and gate-controlled superconducting electronics. Our materials of choice, InAs/Al grown with epitaxially matched single-plane interfaces, and alternative semiconductor/metal combinations allowing epitaxial interface matching in nanowires...

  17. Critical state in disk-shaped superconductors

    Science.gov (United States)

    Däumling, M.; Larbalestier, D. C.

    1989-11-01

    We have calculated the magnetic fields and currents occurring in a disk-shaped superconductor (radius >>thickness) in the critical state in a self-consistent way using finite-element analysis. We find that the field shielded (or trapped) in the center of the disk is roughly equal to Jcd, where d is the thickness of the disk. The shielding currents also create radial fields which are or order Jcd/2 on the disk surface. For low applied fields Happltelsa applied field. The field dependence of the calculated magnetic moment in the self-field dominated regime is independent of whether Jc is weakly or strongly (~1/H) dependent on field. The calculations were validated by comparison to both magnetic and resistive measurements on a disk-shaped section in Nb3Sn tape.

  18. Noncommutative effects of spacetime on holographic superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Ghorai, Debabrata, E-mail: debanuphy123@gmail.com [S.N. Bose National Centre for Basic Sciences, JD Block, Sector III, Salt Lake, Kolkata 700098 (India); Gangopadhyay, Sunandan, E-mail: sunandan.gangopadhyay@gmail.com [Department of Physics, West Bengal State University, Barasat (India); Inter University Centre for Astronomy & Astrophysics, Pune (India)

    2016-07-10

    The Sturm–Liouville eigenvalue method is employed to analytically investigate the properties of holographic superconductors in higher dimensions in the framework of Born–Infeld electrodynamics incorporating the effects of noncommutative spacetime. In the background of pure Einstein gravity in noncommutative spacetime, we obtain the relation between the critical temperature and the charge density. We also obtain the value of the condensation operator and the critical exponent. Our findings suggest that the higher value of noncommutative parameter and Born–Infeld parameter make the condensate harder to form. We also observe that the noncommutative structure of spacetime makes the critical temperature depend on the mass of the black hole and higher value of black hole mass is favourable for the formation of the condensate.

  19. Holographic p-wave superconductor with disorder

    Energy Technology Data Exchange (ETDEWEB)

    Areán, D. [Max-Planck-Institut für Physik (Werner-Heisenberg-Institut),Föhringer Ring 6, D-80805, Munich (Germany); Farahi, A.; Zayas, L.A. Pando [Michigan Center for Theoretical Physics, Randall Laboratory of Physics, University of Michigan,450 Church Street, Ann Arbor, MI 48109 (United States); Landea, I. Salazar [Instituto de Física La Plata (IFLP) and Departamento de Física,Universidad Nacional de La Plata,CC 67, 1900 La Plata (Argentina); International Centre for Theoretical Physics (ICTP),Strada Costiera 11, I 34014 Trieste (Italy); Scardicchio, A. [International Centre for Theoretical Physics (ICTP),Strada Costiera 11, I 34014 Trieste (Italy); Physics Department, Princeton University,77 Nassau Street, Princeton, NJ 08542 (United States); Physics Department, Columbia University,116th Street & Broadway, New York, NY 10027 (United States); ITS, Graduate Center, City University of New York,365 5th Avenue, New York, NY 10016 (United States); INFN, Sezione di Trieste,Strada Costiera 11, 34151, Trieste (Italy)

    2015-07-09

    We implement the effects of disorder on a holographic p-wave superconductor by introducing a random chemical potential which defines the local energy of the charge carriers. Since there are various possibilities for the orientation of the vector order parameter, we explore the behavior of the condensate in the parallel and perpendicular directions to the introduced disorder. We clarify the nature of various branches representing competing solutions and construct the disordered phase diagram. We find that moderate disorder enhances superconductivity as determined by the value of the condensate. Though we mostly focus on uncorrelated noise, we also consider a disorder characterized by its spectral properties and study in detail its influence on the spectral properties of the condensate and charge density. We find fairly universal responses of the resulting power spectra characterized by linear functions of the disorder power spectrum.

  20. Emission of coherent THz radiation from superconductors.

    Science.gov (United States)

    Ozyuzer, L; Koshelev, A E; Kurter, C; Gopalsami, N; Li, Q; Tachiki, M; Kadowaki, K; Yamamoto, T; Minami, H; Yamaguchi, H; Tachiki, T; Gray, K E; Kwok, W-K; Welp, U

    2007-11-23

    Compact solid-state sources of terahertz (THz) radiation are being sought for sensing, imaging, and spectroscopy applications across the physical and biological sciences. We demonstrate that coherent continuous-wave THz radiation of sizable power can be extracted from intrinsic Josephson junctions in the layered high-temperature superconductor Bi2Sr2CaCu2O8. In analogy to a laser cavity, the excitation of an electromagnetic cavity resonance inside the sample generates a macroscopic coherent state in which a large number of junctions are synchronized to oscillate in phase. The emission power is found to increase as the square of the number of junctions reaching values of 0.5 microwatt at frequencies up to 0.85 THz, and persists up to approximately 50 kelvin. These results should stimulate the development of superconducting compact sources of THz radiation.

  1. Holographic p-wave superconductor with disorder

    International Nuclear Information System (INIS)

    Areán, D.; Farahi, A.; Zayas, L.A. Pando; Landea, I. Salazar; Scardicchio, A.

    2015-01-01

    We implement the effects of disorder on a holographic p-wave superconductor by introducing a random chemical potential which defines the local energy of the charge carriers. Since there are various possibilities for the orientation of the vector order parameter, we explore the behavior of the condensate in the parallel and perpendicular directions to the introduced disorder. We clarify the nature of various branches representing competing solutions and construct the disordered phase diagram. We find that moderate disorder enhances superconductivity as determined by the value of the condensate. Though we mostly focus on uncorrelated noise, we also consider a disorder characterized by its spectral properties and study in detail its influence on the spectral properties of the condensate and charge density. We find fairly universal responses of the resulting power spectra characterized by linear functions of the disorder power spectrum.

  2. Two-dimensional Semiconductor-Superconductor Hybrids

    DEFF Research Database (Denmark)

    Suominen, Henri Juhani

    and a hard induced superconducting gap. Furthermore the thin superconducting (application of large in-plane magnetic fields without destroying superconductivity. In such a scenario we investigate the magneto-transport properties in S-Sm-S junctions, revealing anomalous....... 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...... Fraunhofer diffraction, qualitatively in agreement with a complex interplay between Zeeman coupling, spin-orbit interaction and disorder. Finally by patterning quasi-one-dimensional structures we observe coalescing Andreev bound states stabilizing at zero energy in large magnetic fields, in agreement...

  3. Plasma polymerization for high Tc oxide superconductors

    Science.gov (United States)

    Morohashi, Shin'ichi; Tamura, Hirotaka; Yoshida, Akira; Hasuo, Shinya

    1988-05-01

    Plasma polymerization using CHF3 gas, which prevents the degradation of high Tc oxide superconductors due to moisture and annealing, was developed. The resistive transitions of Y1Ba2Cu3Ox thin films, coated by plasma polymerization, did not change before and after soaking in 20 °C water for 60 min. In addition, the critical temperature of those films was unchanged after annealing at 200 °C for 30 min in air, and then soaking in 90 °C water for 10 min. We confirmed that the polymer film grown by this method was dense, and the Y1Ba2Cu3Ox film reacted with the fluorine at the interface using x-ray photoelectron spectroscopy.

  4. Molding of L band niobium superconductor cavity

    Energy Technology Data Exchange (ETDEWEB)

    Inoue, Hitoshi; Funahashi, Yoshisato; Saito, Kenji; Noguchi, Shuichi; Koizumi, Susumu [National Lab. for High Energy Physics, Tsukuba, Ibaraki (Japan)

    1995-07-01

    A cavity to produce high accelerating electron field was developed. The L-band (1.3 GHz) niobium superconductor unit cell cavity was ellipsoid with {phi}217.3 mm outer diameter and 2.5 mm thickness and consisted of two pieces of half cell, two beam pipes and flange. A deep drawing process was adapted. In spite of the first trial manufacture, each good cavity was obtained. Characteristic properties of niobium materials, molding method of cavity, extension of sheet after molding, production of beam pipe, accuracy and the cost were explained. Niobium materials. showed tensile strength 15.6 kg/mm{sup 2}, load-carrying capacity 4.1 kg/mm{sup 2}, density 8.57, extension 42.5% and RRR (resistance residual ratio){>=}200. (S.Y.)

  5. Noncommutative effects of spacetime on holographic superconductors

    Directory of Open Access Journals (Sweden)

    Debabrata Ghorai

    2016-07-01

    Full Text Available The Sturm–Liouville eigenvalue method is employed to analytically investigate the properties of holographic superconductors in higher dimensions in the framework of Born–Infeld electrodynamics incorporating the effects of noncommutative spacetime. In the background of pure Einstein gravity in noncommutative spacetime, we obtain the relation between the critical temperature and the charge density. We also obtain the value of the condensation operator and the critical exponent. Our findings suggest that the higher value of noncommutative parameter and Born–Infeld parameter make the condensate harder to form. We also observe that the noncommutative structure of spacetime makes the critical temperature depend on the mass of the black hole and higher value of black hole mass is favourable for the formation of the condensate.

  6. Low critical temperature superconductors for electromagnets

    International Nuclear Information System (INIS)

    Devred, A.

    2002-01-01

    After a brief history of the main discoveries in applied superconductivity (section 1), we discuss the structure and properties of NbTi and Nb3 Sn (section 2). Then, we explain why low critical-temperature superconductors are produced under the form of multifilamentary composites (section 3), and we review the manufacturing processes of NbTi and Nb3Sn wires (section 4). We follow by a description of the transition from the superconducting to the normal resistive state of multifilamentary composite wires (section 5) and we detail their magnetization properties section 6). Last, we present the most commonly used cable configurations (section 7) and we provide simple formulae illustrating on a few examples the computation of losses generated under time-varying magnetic fields (section 8). (author)

  7. 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......In this thesis, sub-gap states in bottom-gated InAs N–dot–S, N–double dot–S, and N–dot–S–dot–N devices are investigated, and several different theories are developed to model these states. Experimental results include tracking single levels of the dot in an N–dot–S device as the tunnel couplings...... with floating gates. A numerical technique is developed, which predicts the position of Yu-Shiba-Rusinov sub-gap states in the proximitized Anderson model as well as properties of these states. This theory is valid for all occupations of the dot and for weak to intermediate coupling. We compare...

  8. Tc(p) for a disordered superconductor

    Science.gov (United States)

    Yao, K.-L.; Halley, J. W.

    1984-06-01

    We describe a calculation of Tc(p) in a model of a disordered superconductor which is based on the de Gennes-Skal-Shklovskii (dGSS) picture of the large cluster in a percolation system. The calculation is done by carrying out successive decimations on the Landau-Ginzburg Hamiltonian describing the "links" in the model. We calculate Tc(p) by evaluating the renormalized LandauGinzburg coupling when the renormalized Landau-Ginzburg length equals the percolation link length in the dGSS picture. The results reduce to a previous scaling theory in an appropriate limit but contain effects of variations in the amplitude of the superconducting order parameter. The results are in good agreement with experiments on HgxXe1-x mixtures by Epstein, Goldman, Dahlberg, and Mikkelson.

  9. Tl Cuprate Superconductors Studied by XPS

    Energy Technology Data Exchange (ETDEWEB)

    Vasquez, R. P. [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109-8099 (United States); Siegal, M. P. [Sandia National Laboratories, Albuquerque, NM 87185-1421 (United States); Overmyer, D. L. [Sandia National Laboratories, Albuquerque, NM 87185-1421 (United States); Ren, Z. F. [Department of Chemistry, State University of New York, Buffalo, NY 14260-3000 (United States); Lao, J. Y. [Department of Chemistry, State University of New York, Buffalo, NY 14260-3000 (United States); Wang, J. H. [Department of Chemistry, State University of New York, Buffalo, NY 14260-3000 (United States)

    1999-07-01

    XPS measurements on epitaxial thin films of the Tl cuprate superconductors Tl2Ba2CaCu2O8, Tl2Ba2Ca2Cu3O10, and Tl0.78Bi0.22Ba0.4Sr1.6Ca2Cu3O9-{delta} are presented. These data, together with previous measurements in this lab on Tl2Ba2CuO6-{delta} and TlBa2CaCu2O7-{delta}, comprise a comprehensive data set for comparison of Tl cuprates in which the number of Tl-O and Cu-O layers, and hence the chemical and electronic properties, vary. (c) 2000 American Vacuum Society.

  10. Tl Cuprate Superconductors Studied by XPS

    International Nuclear Information System (INIS)

    Vasquez, R. P.; Siegal, M. P.; Overmyer, D. L.; Ren, Z. F.; Lao, J. Y.; Wang, J. H.

    1999-01-01

    XPS measurements on epitaxial thin films of the Tl cuprate superconductors Tl2Ba2CaCu2O8, Tl2Ba2Ca2Cu3O10, and Tl0.78Bi0.22Ba0.4Sr1.6Ca2Cu3O9-δ are presented. These data, together with previous measurements in this lab on Tl2Ba2CuO6-δ and TlBa2CaCu2O7-δ, comprise a comprehensive data set for comparison of Tl cuprates in which the number of Tl-O and Cu-O layers, and hence the chemical and electronic properties, vary. (c) 2000 American Vacuum Society

  11. Magnetism and crystal fields in ternary superconductors

    International Nuclear Information System (INIS)

    Shenoy, G.K.; Crabtree, G.W.; Niarchos, D.; Behroozi, F.; Dunlap, B.D.; Hinks, D.; Noakes, D.R.

    1982-01-01

    In this paper, the present state of knowledge of crystalline electric field (CEF) in two important classes of ternary superconductors has been described. It is clear that in understanding the superconducting and magnetic behavior of RERh 4 B 4 , the CEF plays a very important role. Considerable importance has been given to the specific heat Schottky anomalies in deducing the position and degeneracy of various CEF levels. Interpretation of these data is made difficult because of complicated subtraction of lattice, electronic and superconducting specific heats. Furthermore, the purity of the sample is important in such studies. It is known that a few percent of Rh-B/sub x/, RERh 3 B 2 and RERh 6 B 4 are commonly present in RERh 4 B 4 , while Mo-Ch/sub x/, RE-Ch/sub x/ and RE 2 O 2 Ch phases occur in Chevrel phase compounds. Only single-crystal samples will lead to dependable specific heat data

  12. 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

  13. Paramagnetic Meissner effect in conventional Nb superconductors

    International Nuclear Information System (INIS)

    Thompson, D.J.; Wenger, L.E.; Chen, J.T.

    1996-01-01

    The paramagnetic Meissner effect (PME), in which the field-cooled-magnetization (FCM) of superconducting samples is positive below the superconducting transition temperature T c , has been observed in certain ceramic and single-crystal samples of the high-T c cuprate superconductors and more recently in disk-shaped Nb samples. Through systematic investigations of the conditions for observing the PME in Nb disks, various surface treatments to the Nb disks were found to change both the zero-field-cooled-magnetization (ZFCM) and the FCM, including the appearance of a positive FCM in samples previously not exhibiting the PME as well as the elimination of the PME through surface abrasion. These results suggest that the PME arises from the field distributions created by the flux pinning associated with microstructural defects on the surface layer of the disk

  14. Fidelity approach in topological superconductors with disorders

    International Nuclear Information System (INIS)

    Tian, Wen-Chuan; Huang, Guang-Yao; Wang, Zhi; Yao, Dao-Xin

    2015-01-01

    We apply the fidelity approach to study the topological superconductivity in spin–orbit coupling nanowire system. The wire is modeled as a one layer lattice chain with Zeeman energy and spin–orbit coupling, which is in proximity to a multi-layer superconductor. In particular, we study the effects of disorders and find that the fidelity susceptibility has multiple peaks. It is revealed that one peak indicates the topological quantum phase transition, while other peaks are signaling the pinning of the Majorana bound states by disorders. - Highlights: • We introduce fidelity approach to study the topological superconducting nanowire with disorders. • We study the quantum phase transition in the wire. • We investigate the disorder pinning of the Majorana bound states in the wire

  15. Weak coupling theory of high temperature superconductors

    International Nuclear Information System (INIS)

    Labbe, J.

    1990-01-01

    Many theories of the high T c superconductors are founded on the hypothesis that the electron-electron correlations are so strong in these materials that, in the absence of doping or internal charge transfer, they should be Mott insulators. The authors consider this hypothesis as unlikely for the following reasons. At first, very strong correlations would arise from a very large repulsive Coulomb energy between electrons within each atom. This would be the case only with very strongly localized atomic orbitals, as for instance the f orbitals in the rare earths, leading to very narrow energy bands. But in the copper oxides, the d orbitals of copper, or the p orbitals of oxygen, are not so strongly localized, and thus the intra-atomic repulsive Coulomb energy has no reason to be much larger than in the simple transitional metals or their other compounds

  16. Superconductors Enable Lower Cost MRI Systems

    Science.gov (United States)

    2013-01-01

    The future looks bright, light, and green, especially where aircraft are concerned. The division of NASA s Fundamental Aeronautics Program called the Subsonic Fixed Wing Project is aiming to reach new heights by 2025-2035, improving the efficiency and environmental impact of air travel by developing new capabilities for cleaner, quieter, and more fuel efficient aircraft. One of the many ways NASA plans to reach its aviation goals is by combining new aircraft configurations with an advanced turboelectric distributed propulsion (TeDP) system. Jeff Trudell, an engineer at Glenn Research Center, says, "The TeDP system consists of gas turbines generating electricity to power a large number of distributed motor-driven fans embedded into the airframe." The combined effect increases the effective bypass ratio and reduces drag to meet future goals. "While room temperature components may help reduce emissions and noise in a TeDP system, cryogenic superconducting electric motors and generators are essential to reduce fuel burn," says Trudell. Superconductors provide significantly higher current densities and smaller and lighter designs than room temperature equivalents. Superconductors are also able to conduct direct current without resistance (loss of energy) below a critical temperature and applied field. Unfortunately, alternating current (AC) losses represent the major part of the heat load and depend on the frequency of the current and applied field. A refrigeration system is necessary to remove the losses and its weight increases with decreasing temperature. In 2001, a material called magnesium diboride (MgB2) was discovered to be superconducting. The challenge, however, has been learning to manufacture MgB2 inexpensively and in long lengths to wind into large coils while meeting the application requirements.

  17. The role of oxygen in quinternary superconductors.

    Energy Technology Data Exchange (ETDEWEB)

    Beckman, D.R.; Jamieson, D.N. [Melbourne Univ., Parkville, VIC (Australia). School of Physics

    1996-12-31

    The oxygen composition of the new generation of high temperature superconductors (HTSC) has been found to play a crucial role in determining the superconductivity of these materials. However, measurement of the oxygen stoichiometry in such samples has proven difficult due to the small scattering cross section of oxygen, a light element, which has caused the oxygen scattering signal to be overwhelmed by the far larger signals generated off the heavier elements present in the HTSC samples. It is for this reason that previous ion beam analysis of oxide crystals has often either made no attempt to determine the oxygen content or has used O({alpha},{alpha})O resonances such as that at {approx} 3.05 MeV to probe the crystal. This work continues tests of a new technique for probing oxygen which overcomes the problem of an insignificant O BS signal by exploiting the large nuclear resonance found to occur in the O(p,p)O cross-section near an energy of 3.5 MeV in order to produce a significant oxygen edge in the H{sup +} BS spectrum obtained for the HTSC sample. The use of a H{sup +} beam is preferable to a He{sup 2+} beam for such work due to its enhanced sensitivity to light elements. The quinternary superconductor used for this investigation was a good quality pure Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8+x} (BISCO, 2212) crystal. The size of this crystal was 5x5xl mm{sup 3} with the [001] face perpendicular to the surface. Measurements were performed using the University of Melbourne nuclear microprobe. The sample was mounted on an aluminium target holder using a carbon base adhesive which provided good electrical contact and it was oriented inside the target chamber by means of a four axis precision eucentric goniometer. 6 refs., 3 figs.

  18. Engineered flux-pinning centers in BSCCO TBCCO and YBCO superconductors

    Science.gov (United States)

    Goretta, K.C.; Lanagan, M.T.; Miller, D.J.; Sengupta, S.; Parker, J.C.; Hu, J.; Balachandran, U.; Siegel, R.W.; Shi, D.

    1999-07-27

    A method of preparing a high temperature superconductor is disclosed. A method of preparing a superconductor includes providing a powdered high temperature superconductor and a nanophase material. These components are combined to form a solid compacted mass with the material disposed in the polycrystalline high temperature superconductor. This combined mixture is rapidly heated, forming a dispersion of nanophase size particles without a eutectic reaction. These nanophase particles can have a flat plate or columnar type morphology. 4 figs.

  19. Surface impedance of superconductors in wide frequency ranges for wake field calculations

    International Nuclear Information System (INIS)

    Davidovskii, V.G.

    2006-01-01

    The problem of the surface impedance of superconductors in wide frequency ranges for calculations of wake fields, generated by bunches of charged particles moving axially inside a metallic vacuum chambers, is solved. The case of specular electron reflection at the superconductor surface is considered. The expression for the surface impedance of superconductors suitable for numerical computation is derived [ru

  20. Boundary conditions in Ginsburg Landau theory and critical temperature of high-T superconductors

    Science.gov (United States)

    Lykov, A. N.

    2008-06-01

    New mixed boundary conditions to the Ginsburg-Landau equations are found to limit the critical temperature ( T) of high- T superconductors. Moreover, the value of the pseudogap in these superconductors can be explained by using the method. As a result, the macroscopic approach is proposed to increase T of cuprate superconductors.

  1. Boundary conditions in Ginsburg-Landau theory and critical temperature of high-Tc superconductors

    International Nuclear Information System (INIS)

    Lykov, A.N.

    2008-01-01

    New mixed boundary conditions to the Ginsburg-Landau equations are found to limit the critical temperature (T c ) of high-T c superconductors. Moreover, the value of the pseudogap in these superconductors can be explained by using the method. As a result, the macroscopic approach is proposed to increase T c of cuprate superconductors

  2. Zeroth order phase transition in a holographic superconductor with single impurity

    NARCIS (Netherlands)

    Zeng, Hua Bi; Zhang, Hai-Qing

    We investigate the single normal impurity effect in a superconductor by the holographic method. When the size of impurity is much smaller than the host superconductor, we can reproduce the Anderson theorem, which states that a conventional s-wave superconductor is robust to a normal (non-magnetic)

  3. Processing and characterization of ceramic superconductor/polymer composites

    International Nuclear Information System (INIS)

    Kander, R.G.; Namboodri, S.L.

    1993-01-01

    One way to more easily process a brittle high-temperature ceramic superconductor into a useful structure is to combine it with a polymer to form a composite material. Processing of polymer-based composites into complex shapes is well established and relatively easy when compared with traditional ceramic processing unit operations. In addition, incorporating a ceramic superconductor into a polymer matrix can improve mechanical performance as compared with a monolithic ceramic. Finally, because ceramic superconductors are susceptible to attack by moisture, a polymer-based composite structure can also provide protection from deleterious environmental effects. This paper focuses on the processing and subsequent characterization of ceramic superconductor/polymer composites designed primarily for electromagnetic shielding and diamagnetic applications. YBa 2 Cu 3 O 7-x [YBCO] ceramic superconductor is combined with poly(methyl methacrylate) [PMMA] to form novel composite structures. Composite structures have been molded with both a discontinuous superconducting phase (i.e., ceramic particulate reinforced polymers) and with a continuous superconducting phase (i.e., polymer infiltrated porous ceramics). Characterization of these composite structures includes the determination of diamagnetic strength, electromagnetic shielding effectiveness, mechanical performance, and environmental resistance. The goal of this program is to produce a composite structure with increased mechanical integrity and environmental resistance at liquid nitrogen temperatures without compromising the electromagnetic shielding and diamagnetic properties of the superconducting phase. Composites structures of this type are potentially useful in numerous magnetic applications including electromagnetic shielding, magnetic sensors, energy storage, magnetic levitation, and motor windings

  4. Superconductor digital electronics: Scalability and energy efficiency issues (Review Article)

    Science.gov (United States)

    Tolpygo, Sergey K.

