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Sample records for superconductor includes providing

  1. 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.

  2. Fine uniform filament superconductors

    Science.gov (United States)

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

    2002-01-01

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

  3. NMR studies on the new iron arsenide superconductors including the superconducting state

    Energy Technology Data Exchange (ETDEWEB)

    Grafe, Hans-Joachim; Lang, Guillaume; Hammerath, Franziska; Manthey, Katarina; Behr, Guenther; Werner, Jochen; Buechner, Bernd [IFW Dresden, Helmholtzstr. 20, D-01069 Dresden (Germany); Paar, Dalibor [IFW Dresden, Helmholtzstr. 20, D-01069 Dresden (Germany); Dept. of Physics, Faculty of Science, Univ. of Zagreb (Croatia); Curro, Nicholas [Dept. of Physics, Univ. of California, Davis, CA 95616 (United States)

    2009-07-01

    We summarize our Nuclear Magnetic Resonance (NMR) and Nuclear Quadrupole Resonance (NQR) results on the new iron arsenide superconductor LaO{sub 1-x}F{sub x}FeAs in the normal state, and show new NMR data in the superconducting state. Beyond early evidence of nodes and spin-singlet pairing[2], we find evidence of a deviation of the T{sup 3} behaviour of the spin lattice relaxation rate, 1/T{sub 1}, at temperatures significantly below T{sub c}, which would agree with the suggested extended s-wave symmetry. The deviation of the T{sup 3} behaviour is induced by the pair breaking effect of impurities. Different amounts of impurities would lead to different temperature dependences of 1/T{sub 1}, which would allow to differentiate between d-wave and extended s-wave symmetries.

  4. Recent progress on carbon-based superconductors.

    Science.gov (United States)

    Kubozono, Yoshihiro; Eguchi, Ritsuko; Goto, Hidenori; Hamao, Shino; Kambe, Takashi; Terao, Takahiro; Nishiyama, Saki; Zheng, Lu; Miao, Xiao; Okamoto, Hideki

    2016-08-24

    This article reviews new superconducting phases of carbon-based materials. During the past decade, new carbon-based superconductors have been extensively developed through the use of intercalation chemistry, electrostatic carrier doping, and surface-proving techniques. The superconducting transition temperature T c of these materials has been rapidly elevated, and the variety of superconductors has been increased. This review fully introduces graphite, graphene, and hydrocarbon superconductors and future perspectives of high-T c superconductors based on these materials, including present problems. Carbon-based superconductors show various types of interesting behavior, such as a positive pressure dependence of T c. At present, experimental information on superconductors is still insufficient, and theoretical treatment is also incomplete. In particular, experimental results are still lacking for graphene and hydrocarbon superconductors. Therefore, it is very important to review experimental results in detail and introduce theoretical approaches, for the sake of advances in condensed matter physics. Furthermore, the recent experimental results on hydrocarbon superconductors obtained by our group are also included in this article. Consequently, this review article may provide a hint to designing new carbon-based superconductors exhibiting higher T c and interesting physical features.

  5. Fabrication of high temperature superconductors

    Science.gov (United States)

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

    2003-06-17

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

  6. 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.

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

    Science.gov (United States)

    Goretta, Kenneth C.; Lanagan, Michael T.; Miller, Dean J.; Sengupta, Suvankar; Parker, John C.; Hu, Jieguang; Balachandran, Uthamalingam; Siegel, Richard W.; Shi, Donglu

    1999-01-01

    A method of preparing a high temperature superconductor. 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.

  8. 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.

  9. 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.

  10. 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.

  11. Observability of surface currents in p-wave superconductors

    Science.gov (United States)

    Bakurskiy, S. V.; Klenov, N. V.; Soloviev, I. I.; Kupriyanov, M. Yu; Golubov, A. A.