    2016-05-01

    Superconductor digital electronics using Josephson junctions as ultrafast switches and magnetic-flux encoding of information was proposed over 30 years ago as a sub-terahertz clock frequency alternative to semiconductor electronics based on complementary metal-oxide-semiconductor (CMOS) transistors. Recently, interest in developing superconductor electronics has been renewed due to a search for energy saving solutions in applications related to high-performance computing. The current state of superconductor electronics and fabrication processes are reviewed in order to evaluate whether this electronics is scalable to a very large scale integration (VLSI) required to achieve computation complexities comparable to CMOS processors. A fully planarized process at MIT Lincoln Laboratory, perhaps the most advanced process developed so far for superconductor electronics, is used as an example. The process has nine superconducting layers: eight Nb wiring layers with the minimum feature size of 350 nm, and a thin superconducting layer for making compact high-kinetic-inductance bias inductors. All circuit layers are fully planarized using chemical mechanical planarization (CMP) of SiO2 interlayer dielectric. The physical limitations imposed on the circuit density by Josephson junctions, circuit inductors, shunt and bias resistors, etc., are discussed. Energy dissipation in superconducting circuits is also reviewed in order to estimate whether this technology, which requires cryogenic refrigeration, can be energy efficient. Fabrication process development required for increasing the density of superconductor digital circuits by a factor of ten and achieving densities above 107 Josephson junctions per cm2 is described.

  5. The Berezinskii-Kosterlitz-Thouless Transition in Superconductors

    Science.gov (United States)

    Goldman, A. M.

    2013-06-01

    The Berezinskii-Kosterlitz-Thouless (BKT) transition occurs in thin superconducting films and Josephson junction arrays in a manner closely analogous to what is found for superfluid helium films. Initially it was believed that a BKT thermodynamic instability in which vortex'antivortex pairs, bound at low temperatures dissociate into free vortices at a characteristic temperature, would not occur in superconductors. The reason for this was that the vortex'antivortex interaction potential in bulk superconductors falls off as 1/r, and the requirement for a BKT transition is that the interaction potential between vortex-antivortex pairs be a logarithmic function of their separation. Once it was realized that a logarithmic vortex-antivortex interaction occurs in thin films to a characteristic distance that can be macroscopic, systematic experiments were carried out on such systems establishing the existence of such a transition. In this chapter, we review the elementary theory of the BKT transition in superconductors along with the earliest experimental results leading to the establishment of its existence in thin films and Josephson junction arrays. At the present time, the BKT paradigm plays a central role in the understanding of thin film superconductors, Josephson junction arrays, and complex compounds which have weakly coupled layers, such as many of the high temperature superconductors. The limitations of space preclude a discussion of many issues that are of contemporary interest...

  6. Generic Theory for Majorana Zero Modes in 2D Superconductors

    Science.gov (United States)

    Chan, Cheung; Zhang, Lin; Poon, Ting Fung Jeffrey; He, Ying-Ping; Wang, Yan-Qi; Liu, Xiong-Jun

    2017-07-01

    It is well known that non-Abelian Majorana zero modes (MZM) are located at vortex cores in a px+𝒾 py topological superconductor, which can be realized in a 2D spin-orbit coupled system with a single Fermi surface and by proximity coupling to an s -wave superconductor. Here we show that the existence of non-Abelian MZMs is unrelated to the bulk topology of a 2D superconductor, and propose that such exotic modes can result in a much broader range of superconductors, being topological or trivial. For a generic 2D system with multiple Fermi surfaces that is gapped out by superconducting pairings, we show that at least a single MZM survives if there are only an odd number of Fermi surfaces of which the corresponding superconducting orders have vortices; such a MZM is protected by an emergent Chern-Simons invariant, irrespective of the bulk topology of the superconductor. This result enriches new experimental schemes for realizing non-Abelian MZMs. In particular, we propose a minimal scheme to realize the MZMs in a 2D superconducting Dirac semimetal with trivial bulk topology, which can be well achieved based on recent cold-atom experiments.

  7. Low-Tc ramp-type superconductor-insulator-superconductor Josephson junctions

    International Nuclear Information System (INIS)

    Podt, M; Flokstra, J; Rogalla, H

    2003-01-01

    Superconductor-insulator-superconductor Josephson junctions with an area smaller than 1 μm 2 are increasingly used for many applications because of their low capacitances and short switching times. The characteristics of analogue and digital SQUIDs, for example, can be improved using small-area Josephson junctions. We have developed Nb/Al, AlO x /Al/Nb junctions based on an edge geometry. These low-T c ramp-type junctions allow sub-μm 2 junction areas using micrometre resolution photolithography. The experimental I-V characteristics of the ramp-type junctions showed non-hysteretic behaviour. Using these ramp-type junctions, the first series of dc SQUIDs have been successfully developed. The characteristics of the ramp-type junctions and the dc SQUIDs have been investigated both experimentally and by using numerical simulations. The white flux noise level of a dc SQUID based on ramp-type junctions with an area of 0.2 μm x 12 μm was measured to be √S φ = 1.2μΦ 0 Hz -1/2

  8. Vortex jamming in superconductors and granular rheology

    International Nuclear Information System (INIS)

    Yoshino, Hajime; Nogawa, Tomoaki; Kim, Bongsoo

    2009-01-01

    We demonstrate that a highly frustrated anisotropic Josephson junction array (JJA) on a square lattice exhibits a zero-temperature jamming transition, which shares much in common with those in granular systems. Anisotropy of the Josephson couplings along the horizontal and vertical directions plays roles similar to normal load or density in granular systems. We studied numerically static and dynamic response of the system against shear, i.e. injection of external electric current at zero temperature. Current-voltage curves at various strength of the anisotropy exhibit universal scaling features around the jamming point much as do the flow curves in granular rheology, shear-stress versus shear-rate. It turns out that at zero temperature the jamming transition occurs right at the isotropic coupling and anisotropic JJA behaves as exotic fragile vortex matter: it behaves as a superconductor (vortex glass) in one direction, whereas it is a normal conductor (vortex liquid) in the other direction even at zero temperature. Furthermore, we find a variant of the theoretical model for the anisotropic JJA quantitatively reproduces universal master flow-curves of the granular systems. Our results suggest an unexpected common paradigm stretching over seemingly unrelated fields-the rheology of soft materials and superconductivity.

  9. Optical properties of high-Tc superconductors

    International Nuclear Information System (INIS)

    Aspnes, D.E.; Kelly, M.K.

    1989-01-01

    The authors summarize the present status of optical spectroscopy of high-T c superconductors. The optical properties of these materials resemble those of the more common transition metal oxides except for being highly anisotropic in the infrared (IR). This large IR anisotrophy and a need to rely solely on reflectance techniques has hindered progress in obtaining accurate IR data and interpreting these data in terms of microscopic mechanisms. However, experimental consistency is now being approached with single-crystal samples, although interpretations of these data remain controversial and an unequivocal demonstration of a superconducting gap structure has not yet been achieved. The mid IR exhibits an absorption band whose systematics are neither well established nor understood. The situation in the visible-near-ultraviolet (V-NUV) is better, partly because of greatly reduced optical anisotropy and the availability of alternative measurement techniques that are not strongly affected by the lower optical quality of sintered material. As polycrystalline, sintered samples can be prepared relatively easily over wide ranges of composition, doping, and chemical substitution, most work on studying the chemical systematics of these materials has been done in this spectral range and some of the structure that appears here has been positively identified

  10. Proximity coupling in superconductor-graphene heterostructures.

    Science.gov (United States)

    Lee, Gil-Ho; Lee, Hu-Jong

    2018-02-16

    This review discusses the electronic properties and the prospective research directions of superconductor-graphene heterostructures. The basic electronic properties of graphene are introduced to highlight the unique possibility of combining two seemingly unrelated physics, superconductivity and relativity. We then focus on graphene-based Josephson junctions, one of the most versatile superconducting quantum devices. The various theoretical methods that have been developed to describe graphene Josephson junctions are examined, together with their advantages and limitations, followed by a discussion on the advances in device fabrication and the relevant length scales. The phase-sensitive properties and phase-particle dynamics of graphene Josephson junctions are examined to provide an understanding of the underlying mechanisms of Josephson coupling via graphene. Thereafter, microscopic transport of correlated quasiparticles produced by Andreev reflections at superconducting interfaces and their phase-coherent behaviors are discussed. Quantum phase transitions studied with graphene as an electrostatically tunable 2D platform are reviewed. The interplay between proximity-induced superconductivity and the quantum-Hall phase is discussed as a possible route to study topological superconductivity and non-Abelian physics. Finally, a brief summary on the prospective future research directions is given.

  11. Topological transitions in multi-band superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Continentino, Mucio A., E-mail: mucio@cbpf.br [Centro Brasileiro de Pesquisas Físicas, Rua Dr. Xavier Sigaud, 150, Urca 22290-180, Rio de Janeiro, RJ (Brazil); Deus, Fernanda, E-mail: fernanda@cbpf.br [Centro Brasileiro de Pesquisas Físicas, Rua Dr. Xavier Sigaud, 150, Urca 22290-180, Rio de Janeiro, RJ (Brazil); Padilha, Igor T., E-mail: igorfis@ufam.edu.br [Universidade Federal do Amazonas, Campus Capital, 69077-070, Manaus, AM (Brazil); Caldas, Heron, E-mail: hcaldas@ufsj.edu.br [Departamento de Ciências Naturais, Universidade Federal de São João Del Rei, 36301-000, São João Del Rei, MG (Brazil)

    2014-09-15

    The search for Majorana fermions has been concentrated in topological insulators or superconductors. In general, the existence of these modes requires the presence of spin–orbit interactions and of an external magnetic field. The former implies in having systems with broken inversion symmetry, while the latter breaks time reversal invariance. In a recent paper, we have shown that a two-band metal with an attractive inter-band interaction has non-trivial superconducting properties, if the k-dependent hybridization is anti-symmetric in the wave-vector. This is the case, if the crystalline potential mixes states with different parities as for orbitals with angular momentum l and l+1. In this paper we take into account the effect of an external magnetic field, not considered in the previous investigation, in a two-band metal and show how it modifies the topological properties of its superconducting state. We also discuss the conditions for the appearance of Majorana fermions in this system.

  12. Patents - Superconductor materials, processes and devices

    International Nuclear Information System (INIS)

    Test, A.

    1987-01-01

    A patent is a grant by a country to an inventor or his assignee of the right to exclude others for a limited period of time from making, using or selling the patented invention within its territory. It is reported that basic patents have been filed by IBM and the University of Houston to protect a broad range of warm superconducting materials or compounds. It is believed that other researchers are seeking patents to protect related or improved materials, processes and apparatus. Because of the importance of this field and to speed up the patent process, the United States Patent Office is giving, upon request, special expedited status to these patent applications. A survey of Japanese companies shows that more than 1500 patents have been applied for in Japan relating to superconducting materials, compositions, apparatus using superconductors and improvements. It appears that the goal of the Japanese companies is to obtain a patent position in Japan so that they can trade with companies wishing to do business in Japan for rights in other parts of the world

  13. Growth and characterization of bulk superconductor material

    CERN Document Server

    Chen, Dapeng; Maljuk, Andrey; Zhou, Fang

    2016-01-01

    This book focuses on recently developed crystal growth techniques to grow large and high quality superconducting single crystals. The techniques applied are traveling solvent floating zone (TSFZ) with infrared image furnace, Bridgeman, solution/flux and top seeded solution growth (TSSG) methods. The materials range from cuprates, cobaltates to pnictides including La2CuO4-based (LCO), YBa2Cu3O7-d (YBCO), Bi2Sr2Can−1CunO2n+4+δ (n=1,2,3) (BSCCO) to NaxCoO2. The modified Bridgman “cold finger” method is devoted to the pnictide system with the best quality (transition width DTc~0.5 K) with highest Tc~38.5 K of Ba0.68K0.32Fe2A2. The book presents various iron-based superconductors with different structures, such as 1111, 122, 111, 11 and 42622,10-3-8. Detailed single crystal growth methods (fluxes, Bridgman, floating zone), the associated procedures and their impact to crystal size and quality are presented. The book also describes the influence of doping on the structure and the electric, magnetic, and supe...

  14. High temperature superconductors at optimal doping

    Directory of Open Access Journals (Sweden)

    W. E. Pickett

    2006-09-01

    Full Text Available   Intensive study of the high temperature superconductors has been ongoing for two decades. A great deal of this effort has been devoted to the underdoped regime, where the new and difficult physics of the doped Mott insulator has met extra complications including bilayer coupling/splitting, shadow bands, and hot spots. While these complications continue to unfold, in this short overview the focus is moved to the region of actual high-Tc, that of optimal doping. The focus here also is not on the superconducting state itself, but primarily on the characteristics of the normal state from which the superconducting instability arises, and even these can be given only a broad-brush description. A reminder is given of two issues,(i why the “optimal Tc” varies,for n-layered systems it increases for n up to 3, then decreases for a given n, Tc increases according to the ‘basis’ atom in the order Bi, Tl, Hg (ii how does pressure, or a particular uniaxial strain, increase Tc when the zero-strain system is already optimally doped?

  15. Proximity coupling in superconductor-graphene heterostructures

    Science.gov (United States)

    Lee, Gil-Ho; Lee, Hu-Jong

    2018-05-01

    This review discusses the electronic properties and the prospective research directions of superconductor-graphene heterostructures. The basic electronic properties of graphene are introduced to highlight the unique possibility of combining two seemingly unrelated physics, superconductivity and relativity. We then focus on graphene-based Josephson junctions, one of the most versatile superconducting quantum devices. The various theoretical methods that have been developed to describe graphene Josephson junctions are examined, together with their advantages and limitations, followed by a discussion on the advances in device fabrication and the relevant length scales. The phase-sensitive properties and phase-particle dynamics of graphene Josephson junctions are examined to provide an understanding of the underlying mechanisms of Josephson coupling via graphene. Thereafter, microscopic transport of correlated quasiparticles produced by Andreev reflections at superconducting interfaces and their phase-coherent behaviors are discussed. Quantum phase transitions studied with graphene as an electrostatically tunable 2D platform are reviewed. The interplay between proximity-induced superconductivity and the quantum-Hall phase is discussed as a possible route to study topological superconductivity and non-Abelian physics. Finally, a brief summary on the prospective future research directions is given.

  16. Studies of anisotropy of iron based superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Murphy, Jason A. [Iowa State Univ., Ames, IA (United States)

    2013-01-01

    To study the electronic anisotropy in iron based superconductors, the temperature dependent London penetration depth, Δλ(T), have been measured in several compounds, along with the angular dependent upper critical field, Hc2(T). Study was undertaken on single crystals of Ba(Fe1-xCox)2As2 with x=0.108 and x=0.127, in the overdoped range of the doping phase diagram, characterized by notable modulation of the superconducting gap. Heavy ion irradiation with matching field doses of 6 T and 6.5 T respectively, were used to create columnar defects and to study their effect on the temperature Δλ(T). The variation of the low-temperature penetration depth in both pristine and irradiated samples was fitted with a power-law function Δλ(T) = ATn. Irradiation increases the magnitude of the pre-factor A and decreases the exponent n, similar to the effect on the optimally doped samples. This finding supports the universal s ± scenario for the whole doping range.

  17. Electronic properties of high Tc superconductors

    International Nuclear Information System (INIS)

    Rojo, A.G.

    1989-01-01

    Using analytical and numerical methods, the electronic properties of the copper-oxygen plane in the normal phase of high Tc superconductors are described. Using the slave-boson technique in the saddle point, a theory of the metal insulator transition which generalizes the notions of a Mott insulator to the case of more than a single band for those planes is presented. A phase-diagram is obtained in the parameter space and effective masses, optical gaps and metallization are calculated as a function of the number of carriers. Based on the experimental evidence, the theory permits classification of superconducting compounds as charge transfer insulators in the stoichiometric case. The insulator state is characterized by a non-zero optical gap and a divergent effective mass which corresponds to the breakage of a Fermi-liquid scheme. The results obtained are applicable to metal-transition-oxides whose behaviour has been traditionally controversial and it is concluded that it is necessary to broaden the meaning of a Mott insulator to the case of more than a single band to better understand them. Based on the ideas of group renormalization in a real space, a lattice approximation is presented, which allows: a) To complement the treatment of slave-bosons in phase diagrams and optical gaps; b) Identification of an attraction mechanism between carriers originating from purely repulsive interactions. Numerical calculations in small clusters show the existence of a pairing mechanism showing a superconducting instability from a charge transfer insulator. (Author) [es

  18. Terahertz Generation & Vortex Motion Control in Superconductors

    Science.gov (United States)

    Nori, Franco

    2005-03-01

    A grand challenge is to controllably generate electromagnetic waves in layered superconducting compounds because of its Terahertz frequency range. We propose [1] four experimentally realizable devices for generating continuous and pulsed THz radiation in a controllable frequency range. We also describe [2-4] several novel devices for controlling the motion of vortices in superconductors, including a reversible rectifier made of a magnetic-superconducting hybrid structure [4]. Finally, we summarize a study [5] of the friction force felt by moving vortices. 1) S. Savel'ev, V. Yampol'skii, A. Rakhmanov, F. Nori, Tunable Terahertz radiation from Josephson vortices, preprint 2) S. Savel'ev and F. Nori, Experimentally realizable devices for controlling the motion of magnetic flux quanta, Nature Mat. 1, 179 (2002) 3) S. Savel'ev, F. Marchesoni, F. Nori, Manipulating small particles, PRL 92, 160602 (2004); B. Zhu, F. Marchesoni, F. Nori, Controlling the motion of magnetic flux quanta, PRL 92, 180602 (2004) 4) J.E. Villegas, et al., Reversible Rectifier that Controls the Motion of Magnetic Flux Quanta, Science 302, 1188 (2003) 5) A. Maeda, et al., Nano-scale friction: kinetic friction of magnetic flux quanta and charge density waves, preprint

  19. Holographic superconductor on a novel insulator

    Science.gov (United States)

    Ling, Yi; Liu, Peng; Wu, Jian-Pin; Wu, Meng-He

    2018-01-01

    We construct a holographic superconductor model, based on a gravity theory, which exhibits novel metal-insulator transitions. We investigate the condition for the condensation of the scalar field over the parameter space, and then focus on the superconductivity over the insulating phase with a hard gap, which is supposed to be Mott-like. It turns out that the formation of the hard gap in the insulating phase benefits the superconductivity. This phenomenon is analogous to the fact that the pseudogap phase can promote the pre-pairing of electrons in high {T}{{c}} cuprates. We expect that this work can shed light on understanding the mechanism of high {T}{{c}} superconductivity from the holographic side. Supported by Natural Science Foundation of China (11575195, 11775036, 11305018), Y.L. also acknowledges the support from Jiangxi young scientists (JingGang Star) program and 555 talent project of Jiangxi Province. J. P. Wu is also supported by Natural Science Foundation of Liaoning Province (201602013)

  20. Possible degradation mechanism of BSCCO superconductors

    International Nuclear Information System (INIS)

    Gogia, B.; Kashyap, S.C.; Pandya, D.K.; Chopra, K.L.

    1993-01-01

    A detailed study of the effect of ambient and humid atmosphere on the stability and physical properties of single and multiphasic samples of a BSCCO superconductor has been carried out. It has been observed that, on exposure to atmosphere for a period of one year, the single-phase samples 2223 or 2212 did not show any phase decomposition. However, a decrease in T c was observed in these samples. Mixed-phase samples showed the partial conversion of the 2223 phase into the 2212 phase on the surface with a corresponding decrease in T c , depending upon the initial amount of added Pb. X-ray photoelectron spectroscopy analysis of the multiphase, leaded samples showed the decrease in the ratio of Cu 2+ /Cu 1+ as well as the formation of various surface carbonates responsible for the degradation in the superconducting parameters. In a humid atmosphere, a single-phase 2223 sample did not show any decomposition whereas single-phase 2212 or mixed-phase samples showed partial degradation to Bi 2 CuO 4 , SrCO 3 , CaCO 3 and CuO as evidenced by X-ray diffraction and EDX analysis. Based on these observations a possible degradation mechanism has been proposed and the role of Pb has been discussed. (author)

  1. Magnetic memory effects in high temperature superconductors

    International Nuclear Information System (INIS)

    Rockenbauer, A.

    1989-01-01

    Microwave absorption of high temperature oxide superconductors MBa 2 Cu 3 O 7 (M = Y, Er, Dy, Ho, Lu, Tm, Gd) at 77 K have been studied by ESR. In granular samples diamagnetic zero-field resonance and strong ESR baseline hysteresis have been observed: for increasing field sweep - a high, for decreasing one - a low, while in constant field the baseline approaches the middle position with kinetics typical of spin-glasses. The hysteresis amplitude, i.e. the deviation of high and low baselines, possesses maximum at zero field if the sample is cooled down in zero field. In case of field cooling both the diamagnetic resonance and hysteresis maximum are shifted as a function of relative direction of the fields where the samples are cooled and measured, respectively. The shift is caused by the remanent diamagnetism of trapped fluxons. The hysteresis critically depends on the modulation amplitude of magnetic field, and no hysteresis can be observed if the microwave absorption is detected without field modulation. By applying saw-tooth sweep the spin-glass can be driven between two extreme hysteresis states, and the ESR response is rectangular for large saw-tooth amplitude and linear - for small one, while for intermediate amplitudes the recording shows characteristic memory effects. The hysteresis memory is explained in terms of loop distribution of fluxons. In the single crystal the fluxon absorptions are also detected and the separation of fluxon lines can be related to the hysteresis in granular samples. (author)

  2. EDITORIAL: Focus on Iron-Based Superconductors FOCUS ON IRON-BASED SUPERCONDUCTORS

    Science.gov (United States)

    Hosono, Hideo; Ren, Zhi-An

    2009-02-01

    Superconductivity is the most dramatic and clear cut phenomenon in condensed matter physics. Realization of room temperature superconductors, which would lead to the revolution of our society, is an ultimate goal for researchers. The discovery of high Tc cuprate superconductors in 1986 by Bednorz and Müller triggered intensive research worldwide and the maximum critical temperature has been raised above 100 K. Scientific research on this break-through material clarified a new route to high Tc materials, carrier doping to a Mott insulator with anti-ferromagnetic ordering. High superconductivity occurs in the neighborhood of Mott-insulators and Fermi-metals. Such a view, which was completely new, now stands as a guiding principle for exploring new high Tc materials. Many theoretical approaches to the mechanism for cuprate superconductors have been carried out to understand this unexpected material and to predict new high Tc materials. In 2006 a new superconductor based on iron, LaFeOP, was discovered by a group at Tokyo Institute of Technology, Japan. Iron, as a ferromagnet, was believed to be the last element for the realization of superconductivity because of the way ferromagnetism competes against Cooper pair formation. Unexpectedly, however, the critical temperature remained at 4-6 K irrespective of hole/electron-doping. A large increase in the Tc to 26 K was then found in LaFe[O1-xFx]As by the same group (and was published on 23 February 2008, in the Journal of the American Chemical Society). The Tc of this material was further raised to 43 K under a pressure of 2 GPa and scientists in China then achieved a Tc of 56 K at ambient pressure by replacing La with other rare earth ions with smaller radius—a critical temperature that is second only to the high Tc cuprates. This fast progress has revitalized research within superconductivity and in 2008 there were more than seven international symposia specifically on Fe(Ni)-based superconductors. Through the rapid

  3. Cryogenic recovery analysis of forced flow supercritical helium cooled superconductors

    International Nuclear Information System (INIS)

    Lee, A.Y.

    1977-08-01

    A coupled heat conduction and fluid flow method of solution was presented for cryogenic stability analysis of cabled composite superconductors of large scale magnetic coils. The coils are cooled by forced flow supercritical helium in parallel flow channels. The coolant flow reduction in one of the channels during the spontaneous recovery transient, after the conductor undergoes a transition from superconducting to resistive, necessitates a parallel channel analysis. A way to simulate the parallel channel analysis is described to calculate the initial channel inlet flow rate required for recovery after a given amount of heat is deposited. The recovery capability of a NbTi plus copper composite superconductor design is analyzed and the results presented. If the hydraulics of the coolant flow is neglected in the recovery analysis, the recovery capability of the superconductor will be over-predicted

  4. Probing High Temperature Superconductors with Magnetometry in Ultrahigh Magnetic Fields

    Energy Technology Data Exchange (ETDEWEB)

    Li, Lu [Univ. of Michigan, Ann Arbor, MI (United States)

    2017-07-26

    The objective of this research is to investigate the high-field magnetic properties of high temperature superconductors, materials that conduct electricity without loss. A technique known as high-resolution torque magnetometry that was developed to directly measure the magnetization of high temperature superconductors. This technique was implemented using the 65 Tesla pulsed magnetic field facility that is part of the National High Magnetic Field Laboratory at Los Alamos National Laboratory. This research addressed unanswered questions about the interplay between magnetism and superconductivity, determine the electronic structure of high temperature superconductors, and shed light on the mechanism of high temperature superconductivity and on potential applications of these materials in areas such as energy generation and power transmission. Further applications of the technology resolve the novel physical phenomena such as correlated topological insulators, and spin liquid state in quantum magnets.

  5. Workshop on Accelerator Magnet Superconductors, Design and Optimization

    CERN Document Server

    WAMSDO Workshop

    2009-01-01

    This report contains the proceedings of the CARE-HHH-AMT Workshop on Accelerator Magnet Superconductors, Design and Optimization (WAMSDO) held at CERN from 19 to 23 May 2008. The needs in terms of superconducting magnets for the accelerator projects were discussed, mainly for the LHC interaction regions and injector upgrades, and for the GSI FAIR complex. The first part of the workshop focused on the development of superconductor and cables, i.e., low-loss Nb-Ti cables, Nb$_{3}$Sn and high-temperature superconductors. An industry session summarized the actual plans and status of the activities in the main European industries. Then, a worldwide status of the high field magnets programme was presented. A special session was devoted to fast cycled magnets, including FAIR facilities and LHC injector upgrades. A final session focused on the optimization methods and numerical tools for magnet design.

  6. Possible Measurable Effects of Dark Energy in Rotating Superconductors

    Directory of Open Access Journals (Sweden)

    Clovis Jacinto de Matos

    2009-01-01

    Full Text Available We discuss recent laboratory experiments with rotating superconductors and show that three so far unexplained experimentally observed effects (anomalous acceleration signals, anomalous gyroscope signals, Cooper pair mass excess can be physically explained in terms of a possible interaction of dark energy with Cooper pairs. Our approach is based on a Ginzburg-Landau-like model of electromagnetic dark energy, where gravitationally active photons obtain mass in the superconductor. We show that this model can account simultaneously for the anomalous acceleration and anomalous gravitomagnetic fields around rotating superconductors measured by Tajmar et al. and for the anomalous Cooper pair mass in superconductive Niobium, measured by Cabrera and Tate. It is argued that these three different physical effects are ultimately different experimental manifestations of the simultaneous spontaneous breaking of gauge invariance and of the principle of general covariance in superconductive materials.

  7. TECHNICAL TRAINING SEMINAR: High Temperature Superconductors: Progress and Issues

    CERN Multimedia

    Davide Vitè

    2002-01-01

    Monday 24 June from 14:30 to 15:30 - Training Centre Auditorium - bldg. 593-11 High Temperature Superconductors: Progress and Issues Prof. Jan Evetts / UNIVERSITY OF CAMBRIDGE, Department of Materials Science and Metallurgy, UK Grappling with grain boundaries: Current transport processes in granular High Temperature Superconductors (HTS) The development of High Temperature Superconductors, seen from a materials scientist's point of view, is relevant to the superconductivity community at CERN: their possible high current applications can include high performance magnets for future accelerators. There is an urgent need to develop a quantitative description of HTS conductors in terms of their complex anisotropy, inhomogeneity and dimensionality. This is essential both for the practical specification of a conductor and for charting routes to conductor optimisation. The critical current, the n-value, dissipation and quenching characteristics are amongst most important parameters that make up an engineering specifi...

  8. Holographic entanglement entropy in general holographic superconductor models

    Energy Technology Data Exchange (ETDEWEB)

    Peng, Yan [School of Mathematics and Computer Science, Shaanxi University of Technology,Hanzhong, Shaanxi 723000 (China); Pan, Qiyuan [Institute of Physics and Department of Physics, Hunan Normal University,Changsha, Hunan 410081 (China)

    2014-06-03

    We study the entanglement entropy of general holographic dual models both in AdS soliton and AdS black hole backgrounds with full backreaction. We find that the entanglement entropy is a good probe to explore the properties of the holographic superconductors and provides richer physics in the phase transition. We obtain the effects of the scalar mass, model parameter and backreaction on the entropy, and argue that the jump of the entanglement entropy may be a quite general feature for the first order phase transition. In strong contrast to the insulator/superconductor system, we note that the backreaction coupled with the scalar mass can not be used to trigger the first order phase transition if the model parameter is below its bottom bound in the metal/superconductor system.

  9. Microwave impedance of epitaxial high-temperature superconductor films

    International Nuclear Information System (INIS)

    Melkov, G.A.; Malyshev, V.Yu.; Bagada, A.V.

    1995-01-01

    In the 3 cm band dependences of the epitaxial HTS film surface resistance on the magnitude of ac and dc magnetic fields have been measured. YBa 2 Cu 3 O 7-σ films on sapphire were investigated. It was established that alternating magnetic field produces a stronger impact on the surface resistance than dc field. To explain experimental results the assumption is made that a HTS film is not an ideal superconductor and consists of series-connected sections of various types: sections of an ideal superconductor, sections of low and large resistance intragranular Josephson junctions, shunted by the ideal superconductor, and finally, sections of intergranular Josephson junctions few for epitaxial films. In these conditions the dependences of the surface resistance on dc magnetic field are caused by Abrikosov's vortices moving in ideal superconductive sections, and dependences on the amplitude of ac magnetic field are caused by switching of large resistance junctions to a low resistance state

  10. Gapless Fermi Surfaces in anisotropic multiband superconductors in magnetic field.

    Science.gov (United States)

    Barzykin, Victor; Gor'kov, Lev P.

    2007-03-01

    We propose that a new state with a fully gapless Fermi surface appears in quasi-2D multiband superconductors in magnetic field applied parallel to the plane. It is characterized by a paramagnetic moment caused by a finite density of states on the open Fermi surface. We calculate thermodynamic and magnetic properties of the gapless state for both s-wave and d-wave cases, and discuss the details of the 1-st order metamagnetic phase transition that accompanies the appearance of the new phase in s-wave superconductors. We suggest possible experiments to detect this state both in the s-wave (2-H NbSe2) and d-wave (CeCoIn5) superconductors.

  11. The Born-Mayer-Huggins potential in high temperature superconductors

    Science.gov (United States)

    Singh, Hempal; Singh, Anu; Indu, B. D.

    2016-07-01

    The Born-Mayer-Huggins potential which has been found the best suitable potential to study the YBa2Cu3O7-δ type high temperature superconductors is revisited in a new framework. A deeper insight in it reveals that the Born-Mayer parameters for different interactions in high temperature superconductor are not simple quantities but several thermodynamic and spatial functions enter the problem. Based on the new theory, the expressions for pressure, bulk modulus and Born-Mayer parameters have been derived and it is established that these quantities depend upon Gruneisen parameter which is the measure of the strength of anharmonic effects in high temperature superconductors. This theory has been applied to a specific model YBa2Cu3O7-δ crystal for the purpose of numerical estimates to justify the new results.

  12. Calculation and analysis of thermodynamic relations for superconductors

    International Nuclear Information System (INIS)

    Nazarenko, A.B.

    1989-01-01

    The absorption coefficients of high-frequency and low-frequency sound have been calculated on the basis of the Ginzburg-Landau theory. This sound is a wave of periodic adiabatic bulk compressions and rarefactions of the frequency ω in an isotropic superconductor near the transition temperature. Thermodynamic relations have been obtained for abrupt changes in the physical quantities produced as a result of a transition from the normal state to the superconducting state. These relations are similar to the Ehrenfest relations. The above--mentioned thermodynamic quantities are compared with the published experimental results on YBa 2 Cu 3 O 7-δ . The experiments on the absorption of ultrasound in recently discovered superconductors mainformation on the phase transition type and thermodynamic relations for these superconductors, in particular, the T c -vs-dp curve. Similar calculations have been carried out for 2 He-transition experiments with ferromagnetic materials. The order parameter in the thermodynamic potential was assumed to be isotropic

  13. Transport theory for a two-flavor color superconductor

    CERN Document Server

    Litim, Daniel F.; Litim, Daniel F.; Manuel, Cristina

    2001-01-01

    QCD with two light quark flavors at high baryonic density and low temperature is a color superconductor. The diquark condensate partially breaks the SU(3) gauge symmetry down to an SU(2) subgroup. We study thermal fluctuations of the superconductor for temperatures below the gap. These are described by a simple transport equation, linked to a quasiparticle behavior of the thermal excitations of the condensate. When solved in the collisionless limit and close to equilibrium, it gives rise to the ``hard superconducting loop'' (HSL) effective theory for the unbroken SU(2) gauge fields with momenta much smaller than the gap. This theory describes Debye screening and Landau damping of the gauge fields in the presence of the diquark condensate. We also explain how our effective theory follows to one-loop order from quantum field theory. Our approach provides a convenient starting point for the computation of transport coefficients of the two-flavor color superconductor.

  14. Neutron and Synchrotron X-Ray Scattering Studies of Superconductors

    International Nuclear Information System (INIS)

    Tranquada, J.M.

    2008-01-01

    Superconductors hold the promise for a more stable and efficient electrical grid, but new isotropic, high-temperature superconductors are needed in order to reduce cable manufacturing costs. The effort to understand high-temperature superconductivity, especially in the layered cuprates, provides guidance to the search for new superconductors. Neutron scattering has long provided an important probe of the collective excitations that are involved in the pairing mechanism. For the cuprates, neutron and x-ray diffraction techniques also provide information on competing types of order, such as charge and spin stripes, that appear to be closely connected to the superconductivity. Recently, inelastic x-ray scattering has become competitive for studying phonons and may soon provide valuable information on electronic excitations. Examples of how these techniques contribute to our understanding of superconductivity are presented

  15. Spin injection from a normal metal into a mesoscopic superconductor

    Energy Technology Data Exchange (ETDEWEB)

    Wolf, Michael J.; Kolenda, Stefan [Institut fuer Nanotechnologie, KIT, 76021 Karlsruhe (Germany); Huebler, Florian [Institut fuer Nanotechnologie, KIT, 76021 Karlsruhe (Germany); Center for Functional Nanostructures, KIT, 76131 Karlsruhe (Germany); Institut fuer Festkoerperphysik, KIT, 76021 Karlsruhe (Germany); Loehneysen, Hilbert v. [Center for Functional Nanostructures, KIT, 76131 Karlsruhe (Germany); Institut fuer Festkoerperphysik, KIT, 76021 Karlsruhe (Germany); Physikalisches Institut, KIT, 76128 Karlsruhe (Germany); Beckmann, Detlef [Institut fuer Nanotechnologie, KIT, 76021 Karlsruhe (Germany); Center for Functional Nanostructures, KIT, 76131 Karlsruhe (Germany)

    2013-07-01

    We report on nonlocal transport in superconductor hybrid structures, with ferromagnetic as well as normal-metal tunnel junctions attached to the superconductor. In the presence of a strong Zeeman splitting of the density of states, both charge and spin imbalance is injected into the superconductor. While previous experiments demonstrated spin injection from ferromagnetic electrodes, we show that spin imbalance is also created for normal-metal injector contacts. Using the combination of ferromagnetic and normal-metal detectors allows us to directly discriminate between charge and spin injection, and demonstrate a complete separation of charge and spin imbalance. The relaxation length of the spin imbalance is of the order of several μm and is found to increase with a magnetic field, but is independent of temperature. We further discuss possible relaxation mechanisms for the explanation of the spin relaxation length.

  16. A universal explanation of tunneling conductance in exotic superconductors.

    Science.gov (United States)

    Hong, Jongbae; Abergel, D S L

    2016-08-11

    A longstanding mystery in understanding cuprate superconductors is the inconsistency between the experimental data measured by scanning tunneling spectroscopy (STS) and angle-resolved photoemission spectroscopy (ARPES). In particular, the gap between prominent side peaks observed in STS is much bigger than the superconducting gap observed by ARPES measurements. Here, we reconcile the two experimental techniques by generalising a theory which was previously applied to zero-dimensional mesoscopic Kondo systems to strongly correlated two-dimensional (2D) exotic superconductors. We show that the side peaks observed in tunneling conductance measurements in all these materials have a universal origin: They are formed by coherence-mediated tunneling under bias and do not directly reflect the underlying density of states (DOS) of the sample. We obtain theoretical predictions of the tunneling conductance and the density of states of the sample simultaneously and show that for cuprate and pnictide superconductors, the extracted sample DOS is consistent with the superconducting gap measured by ARPES.

  17. Calculation and analysis of thermodynamical relations for superconductors

    International Nuclear Information System (INIS)

    Nazarenko, A.B.

    1989-01-01

    Absorption of low-frequency and high-frequency sounds, representing a wave of adiabatic periodic volumetric compressions and frequency discharges ω in an isotropic superconductor near transition temperature, are calculated on the basis of the Gizburg-Landau theory. Thermodynamic ratios for sudden changes in thermodynamic values, when transition from normal state to superconducting occurs, analogous Erenfest ratios are obtained. Comparison of the mentioned thermodynamic values with the experimental data given in literature on YBa 2 Cu 3 O 7-δ is carried out. Experiments on ultrasound absorption in new superconductors can give the information about the type of phase transition and thermodynamic ratios for these superconductors, in particular, about dependence of critical temperature on pressure. Similar calculations were carried out for experiments on He2 transition and in ferromagnets. The order parameter in the thermodynamic potential was chosen as isotropic

  18. Prospects for utilization of superconductors in the power industry

    International Nuclear Information System (INIS)

    Chernolepkov, N.A.

    1993-01-01

    Utilization of superconducting technology is greatly influenced by the discovery of the so-called high-temperature superconductors (HTS). The present report considers to what extent there is a need for HTS in up-to-date engineering and how much they are prepared for practical applications. The work on the practical use of superconductors was started about 30 years ago. As a results, two fields of the high-current superconductivity have emerged. The first category is the field in which other alternatives were inconceivable from techno-economic points of view (magnets of thermo-nuclear installations, MHD generators, inductive energy storage systems, etc.). The second category involves areas where superconductors must demonstrate the ability to compete with existing technologies (electrical devices, magnetic separators, etc.). The present overview discusses developments of various low temperature superconducting devices, estimate their potential and evaluates future applications of HTS based on the experience accumulated in the USSR and other countries. (author)

  19. Signature of electron-phonon interaction in high temperature superconductors

    Directory of Open Access Journals (Sweden)

    Vinod Ashokan

    2011-09-01

    Full Text Available The theory of thermal conductivity of high temperature superconductors (HTS based on electron and phonon line width (life times formulation is developed with Quantum dynamical approach of Green's function. The frequency line width is observed as an extremely sensitive quantity in the transport phenomena of HTS as a collection of large number of scattering processes. The role of resonance scattering and electron-phonon interaction processes is found to be most prominent near critical temperature. The theory successfully explains the spectacular behaviour of high Tc superconductors in the vicinity of transition temperature. A successful agreement between theory and experiment has been obtained by analyzing the thermal conductivity data for the sample La1.8Sr0.2CuO4 in the temperature range 0 − 200K. The theory is equally and successfully applicable to all other high Tc superconductors.

  20. Josephson effect in point contacts between 'f-wave' superconductors

    International Nuclear Information System (INIS)

    Mahmoodi, R.; Shevchenko, S.N.; Kolesnichenko, Yu.A

    2002-01-01

    A stationary Josephson effect in point contacts between triplet superconductors is analyzed theoretically for most probable models of the order parameter in UPt 3 and Sr 2 RuO 4 . The consequence of misorientation of crystals in the superconducting banks on this effect is considered. We show that different models for the order parameter lead to quit different current-phase relations. For certain angles of misorientation a boundary between superconductors can generate a spontaneous current parallel to the surface. In a number of cases the state with a zero Josephson current and minimum of the free energy corresponds to a spontaneous phase difference. This phase difference depends on the misorientation angle and may possess any value. We conclude that experimental investigations of the current-phase relations of small junctions can be used for determination of the order parameter symmetry in the superconductors mentioned above

  1. Electromechanical properties of superconductors for DOE/OFE applications. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Ekin, J.W.; Bray, S.L.

    1998-09-01

    In many superconductor applications, especially large magnets, the superconductor is required to perform while under the influence of strong mechanical forces. These forces are commonly due to residual fabrication stress, differential thermal contraction of dissimilar materials, and electromagnetic forces generated within an energized magnet coil. Thorough knowledge of a superconductor`s electrical performance under the influence of these forces (electromechanical properties) is required for successful magnet engineering. This report presents results of research conducted during the period from august 1993 through March 1997 on the electromechanical properties of superconductors for DOE/OFE fusion applications.

  2. Electric field effect in superconductor-ferroelectric structures

    Science.gov (United States)

    Lemanov, V. V.

    1995-01-01

    Electric field effect (the E-effect) in superconductors has been studied since 1960 when Glover and Sherill published their results on a shift of the critical temperature T(sub c) about 0.1 mK in Sn and In thin films under the action Off the field E=300 kV/cm. Stadler was the first to study the effect or spontaneous polarization of ferroelectric substrate on the electric properties of superconductors. He observed that the reversal of polarization of TGS substrate under action of external electric field in Sn-TGS structures induced the T(sub c) shift in Sn about 1.3 mK. Since in this case the effect is determined not by the electric field but by the spontaneous polarization, we may call this effect the P-effect. High-T(sub c) superconductors opened the new possibilities to study the E- and P-effects due to low charge carrier density, as compared to conventional superconductors, and to anomalously small coherence length. Experiments in this field began in many laboratories but a breakthrough was made where a shift in T(sub c) by 50 mK was observed in YBCO thin films. Much higher effects were observed in subsequent studies. The first experiments on the P-effect in high-T(sub c) superconductors were reported elsewhere. In this report we shall give a short description of study on the P-effect in high-T(sub c) superconductors.

  3. 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)

  4. Magneto-Thermal Instabilities in AN Organic Superconductor

    Science.gov (United States)

    Mola, M. M.; Hill, S.; Qualls, J. S.; Brooks, J. S.

    Angle and temperature dependent torque magnetization measurements are reported for the organic superconductor κ-(ET)2Cu(NCS)2, at extremely low temperatures (~ Tc/103). Magneto-thermal instabilities are observed in the form of abrupt magnetization (flux) jumps. We carry out an analysis of the temperature and field orientation dependence of these flux jumps based on accepted models for layered type-II superconductors. Using a simple Bean model, we also find a critical current density of 4 × 108 A/m2 from the remnant magnetization, in agreement with previous measurements.

  5. Aluminum-stabilized Nb/sub 3/Sn superconductor

    Science.gov (United States)

    Scanlan, R.M.

    1984-02-10

    This patent discloses an aluminum-stabilized Nb/sub 3/Sn superconductor and process for producing same, utilizing ultrapure aluminum. Ductile components are co-drawn with aluminum to produce a conductor suitable for winding magnets. After winding, the conductor is heated to convert it to the brittle Nb/sub 3/Sn superconductor phase, using a temperature high enough to perform the transformation but still below the melting point of the aluminum. This results in reaction of substantially all of the niobium, while providing stabilization and react-in-place features which are beneficial in the fabrication of magnets utilizing superconducting materials.

  6. Aluminum-stabilized Nb[sub 3]Sn superconductor

    Science.gov (United States)

    Scanlan, R.M.

    1988-05-10

    Disclosed are an aluminum-stabilized Nb[sub 3]Sn superconductor and process for producing same, utilizing ultrapure aluminum. Ductile components are co-drawn with aluminum to produce a conductor suitable for winding magnets. After winding, the conductor is heated to convert it to the brittle Nb[sub 3]Sn superconductor phase, using a temperature high enough to perform the transformation but still below the melting point of the aluminum. This results in reaction of substantially all of the niobium, while providing stabilization and react-in-place features which are beneficial in the fabrication of magnets utilizing superconducting materials. 4 figs.

  7. New superconductors from granular to high T$_{c}$

    CERN Document Server

    Deutscher, Guy

    2006-01-01

    How new are the high Tc superconductors, as compared to the conventional low Tc ones? In what sense are these oxides different from regular metals in their normal state? How different is the mechanism for high Tc superconductivity from the well-known electron-phonon interaction that explains so well superconductivity in metals and alloys? What are the implications of the new features of the high Tc oxides for their practical applications? This book aims to give some answers to those questions, drawing particularly on similarities between the high Tc oxides and granular superconductors, which also present a maximum of their critical temperature near the metal-insulator transition.

  8. New superconductors from granular to high T$_{c}$

    CERN Document Server

    Deutscher, Guy

    2018-01-01

    How new are the high Tc superconductors, as compared to the conventional low Tc ones? In what sense are these oxides different from regular metals in their normal state? How different is the mechanism for high Tc superconductivity from the well-known electron-phonon interaction that explains so well superconductivity in metals and alloys? What are the implications of the new features of the high Tc oxides for their practical applications? This interesting book aims to provide some answers to those questions, drawing particularly on similarities between the high Tc oxides and granular superconductors, which also present a short coherence length, a small superfluid density and an inhomogeneous structure.

  9. Effect of disorder on S-wave superconductors

    International Nuclear Information System (INIS)

    Ghosal, Amit; Randeria, Mohit; Trivedi, Nandini

    1997-01-01

    Experiment on conventional s-wave superconducting thin films have found a strong suppression of T c , with a subsequent transition from a superconductor (SC) to an insulator (I) with increasing disorder. Anderson proposed that even in the presence of disorder the Cooper pairs can be formed by pairing the time-reversed exact eigenstates of the non interacting disordered problem. Hence he argued that T c and the thermodynamic properties should be unaffected by disorder (Anderson's theorem). This is however valid for extremely small disorder. The aim here is to calculate the properties of a superconductor at high disorder, close to the SC-I transition

  10. Electron correlation effects on magnetism in superconductors without inversion symmetry

    International Nuclear Information System (INIS)

    Fujimoto, Satoshi

    2007-01-01

    We investigate magnetic properties of superconductors without inversion symmetry with particular emphasis on the role played by electron correlation effects. It is found that the strong electron correlation seriously affects the temperature dependence of the spin susceptibility which consists of the Pauli term and the van-Vleck-like term, of which the existence is due to parity violating spin-orbit interaction. The implication of the results for the recent NMR measurement of the heavy fermion superconductor CePt 3 Si, which indicates the unchanged Knight shift below T c for any directions of a magnetic field, is presented

  11. Entanglement entropy and complexity for one-dimensional holographic superconductors

    Directory of Open Access Journals (Sweden)

    Mahdi Kord Zangeneh

    2017-08-01

    Full Text Available Holographic superconductor is an important arena for holography, as it allows concrete calculations to further understand the dictionary between bulk physics and boundary physics. An important quantity of recent interest is the holographic complexity. Conflicting claims had been made in the literature concerning the behavior of holographic complexity during phase transition. We clarify this issue by performing a numerical study on one-dimensional holographic superconductor. Our investigation shows that holographic complexity does not behave in the same way as holographic entanglement entropy. Nevertheless, the universal terms of both quantities are finite and reflect the phase transition at the same critical temperature.