    2017-04-01

    A general approach is formulated to describe spontaneous surface current distribution in a chiral p-wave superconductor. We use the quasiclassical Eilenberger formalism in the Ricatti parametrization to describe various types of the superconductor surface, including arbitrary roughness and metallic behavior of the surface layer. We calculate angle resolved distributions of the spontaneous surface currents and formulate the conditions of their observability. We argue that local measurements of these currents by muon spin rotation technique may provide an information on the underlying pairing symmetry in the bulk superconductor.

  12. Superconductor cable

    Science.gov (United States)

    Allais, Arnaud; Schmidt, Frank (Langenhagen, DE

    2009-12-15

    A superconductor cable includes a superconductive cable core (1) and a cryostat (2) enclosing the same. The cable core (1) has a superconductive conductor (3), an insulation (4) surrounding the same and a shielding (5) surrounding the insulation (4). A layer (3b) of a dielectric or semiconducting material is applied to a central element (3a) formed from a normally conducting material as a strand or tube and a layer (3c) of at least one wire or strip of superconductive material is placed helically on top. The central element (3a) and the layer (3c) are connected to each other in an electrically conducting manner at the ends of the cable core (1).

  13. Superconductor Composite

    Science.gov (United States)

    Dorris, Stephen E.; Burlone, Dominick A.; Morgan; Carol W.

    1999-02-02

    A superconducting conductor fabricated from a plurality of wires, e.g., fine silver wires, coated with a superconducting powder. A process of applying superconducting powders to such wires, to the resulting coated wires and superconductors produced therefrom.

  14. Granular Superconductors and Gravity

    Science.gov (United States)

    Noever, David; Koczor, Ron

    1999-01-01

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

  15. Lightning in superconductors.

    Science.gov (United States)

    Vestgården, J I; Shantsev, D V; Galperin, Y M; Johansen, T H

    2012-01-01

    Crucially important for application of type-II superconductor films is the stability of the vortex matter--magnetic flux lines penetrating the material. If some vortices get detached from pinning centres, the energy dissipated by their motion will facilitate further depinning, and may trigger a massive electromagnetic breakdown. Up to now, the time-resolved behaviour of these ultra-fast events was essentially unknown. We report numerical simulation results revealing the detailed dynamics during breakdown as within nanoseconds it develops branching structures in the electromagnetic fields and temperature, with striking resemblance of atmospheric lightning. During a dendritic avalanche the superconductor is locally heated above its critical temperature, while electrical fields rise to several kV/m as the front propagates at instant speeds near up to 100 km/s. The numerical approach provides an efficient framework for understanding the ultra-fast coupled non-local dynamics of electromagnetic fields and dissipation in superconductor films.

  16. Current fluctuations in unconventional superconductor junctions with impurity scattering

    Science.gov (United States)

    Burset, Pablo; Lu, Bo; Tamura, Shun; Tanaka, Yukio

    2017-06-01

    The order parameter of bulk two-dimensional superconductors is classified as nodal if it vanishes for a direction in momentum space, or gapful if it does not. Each class can be topologically nontrivial if Andreev bound states are formed at the edges of the superconductor. Nonmagnetic impurities in the superconductor affect the formation of Andreev bound states and can drastically change the tunneling spectra for small voltages. Here, we investigate the mean current and its fluctuations for two-dimensional tunnel junctions between normal-metal and unconventional superconductors by solving the quasiclassical Eilenberger equation self-consistently, including the presence of nonmagnetic impurities in the superconductor. As the impurity strength increases, we find that superconductivity is suppressed for almost all order parameters since (i) at zero applied bias, the effective transferred charge calculated from the noise-current ratio tends to the electron charge e , and (ii) for finite bias, the current-voltage characteristics follows that of a normal-state junction. There are notable exceptions to this trend. First, gapful nontrivial (chiral) superconductors are very robust against impurity scattering due to the linear dispersion relation of their surface Andreev bound states. Second, for nodal nontrivial superconductors, only px-wave pairing is almost immune to the presence of impurities due to the emergence of odd-frequency s -wave Cooper pairs near the interface. Due to their anisotropic dependence on the wave vector, impurity scattering is an effective pair-breaking mechanism for the remaining nodal superconductors. All these behaviors are neatly captured by the noise-current ratio, providing a useful guide to find experimental signatures for unconventional superconductivity.