  12. Survey of potential electronic applications of high temperature superconductors

    International Nuclear Information System (INIS)

    Hammond, R.B.; Bourne, L.C.

    1991-01-01

    In this paper the authors present a survey of the potential electronic applications of high temperature superconductor (HTSC) thin films. During the past four years there has been substantial speculation on this topic. The authors will cover only a small fraction of the potential electronic applications that have been identified. Their treatment is influenced by the developments over the past few years in materials and device development and in market analysis. They present their view of the most promising potential applications. Superconductors have two important properties that make them attractive for electronic applications. These are (a) low surface resistance at high frequencies, and (b) the Josephson effect

  13. Isotope effect in impure high T_c superconductors

    OpenAIRE

    Mierzynska, M.; Wysokinski, K. I.

    2003-01-01

    The influence of various kinds of impurities on the isotope shift exponent \\alpha of high temperature superconductors has been studied. In these materials the dopant impurities, like Sr in La_{2-x}Sr_xCuO_4, play different role and usually occupy different sites than impurities like Zn, Fe, Ni {\\it etc} intentionally introduced into the system to study its superconducting properties. In the paper the in-plane and out-of-plane impurities present in layered superconductors have been considered....

  14. Broad-Based Search for New and Practical Superconductors

    Science.gov (United States)

    2014-10-31

    which are potentially superconductors. In particular, we are exploring BaSnO3 as the base system to look for new superconductors. Doped BaSnO3 is a...doped (A- site and B-site) BaSnO3 composition spreads. Figure 1 is a summary of one spread where we made a continuous spread of (Ba,La)SnO3. X-ray...substitution into BaSnO3 . Fig. 1 summary of (Ba,La)SnO3 spread We have found that low La doping gives rise to good conductivity. The table on the

  15. Neutron diffraction, structural inorganic chemistry and high-temperature superconductors

    International Nuclear Information System (INIS)

    Hewat, A.W.

    1992-01-01

    This paper discusses neutron diffraction which has been of fundamental importance for the determination of the structure of high-temperature superconductors and for understanding the influence of structure on the critical temperature. This is because the new superconductors are heavy metal oxides; X-rays are mainly scattered by the metal atoms, but thermal neutrons are scattered as strongly by oxygen, which is the atom of most interest in these materials. In fact, for the past 20 yr, neutron diffraction has been steadily gaining ground as an important technique in structural inorganic chemistry

  16. Superconducting proximity effect in mesoscopic superconductor/normal-metal junctions

    CERN Document Server

    Takayanagi, H; Toyoda, E

    1999-01-01

    The superconducting proximity effect is discussed in mesoscopic superconductor/normal-metal junctions. The newly-developed theory shows long-range phase-coherent effect which explaines early experimental results of giant magnetoresistance oscillations in an Andreev interferometer. The theory also shows that the proximity correction to the conductance (PCC) has a reentrant behavior as a function of energy. The reentrant behavior is systematically studied in a gated superconductor-semiconductor junction. A negative PCC is observed in the case of a weak coupling between the normal metal and the external reservoir. Phase coherent ac effect is also observed when rf is irradiated to the junction.

  17. Cathodoluminescence study of thin films of high Tc superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Barkay, Z.; Azoulay, J.; Lereah, Y.; Dai, U.; Hess, N.; Racah, D.; Gruenbaum, E.; Deutscher, G. (School of Physics and Astronomy, Raymond and Beverly Sackler Faculty of Exact Sciences, Tel Aviv University, 69978 Ramat Aviv (Israel))

    1990-10-22

    Cathodoluminescence (CL) of thin films of high {ital T}{sub {ital c}} superconductors was studied in the scanning electron microscope. The depth and the lateral locations of the different phases can be revealed. In thin films, unlike the bulk superconductors, the CL information can be obtained either from the film itself or the substrate by varying the primary beam energy. At high beam energy, substrate defects and slight thickness variations of a single high {ital T}{sub {ital c}} phase are observed. The resolution of the CL measurements improves at low temperatures.

  18. Correlated spin currents generated by resonant-crossed Andreev reflections in topological superconductors

    Science.gov (United States)

    He, James J.; Wu, Jiansheng; Choy, Ting-Pong; Liu, Xiong-Jun; Tanaka, Y.; Law, K. T.

    2014-01-01

    Topological superconductors, which support Majorana fermion excitations, have been the subject of intense studies due to their novel transport properties and their potential applications in fault-tolerant quantum computations. Here we propose a new type of topological superconductors that can be used as a novel source of correlated spin currents. We show that inducing superconductivity on a AIII class topological insulator wire, which respects a chiral symmetry and supports protected fermionic end states, will result in a topological superconductor. This topological superconductor supports two topological phases with one or two Majorana fermion end states, respectively. In the phase with two Majorana fermions, the superconductor can split Cooper pairs efficiently into electrons in two spatially separated leads due to Majorana-induced resonant-crossed Andreev reflections. The resulting currents in the leads are correlated and spin-polarized. Importantly, the proposed topological superconductors can be realized using quantum anomalous Hall insulators in proximity to superconductors. PMID:24492649

  19. Nonlocal conductivity in type-II superconductors

    International Nuclear Information System (INIS)

    Mou, C.; Wortis, R.; Dorsey, A.T.; Huse, D.A.

    1995-01-01

    Multiterminal transport measurements on YBa 2 Cu 2 O 7 crystals in the vortex liquid regime have shown nonlocal conductivity on length scales up to 50 microns. Motivated by these results we explore the wave vector (k) dependence of the dc conductivity tensor, σ μν (k), in the Meissner, vortex lattice, and disordered phases of a type-II superconductor. Our results are based on time-dependent Ginzburg-Landau (TDGL) theory and on phenomenological arguments. We find four qualitatively different types of behavior. First, in the Meissner phase, the conductivity is infinite at k=0 and is a continuous function of k, monotonically decreasing with increasing k. Second, in the vortex-lattice phase, in the absence of pinning, the conductivity is finite (due to flux flow) at k=0; it is discontinuous there and remains qualitatively like the Meissner phase for k>0. Third, in the vortex liquid regime in a magnetic field and at low temperature, the conductivity is finite, smooth and nonmonotonic, first increasing with k at small k and then decreasing at larger k. This third behavior is expected to apply at temperatures just above the melting transition of the vortex lattice, where the vortex liquid shows strong short-range order and a large viscosity. Finally, at higher temperatures in the disordered phase, the conductivity is finite, smooth and again monotonically decreasing with k. This last, monotonic behavior applies in zero magnetic field for the entire disordered phase, i.e., at all temperatures above T c , while in a field the nonmonotonic behavior may occur in a low-temperature portion of the disordered phase

  20. Method of producing Pb-stabilized superconductor precursors and method of producing superconductor articles therefrom

    Science.gov (United States)

    Kroeger, Donald M.; Hsu, Huey S.; Brynestad, Jorulf

    1995-01-01

    Metal oxide superconductor powder precursors are prepared in an aerosol pyrolysis process. A solution of the metal cations is introduced into a furnace at 600.degree.-1000.degree. C. for 0.1 to 60 seconds. The process produces micron to submicron size powders without the usual loss of the lead stabilizer. The resulting powders have a narrow particle size distribution, a small grain size, and are readily converted to a superconducting composition upon subsequent heat treatment. The precursors are placed in a metal body deformed to form a wire or tape and heated to form a superconducting article. The fine powders permit a substantial reduction in heat treatment time, thus enabling a continuous processing of the powders into superconducting wire, tape or multifilamentary articles by the powder-in-tube process.

  1. Stability analysis of magnetic flux in thin-film superconductors

    International Nuclear Information System (INIS)

    Denisov, Dmitry

    2007-01-01

    This work presents theoretical results in the physics of superconductivity. The first part of the work is dedicated to the problem of thermomagnetic instabilities and flux avalanches in thin film superconductors. The second part describes the problem of flux trapped in the hole of the superconducting ring (author)

  2. Contamination of YBCO bulk superconductors by samarium and ytterbium

    Czech Academy of Sciences Publication Activity Database

    Volochová, D.; Jurek, Karel; Radušovská, M.; Piovarči, S.; Antal, V.; Kováč, J.; Jirsa, Miloš; Diko, P.

    2014-01-01

    Roč. 496, JAN (2014), s. 14-17 ISSN 0921-4534 Institutional support: RVO:68378271 Keywords : YBCO bulk superconductors * critical temperature * critical current density * peak effect Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.942, year: 2014

  3. Numerical analysis of thermally actuated magnets for magnetization of superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Li Quan; Yan Yu; Rawlings, Colin; Coombs, Tim, E-mail: ql229@cam.ac.u [EPEC Superconductivity Group, Engineering Department, University of Cambridge, Trumpington Street. Cambridge, CB2 1PZ (United Kingdom)

    2010-06-01

    Superconductors, such as YBCO bulks, have extremely high potential magnetic flux densities, comparing to rare earth magnets. Therefore, the magnetization of superconductors has attracted broad attention and contribution from both academic research and industry. In this paper, a novel technique is proposed to magnetize superconductors. Unusually, instead of using high magnetic fields and pulses, repeatedly magnetic waves with strength of as low as rare earth magnets are applied. These magnetic waves, generated by thermally controlling a Gadolinium (Gd) bulk with a rare earth magnet underneath, travel over the flat surface of a YBCO bulk and get trapped little by little. Thus, a very small magnetic field can be used to build up a very large magnetic field. In this paper, the modelling results of thermally actuated magnetic waves are presented showing how to transfer sequentially applied thermal pulses into magnetic waves. The experiment results of the magnetization of YBCO bulk are also presented to demonstrate how superconductors are progressively magnetized by small magnetic field

  4. Proceedings, phenomenology and applications of high temperature superconductors

    International Nuclear Information System (INIS)

    Bedell, K.S.

    1991-01-01

    Phenomenology and Applications of High Temperature Superconductors, The Los Alamos Symposium: 1991, was sponsored by the Los Alamos National Laboratory, Center for Materials Science, the Advanced Studies Program on High Temperature Superconductivity Theory (ASP) and the Exploratory Research and Development Center. This is the second symposium in the series. High Temperature Superconductivity, The Los Alamos Symposium: 1989, also published by Addison Wesley, focused on the cutting-edge theoretical and experimental issues in high temperature superconductors. This symposium, with its focus on the phenomenology and applications of high temperature superconductors, gives a complementary review of the aspects of the field closely related to the impact of high temperature superconductors on technology. The objective of ASP is to advance the field on a broad front with no specific point of view by bringing a team of leading academic theorists into a joint effort with the theoretical and experimental scientists of a major DOE national laboratory. The ASP consisted of fellows led by Robert Schrieffer (UCSB and now FSU) joined by David Pines (University of illinois), Elihu Abrahams (Rutgers), Sebastian Doniach (Stanford), and Maurice Rice (ETH, Zurich) and theoretical and experimental staff of Los Alamos National Laboratory. This synergism of academic, laboratory, theoretical and experimental research produced a level of interaction and excitement that would not be possible otherwise. This publication and the previous one in the series are just examples of how this approach to advancing science can achieve significant contributions

  5. Phonons and charge-transfer excitations in HTS superconductors

    International Nuclear Information System (INIS)

    Bishop, A.R.

    1989-01-01

    Some of the experimental and theoretical evidence implicating phonons and charge-transfer excitations in HTS superconductors is reviewed. It is suggested that superconductivity may be driven by a synergistic interplay of (anharmonic) phonons and electronic degrees of freedom (e.g., charge fluctuations, excitons). 47 refs., 5 figs

  6. Modulated spin and charge densities in cuprate superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Tranquada, J.M.

    1997-08-01

    Neutron scattering experiments have played a crucial role in characterizing the spin and charge correlations in copper-oxide superconductors. While the data are often interpreted with respect to specific theories of the cuprates, an attempt is made here to distinguish those facts that can be extracted empirically, and the connections that can be made with minimal assumptions.

  7. Cuprate-titanate superconductor and method for making

    Science.gov (United States)

    Toreki, Robert; Poeppelmeier, Kenneth; Dabrowski, Bogdan

    1995-01-01

    A new copper oxide superconductor of the formula Ln.sub.1-x M.sub.x Sr.sub.2 Cu.sub.3-y Ti.sub.y O.sub.7+.delta. is disclosed, and exhibits a Tc of 60.degree. K. with deviations from linear metallic behavior as high as 130.degree. K.

  8. Proximity effect in normal metal-multiband superconductor hybrid structures

    NARCIS (Netherlands)

    Brinkman, Alexander; Golubov, Alexandre Avraamovitch; Kupriyanov, M. Yu

    2004-01-01

    A theory of the proximity effect in normal metal¿multiband superconductor hybrid structures is formulated within the quasiclassical Green's function formalism. The quasiclassical boundary conditions for multiband hybrid structures are derived in the dirty limit. It is shown that the existence of

  9. Observation of Antiferromagnetic Resonance in an Organic Superconductor

    DEFF Research Database (Denmark)

    Torrance, J. B.; Pedersen, H. J.; Bechgaard, K.

    1982-01-01

    Anomalous microwave absorption has been observed in the organic superconductor TMTSF2AsF6 (TMTSF: tetramethyltetraselenafulvalene) below its metal-nonmetal transition near 12 K. This absorption is unambiguously identified as antiferromagnetic resonance by the excellent agreement between a spin...

  10. Spin-Dependent Transparency of Ferromagnet/Superconductor Interfaces

    Czech Academy of Sciences Publication Activity Database

    Xia, K.; Kelly, P. J.; Bauer, G. E. W.; Turek, Ilja

    2002-01-01

    Roč. 89, č. 16 (2002), s. 166603 ISSN 0031-9007 R&D Projects: GA ČR GA202/00/0122 Institutional research plan: CEZ:AV0Z2041904 Keywords : interface * ferromagnet * superconductor Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 7.323, year: 2002

  11. High Temperature Superconductor/Semiconductor Hybrid Microwave Devices and Circuits

    Science.gov (United States)

    Romanofsky, Robert R.; Miranda, Felix A.

    1999-01-01

    Contents include following: film deposition technique; laser ablation; magnetron sputtering; sequential evaporation; microwave substrates; film characterization at microwave frequencies; complex conductivity; magnetic penetration depth; surface impedance; planar single-mode filters; small antennas; antenna arrays phase noise; tunable oscillations; hybrid superconductor/semiconductor receiver front ends; and noise modeling.

  12. Electron entanglement near a superconductor and Bell inequalities

    Indian Academy of Sciences (India)

    Near the interface between a normal metal and a superconductor, Cooper pairs pene- trate into the normal side, ... The tunneling Hamiltonian acts on a single electron in the Cooper pair. The BCS wave function with ..... to test electronic devices with applications in quantum communication [10] and quantum computation.

  13. PR IN HIGH-TEMPERATURE SUPERCONDUCTORS - INSULATING PLANES, METALLIC CHAINS

    NARCIS (Netherlands)

    KHOMSKII, D

    Critical discussion is given of the properties of Pr-containing high-T(c) superconductors, especially Y1-xPrxBa2Cu3O7. It is argued that the models proposed to explain suppression of T(c) and other properties of this system (pairbreaking; hole filling; strong p-f hybridization) are inadequate and

  14. Controlling the flux dynamics in superconductors by nanostructured magnetic arrays

    Science.gov (United States)

    Kapra, Andrey

    In this thesis we investigate theoretically how the critical current jc of nano-engineered mesoscopic superconducting film can be improved and how one can control the dynamics of the magnetic flux, e.g., the transition from flux-pinned to flux-flow regime, using arrays of magnetic nanostructures. In particularly we investigate: (1) Vortex transport phenomena in superconductors with deposited ferromagnetic structures on top, and the influence of the sample geometry on the critical parameters and on the vortex configurations. Changing geometry of the magnetic bars and magnetization of the bars will affect the critical current jc of the superconducting film. Such nanostructured ferromagnets strongly alter the vortex structure in its neighborhood. The influence of geometry, position and magnetization of the ferromagnet (single bar or regular lattice of the bars) on the critical parameters of the superconductor is investigated. (2) Effect of flux confinement in narrow superconducting channels with zigzag-shaped banks: the flux motion is confined in the transverse (perpendicular) direction of a diamond-cell-shape channel. The matching effect for the magnetic flux is found in the system relevantless of boundary condition. We discuss the dynamics of vortices in the samples and vortex pattern formation in the channel. We show how the inclusion of higher-Tc superconductor into the sample can lead to enhanced properties of the system. By adding an external driving force, we study the vortex dynamics. The different dynamic regimes are discussed. They allowed an effective control of magnetic flux in superconductors.

  15. Nonlinear response of superconductors to alternating fields and currents

    Energy Technology Data Exchange (ETDEWEB)

    McDonald, Jason [Iowa State Univ., Ames, IA (United States)

    1997-10-08

    This report discusses the following topics on superconductivity: nonlinearities in hard superconductors such as surface impedance of a type II superconductimg half space and harmonic generation and intermodulation due to alternating transport currents; and nonlinearities in superconducting weak links such as harmonic generation by a long Josephson Junction in a superconducting slab.

  16. Mass production system and technology of NbTi superconductors

    International Nuclear Information System (INIS)

    Fukutsuka, Toshiro; Monju, Yoshiyuki; Tatara, Isamu; Noguchi, Masataka; Yokochi, Katsuhiro; Matsubara, Mitsuharu.

    1984-01-01

    A mass production system for NbTi superconductors is described, involving vacuum arc melting of the alloys, hot hydrostatic extrusion of the composite billets and special drawing and stranding techniques for the rods and wires. The qualities required for superconducting wires are assured by a variety of instrument measurement and inspection techniques drawn from accumulated cryogenic experiences. (author)

  17. Preparation and characterization of MgB2 superconductor

    Indian Academy of Sciences (India)

    characteristics recorded under an applied magnetic field revealed the existence of vortex glass tran- sition. The surface analysis using X-ray photoelectron spectroscopy shows that MgB2 is sensitive to atmospheric degradation. Keywords. MgB2 superconductor; vortex glass transition; X-ray photoelectron spectroscopy.

  18. Microwave absorption studies of MgB 2 superconductor

    Indian Academy of Sciences (India)

    Microwave absorption studies have been carried out on MgB2 superconductor using a standard X-band EPR spectrometer. The modulated low-field microwave absorption signals recorded for polycrystalline (grain size ∼ 10m) samples suggested the absence of weak-link character. The field dependent direct microwave ...

  19. Tunneling conductance in semiconductor-superconductor hybrid structures

    Science.gov (United States)

    Stenger, John; Stanescu, Tudor D.

    2017-12-01

    We study the differential conductance for charge tunneling into a semiconductor wire-superconductor hybrid structure, which is actively investigated as a possible scheme for realizing topological superconductivity and Majorana zero modes. The calculations are done based on a tight-binding model of the heterostructure using both a Blonder-Tinkham-Klapwijk approach and a Keldysh nonequilibrium Green's function method. The dependence of various tunneling conductance features on the coupling strength between the semiconductor and the superconductor, the tunnel barrier height, and temperature is systematically investigated. We find that treating the parent superconductor as an active component of the system, rather than a passive source of Cooper pairs, has qualitative consequences regarding the low-energy behavior of the differential conductance. In particular, the presence of subgap states in the parent superconductor, due to disorder and finite magnetic fields, leads to characteristic particle-hole asymmetric features and to the breakdown of the quantization of the zero-bias peak associated with the presence of Majorana zero modes localized at the ends of the wire. The implications of these findings for the effort toward the realization of Majorana bound states with true non-Abelian properties are discussed.

  20. Final Report. Novel Behavior of Ferromagnet/Superconductor Hybrid Systems

    Energy Technology Data Exchange (ETDEWEB)

    Birge, Norman [Michigan State Univ., East Lansing, MI (United States)

    2016-09-26

    Final report for grant DE-FG02-06ER46341. This work has produced a most convincing experimental demonstration that spin-triplet supercurrent can appear in Josephson junctions containing ferromagnetic materials, even when the superconducting electrodes are conventional, spin-singlet superconductors.

  1. Advanced nuclear materials development -Development of superconductor application technology-

    Energy Technology Data Exchange (ETDEWEB)

    Hong, Kye Won; Lee, Heui Kyoon; Lee, Hoh Jin; Kim, Chan Joong; Jang, Kun Ik; Kim, Kee Baek; Kwon, Sun Chil; Park, Hae Woong; Yoo, Jae Keun; Kim, Jong Jin; Jang, Joong Chul; Yang, Suk Woo [Korea Atomic Energy Research Institute, Taejon (Korea, Republic of)

    1995-07-01

    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 fly wheel energy storage device was designed basically. The superconducting levitation force measuring device was made to examine the property of prepared superconductor specimen. Systematic studies on the 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 powder with good reactivity and fine particle size was obtained by emulsion drying method. Ag/BSCCO tape with good cross sectional shape and Tc of 16,000 A/cm{sup 2} was fabricated by applying CIP packing procedure. Multifilamentary wire with the Jc of approx. 10000 A/cm{sup 2} was fabricated by rolling method using square billet as starting shape. The joining of the multifilament 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. 126 figs, 14 tabs, 214 refs. (Author).

  2. Comment on "Magnus Force in Superfluids and Superconductors"

    OpenAIRE

    Volovik, G. E.

    1997-01-01

    The effective action for the Josephson junction arrays should contain the topological term, which violates the particle-hole symmetry. This term is responsible for the nonzero Magnus force acting on the vortex. The Magnus force is however small because the parameter of the particle-hole asymmetry in superconductors is small.

  3. Theory of Tunneling Spectroscopy of Multi-Band Superconductors

    NARCIS (Netherlands)

    Burmistrova, Angelina V.; Devyatov, Igor A.; Golubov, Alexandre Avraamovitch; Yada, Keiji; Tanaka, Yukio

    2013-01-01

    We present the derivation of boundary conditions on a wave function at the normal metal/superconductor (N/S) interface by extending the tight-binding approach developed for semiconducting heterostructures [Phys. Rev. 27 (1983) 3519]. Based on these boundary conditions, we formulate a quantitative

  4. Spins in the vortices of a high-temperature superconductor

    DEFF Research Database (Denmark)

    Lake, B.; Aeppli, G.; Clausen, K.N.

    2001-01-01

    Neutron scattering is used to characterize the magnetism of the vortices for the optimally doped high-temperature superconductor La2-xSrxCuO4 (x = 0.163) in an applied magnetic field. As temperature is reduced, Low-frequency spin fluctuations first disappear with the loss of vortex mobility...

  5. New application of superconductors: High sensitivity cryogenic light detectors

    Energy Technology Data Exchange (ETDEWEB)

    Cardani, L., E-mail: laura.cardani@roma1.infn.it [Dipartimento di Fisica, Sapienza Università di Roma, Piazzale Aldo Moro 2, 00185 Roma (Italy); Physics Department, Princeton University, Washington Road, 08544 Princeton, NJ (United States); Bellini, F.; Casali, N. [Dipartimento di Fisica, Sapienza Università di Roma, Piazzale Aldo Moro 2, 00185 Roma (Italy); INFN – Sezione di Roma, Piazzale Aldo Moro 2, 00185 Roma, Italy (Italy); Castellano, M.G. [Istituto di Fotonica e Nanotecnologie – CNR, Via Cineto Romano 42, 00156 Roma (Italy); Colantoni, I.; Coppolecchia, A. [Dipartimento di Fisica, Sapienza Università di Roma, Piazzale Aldo Moro 2, 00185 Roma (Italy); Cosmelli, C.; Cruciani, A. [Dipartimento di Fisica, Sapienza Università di Roma, Piazzale Aldo Moro 2, 00185 Roma (Italy); INFN – Sezione di Roma, Piazzale Aldo Moro 2, 00185 Roma, Italy (Italy); D' Addabbo, A. [INFN – Laboratori Nazionali del Gran Sasso, Assergi (L' Aquila) 67010 (Italy); Di Domizio, S. [INFN – Sezione di Genova, Via Dodecaneso 33, 16146 Genova (Italy); Dipartimento di Fisica, Università degli Studi di Genova, Via Dodecaneso 33, 16146 Genova (Italy); Martinez, M. [Dipartimento di Fisica, Sapienza Università di Roma, Piazzale Aldo Moro 2, 00185 Roma (Italy); INFN – Sezione di Roma, Piazzale Aldo Moro 2, 00185 Roma, Italy (Italy); Laboratorio de Fisica Nuclear y Astroparticulas, Universidad de Zaragoza, Zaragoza 50009 (Spain); Tomei, C. [INFN – Sezione di Roma, Piazzale Aldo Moro 2, 00185 Roma, Italy (Italy); and others

    2017-02-11

    In this paper we describe the current status of the CALDER project, which is developing ultra-sensitive light detectors based on superconductors for cryogenic applications. When we apply an AC current to a superconductor, the Cooper pairs oscillate and acquire kinetic inductance, that can be measured by inserting the superconductor in a LC circuit with high merit factor. Interactions in the superconductor can break the Cooper pairs, causing sizable variations in the kinetic inductance and, thus, in the response of the LC circuit. The continuous monitoring of the amplitude and frequency modulation allows to reconstruct the incident energy with excellent sensitivity. This concept is at the basis of Kinetic Inductance Detectors (KIDs) that are characterized by natural aptitude to multiplexed read-out (several sensors can be tuned to different resonant frequencies and coupled to the same line), resolution of few eV, stable behavior over a wide temperature range, and ease in fabrication. We present the results obtained by the CALDER collaboration with 2×2 cm{sup 2} substrates sampled by 1 or 4 Aluminum KIDs. We show that the performances of the first prototypes are already competitive with those of other commonly used light detectors, and we discuss the strategies for a further improvement.

  6. Five-fold way to new high Tc superconductors

    Indian Academy of Sciences (India)

    Some of the difficulties in this route is explained by the mineral tenorite CuO ..... CuO should undergo a Mott insulator superconductor transition, perhaps with an intermediate antifer- romagnetic metallic state. The superconducting Tc will ... Last century witnessed the birth of semiconductor electronics and nanotechnology.

  7. Angle dependence of Andreev scattering at semiconductor-superconductor interfaces

    DEFF Research Database (Denmark)

    Mortensen, Asger; Flensberg, Karsten; Jauho, Antti-Pekka

    1999-01-01

    We study the angle dependence of the Andreev scattering at a semiconductor-superconductor interface, generalizing the one-dimensional theory of Blonder, Tinkham, and Klapwijk (BTK),An increase of the momentum parallel to the interface leads to suppression of the probability of Andreev reflection...

  8. Superconductors-A Review of Their Properties and Applications ...

    African Journals Online (AJOL)

    Superconductors are a special class of materials which exhibit a number of remarkable properties distinct from normal materials. These materials have found varied industrial and technological applications since the phenomenon of superconductivity was first discovered in 1911. A great deal of efforts are being made world ...

  9. Transport theory and low energy properties of colour superconductors

    CERN Document Server

    Litim, Daniel F

    2002-01-01

    The one-loop polarisation tensor and the propagation of ``in-medium'' photons of colour superconductors in the 2SC and CFL phase is discussed. For a study of thermal corrections to the low energy effective theory in the 2SC phase, a classical transport theory for fermionic quasiparticles is invoked.

  10. Controlled Manipulation of Individual Vortices in a Superconductor

    Energy Technology Data Exchange (ETDEWEB)

    Straver, E.W.J.

    2010-04-05

    We report controlled local manipulation of single vortices by low temperature magnetic force microscope (MFM) in a thin film of superconducting Nb. We are able to position the vortices in arbitrary configurations and to measure the distribution of local depinning forces. This technique opens up new possibilities for the characterization and use of vortices in superconductors.

  11. Numerical analysis of thermally actuated magnets for magnetization of superconductors

    International Nuclear Information System (INIS)

    Li Quan; Yan Yu; Rawlings, Colin; Coombs, Tim

    2010-01-01

    Superconductors, such as YBCO bulks, have extremely high potential magnetic flux densities, comparing to rare earth magnets. Therefore, the magnetization of superconductors has attracted broad attention and contribution from both academic research and industry. In this paper, a novel technique is proposed to magnetize superconductors. Unusually, instead of using high magnetic fields and pulses, repeatedly magnetic waves with strength of as low as rare earth magnets are applied. These magnetic waves, generated by thermally controlling a Gadolinium (Gd) bulk with a rare earth magnet underneath, travel over the flat surface of a YBCO bulk and get trapped little by little. Thus, a very small magnetic field can be used to build up a very large magnetic field. In this paper, the modelling results of thermally actuated magnetic waves are presented showing how to transfer sequentially applied thermal pulses into magnetic waves. The experiment results of the magnetization of YBCO bulk are also presented to demonstrate how superconductors are progressively magnetized by small magnetic field

  12. Quality system design and development for SSC superconductor cable

    International Nuclear Information System (INIS)

    Fuse, M.; Saito, S.; Sashida, T.; Koganeya, M.; Ayai, N.; Takai, K.; Nagata, M.

    1992-01-01

    In order to develop a quality system for the SSC superconductor cable, Sumitomo Electric followed a very formal, systematic approach, comparable to those employed for such major projects as developing a new car model. This paper presents our approach, as well as the resulting computerized environment for quality assurance (QA)

  13. Microwave absorption studies of MgB 2 superconductor

    Indian Academy of Sciences (India)

    Microwave absorption studies have been carried out on MgB2 superconductor using a standard X-band EPR spectrometer. ... Radiochemistry Division, Bhabha Atomic Research Centre, Mumbai 400 085, India; Technical Physics and Prototype Engineering Division, Bhabha Atomic Research Centre, Mumbai 400 085, India ...

  14. Electron entanglement near a superconductor and Bell inequalities

    Indian Academy of Sciences (India)

    Near the interface between a normal metal and a superconductor, Cooper pairs penetrate into the normal side, giving rise to the proximity effect. The two electrons of these pairs have entangled spin and orbital degrees of freedom. Nonlocal features of quantum mechanics can be probed by separating these two electrons.

  15. Some new aspects of super-high temperature superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Huang, C.Y. (Research and Development Div., Lockheed Missiles and Space Co., Palto Alto, CA (US)); Rabinowitz, M. (Electric Power Research Inst., Palo Alto, CA (USA). Electrical Systems Div.)

    1990-05-01

    The authors review some salient features of the recently observed experimental evidence of ceramic super-high temperature superconductivity (T{sub c} {gt} 200 K). Two theoretical estimates which are capable of accounting for super-high T{sub c} are presented. For comparison, several reports on non-ceramic oxide super-high temperature superconductors are discussed.

  16. Magnetic flux annihilation waves in inhomogeneous high-temperature superconductors

    NARCIS (Netherlands)

    Rudnev, IA; Khodot, AE; Eremin, AV; Mikhailov, BP

    2004-01-01

    The process of magnetic field penetration into polycrystalline high-T-c superconductors of the YBa2Cu3O7 - x and Bi2Sr2Ca2Cu3O10 - x systems has been studied using traditional magnetooptical methods and scanning Hall probe microscopy. It is established that remagnetization of a sample is accompanied

  17. XRD spectra of new YBaCuO superconductors

    Indian Academy of Sciences (India)

    Nakhon Pathom 73140, Thailand. MS received 4 October 2010; revised 17 February 2011. Abstract. XRD spectra of new YBaCuO superconductors were studied. There were 2 phases found in our samples, the superconducting phase and the non-superconducting phase. The more non-superconducting phase, the more.

  18. ESR and magnetic susceptibilities in the '2223' superconductors

    International Nuclear Information System (INIS)

    Geru, I.I.; Pop, A.V.; Konopko, L.A.; Ilonca, Gh.; Pop, V.; Cosma, I.

    1995-01-01

    Electron paramagnetic resonance (EPR) of the (Bi Pb)-(Sr Ba)-Ca-Cu-O high T c superconductor was performed. The a.c. susceptibility shows two superconducting transitions at 109 K and 88 K respectively. An unusual behaviour is observed at 240 K in the EPR linewidth and in the Lande factor (the g value). (author) 3 figs., 12 refs

  19. Neutron-diffraction investigations of flux-lines in superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Forgan, E.M. [Birmingham Univ. (United Kingdom); Lee, S.L. [Saint Andrews Univ. (United Kingdom); McKPaul, D. [Warwick Univ., Coventry (United Kingdom); Mook, H.A. [Oak Ridge National Lab., TN (United States); Cubitt, R. [Institut Max von Laue - Paul Langevin (ILL), 38 - Grenoble (France)

    1997-04-01

    SANS has proved an extremely useful tool for investigating flux-line structures within the bulk of superconductors. With high-T{sub c} materials, the scattered intensities are weak, but careful measurements are giving important new information about flux lattices, flux pinning and flux-lattice melting. (author). 10 refs.

  20. Bottlenecks reduction using superconductors in high voltage transmission lines

    Directory of Open Access Journals (Sweden)

    Daloub Labib

    2016-01-01

    Full Text Available Energy flow bottlenecks in high voltage transmission lines known as congestions are one of the challenges facing power utilities in fast developing countries. Bottlenecks occur in selected power lines when transmission systems are operated at or beyond their transfer limits. In these cases, congestions result in preventing new power supply contracts, infeasibility in existing contracts, price spike and market power abuse. The “Superconductor Technology” in electric power transmission cables has been used as a solution to solve the problem of bottlenecks in energy transmission at high voltage underground cables and overhead lines. The increase in demand on power generation and transmission happening due to fast development and linked to the intensive usage of transmission network in certain points, which in turn, lead to often frequent congestion in getting the required power across to where it is needed. In this paper, a bottleneck in high voltage double overhead transmission line with Aluminum Conductor Steel Reinforced was modeled using conductor parameters and replaced by Gap-Type Superconductor to assess the benefit of upgrading to higher temperature superconductor and obtain higher current carrying capacity. This proved to reduce the high loading of traditional aluminum conductors and allow more power transfer over the line using superconductor within the same existing right-of-way, steel towers, insulators and fittings, thus reducing the upgrade cost of building new lines.

  1. Coherent and correlated spin transport in nanoscale superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Morten, Jan Petter

    2008-03-15

    Motivated by the desire for better understanding of nano electronic systems, we theoretically study the conductance and noise characteristics of current flow between superconductors, ferromagnets, and normal-metals. Such nano structures can reveal information about superconductor proximity effects, spin-relaxation processes, and spintronic effects with potential applications for different areas of mesoscopic physics. We employ the quasiclassical theory of superconductivity in the Keldysh formalism, and calculate the nonequilibrium transport of spin and charge using various approaches like the circuit theory of quantum transport and full counting statistics. For two of the studied structures, we have been able to compare our theory to experimental data and obtain good agreement. Transport and relaxation of spin polarized current in superconductors is governed by energy-dependent transport coefficients and spin-flip rates which are determined by quantum interference effects. We calculate the resulting temperature-dependent spin flow in ferromagnet-superconductor devices. Experimental data for spin accumulation and spin relaxation in a superconducting nano wire is in agreement with the theory, and allows for a spin-flip spectroscopy that determines the dominant mechanism for spin-flip relaxation in the studied samples. A ferromagnet precessing under resonance conditions can give rise to pure spin current injection into superconductors. We find that the absorbed spin current is measurable as a temperature dependent Gilbert damping, which we calculate and compare to experimental data. Crossed Andreev reflection denotes superconducting pairing of electrons flowing from different normal-metal or ferromagnet terminals into a superconductor. We calculate the nonlocal currents resulting from this process in competition with direct electron transport between the normal-metal terminals. We take dephasing into account, and study the nonlocal current when the types of contact in

  2. Unconventional properties of non-centrosymmetric superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Klam, Ludwig

    2010-10-28

    A kinetic theory for non-centrosymmetric superconductors (NCS) is formulated for low temperatures and in the clean limit. The transport equations are solved quite generally for any kind of antisymmetric spin-orbit coupling (ASOC) in an extended momentum and frequency range. The result is a particle-hole symmetric, gauge-invariant and charge conserving description, which is used to calculate the current response, the specific heat capacity, and the Raman response function. A detailed analysis of the gauge invariance and the associated phase fluctuations of the superconducting order parameter revealed two gauge modes: the Anderson-Bogoliubov mode on the one side and a new gauge mode on the other side, which strongly depends on the symmetry of the ASOC. As application of the kinetic theory, the polarization-dependence of the T = 0 electronic Raman response in NCS is studied for two important classes of ASOC with the representative systems CePt{sub 3}Si and Li{sub 2}Pd{sub x}Pt{sub 3-x}B. Analytical expressions for the Raman vertices are derived, and the frequency power laws and pair-breaking peaks are calculated. A characteristic two- peak structure is predicted for NCS and might serve as an indicator for the unknown relative magnitude of the singlet and triplet contributions to the superconducting order parameter. An efficient numerical method is introduced in order to calculate the dynamical spin and charge response of CePt{sub 3}Si, using an itinerant description for the electrons. With a realistic parameterization of the band structure, the nesting function, inelastic neutron scattering cross sections, and Kohn anomalies are calculated for a selected band in the normal non-magnetic state. From the spin and charge susceptibility, a superconducting pairing interaction is constructed for the weak-coupling gap equation. A sign analysis of the decoupled gap equation supports the experimental evidence of a strong triplet contribution to the order parameter in CePt{sub 3

  3. High field superconductor development and understanding

    Energy Technology Data Exchange (ETDEWEB)

    Larbalestier, David C. [Florida State Univ., Tallahassee, FL (United States); Lee, Peter J. [Florida State Univ., Tallahassee, FL (United States); Tarantini, Chiara [Florida State Univ., Tallahassee, FL (United States)

    2014-09-28

    All present circular accelerators use superconducting magnets to bend and to focus the particle beams. The most powerful of these machines is the large hadron collider (LHC) at CERN. The main ring dipole magnets of the LHC are made from Nb-Ti but, as the machine is upgraded to higher luminosity, more powerful magnets made of Nb3Sn will be required. Our work addresses how to make the Nb3Sn conductors more effective and more suitable for use in the LHC. The most important property of the superconducting conductor used for an accelerator magnet is that it must have very high critical current density, the property that allows the generation of high magnetic fields in small spaces. Nb3Sn is the original high field superconductor, the material which was discovered in 1960 to allow a high current density in the field of about 9 T. For the high luminosity upgrade of the LHC, much higher current densities in fields of about 12 Tesla will be required. The critical value of the current density is of order 2600 A/mm2 in a field of 12 Tesla. But there are very important secondary factors that complicate the attainment of this critical current density. The first is that the effective filament diameter must be no larger than about 40 µm. The second factor is that 50% of the cross-section of the Nb3Sn conductor that is pure copper must be protected from any poisoning by any Sn leakage through the diffusion barrier that protects the package of niobium and tin from which the Nb3Sn is formed by a high temperature reaction. These three, somewhat conflicting requirements, mean that optimization of the conductor is complex. The work described in this contract report addresses these conflicting requirements. They show that very sophisticated characterizations can uncover the way to satisfy all 3 requirements and they also suggest that the ultimate optimization of Nb3Sn is still not yet in sight

  4. High-T(sub c) Superconductor-Normal-Superconductor Junctions with Polyimide-Passivated Ambient Temperature Edge Formation

    Science.gov (United States)

    Barner, J. B.; Kleinsasser, A. W.; Hunt, B. D.

    1996-01-01

    The ability to controllably fabricate High-Temperature Superconductor (HTS) S-Normal-S (SNS) Josephson Juntions (JJ's) enhances the possibilities fro many applications, including digital circuits, SQUID's, and mixers. A wide variety of approaches to fabricating SNS-like junctions has been tried and analyzed in terms of proximity effect behavior.

  5. Effect of hybridization and dispersion of quasiparticles on the ...

    Indian Academy of Sciences (India)

    RNi2B2C (R = Tm, Er, Ho, Dy) show the coexistence of superconductivity and mag- netism [1–3] with high magnetic ordering temperatures. It is indeed .... However, we introduce a staggered magnetic field of strength h which simulates strong. AFM correlation of nickel electrons which is represented in the 2nd term of eq. (1).

  6. 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

  7. Studies of anisotropy of iron based superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Murphy, Jason [Iowa State Univ., Ames, IA (United States)

    2013-01-01

    To study the electronic anisotropy in iron based superconductors, the temperature dependent London penetration depth, Δλ (T), have been measured in several compounds, along with the angular dependent upper critical field, Hc2(T). Study was undertaken on single crystals of Ba(Fe1-xCox)2As2 with x=0.108 and x=0.127, in the overdoped range of the doping phase diagram, characterized by notable modulation of the superconducting gap. Heavy ion irradiation with matching field doses of 6 T and 6.5 T respectively, were used to create columnar defects and to study their effect on the temperature Δλ (T). The variation of the low-temperature penetration depth in both pristine and irradiated samples was fitted with a power-law function Δλ (T) = ATn. Irradiation increases the magnitude of the pre-factor A and decreases the exponent n, similar to the effect on the optimally doped samples. This finding supports the universal s± scenario for the whole doping range. Knowing that the s± gap symmetry exists across the superconducting dome for the electron doped systems, we next looked at λ (T), in optimally - doped, SrFe2(As1-xPx)2, x =0.35. Both, as-grown (Tc ~ 25 K) and annealed (Tc ~ 35 K) single crystals of SrFe2(As1-xPx)2 were measured. Annealing decreases the absolute value of the London penetration depth from λ(0) = 300 ± 10 nm in as-grown samples to λ (0) = 275±10 nm. At low temperatures, λ (T) ~ T indicates a superconducting gap with line nodes. Analysis of the full-temperature range superfluid density is consistent with the line nodes, but differs from the simple single-gap d-wave. The observed behavior is very similar to that of BaFe2(As1-xPx)2, showing that isovalently substituted pnictides are inherently different from

  8. Modeling of superconductors based on the timedependent Ginsburg-Landau equations

    Science.gov (United States)

    Grishakov, K. S.; Degtyarenko, P. N.; Degtyarenko, N. N.; Elesin, V. F.; Kruglov, V. S.

    2009-11-01

    Results of modeling of superconductor magnetization process based on a numerical solution of the timedependent Ginsburg-Landau equations are presented. Methods of grid approximation of the equations and method of finite elements are used. Two-dimensional patterns of changes in the order parameter and supercurrent distribution in superconductors are calculated and visualized. The main results are in agreement with the well-known representations for type I and II superconductors.

  9. Ambient-temperature superconductor symetrical metal-dihalide bis-(ethylenedithio)-tetrathiafulvalene compounds

    Science.gov (United States)

    Williams, Jack M.; Wang, Hsien-Hau; Beno, Mark A.

    1987-01-01

    A new class of organic superconductors having the formula (ET).sub.2 MX.sub.2 wherein ET represents bis(ethylenedithio)-tetrathiafulvalene, M is a metal such as Au, Ag, In, Tl, Rb, Pd and the like and X is a halide. The superconductor (ET).sub.2 AuI.sub.2 exhibits a transition temperature of 5 K. which is high for organic superconductors.

  10. Design and Demonstration of a 30 GHz 16-bit Superconductor RSFQ Microprocessor

    Science.gov (United States)

    2015-03-10

    for Public Release; Distribution Unlimited Final Report: Design and Demonstration of a 30 GHz 16-bit Superconductor RSFQ Microprocessor The views...P.O. Box 12211 Research Triangle Park, NC 27709-2211 Superconductor technology, RSFQ, RQL, processor design, arithmetic units, high-performance...Demonstration of a 30 GHz 16-bit Superconductor RSFQ Microprocessor Report Title The major objective of the project was to design and demonstrate operation

  11. Particle-Hole Transformation in Strongly-Doped Iron-Based Superconductors

    OpenAIRE

    Rodriguez, J. P.

    2016-01-01

    An exact particle-hole transformation is discovered in a local-moment description of a single layer in an iron-based superconductor. Application of the transformation to a surface layer of heavily electron-doped FeSe predicts a surface-layer high-temperature superconductor at strong hole doping. Comparison with existing low-T_c iron superconductors suggests that the critical temperature at heavy hole doping can be increased by increasing direct ferromagnetic exchange in between nearest neighb...

  12. Electromechanical properties of superconductors for DOE/OFE applications. Final report

    International Nuclear Information System (INIS)

    Ekin, J.W.; Bray, S.L.

    1998-01-01

    In many superconductor applications, especially large magnets, the superconductor is required to perform while under the influence of strong mechanical forces. These forces are commonly due to residual fabrication stress, differential thermal contraction of dissimilar materials, and electromagnetic forces generated within an energized magnet coil. Thorough knowledge of a superconductor's electrical performance under the influence of these forces (electromechanical properties) is required for successful magnet engineering. This report presents results of research conducted during the period from august 1993 through March 1997 on the electromechanical properties of superconductors for DOE/OFE fusion applications

  13. Status of high temperature superconductor cable and fault current limiter projects at American Superconductor

    Science.gov (United States)

    Maguire, J. F.; Yuan, J.

    2009-10-01

    This paper will describe the status of three key programs currently underway at American Superconductor Corp. The first program is the LIPA project which is a transmission voltage high temperature superconducting cable program, with funding support from the US Department of Energy. The 600 m cable, capable of carrying 574 MVA, was successfully installed and commissioned in LIPA grid on April 22, 2008. An overview of the project, system level design details and operational data will be provided. In addition, the status of the newly awarded LIPA II project will be described. The second program is Project Hydra, with funding support from the US Department of Homeland Security, to design, develop and demonstrate an HTS cable with fault current limiting functionality. The cable is 300 m long and is being designed to carry 96 MVA at a distribution level voltage of 13.8 kV. The cable will be permanently installed and energized in Manhattan, New York in 2010. The initial status of Project Hydra will be presented. The final program to be discussed is a transmission voltage, high temperature superconducting fault current limiter funded by the US DOE. The project encompasses the design, construction and test of a 115 kV FCL for power transmission within a time frame of 4-5 years. Installation and testing are planned for a Southern California Edison substation. A project overview and progress under the first phase will be reported.

  14. Instability in the magnetic field penetration in type II superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Oliveira, Isaías G. de, E-mail: isaias@ufrrj.br

    2015-07-17

    Under the view of the time-dependent Ginzburg–Landau theory we have investigated the penetration of the magnetic field in the type II superconductors. We show that the single vortices, situated along the borderline, between the normal region channel and the superconducting region, can escape to regions still empty of vortices. We show that the origin of this process is the repulsive nature of vortex–vortex interaction, in addition to the non-homogeneous distribution of the vortices along the normal region channel. Using London theory we explain the extra gain of kinetic energy by the vortices situated along this borderline. - Highlights: • TDGL is used to study the magnetic field penetration in type II superconductors. • Instability process is found during the magnetic field penetration. • Vortices along the front of the normal region escape to superconducting region. • We explain the extra-gain of kinetic energy by vortices along the borderline.