  17. 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)

  18. Superconductor cable

    Science.gov (United States)

    Allais, Arnaud; Schmidt, Frank; Marzahn, Erik

    2010-05-04

    A superconductor cable is described, having a superconductive flexible cable core (1) , which is laid in a cryostat (2, 3, 4), in which the cable core (1) runs in the cryostat (2, 3, 4) in the form of a wave or helix at room temperature.

  19. Superconductor Dynamics

    CERN Document Server

    Gömöry, F

    2014-01-01

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

  20. 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

  1. Chiral superconductors.

    Science.gov (United States)

    Kallin, Catherine; Berlinsky, John

    2016-05-01

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

  2. Simultaneous constraint and phase conversion processing of oxide superconductors

    Science.gov (United States)

    Li, Qi; Thompson, Elliott D.; Riley, Jr., Gilbert N.; Hellstrom, Eric E.; Larbalestier, David C.; DeMoranville, Kenneth L.; Parrell, Jeffrey A.; Reeves, Jodi L.

    2003-04-29

    A method of making an oxide superconductor article includes subjecting an oxide superconductor precursor to a texturing operation to orient grains of the oxide superconductor precursor to obtain a highly textured precursor; and converting the textured oxide superconducting precursor into an oxide superconductor, while simultaneously applying a force to the precursor which at least matches the expansion force experienced by the precursor during phase conversion to the oxide superconductor. The density and the degree of texture of the oxide superconductor precursor are retained during phase conversion. The constraining force may be applied isostatically.

  3. Bearing design for flywheel energy storage using high-TC superconductors

    Science.gov (United States)

    Hull, John R.; Mulcahy, Thomas M.

    2000-01-01

    A high temperature superconductor material bearing system (38) This system (38) includes a rotor (50) having a ring permanent magnet (60), a plurality of permanent magnets (16, 20 and 70) for interacting to generate levitation forces for the system (38). This group of magnets are a push/pull bearing (75). A high temperature superconductor structure (30) interacts with the ting permanent magnet (60) to provide stabilizing forces for the system (38).

  4. Iron-Based Superconductors as topological matter

    Science.gov (United States)

    Hu, Jiangping

    We show the existence of non-trivial topological properties in Iron-based superconductors. Several examples are provided, including (1) the single layer FeSe grown on SrTiO3 substrate, in which an topological insulator phase exists due to the band inversion at M point; (2) CaFeAs2, a staggered intercalation compound that integrates both quantum spin hall and superconductivity in which the nontrivial topology stems from the chain-like As layers away from FeAs layers; (3) the Fe(Te,Se) thin films in which the nontrivial Z2 topological invariance originates from the parity exchange at Γ point that is controlled by the Te(Se) height; (4 nontrivial topology that is driven by the nematic order in FeSe. These results lay ground for integrating high Tc superconductivity with topological properties to realize new emergent phenomena, such as majorana particles, in iron-based high temperature superconductors

  5. Topological properties in Iron-Based Superconductors

    Science.gov (United States)

    Hu, Jiangping; Hao, Ningning; Wu, X. X.

    2015-03-01

    We show the existence of non-trivial topological properties in Iron-based superconductors. Several examples are provided, including (1) the single layer FeSe grown on SrTiO3 substrate, in which an topological insulator phase exists due to the band inversion at M point; (2) CaFeAs2, a staggered intercalation compound that integrates both quantum spin hall and superconductivity in which the nontrivial topology stems from the chain-like As layers away from FeAs layers; (3) the Fe(Te,Se) thin films in which the nontrivial Z2 topological invariance originates from the parity exchange at ? point that is controlled by the Te(Se) height. These results lay ground for integrating high Tc superconductivity with topological properties to realize new emergent phenomena, such as majorana particles, in iron-based high temperature superconductors. The work is supported by NSFC and the Ministry of Science and Technology of China.