  15. The local structure of high-temperature superconductors

    International Nuclear Information System (INIS)

    Mustre de Leon, J.; Conradson, S.D.; Bishop, A.R.; Raistrick, I.D.

    1992-01-01

    We show how x-ray absorption fine structure (XAFS) has been successfully used in the determination of the local crystal structure of high-temperature superconductors, with advantages over traditional diffraction techniques. We review the experimental results that yielded the first evidence for an axial-oxygen-centered lattice instability connected with the superconductivity transition. The interpretation of this instability in terms of a dynamical tunneling model suggests the presence of polarons in these materials. XAFS on Tl 2 Ba 2 CuO 6 and other Tl-based superconductors indicate the presence of local instabilities in the CuO 2 planes of these materials, in addition to axial-oxygen instabilities

  16. Superconductor homopolar machines with liquid-metal contacts

    International Nuclear Information System (INIS)

    Aliyevsky, B.L.; Bazarnov, B.A.; Oktyabrsky, A.M.; Popov, N.N.; Sherstuk, A.G.; Shopen, D.P.

    1992-01-01

    Alongside with the power increase of Electric Superconductor (SC) Machines including Homopolar Machines (HM) there is a strong need of improving their working characteristics, raising the efficiency, reducing the superconductor consumption. In the paper, the results of investigating the mass, dimensional and energetic properties of SCHM are given which are illustrated by the calculation of homopolar generators in the band of nominal power per unit P n = (2-250) MW at the voltage of 12, 24, 60, 230 V and rotation frequency of 25 and 50 rps. Screened and unscreened HM of a cylindrical type with liquid-metal current collector devices (LCD) and inductor consisting of 2 opposing SC coils mounted in a fixed cryostat inside the rotating armature are investigated

  17. Effect of twinning plane on superconductor magnetic properties

    International Nuclear Information System (INIS)

    Buzdin, A.I.; Kuptsov, D.A.

    1989-01-01

    Effect of twinning planes on pinning of the Abrikosov vortices in superconductors of the second order with the Ginsburg-Landau parameter, κ >> 1, is considered. The modified Ginsburg-Landau functional, where the effect of superconducting properties improvement near the twinning plane is taken into account by adding the additional δ-function component, is used to descibe superconductivity of twinning plane. Force of interaction of a vortex filament and the twinning plane is calculated. It is shown that in case of the twinning plane opaque to electrons, additional attractive force, being analogous to that occurring in the problem on the surface Been-Livingston barrier, affects the vortex filament. The results can explain anisotropy of vortex pinning observed in the periodic twinning structure in high-temperature superconductors

  18. Intrinsic pinning in superconductors with extremely small coherence lengths

    International Nuclear Information System (INIS)

    Schimmele, L.; Kronmueller, H.; Teichler, H.

    1988-01-01

    By means of a Ginsburg-Landau-type theory which takes into account the discrete lattice structure the variation of the energy ('Peierls potential') of an isolated flux line is calculated when shifted relatively to the crystal lattice. In particular, a primitive cubic lattice is considered with a straight flux line, aligned parallel to a cubic axis. The resulting Peierls potential may lead to intrinsic pinning if the coherence length is smaller than about two nearest neighbour distances. The coherence lengths at low temperatures determined for the recently discovered high T c superconductors of the YBa 2 Cu 3 O 7 class come very close to this value so that intrinsic pinning might possibly be relevant for these superconductors. (author)

  19. Low-energy physics of high-temperature superconductors

    International Nuclear Information System (INIS)

    Emery, V.J.; Kivelson, S.A.

    1992-01-01

    It is argued that the low-energy properties of high temperature superconductors are dominated by the interaction between the mobile holes and a particular class of collective modes, corresponding to local large-amplitude low-energy fluctuations in the hole density. The latter are a consequence of the competition between the effects of long-range Coulomb interactions and the tendency of a low concentration of holes in an antiferromagnet to phase separate. The low-energy behavior of the system is governed by the same fixed point as the two-channel Kondo problem, which accounts for the ''universality'' of the properties of the cuprate superconductors. Predictions of the optical properties and the spin dynamics are compared with experiment. The pairing resonance of the two Kondo problem gives a mechanism of high temperature superconductivity with an unconventional symmetry of the order parameter

  20. Creating and manipulating nonequilibrium spins in nanoscale superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Wolf, Michael J.; Kolenda, Stefan; Beckmann, Detlef [Institut fuer Nanotechnologie, Karlsruher Institut fuer Technologie (Germany); Huebler, Florian [Institut fuer Nanotechnologie, Karlsruher Institut fuer Technologie (Germany); Institut fuer Festkoerperphysik, Karlsruher Institut fuer Technologie (Germany); Suergers, Christoph; Fischer, Gerda [Physikalisches Institut, Karlsruher Institut fuer Technologie (Germany); Loehneysen, Hilbert von [Institut fuer Festkoerperphysik, Karlsruher Institut fuer Technologie (Germany); Physikalisches Institut, Karlsruher Institut fuer Technologie (Germany)

    2015-07-01

    We report on nonlocal transport in superconductor hybrid structures, with ferromagnetic as well as normal-metal tunnel junctions attached to the superconductor. In the presence of a strong Zeeman splitting of the density of states, we find signatures of spin transport over distances of several μm, exceeding other length scales such as the coherence length, the normal-state spin-diffusion length, and the charge-imbalance length. Using a combination of ferromagnetic and normal-metal contacts, we demonstrate spin injection from a normal metal, and show a complete separation of charge and spin imbalance. An exchange splitting induced by the ferromagnetic insulator europium sulfide enables spin transport at very small applied magnetic fields, and therefore paves the way to manipulating spin currents by local exchange fields.

  1. Ultrafast probes of coherent oscillations in Fe-based superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Kim, K. W. [Dept. of Physics, Chungbuk National University, Cheongju (Korea, Republic of)

    2017-03-15

    Forefront ultrafast experimental techniques have recently proven their potential as new approaches to understand materials based on non-equilibrium dynamics in the time domain. The time domain approach is useful especially in disentangling complicated coupling among charge, spin and lattice degrees of freedom. Various ultrafast experiments on Fe-based superconductors have observed strong coherent oscillations of an A1g phonon mode of arsenic ions, which shows strong coupling to the electronic and magnetic states. This paper reviews the recent reports of ultrafast studies on Fe-based superconductor with a focus on the coherent oscillations. Experimental results with ultrashort light sources from the terahertz-infrared pulses to the hard X-rays from a free electron laser will be presented.

  2. Terahertz frequency superconductor-nanocomposite photonic band gap

    Science.gov (United States)

    Elsayed, Hussein A.; Aly, Arafa H.

    2018-02-01

    In the present work, we discuss the transmittance properties of one-dimensional (1D) superconductor nanocomposite photonic crystals (PCs) in THz frequency regions. Our modeling is essentially based on the two-fluid model, Maxwell-Garnett model and the characteristic matrix method. The numerical results investigate the appearance of the so-called cutoff frequency. We have obtained the significant effect of some parameters such as the volume fraction, the permittivity of the host material, the size of the nanoparticles and the permittivity of the superconductor material on the properties of the cutoff frequency. The present results may be useful in the optical communications and photonic applications to act as tunable antenna in THz, reflectors and high-pass filter.

  3. Homes’ law in holographic superconductor with Q-lattices

    International Nuclear Information System (INIS)

    Niu, Chao; Kim, Keun-Young

    2016-01-01

    Homes’ law, ρ s =Cσ DC T c , is an empirical law satisfied by various superconductors with a material independent universal constant C, where ρ s is the superfluid density at zero temperature, T c is the critical temperature, and σ DC is the electric DC conductivity in the normal state close to T c . We study Homes’ law in holographic superconductor with Q-lattices and find that Homes’ law is realized for some parameter regime in insulating phase near the metal-insulator transition boundary, where momentum relaxation is strong. In computing the superfluid density, we employ two methods: one is related to the infinite DC conductivity and the other is related to the magnetic penetration depth. With finite momentum relaxation both yield the same results, while without momentum relaxation only the latter gives the superfluid density correctly because the former has a spurious contribution from the infinite DC conductivity due to translation invariance.

  4. Nobel Prize winner visits CERN’s superconductors

    CERN Multimedia

    2008-01-01

    On Wednesday 23 April Georg Bednorz, who won the Nobel Prize for physics in 1987, visited CERN along with 44 of his colleagues from the IBM Zurich Research Laboratory. Georg Bednorz (second from right) with colleagues from the IBM Zurich Research Laboratory in the LHC tunnel. On their arrival, Jos Engelen, the Chief Scientific Officer, gave the IBM group an introduction to CERN. Bednorz came to CERN only recently for the Open Days to give a seminar, but unfortunately did not have time to visit the experiments, so this trip was organised instead. Along with Alex Müller, Bednorz was awarded the Noble Prize for his discovery of superconductivity for the so-called high temperature superconductors, essentially copper-oxide-based compounds showing superconductivity at temperatures much higher than had previously been thought possible. The LHC magnets are built with low-temperature superconductors but many current leads that supply power to the LHC cryostats are made with...

  5. Progress in melt-texturing of YBCO superconductors

    International Nuclear Information System (INIS)

    Salama, K.; Lee, D.F.; Selvamanickam, V.

    1993-01-01

    Since the discovery of high temperature superconductors (HTS), tremendous efforts have been expanded toward the improvement of these materials. Due to the weak-link problem associated with grain boundaries, sintered bulk HTS possess a transport critical current density (J c ) on the order of 10 2 -10 3 A/cm 2 at 77 K. While these sintered superconductors may be utilized in low current applications, novel processing methods have to be developed to obtain HTS that can sustain high currents. Melt-texturing of HTS was found to result in a high degree of grain orientation, and is presently the most prominent processing method used to manufacture bulk YBa 2 Cu 3 O x (123) with superior transport and magnetic properties. In this review paper, various melt-texturing methods will be discussed, and the variation in J c with processing will be presented. (orig.)

  6. Vortex edge barriers and critical current density in granular superconductors

    CERN Document Server

    Belevtsov, L V

    2003-01-01

    Type-II superconductors, even without bulk pinning and in the absence of a macroscopic Bean-Livingston surface barrier for vortex penetration, can exhibit barriers for flux penetration. We investigated some new edge barriers based on the laminar model, that are governed by the anisotropy ratio, grain coupling strength, and grain size. Expressions describing the pinning potential U sub p and critical current density J sub c are derived for magnetic fields near H sub c sub 1. It is shown that edge barrier effects play a substantial role in a realistic description of the critical current density for both MgB sub 2 and high-T sub c superconductors. (Abstract Copyright [2003], Wiley Periodicals, Inc.)

  7. Unconventional superconductors experimental investgation of the order-parameter symmetry

    CERN Document Server

    Goll, Gernot

    2006-01-01

    This book offers a comprehensive summary of experiments that are especially suited to reveal the order-parameter symmetry of unconventional superconductors. It briefly introduces readers to the basic theoretical concepts and terms of unconventional superconductivity, followed by a detailed overview of experimental techniques and results investigating the superconducting energy gap and phase, plus the pairing symmetry. This review includes measurements of specific heat, thermal conductivity, penetration depth and nuclearmagnetic resonance and muon-spin rotation experiments. Further, point-contact and tunnelling spectroscopy and Josephson experiments are addressed. Current understanding is reviewed from the experimental point of view. With an appendix offering five tables with almost 200 references that summarize the present results from ambient pressure heavy-fermion and noncopper-oxide superconductors, the monograph provides a valuable resource for further studies in this field.

  8. Unified Phase Diagram for Iron-Based Superconductors

    Science.gov (United States)

    Gu, Yanhong; Liu, Zhaoyu; Xie, Tao; Zhang, Wenliang; Gong, Dongliang; Hu, Ding; Ma, Xiaoyan; Li, Chunhong; Zhao, Lingxiao; Lin, Lifang; Xu, Zhuang; Tan, Guotai; Chen, Genfu; Meng, Zi Yang; Yang, Yi-feng; Luo, Huiqian; Li, Shiliang

    2017-10-01

    High-temperature superconductivity is closely adjacent to a long-range antiferromagnet, which is called a parent compound. In cuprates, all parent compounds are alike and carrier doping leads to superconductivity, so a unified phase diagram can be drawn. However, the properties of parent compounds for iron-based superconductors show significant diversity and both carrier and isovalent dopings can cause superconductivity, which casts doubt on the idea that there exists a unified phase diagram for them. Here we show that the ordered moments in a variety of iron pnictides are inversely proportional to the effective Curie constants of their nematic susceptibility. This unexpected scaling behavior suggests that the magnetic ground states of iron pnictides can be achieved by tuning the strength of nematic fluctuations. Therefore, a unified phase diagram can be established where superconductivity emerges from a hypothetical parent compound with a large ordered moment but weak nematic fluctuations, which suggests that iron-based superconductors are strongly correlated electron systems.

  9. Holographic p-wave superconductor models with Weyl corrections

    Directory of Open Access Journals (Sweden)

    Lu Zhang

    2015-04-01

    Full Text Available We study the effect of the Weyl corrections on the holographic p-wave dual models in the backgrounds of AdS soliton and AdS black hole via a Maxwell complex vector field model by using the numerical and analytical methods. We find that, in the soliton background, the Weyl corrections do not influence the properties of the holographic p-wave insulator/superconductor phase transition, which is different from that of the Yang–Mills theory. However, in the black hole background, we observe that similarly to the Weyl correction effects in the Yang–Mills theory, the higher Weyl corrections make it easier for the p-wave metal/superconductor phase transition to be triggered, which shows that these two p-wave models with Weyl corrections share some similar features for the condensation of the vector operator.

  10. Self-organizing of critical state in granulated superconductors

    International Nuclear Information System (INIS)

    Ginzburg, S.L.; Savitskaya, N.E.

    2000-01-01

    Critical state in granulated superconductors was studied on the basis of two mathematical models - the system of differential equations for calibration and invariant difference of phases and a simplified model describing the system of associated images and equivalent to the standard models to study self-organizing criticality. The critical state of granulated superconductors in all studied cases was shown to be self-organized. Besides, it is shown that the applied models are practically equivalent ones, that is they both show similar critical behavior and lead to coincidence of noncritical phenomena. For the first time one showed that the occurrence of self-organized critically within the system of nonlinear differential equations and its equivalence to self-organized critically in the standard models [ru

  11. On the prospects of increasing critical parameters of superconductors

    International Nuclear Information System (INIS)

    Lazarev, B.G.; Pan, V.M.

    1979-01-01

    Noted is the importance of the production of materials with high critical parameters for modern science and technology. Considered are present notions about the nature of high critical densities of critical current. The opinion is expressed that the search of most high-temperature and high-field superconductors should be carried out, in the first place, among compounds based on transition metals displaying structural instability. Noted are prospects of the work over the synthesis of metastabile compounds with A15 structure (e.g. Nb 3 Si), three-component and more complex compounds, and superconductive amorphous systems(metglasses). It is emphasized that the exceeding of the paramagnetic limit of the critical magnetic field is often observed experimentally, and the prospects of critical field increase are sufficiently favourable. Considered is the role of narrow current channels in the formation of critical current density of superconductors

  12. Superconductor Requirements and Characterization for High Field Accelerator Magnets

    Energy Technology Data Exchange (ETDEWEB)

    Barzi, E.; Zlobin, A. V.

    2015-05-01

    The 2014 Particle Physics Project Prioritization Panel (P5) strategic plan for U.S. High Energy Physics (HEP) endorses a continued world leadership role in superconducting magnet technology for future Energy Frontier Programs. This includes 10 to 15 T Nb3Sn accelerator magnets for LHC upgrades and a future 100 TeV scale pp collider, and as ultimate goal that of developing magnet technologies above 20 T based on both High Temperature Superconductors (HTS) and Low Temperature Superconductors (LTS) for accelerator magnets. To achieve these objectives, a sound conductor development and characterization program is needed and is herein described. This program is intended to be conducted in close collaboration with U.S. and International labs, Universities and Industry.

  13. p-wave holographic superconductors with Weyl corrections

    Science.gov (United States)

    Momeni, D.; Majd, N.; Myrzakulov, R.

    2012-03-01

    We study the (3+1)-dimensional p-wave holographic superconductors with Weyl corrections both numerically and analytically. We describe numerically the behavior of the critical temperature Tc with respect to charge density ρ in a limited range of Weyl coupling parameter γ and we find in general that the condensation becomes harder with the increase of the parameter γ. In the strong-coupling limit of Yang-Mills theory, we show that the minimum value of Tc obtained from the analytical approach is in good agreement with the numerical results, and finally show how we got remarkably a similar result for the critical exponent \\frac{1}{2} of the chemical potential μ and the order parameterlangJ1xrang with the numerical curves of the superconductors.

  14. Distinct magnetic signatures of fractional vortex configurations in multiband superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Silva, R. M. da [Programa de Pós-Graduação em Ciência dos Materiais, Universidade Federal de Pernambuco, Av. Prof. Luiz Freire, s/n, 50670-901 Recife-PE (Brazil); Milošević, M. V.; Peeters, F. M. [Departement Fysica, Universiteit Antwerpen, Groenenborgerlaan 171, B-2020 Antwerpen (Belgium); Domínguez, D. [Centro Atómico Bariloche, 8400 San Carlos de Bariloche, Río Negro (Argentina); Aguiar, J. Albino, E-mail: albino@df.ufpe.br [Departamento de Física, Universidade Federal de Pernambuco, Av. Prof. Luiz Freire, s/n, 50670-901 Recife-PE (Brazil); Programa de Pós-Graduação em Ciência dos Materiais, Universidade Federal de Pernambuco, Av. Prof. Luiz Freire, s/n, 50670-901 Recife-PE (Brazil)

    2014-12-08

    Vortices carrying fractions of a flux quantum are predicted to exist in multiband superconductors, where vortex core can split between multiple band-specific components of the superconducting condensate. Using the two-component Ginzburg-Landau model, we examine such vortex configurations in a two-band superconducting slab in parallel magnetic field. The fractional vortices appear due to the band-selective vortex penetration caused by different thresholds for vortex entry within each band-condensate, and stabilize near the edges of the sample. We show that the resulting fractional vortex configurations leave distinct fingerprints in the static measurements of the magnetization, as well as in ac dynamic measurements of the magnetic susceptibility, both of which can be readily used for the detection of these fascinating vortex states in several existing multiband superconductors.

  15. Mixed-state quasiparticle spectrum for d-wave superconductors

    International Nuclear Information System (INIS)

    Wang, Y.; MacDonald, A.H.

    1995-01-01

    Controversy concerning the pairing symmetry of high-T c materials has motivated an interest in those measurable properties of superconductors for which qualitative differences exist between the s-wave and d-wave cases. We report on a comparison between the microscopic electronic properties of d-wave and s-wave superconductors in the mixed state. Our study is based on self-consistent numerical solutions of the mean-field Bogoliubov--de Gennes equations for phenomenological BCS models which have s-wave and d-wave condensates in the absence of a magnetic field. We discuss differences between the s-wave and the d-wave local density of states, both near and away from vortex cores. Experimental implications for both scanning-tunneling-microscopy measurements and specific-heat measurements are discussed

  16. Holographic superconductors in the presence of dark matter

    Science.gov (United States)

    Rogatko, Marek; Wysokiński, Karol I.

    2017-10-01

    The application of the gauge-gravity duality, also known as anti-de Sitter/conformal field theory (AdS/CFT) correspondence to study condensed matter systems has resulted in a number of important findings. Using the analogy, we have studied the phase transitions between a holographic insulator and a metal at zero temperature as well as finite temperature transition between a metal and a holographic superconductor of s- and p-wave symmetry. The main aim of this note is to look in which way the dark matter might affect the properties of superconductors. The hope is that some of the observed modifications could be used to detect this ubiquitous but still elusive component of matter in the Universe.

  17. Magnetization effects from the g-2 inflector magnet superconductor

    International Nuclear Information System (INIS)

    Green, M.A.; Meng, W.

    1994-01-01

    The g-2 muon storage ring at Brookhaven National Laboratory will have a 1.7 meter long superconducting inflector magnet for injection of the muon beam into the storage ring. The field within the inflector is designed to be nearly zero. The inflector bucks out the main dipole field, but generates little or no stray field of its own. A portion of the field that remains is the field that is generated by circulating currents in the inflector magnet superconductor. Because the magnetization field has a different structure from field generated by the transport current, the magnetization field can adversely affect the field quality within the muon storage ring good field region. Correction of the effects of inflector superconductor magnetization and its effect on the good field region in the storage ring is discussed

  18. Study of high-temperature superconductors by IBA methods

    Science.gov (United States)

    Chamera, D.; Suchańska, M.; Kozel, V. V.

    1992-02-01

    The ion-induced electron emission (IIEE) technique to study the high- Tc superconductor of the Y 1Ba 2Cu 3O7 - x type was used. The temperature dependence of the IIEE intensity I( T) within the range of 77-300 K was measured. The change of the shape of the I( T) curve at the point 140 K was observed. The ion-induced photon emission technique (IIPE) to study the same high-temperature superconductor was also used. The temperature dependence of the intensity of some emission lines (BaI — 455.5 nm, CuI — 324.7 nm, YI — 467.4 nm) was measured. No anomaly at the point 140 K was observed. The nonmonotonic dependence of the IIEE intensity on the target temperature and the behaviour of the temperature dependence of the IIPE intensity are discussed.

  19. Study of high-temperature superconductors by IBA methods

    Energy Technology Data Exchange (ETDEWEB)

    Chamera, D.; Suchanska, M. (Inst. of Physics, Pedagogical Univ., Kielce (Poland)); Kozel, V.V. (Dept. of Physics, State Univ., Donetsk (USSR))

    1992-02-01

    The ion-induced electron emission (IIEE) technique to study the high-Tc superconductor of the Y{sub 1}Ba{sub 2}Cu{sub 3}O{sub 7-x} type was used. The temperature dependence of the IIEE intensity I(T) within the range of 77-300 K was measured. The change of the shape of the I(T) curve at the point 140 K was observed. The ion-induced photon emission technique (IIPE) to study the same high-temperature superconductor was also used. The temperature dependence of the intensity of some emission lines (BaI - 455.5 nm, CuI - 324.7 nm, YI - 467.4 nm) was measured. No anomaly at the point 140 K was observed. The nonmonotonic dependence of the IIEE intensity on the target temperature and the behaviour of the temperature dependence of the IIPE intensity are discussed. (orig.).

  20. Use of superconductors for storage and discharge of electrical energy

    International Nuclear Information System (INIS)

    Sole, J.

    1968-01-01

    After recalling the elementary properties which led to superconductors being used for generating very strong magnetic fields, as well as the methods used to attain the required very low temperatures in practice, the author presents in its elementary form the principle of storage and liberation of energy. A more detailed analysis of the successive charging, trapping, storage and discharge operations shows up the different aspects of the problem and is followed by a review of the very small amount of research published up to now and also by a presentation of the original work which has been carried out in this field. It is already possible to use superconducting materials as they are (i.e. although their characteristics have been adjusted with a view only to obtain very strong magnetic fields). Much more will be obtained from superconductors when they have been correctly adapted to this new very promising application to the storage and discharge of electrical energy. (authors) [fr

  1. Physics and Materials Science of High Temperature Superconductors

    Science.gov (United States)

    1989-08-26

    MEASUREMENTS OF YBaCuO SUPERCONDUCTORS. T. Puig, L. M. Martinez, M. T. Aurell, A. Sanchez, D. X. Chen and J. S. Mufioz, Dept. Fisica (Electromagnetisme...3800 Aveiro, Portugal; and A. P. Gonqalves and M. L. Almeida, Departamento de Quimica ICEN-LNETI, 2686 Sacaven, Portugal. The sintered bulk sample of...I I I I I I, THERMOELECTRIC POWER IN SUPERCONDUCTING CERAMIC OXIDES. ! E. B. Lopes, R. T. Henriques and M. Almeida, Dep. Quimica , ICEN-LNETI, P-2686

  2. Cryocooler applications for high-temperature superconductor magnetic bearings

    International Nuclear Information System (INIS)

    Niemann, R. C.

    1998-01-01

    The efficiency and stability of rotational magnetic suspension systems are enhanced by the use of high-temperature superconductor (HTS) magnetic bearings. Fundamental aspects of the HTS magnetic bearings and rotational magnetic suspension are presented. HTS cooling can be by liquid cryogen bath immersion or by direct conduction, and thus there are various applications and integration issues for cryocoolers. Among the numerous cryocooler aspects to be considered are installation; operating temperature; losses; and vacuum pumping

  3. Process for producing fine and ultrafine filament superconductor wire

    Science.gov (United States)

    Kanithi, Hem C.

    1992-01-01

    A process for producing a superconductor wire made up of a large number of round monofilament rods is provided for, comprising assembling a multiplicity of round monofilaments inside each of a multiplicity of thin wall hexagonal tubes and then assembling a number of said thin wall hexagonal tubes within an extrusion can and subsequently consolidating, extruding and drawing the entire assembly down to the desired wire size.

  4. Reversible magnetization of melt-processed NEG-123 superconductor

    Czech Academy of Sciences Publication Activity Database

    Jirsa, Miloš; Rameš, Michal; Muralidhar, M.; Kacmarcik, J.; Marcenat, C.

    2010-01-01

    Roč. 118, č. 5 (2010), 1022-1023 ISSN 0587-4246. [Czech and Slovak Conference on Magnetism /14./. Košice, 06.07.2010-09.07.2010] R&D Projects: GA MŠk(CZ) ME10069 Institutional research plan: CEZ:AV0Z10100520 Keywords : electronic specific heat * NEG-123 * high-Tc superconductor s * thermodynamic characteristics Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.467, year: 2010

  5. Gamma-stability and vortex motion in type II superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Kurzke, Matthias; Spirn, Daniel

    2009-07-15

    We consider a time-dependent Ginzburg-Landau equation for superconductors with a strictly complex relaxation parameter, and derive motion laws for the vortices in the case of a finite number of vortices in a bounded magnetic field. The motion laws correspond to the flux-flow Hall effect. As our main tool, we develop a quantitative {gamma}-stability result relating the Ginzburg-Landau energy to the renormalized energy. (orig.)

  6. Terahertz field control of interlayer transport modes in cuprate superconductors

    Science.gov (United States)

    Schlawin, Frank; Dietrich, Anastasia S. D.; Kiffner, Martin; Cavalleri, Andrea; Jaksch, Dieter

    2017-08-01

    We theoretically show that terahertz pulses with controlled amplitude and frequency can be used to switch between stable transport modes in layered superconductors, modeled as stacks of Josephson junctions. We find pulse shapes that deterministically switch the transport mode between superconducting, resistive, and solitonic states. We develop a simple model that explains the switching mechanism as a destabilization of the center-of-mass excitation of the Josephson phase, made possible by the highly nonlinear nature of the light-matter coupling.

  7. Experiments of the superconducting proximity effect between superconductor and semiconductor

    Science.gov (United States)

    Hatano, Mutsuko; Nishino, Toshikazu; Kawabe, Ushio

    1987-01-01

    Coherence length in a semiconductor induced by the superconductor proximity effect is obtained experimentally from superconducting transition temperature measurements based on the de Gennes-Werthamer-Hauser theory. It was found that the coherence length in the semiconductor increases with increase in the carrier concentration n as a function of n1/3. This result agreed with the numerical result derived from the Seto-Van Duzer theory.

  8. Phase stratification of the electron fluid in new superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Gor' kov, L.P.; Sokol, A.V.

    1987-10-01

    Experimental data obtained for lanthanum cuprate (La/sub 2/CuO/sub 4/), a high-temperature superconductor, are examined in an attempt to identify some extraordinary properties of this material in its normal (nonsuperconducting) state. An analysis of the experimental data suggests that La/sub 2/CuO/sub 4/ contains two coexisting phases, a conducting phase and a dielectric phase, which explains some of the observed characteristics of the normal state of this material. 6 references.

  9. Analysis of some experimental data for high-Tc superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Gor' kov, L.P.; Kopin, N.B.

    1988-04-01

    Experimental data on new superconductors, YBa/sub 2/Cu/sub 3/O/sub 7/ and La(1.85)Sr(0.15)Cu/sub 4/, are analyzed with the objective of estimating the width of the fluctuation region near Tc and electron band parameters. The data are not inconsistent with the presence of delocalized electrons and indicate the narrowness of the fluctuation region. 16 references.

  10. Preparation of Bismuth- and Thallium-Based Cuprate Superconductors

    Science.gov (United States)

    1991-10-01

    erage work period (29); early symptoms of thallium - poisoning include hair loss. Safety considerations in handling thallium compounds should include... Thallium -Based Cuprate Superconductors by S. A. Sunshine and T. A. Vanderah Chemistry Division, Research Department Naval Weapons Center, China Lake, CA...Technical Report #2 10/90-9/91 4. TITLE AND SUBTITLE 5. FUNDING NUMBERS Preparation of Bismuth- and Thallium -Based Cuprate Suoerconductors NOOO14-91 WX

  11. Interaction of Ultrasound with Vortices in Type-II Superconductors

    OpenAIRE

    Sonin, E. B.

    1996-01-01

    The theory of the ultrasound propagation in the mixed state of type-II superconductors is suggested which takes into account the Magnus force on vortices, the anti-Magnus force on ions, and diamagnetism of the mixed state. The acoustic Faraday effect (rotation of polarization of the transverse ultrasonic wave propagating along vortices) is shown to be linear in the Magnus force in any regime of the flux flow for wavelengths used in the ultrasound experiments now. Therefore, in contrast to pre...

  12. Electron spectroscopy on high-temperature superconductors and related compounds

    International Nuclear Information System (INIS)

    Knupfer, M.

    1994-01-01

    In the last two classes of materials have been discovered which distinguish themselves due to a transition into the superconducting state at relatively high temperatures. These are the cuprate superconductors and the alkali metal doped fullerenes. In this work the electronic structure of representatives of these materials, undoped and Ca-doped YBa 2 Cu 4 O 8 and A 3 C 60 (A=K, Rb), has been investigated using electron energy-loss spectroscopy and photoemission spectroscopy. (orig.) [de

  13. Time dependence of magnetization of high temperature superconductors

    International Nuclear Information System (INIS)

    Larkin, A.I.; Geshkenbein, V.B.

    1988-10-01

    Magnetization of high T c superconductors logarithmically decreases with time. There is a maximum in the temperature dependence of the coefficient at this logarithm. If one assumes that there do exist two kinds of pinning centers, then this dependence can be described in the Anderson theory of thermal creeps of Abrikosov's vortices. The temperature dependence of the critical current is also discussed. (author). 23 refs

  14. 1/f Noise in Ceramic Superconductors and Granular Resistors

    OpenAIRE

    Takagi, Keiji; Mizunami, Toru; Okayama, Hideyuki; Shiyuan, Yang

    1990-01-01

    The authors have measured the current noise in some components of granular structure. The samples are ceramic superconductors, carbon-black graft-polymer resistors, and positive temperature coefficient(PTe) ceramics. All noise spectra are of the 1/! type. The temperature dependence of the noise level is measured and compared with the temperature dependence of the resistance, It is shown that in these components the temperature coefficient of the resistance is related to the noise level as pre...

  15. Anomalous transport phenomena in px+i py superconductors

    Science.gov (United States)

    Li, Songci; Andreev, A. V.; Spivak, B. Z.

    2015-09-01

    Spontaneous breaking of time-reversal symmetry in superconductors with the px+i py symmetry of the order parameter allows for a class of effects which are analogous to the anomalous Hall effect in ferromagnets. These effects exist below the critical temperature, T

  16. The discovery and some properties of high-T superconductors

    International Nuclear Information System (INIS)

    Mueller, Karl A.

    1996-01-01

    Full text: Starting with the first observation of superconductivity in an oxide, the history of its development is traced. Basically and consecutively, three kinds of oxide superconductors have been found. Compounds with normal transition-metal condition bands, oxides with cations exhibiting charge disproportion, and finally the cuprates with large coulomb on-site repulsion, U. This discussion will lead over to a characterization of the highest-T materials both concerning their physical properties and application perspectives

  17. The paramagnetic effect in Type-I superconductors

    International Nuclear Information System (INIS)

    Rothen, F.; Lievre, C.

    1975-01-01

    The paramagnetic effect in superconductors was first observed by Steiner and Schoeneck in 1943. This effect takes place in a cylindrical wire if superconductivity is destroyed by a current J in the presence of a magnetic field He parallel to the axis: one notices that the average longitudinal magnetic induction inside the wire can greatly exceed He. An attempt is made to compute the maximal value of the longitudinal magnetic permeability of the current-carrying wire. (Auth.)

  18. Theory of Equilibrium Flux Lattices in Unconventional Superconductors

    International Nuclear Information System (INIS)

    Franz, M.; Affleck, I.; Amin, M.H.; Affleck, I.

    1997-01-01

    We investigate equilibrium flux lattice structures in superconductors with unconventional order parameters, such as high-T c cuprates, using a generalized London model with nonlocal electrodynamics derived from a simple microscopic model. We find a rich phase diagram containing triangular, centered rectangular, and square lattices with various orientations relative to the ionic lattice, as a function of magnetic field and temperature. copyright 1997 The American Physical Society

  19. Superconductor devices useful for disk drives and the like

    International Nuclear Information System (INIS)

    Barnes, F.S.

    1989-01-01

    This patent describes an apparatus for exchanging information with a circular media and which includes a drive mechanism for radially positioning a head relative to the media with the head including structure for imparting information to the media, for detecting information on the media, or both, comprising: an arm having at least one head attached thereto wherein the head is capable of interchanging information with the media; and bearing means for suspending the arm, the bearing means including a superconductor layer element, a magnetic field source element and means mounting one of the elements on the arm and the other the element in interfacing relationship to the one of the elements so that the interfacing relationship is maintained throughout the radial travel of the arm. A drive for exchanging information between a circular media mounted on a spindle and a head comprising an elongated arm having the head attached thereto and a layer of superconductor material on one side thereof, the arm being radially positionable over the surface of the circular media, an annular magnet means in peripheral relation to the circular media and oriented to direct a magnetic field towards the arm superconductor layer for maintaining a relatively constant spacing between the arm and the media throughout the radial travel of the arm relative to the circular media

  20. Gravitational Field Shielding by Scalar Field and Type II Superconductors

    Directory of Open Access Journals (Sweden)

    Zhang B. J.

    2013-01-01

    Full Text Available The gravitational field shielding by scalar field and type II superconductors are theoret- ically investigated. In accord with the well-developed five-dimensional fully covariant Kaluza-Klein theory with a scalar field, which unifies the Einsteinian general relativity and Maxwellian electromagnetic theory, the scalar field cannot only polarize the space as shown previously, but also flatten the space as indicated recently. The polariza- tion of space decreases the electromagnetic field by increasing the equivalent vacuum permittivity constant, while the flattening of space decreases the gravitational field by decreasing the equivalent gravitational constant. In other words, the scalar field can be also employed to shield the gravitational field. A strong scalar field significantly shield the gravitational field by largely decreasing the equivalent gravitational constant. According to the theory of gravitational field shielding by scalar field, the weight loss experimentally detected for a sample near a rotating ceramic disk at very low tempera- ture can be explained as the shielding of the Earth gravitational field by the Ginzburg- Landau scalar field, which is produced by the type II superconductors. The significant shielding of gravitational field by scalar field produced by superconductors may lead to a new spaceflight technology in future.

  1. Processing of bulk Bi-2223 high-temperature superconductor

    Directory of Open Access Journals (Sweden)

    Alexander Polasek

    2005-12-01

    Full Text Available The Bi2Sr2Ca2Cu3 O10+x (Bi-2223 is one of the main high temperature superconductors for applications. One of these applications is the Superconductor Fault Current Limiter (SCFCL, which is a very promising high temperature superconducting device. SCFCL's can be improved by using bulk superconductors with high critical currents, which requires a sufficiently dense and textured material. In the present work, a process for improving the microstructure of Bi-2223 bulk samples is investigated. Pressed precursor blocks are processed by sintering with a further partial melting step, in order to enhance the Bi-2223 grain texture and to healing cracks induced by pressing. In order to improve the microstructure, the precursor is mixed with silver powder before pressing. Samples with and without silver powder have been studied, with the aim of investigating the influence of silver on the microstructure evolution. The phase contents and the microstructure obtained have been analyzed through XRD and SEM/EDS. The electromagnetic characterization has been performed by Magnetic Susceptibility Analysis. We present and discuss the process and the properties of the superconducting blocks. High fractions of textured Bi-2223 grains have been obtained.

  2. Numerical solution of a model for a superconductor field problem

    International Nuclear Information System (INIS)

    Alsop, L.E.; Goodman, A.S.; Gustavson, F.G.; Miranker, W.L.

    1979-01-01

    A model of a magnetic field problem occurring in connection with Josephson junction devices is derived, and numerical solutions are obtained. The model is of mathematical interest, because the magnetic vector potential satisfies inhomogeneous Helmholtz equations in part of the region, i.e., the superconductors, and the Laplace equation elsewhere. Moreover, the inhomogeneities are the guage constants for the potential, which are different for each superconductor, and their magnitudes are proportional to the currents flowing in the superconductors. These constants are directly related to the self and mutual inductances of the superconducting elements in the device. The numerical solution is obtained by the iterative use of a fast Poisson solver. Chebyshev acceleration is used to reduce the number of iterations required to obtain a solution. A typical problem involves solving 100,000 simultaneous equations, which the algorithm used with this model does in 20 iterations, requiring three minutes of CPU time on an IBM VM/370/168. Excellent agreement is obtained between calculated and observed values for the inductances

  3. Spin excitations in hole-overdoped iron-based superconductors.

    Science.gov (United States)

    Horigane, K; Kihou, K; Fujita, K; Kajimoto, R; Ikeuchi, K; Ji, S; Akimitsu, J; Lee, C H

    2016-09-12

    Understanding the overall features of magnetic excitation is essential for clarifying the mechanism of Cooper pair formation in iron-based superconductors. In particular, clarifying the relationship between magnetism and superconductivity is a central challenge because magnetism may play a key role in their exotic superconductivity. BaFe2As2 is one of ideal systems for such investigation because its superconductivity can be induced in several ways, allowing a comparative examination. Here we report a study on the spin fluctuations of the hole-overdoped iron-based superconductors Ba1-xKxFe2As2 (x = 0.5 and 1.0; Tc = 36 K and 3.4 K, respectively) over the entire Brillouin zone using inelastic neutron scattering. We find that their spin spectra consist of spin wave and chimney-like dispersions. The chimney-like dispersion can be attributed to the itinerant character of magnetism. The band width of the spin wave-like dispersion is almost constant from the non-doped to optimum-doped region, which is followed by a large reduction in the overdoped region. This suggests that the superconductivity is suppressed by the reduction of magnetic exchange couplings, indicating a strong relationship between magnetism and superconductivity in iron-based superconductors.

  4. Quantum phase transitions in highly crystalline two-dimensional superconductors.

    Science.gov (United States)

    Saito, Yu; Nojima, Tsutomu; Iwasa, Yoshihiro

    2018-02-22

    Superconductor-insulator transition is one of the remarkable phenomena driven by quantum fluctuation in two-dimensional (2D) systems. Such a quantum phase transition (QPT) was investigated predominantly on highly disordered thin films with amorphous or granular structures using scaling law with constant exponents. Here, we provide a totally different view of QPT in highly crystalline 2D superconductors. According to the magneto-transport measurements in 2D superconducting ZrNCl and MoS 2 , we found that the quantum metallic state commonly observed at low magnetic fields is converted via the quantum Griffiths state to the weakly localized metal at high magnetic fields. The scaling behavior, characterized by the diverging dynamical critical exponent (Griffiths singularity), indicates that the quantum fluctuation manifests itself as superconducting puddles, in marked contrast to the thermal fluctuation. We suggest that an evolution from the quantum metallic to the quantum Griffiths state is generic nature in highly crystalline 2D superconductors with weak pinning potentials.

  5. Nematicity at the Hund's metal crossover in iron superconductors

    Science.gov (United States)

    Fanfarillo, L.; Giovannetti, G.; Capone, M.; Bascones, E.

    2017-04-01

    The theoretical understanding of the nematic state of iron-based superconductors and especially of FeSe is still a puzzling problem. Although a number of experiments call for a prominent role of local correlations and place iron superconductors at the entrance of a Hund's metal state, the effect of the electronic correlations on the nematic state has been theoretically poorly investigated. In this work we study the nematic phase of iron superconductors accounting for local correlations, including the effect of the Hund's coupling. We show that Hund's physics strongly affects the nematic properties of the system. It severely constrains the precise nature of the feasible orbital-ordered state and induces a differentiation in the effective masses of the z x /y z orbitals in the nematic phase. The latter effect leads to distinctive signatures in different experimental probes overlooked so far in the interpretation of experiments. As notable examples the splittings between z x and y z bands at Γ and M points are modified, with important consequences for angle-resolved photoemission spectroscopy measurements.

  6. Magnetic flux periodicities and finite momentum pairing in unconventional superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Loder, Florian

    2009-12-22

    This work contains a thorough study of the magnetic flux periodicity of loops of conventional and unconventional, especially d-wave, superconductors. Although already in 1961, several independent works showed that the flux period of a conventional superconducting loop is the superconducting flux quantum hc/2e, this question has never been investigated deeply for unconventional superconductors. And indeed, we show here that d-wave superconducting loops show a basic flux period of the normal flux quantum hc/e, a property originating from the nodal quasi-particle states. This doubling of the flux periodicity is best visible in the persistent current circulating in the loop, and it affects other properties of the superconductor such as the periodicity of d-wave Josephson junctions. In the second part of this work, the theory of electron pairing with finite center-of-mass momentum, necessary for the description of superconducting loops, is extended to systems in zero magnetic field. We show that even in the field free case, an unconventional pairing symmetry can lead to a superconducting ground state with finite-momentum electron pairs. Such a state has an inhomogeneous charge density and therefore is a basis for the description of coexistence of superconductivity and stripe order. (orig.)

  7. Studies on advanced superconductors for fusion device. Pt. 2. Metallic superconductors other than Nb{sub 3}Sn

    Energy Technology Data Exchange (ETDEWEB)

    Tachikawa, K.; Yamamoto, J.; Mito, T. [eds.

    1997-03-01

    A comprehensive report on the present status of the development of Nb{sub 3}Sn superconductors was published as the NIFS-MEMO-20 in March, 1996 (Part 1 of this report series). The second report of this study covers various progress so far achieved in the research and development on advanced metallic superconductors other than Nb{sub 3}Sn. Among different A15 crystal-type compounds, Nb{sub 3}Al has been fabricated into cables with large current-carrying capacity for fusion device referring its smaller sensitivity to mechanical strain than Nb{sub 3}Sn. Other high-field A15 superconductors, e.g. V{sub 3}Ga, Nb{sub 3}Ge and Nb{sub 3}(Al,Ge), have been also fabricated through different novel processes as promising alternatives to Nb{sub 3}Sn conductors. Meanwhile, B1 crystal-type NbN and C15 crystal-type V{sub 2}(Hf,Zr) high-field superconductors are characterized by their excellent tolerance to mechanical strain and neutron irradiation. Chevrel-type PbMo{sub 6}S{sub 8} compound has gained much interests due to its extremely high upper critical field. In addition, this report includes the recent progress in ultra-fine filamentary NbTi wires for AC use, and that in NbTi/Cu magnetic shields necessary in the application of high magnetic field. The data on the decay of radioactivity in a variety of metals relating to fusion superconducting magnet are also attached as appendices. We hope that this report might contribute substantially as a useful reference for the planning of fusion apparatus of next generation as well as that of other future superconducting devices. (author)

  8. Low-Temperature Synthesis Routes to Intermetallic Superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Schaak, Raymond E

    2008-01-08

    Over the past few years, our group has gained expertise at developing low-temperature solution-based synthetic pathways to complex nanoscale solids, with particular emphasis on nanocrystalline intermetallic compounds. Our synthetic capabilities are providing tools to reproducibly generate intermetallic nanostructures with simultaneous control over crystal structure, composition, and morphology. This DOE-funded project aims to expand these capabilities to intermetallic superconductors. This could represent an important addition to the tools that are available for the synthesis and processing of intermetallic superconductors, which traditionally utilize high-temperature, high-pressure, thin film, or gas-phase vacuum deposition methods. Our current knowledge of intermetallic superconductors suggests that significant enhancements could result from the inherent benefits of low-temperature solution synthesis, e.g. metastable phase formation, control over nanoscale morphology to facilitate size-dependent property studies, robust and inexpensive processability, low-temperature annealing and consolidation, and impurity incorporation (for doping, stoichiometry control, flux pinning, and improving the critical fields). Our focus is on understanding the superconducting properties as a function of synthetic route, crystal structure, crystallite size, and morphology, and developing the synthetic tools necessary to accomplish this. This research program can currently be divided into two classes of superconducting materials: intermetallics (transition metal/post transition metal) and metal carbides/borides. Both involve the development and exploitation of low-temperature synthesis routes followed by detailed characterization of structures and properties, with the goal of understanding how the synthetic pathways influence key superconducting properties of selected target materials. Because of the low-temperature methods used to synthesize them and the nanocrystalline morphologies

  9. Instabilities in superconductors and in intense laser produced plasma's

    International Nuclear Information System (INIS)

    Banerjee, Satyajit S.; Mohan, Shyam; Sinha, Jaivardhan; Kahaly, Subendhu; Ravindra Kumar, G.

    2007-01-01

    In this talk I will attempt to discuss phenomena's in two areas of physics which appear quite divorced from each other, viz., superconductivity and plasma's. The first portion of the talk will describe the behavior of a collection of vortices in superconductors in a random pinning environment. Vortices manifest themselves in a variety of systems, like in fluids and in type II superconductors. A collection of vortices inside superconductors behaves like an elastic media. Investigating this elastic medium of the vortex state is a convenient prototype for investigating similar physics in a wide variety of systems, viz., charge density waves, Wigner crystals, magnetic domains, etc. The behavior of all these systems can be generalized under, nature of elastic media in the presence of a random pinning environment and thermal fluctuations. Based on the idea that softer matter is easy to pin we have attempted to investigate how the vortex lattice disorders as its gets softer. Surprisingly we find evidence to two distinct types of instabilities in the vortex lattice instead of one. These two instabilities produce vastly different effects on certain quantities associated with the extent of disorder in the superconductor. It appears that prior to softening of the vortex state, a heterogeneously pinned state of the vortex matter appears, perhaps through a KT like transition. In the second part of the talk, I will attempt to describe some of our recent results pertaining to instabilities and the appearance of giant magnetic fields in plasma's. These results have been obtained with a high sensitivity magneto-optical imaging setup we have developed at IIT Kanpur. Using the setup, we investigate distribution of magnetic fields around dense solid plasmas generated by intense p-polarized laser (∼10 16 Wcm -2 , 100 fs) irradiation of magnetic tapes, using high sensitivity magneto optical imaging technique. We demonstrate giant axial magnetic fields and map out for the first time

  10. Fundamental studies of superconductors using scanning magnetic imaging

    Energy Technology Data Exchange (ETDEWEB)

    Kirtley, J R [Center for Probing the Nanoscale, Stanford University, Stanford, CA (United States)

    2010-12-01

    In this review I discuss the application of scanning magnetic imaging to fundamental studies of superconductors, concentrating on three scanning magnetic microscopies-scanning SQUID microscopy (SSM), scanning Hall bar microscopy (SHM) and magnetic force microscopy (MFM). I briefly discuss the history, sensitivity, spatial resolution, invasiveness and potential future developments of each technique. I then discuss a selection of applications of these microscopies. I start with static imaging of magnetic flux: an SSM study provides deeper understanding of vortex trapping in narrow strips, which are used to reduce noise in superconducting circuitry. Studies of vortex trapping in wire lattices, clusters and arrays of rings and nanoholes show fascinating ordering effects. The cuprate high-T{sub c} superconductors are shown to have predominantly d-wave pairing symmetry by magnetic imaging of the half-integer flux quantum effect. Arrays of superconducting rings act as a physical analog for the Ising spin model, with the half-integer flux quantum effect helping to eliminate one source of disorder in antiferromagnetic arrangements of the ring moments. Tests of the interlayer tunneling model show that the condensation energy available from this mechanism cannot account for the high critical temperatures observed in the cuprates. The strong divergence in the magnetic fields of Pearl vortices allows them to be imaged using SSM, even for penetration depths of a millimeter. Unusual vortex arrangements occur in samples comparable in size to the coherence length. Spontaneous magnetization is not observed in Sr{sub 2}RuO{sub 4}, which is believed to have p{sub x} {+-} ip{sub y} pairing symmetry, although effects hundreds of times bigger than the sensitivity limits had been predicted. However, unusual flux trapping is observed in this superconductor. Finally, unusual flux arrangements are also observed in magnetic superconductors. I then turn to vortex dynamics: imaging of vortices

  11. Fundamental studies of superconductors using scanning magnetic imaging

    Science.gov (United States)

    Kirtley, J. R.

    2010-12-01

    In this review I discuss the application of scanning magnetic imaging to fundamental studies of superconductors, concentrating on three scanning magnetic microscopies—scanning SQUID microscopy (SSM), scanning Hall bar microscopy (SHM) and magnetic force microscopy (MFM). I briefly discuss the history, sensitivity, spatial resolution, invasiveness and potential future developments of each technique. I then discuss a selection of applications of these microscopies. I start with static imaging of magnetic flux: an SSM study provides deeper understanding of vortex trapping in narrow strips, which are used to reduce noise in superconducting circuitry. Studies of vortex trapping in wire lattices, clusters and arrays of rings and nanoholes show fascinating ordering effects. The cuprate high-Tc superconductors are shown to have predominantly d-wave pairing symmetry by magnetic imaging of the half-integer flux quantum effect. Arrays of superconducting rings act as a physical analog for the Ising spin model, with the half-integer flux quantum effect helping to eliminate one source of disorder in antiferromagnetic arrangements of the ring moments. Tests of the interlayer tunneling model show that the condensation energy available from this mechanism cannot account for the high critical temperatures observed in the cuprates. The strong divergence in the magnetic fields of Pearl vortices allows them to be imaged using SSM, even for penetration depths of a millimeter. Unusual vortex arrangements occur in samples comparable in size to the coherence length. Spontaneous magnetization is not observed in Sr2RuO4, which is believed to have px ± ipy pairing symmetry, although effects hundreds of times bigger than the sensitivity limits had been predicted. However, unusual flux trapping is observed in this superconductor. Finally, unusual flux arrangements are also observed in magnetic superconductors. I then turn to vortex dynamics: imaging of vortices in rings of highly underdoped

  12. Theoretical study of magnetoelectric effects in noncentrosymmetric and cuprate superconductors

    Science.gov (United States)

    Kashyap, Manoj K.

    A century after the discovery of superconductivity at the lab of Kamerlingh Onnes in 1911, it is noticeable that the phenomenon is quite ubiquitous in nature. In addition to a long list of superconducting alloys and compounds, almost half the elements in the periodic table superconduct. By the late seventies, superconductivity was thought to be well understood. This turned out to be a myth, with the discovery of unconventional superconductors that defied Bardeen-Cooper-Schrieffer (BCS) theory. Cuprates have been the most prominent example among them ever since their discovery in 1986 by Bednorz and Muller. Another example of non-compliance with BCS theory lie among noncentrosymmetric superconductors. In this dissertation, magnetoelectric (ME) effects in these two classes of superconductors have been studied from different perspectives, utilizing Ginzburg-Landau (GL) theory. Even though GL theory was proposed before the BCS theory, it was not given much importance due to its phenomenological nature until Gor'kov proved that it is a limiting form of the microscopic BCS theory. However today, in the absence of any complete microscopic theory to explain superconductivity in unconventional superconductors, Ginzburg-Landau theory is an important tool to move ahead and qualitatively understand the behavior of varied superconducting systems. Noncentrosymmetric superconductors have generated much theoretical interest since 2004 despite been known for long. The absence of inversion symmetry in non- centrosymmetric superconductors allows for extra terms called Lifshitz invariants in the Ginzburg-Landau functional. This leads to magnetoelectric effects that do not exist in centrosymmetric superconductors. One manifestation of this is in the vortex structure in materials with a cubic point group O. In particular, a current is predicted to flow parallel to the applied magnetic field in such a vortex in addition to the usual vortex supercurrents. In this work, we present both

  13. Meissner effect in diffusive normal metal/d-wave superconductor junctions

    NARCIS (Netherlands)

    Yokoyama, Takehito; Tanaka, Yukio; Golubov, Alexandre Avraamovitch; Inoue, Jun-ichiro; Asano, Yasuhiro

    2005-01-01

    The Meissner effect in diffusive normal metal/insulator/d-wave superconductor junctions is studied theoretically in the framework of the Usadel equation under the generalized boundary condition. The effect of midgap Andreev resonant states (MARS) formed at the interface of d-wave superconductor is

  14. Electrochemical investigations of high-Tc superconductors - low-temperature electrochemistry

    International Nuclear Information System (INIS)

    Lorenz, W.J.

    1992-01-01

    This research report presents a summary of results obtained by electrochemical investigations of high-Tc superconductors at room temperature and below the critical temperature (Tc). The studies were to reveal the behaviour of the ceramic superconducting materials at the interface between superconductor and ionic conductor. (MM) With 4 tabs., 8 figs [de

  15. Carrier transport in multi-terminal superconductor/two-dimensional electron gas Josephson junctions

    NARCIS (Netherlands)

    Guzenko, V.A.; Schäpers, Th.; Müller, R.P.; Golubov, Alexandre Avraamovitch; Brinkman, Alexander; Crecelius, G.; Kaluza, A.; Lüth, H.

    2001-01-01

    The critical current in a superconductor/two-dimensional electron gas junction/superconductor junction is controlled by an injection current. In case of a carrier injection from one contact to the semiconductor through the two-dimensional electron gas region of the junction to an ohmic contact at

  16. The use of the special theory of relativity for the Meissner Effect in superconductor

    NARCIS (Netherlands)

    Rashid, M.

    2011-01-01

    The electromagnetic waves are considered in this article as the mediators of interaction in the Meissner Effect or the diamagnetic property of the superconductors. During the cooling of a superconductor electromagnetic waves may be released when the electrons occupy lower states of the energy. These

  17. High temperature superconductivity: Concept, preparation and testing of high Tc superconductor compounds, and applications

    International Nuclear Information System (INIS)

    Harara, Wafik

    1992-06-01

    Many studies have been carried out on high temperature superconductors with transition temperature above that of the liquid nitrogen. In this scientific study the concept and the mechanism of this phenomena are discussed, in addition the examples of preparation and testing of high temperature superconductors compounds are shown. Also the most important applications in industry are explained. (author). 15 refs., 2 tabs., 18 figs

  18. Temperature dependence of the kinetic coefficients of superconductors in the intermediate state

    International Nuclear Information System (INIS)

    Gorelik, L.Y.; Kadigrobov, A.M.

    1981-01-01

    It is demonstrated that in the case of a superconductor in the intermediate state at temperature T such that e0/T 0 denoting the characteristic superconductor energy gap) the sound absorption coefficient can be strongly temperature dependent and thermal conductivity along the layers of normal metal can be nonlinearly dependent on the temperature

  19. Macroscopic quantum coherence in a magnetic nanoparticle above the surface of a superconductor

    Science.gov (United States)

    Chudnovsky; Friedman

    2000-12-11

    We study macroscopic quantum tunneling of the magnetic moment in a single-domain particle placed above the surface of a superconductor. Such a setup allows one to manipulate the height of the energy barrier, preserving the degeneracy of the ground state. The tunneling amplitude and the effect of the dissipation in the superconductor are computed.

  20. Macroscopic Quantum Coherence in a Magnetic Nanoparticle Above the Surface of a Superconductor

    Energy Technology Data Exchange (ETDEWEB)

    Chudnovsky, Eugene M.; Friedman, Jonathan R.

    2000-12-11

    We study macroscopic quantum tunneling of the magnetic moment in a single-domain particle placed above the surface of a superconductor. Such a setup allows one to manipulate the height of the energy barrier, preserving the degeneracy of the ground state. The tunneling amplitude and the effect of the dissipation in the superconductor are computed.

  1. Macroscopic Quantum Coherence in a Magnetic Nanoparticle Above the Surface of a Superconductor

    International Nuclear Information System (INIS)

    Chudnovsky, Eugene M.; Friedman, Jonathan R.

    2000-01-01

    We study macroscopic quantum tunneling of the magnetic moment in a single-domain particle placed above the surface of a superconductor. Such a setup allows one to manipulate the height of the energy barrier, preserving the degeneracy of the ground state. The tunneling amplitude and the effect of the dissipation in the superconductor are computed

  2. Static Test for a Gravitational Force Coupled to Type 2 YBCO Superconductors

    Science.gov (United States)

    Li, Ning; Noever, David; Robertson, Tony; Koczor, Ron; Brantley, Whitt

    1997-01-01

    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 cc. Recent experiments have reported anomalous weight loss for a test mass suspended above a rotating type II, YBCO superconductor, with the percentage change (0.05 - 2.1 %) independent of the test mass' chemical composition and diamagnetic properties. A variation of 5 parts per 10' 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. Changes in acceleration were measured to be less than 2 parts in 108 of the normal gravitational acceleration. This result puts new limits on the strength and range of the proposed coupling between static superconductors and gravity.

  3. Quantum theory of an atom in proximity to a superconductor

    Science.gov (United States)

    Le Dall, Matthias; Diniz, Igor; Dias da Silva, Luis G. G. V.; de Sousa, Rogério

    2018-02-01

    The impact of superconducting correlations on localized electronic states is important for a wide range of experiments in fundamental and applied superconductivity. This includes scanning tunneling microscopy of atomic impurities at the surface of superconductors, as well as superconducting-ion-chip spectroscopy of neutral ions and Rydberg states. Moreover, atomlike centers close to the surface are currently believed to be the main source of noise and decoherence in qubits based on superconducting devices. The proximity effect is known to dress atomic orbitals in Cooper-pair-like states known as Yu-Shiba-Rusinov (YSR) states, but the impact of superconductivity on the measured orbital splittings and optical-noise transitions is not known. Here we study the interplay between orbital degeneracy and particle-number admixture in atomic states, beyond the usual classical spin approximation. We model the atom as a generalized Anderson model interacting with a conventional s -wave superconductor. In the limit of zero on-site Coulomb repulsion (U =0 ), we obtain YSR subgap energy levels that are identical to the ones obtained from the classical spin model. When Δ is large and U >0 , the YSR spectra are no longer quasiparticle-like, and the highly degenerate orbital subspaces are split according to their spin, orbital, and number-parity symmetry. We show that U >0 activates additional poles in the atomic Green's function, suggesting an alternative explanation for the peak splittings recently observed in scanning tunneling microscopy of orbitally-degenerate impurities in superconductors. We describe optical excitation and absorption of photons by YSR states, showing that many additional optical channels open up in comparison to the nonsuperconducting case. Conversely, the additional dissipation channels imply increased electromagnetic noise due to impurities in superconducting devices.

  4. Anisotropic superconducting state parameters of Tl-2212 superconductors

    International Nuclear Information System (INIS)

    Khaskalam, Amit K.; Singh, R.K.; Varshney, Dinesh

    2001-01-01

    We have estimated the superconducting state parameters and their anisotropy in thallium based superconductors (Tl-2212), in the frame work of Fermi liquid approach. Determination of the effective mass of the charge carriers from the Fermi velocity and estimated anisotropic superconducting state parameters, particularly, the magnetic penetration depth along and perpendicular to the conducting plane. The coherence length along and perpendicular to the ab plane is evaluated and appears to be higher. The temperature dependence of penetration depth, their anisotropy and Ginsburg Landau parameter for optimised doped Tl based cuprates shows the power law. The technique permits a consistency with the reported data. (author)

  5. Qualification tests and facilities for the ITER superconductors

    International Nuclear Information System (INIS)

    Bruzzone, P.; Wesche, R.; Stepanov, B.; Cau, F.; Bagnasco, M.; Calvi, M.; Herzog, R.; Vogel, M.

    2009-01-01

    All the ITER superconductors are tested as short length samples in the SULTAN test facility at CRPP. Twenty-four TF conductor samples with small layout variations were tested since February 2007 with the aim of verifying the design and qualification of the manufacturers. The sample assembly and the measurement techniques at CRPP are discussed. Starting in 2010, another test facility for ITER conductors, named EDIPO, will be operating at CRPP to share with SULTAN the load of the samples for the acceptance tests during the construction of ITER.

  6. Electrical contacting techniques for high Tc superconductor applications

    International Nuclear Information System (INIS)

    Tzeng, Y.; Belser, M.

    1988-01-01

    Three methods for making low resistivity electrical contacts to high Tc superconductors have been studied. This includes vacuum deposition of silver thin films, welding of silver to HTSC, and painting or printing of silver contacts to HTSC. Specific contact resistance lower than 1 . E-8 Ohm-cm2 can routinely be achieved for both electronic and power applications. Oxygen annealing is found to improve the contact resistance significantly. Both the contact fabrication processes and the electrical properties of these contacts will be discussed

  7. Ceramic high temperature superconductors for high current applications

    Energy Technology Data Exchange (ETDEWEB)

    Christiansen, J.

    1996-12-31

    Composite Reaction Texturing (CRT) is a technique which uses a fine distribution of pre-aligned seeds as nucleating sites for texturing oxide superconductors. It has successfully been applied to the texturing of Bi-2212 compounds. A furhter application of CRT is reported in which Y-123 is biaxially textured using seeds of other Rare Earth-123 compounds with higher melting points as nucleating sites. The resultant textured microstructure exhibits mainly low angle grain boundaries (up to 5 deg. misorientation). Results will be presented on the seed alignment techniques, the development of microstructure during reaction of the composite preform and preliminary measurements of electromagnetic properties. (au). 111 refs.

  8. Ceramic high temperature superconductors for high current applications

    International Nuclear Information System (INIS)

    Christiansen, J.

    1996-01-01

    Composite Reaction Texturing (CRT) is a technique which uses a fine distribution of pre-aligned seeds as nucleating sites for texturing oxide superconductors. It has successfully been applied to the texturing of Bi-2212 compounds. A furhter application of CRT is reported in which Y-123 is biaxially textured using seeds of other Rare Earth-123 compounds with higher melting points as nucleating sites. The resultant textured microstructure exhibits mainly low angle grain boundaries (up to 5 deg. misorientation). Results will be presented on the seed alignment techniques, the development of microstructure during reaction of the composite preform and preliminary measurements of electromagnetic properties. (au)

  9. Superconductor procurement and R and D for SSC

    International Nuclear Information System (INIS)

    Scanlan, R.; Royet, J.; Hannaford, R.; Horler, D.

    1985-06-01

    We describe the results of superconductor procurements for SSC dipole model magnets. Most results will pertain to LBL procurements for the LBL-BNL collaboration; however, where appropriate to complete the SSC data base, reference will be made to material purchased by FNAL and TAC. Also, most of the results to be presented will relate to the conventional SSC conductors, i.e., with filament sizes in the range of 15 to 25 μm. Some information on fine filament NbTi material, such as quantities and delivery schedules, will be presented here; fine filament NbTi R and D is described in another section

  10. Simulation of the vortex motion in the high Tc superconductors

    International Nuclear Information System (INIS)

    Dong Jinming.

    1992-11-01

    1d and 2d simulations of the single vortex dynamics in the presence of random pinning potential and periodical one have been carried out. It is shown that the randomness of the pinning sites distribution does not have considerable effect on the transport properties such as I-V characteristics of the high T c superconductors, which has been widely discussed in the approximation of a periodical pinning potential using analytical method. The randomness effect probably only reduces the vortex diffusing mobility more below the depinning current value, which is more obvious at lower temperature. (author). 12 refs, 4 figs

  11. The development of research on high temperature superconductors in Malaysia

    International Nuclear Information System (INIS)

    Shaari, A.H.; Hashim, M.; Dalimin, M.N.

    1989-01-01

    The background of the recent discovery of high-temperature oxide superconductor is given. This new discovery has driven scientists of different disciplines from many parts of the world into the race. Even those researchers from the developing countries are able to join the band wagon of the frontier research due to the convenience of working at temperatures well above that of liquid nitrogen. In Malaysia, some aspects of preparations and characterization of Y-Ba-Cu-O and Bi-Sr-Ca-Cu-O ceramics are studied. The 90 K transition temperature is observed in Y-Ba-Cu-O. (Auth.). 10 figs.; 5 refs

  12. A small Maglev car model using YBCO bulk superconductors

    International Nuclear Information System (INIS)

    Yang, W M; Zhou, L; Yong, Feng; Zhang, P X; Chao, X X; Bian, X B; Zhu, S H; Wu, X L; Liu, P

    2006-01-01

    Models of two small Maglev cars have been made. The track was paved with NdFeB magnets. The arrangement of the magnets made it easy to get a uniform magnetic field distribution along the length of the track and a magnetic field gradient in the lateral direction. When the car with YBCO bulk superconductors was field cooled to LN 2 temperature at a certain distance above the track, the car could be automatically levitated over the track and moved along the track without any obvious friction. The model can be used to demonstrate the Meissner effect and a fast transportation system to students and adults

  13. Microstructures and strucural defects in high-temperature superconductors

    CERN Document Server

    Cai, Zhi Xiong

    1998-01-01

    This book provides an extensive introduction to the microstructures and structural defects in high-temperature superconductors. It illustrates the application of modern experimental techniques as well as theoretical modeling tools in the study of these complex materials.The readers are given an overview of the structure-sensitive properties, such as transport properties, and the effort to develop large-scale (high-current, high-field) applications for these materials. The effects of defects on the superconducting properties of these materials are described when feasible to put the study of mic

  14. Phase Equilibria Relationships of High-Tc Superconductors

    International Nuclear Information System (INIS)

    Wong-Ng, Winnie

    2011-01-01

    As an integral part of a R and D program partially supported by the Electricity Delivery and Energy Reliability Office of DOE, we have determined phase equilibria data and phase diagrams for the three generations of superconductor materials: 1st generation, (Bi,Pb)-Sr-Ca- Cu-O systems; 2nd generation, Ba-R-Cu-O systems (R=lanthanides and yttrium); and 3rd generation, MgB2 systems. Our studies involved bulk materials, single crystals and thin films. This report gives a summary of our accomplishments, a list of publications, and 15 selected journal publications.

  15. Hard gap in epitaxial semiconductor-superconductor nanowires

    DEFF Research Database (Denmark)

    Chang, W.; Albrecht, S. M.; Jespersen, T. S.

    2015-01-01

    information processing. Proposals in this direction based on proximity effect in semiconductor nanowires are appealing because the key ingredients are currently in hand. However, previous instances of proximitized semiconductors show significant tunneling conductance below the superconducting gap, suggesting...... a continuum of subgap states---a situation that nullifies topological protection. Here, we report a hard superconducting gap induced by proximity effect in a semiconductor, using epitaxial Al-InAs superconductor-semiconductor nanowires. The hard gap, along with favorable material properties and gate......-tunability, makes this new hybrid system attractive for a number of applications, as well as fundamental studies of mesoscopic superconductivity....

  16. Probing superconductors. Spectroscopic-imaging scanning tunneling microscopy

    International Nuclear Information System (INIS)

    Hanaguri, Tetsuo

    2011-01-01

    Discovery of high-temperature superconductivity in a cuprate triggered developments of various spectroscopic tools which have been utilized to elucidate electronic states of this mysterious compound. Particularly, angle-resolved photoemission spectroscopy and scanning-tunneling microscopy/spectroscopy are improved considerably. It is now possible to map the superconducting gap in both momentum and real spaces using these two techniques. Here we review spectroscopic-imaging scanning tunneling microscopy which is able to explore momentum-space phase structure of the superconducting gap, as well as real-space structure. Applications of this technique to a cuprate and an iron-based superconductor are discussed. (author)

  17. Quasiparticle interference in an iron-based superconductor

    OpenAIRE

    Sykora, Steffen; Coleman, Piers

    2010-01-01

    We develop a model for the effect of a magnetic field on quasiparticle interference in an iron-based superconductor. Recently, scanning tunneling experiments have been performed on Fe(Se, Te) to determine the relative sign of the superconducting gap from the magnetic-field dependence of quasiparticle scattering amplitudes. Using a simple two-band BCS model, we study three different cases of scattering in a spin-split spectrum. The dominant effect of a magnetic field in iron-based superconduct...

  18. Spins in the Vortices of a High Temperature Superconductor

    OpenAIRE

    Lake, B; Aeppli, G; Clausen, KN; McMorrow, DF; Lefmann, K; Hussey, NE; Mangkorntong, N; Nohara, M; Takagi, H; Mason, TE; Schröder, A

    2002-01-01

    Neutron scattering is used to characterise the magnetism of the vortices for the optimally doped high-temperature superconductor La(2-x)Sr(x)CuO(4) (x=0.163) in an applied magnetic field. As temperature is reduced, low frequency spin fluctuations first disappear with the loss of vortex mobility, but then reappear. We find that the vortex state can be regarded as an inhomogeneous mixture of a superconducting spin fluid and a material containing a nearly ordered antiferromagnet. These experimen...

  19. Neutron scattering from the flux lattice in high temperature superconductors

    International Nuclear Information System (INIS)

    Paul, D.McK.; Forgan, E.M.; Cubitt, R.; Lee, S.L.; Mook, H.A.; Timmins, P.

    1992-01-01

    Neutron scattering has been used to observe diffraction from the flux-line lattice in high temperature superconductors. This technique is particularly useful in such system as it allows observations to be made over a wide range of temperature and magnetic field. Experiments on the systems K 0.4 Ba 0.6 BiO 3 and YBa 2 Cu 3 O 7-δ will be described with applied magnetic fields of up to 4 T and for temperatures from 2 K to Tc. (orig.)

  20. Normal-metal-superconductor tunnel junction as a Brownian refrigerator.

    Science.gov (United States)

    Pekola, J P; Hekking, F W J

    2007-05-25

    Thermal noise generated by a hot resistor (resistance R) can, under proper conditions, catalyze heat removal from a cold normal metal (N) in contact with a superconductor (S) via a tunnel barrier (I). Such a NIS junction is reminiscent of Maxwell's demon, rectifying the heat flow. Upon reversal of the temperature gradient between the resistor and the junction, the heat fluxes are reversed: this presents a regime which is not accessible in an ordinary voltage-biased NIS structure. We obtain analytical results for the cooling performance in an idealized high impedance environment and perform numerical calculations for general R. We conclude by assessing the experimental feasibility of the proposed effect.