  6. Proximity-induced low-energy renormalization in hybrid semiconductor-superconductor Majorana structures

    Science.gov (United States)

    Stanescu, Tudor D.; Das Sarma, Sankar

    2017-07-01

    A minimal model for the hybrid superconductor-semiconductor nanowire Majorana platform is developed that fully captures the effects of the low-energy renormalization of the nanowire modes arising from the presence of the parent superconductor. In this model, the parent superconductor is an active component that participates explicitly in the low-energy physics, not just a passive partner that only provides proximity-induced Cooper pairs for the nanowire. This treatment on an equal footing of the superconductor and the semiconductor has become necessary in view of recent experiments, which do not allow a consistent interpretation based just on the bare semiconductor properties. The general theory involves the evaluation of the exact semiconductor Green's function that includes a dynamical self-energy correction arising from the tunnel-coupled superconductor. Using a tight-binding description, the nanowire Green's function is obtained in various relevant parameter regimes, with the parent superconductor being treated within the BCS-BdG prescription. General conditions for the emergence of topological superconductivity are worked out for single-band as well as multiband nanowires and detailed numerical results are given for both infinite and finite wire cases. The topological quantum phase diagrams are provided numerically and the Majorana bound states are obtained along with their oscillatory energy-splitting behaviors due to wave function overlap in finite wires. Renormalization effects are shown to be both qualitatively and quantitatively important in modifying the low-energy spectrum of the nanowire. The results of the theory are found to be in good qualitative agreement with Majorana nanowire experiments, leading to the conclusion that the proximity-induced low-energy renormalization of the nanowire modes by the parent superconductor is of fundamental importance in superconductor-semiconductor hybrid structures, except perhaps in the uninteresting limit of

  7. 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...

  8. Vortex cutting in superconductors

    Science.gov (United States)

    Glatz, A.; Vlasko-Vlasov, V. K.; Kwok, W. K.; Crabtree, G. W.

    2016-08-01

    Vortex cutting and reconnection is an intriguing and still-unsolved problem central to many areas of classical and quantum physics, including hydrodynamics, astrophysics, and superconductivity. Here, we describe a comprehensive investigation of the crossing of magnetic vortices in superconductors using time dependent Ginsburg-Landau modeling. Within a macroscopic volume, we simulate initial magnetization of an anisotropic high temperature superconductor followed by subsequent remagnetization with perpendicular magnetic fields, creating the crossing of the initial and newly generated vortices. The time resolved evolution of vortex lines as they approach each other, contort, locally conjoin, and detach, elucidates the fine details of the vortex-crossing scenario under practical situations with many interacting vortices in the presence of weak pinning. Our simulations also reveal left-handed helical vortex instabilities that accompany the remagnetization process and participate in the vortex crossing events.

  9. 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.

  10. Sealed glass coating of high temperature ceramic superconductors

    Science.gov (United States)

    Wu, Weite; Chu, Cha Y.; Goretta, Kenneth C.; Routbort, Jules L.

    1995-01-01

    A method and article of manufacture of a lead oxide based glass coating on a high temperature superconductor. The method includes preparing a dispersion of glass powders in a solution, applying the dispersion to the superconductor, drying the dispersion before applying another coating and heating the glass powder dispersion at temperatures below oxygen diffusion onset and above the glass melting point to form a continuous glass coating on the superconductor to establish compressive stresses which enhance the fracture strength of the superconductor.

  11. Ferromagnetic superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Huxley, Andrew D.

    2015-07-15

    Highlights: • Review of ferromagnetic superconductors. • Covers UGe{sub 2}, URhGe and UCoGe and briefly other materials. • The focus is on experimental data and the pairing mechanism. - Abstract: The co-existence of superconductivity and ferromagnetism is of potential interest for spintronics and high magnetic field applications as well as a fascinating fundamental state of matter. The recent focus of research is on a family of ferromagnetic superconductors that are superconducting well below their Curie temperature, the first example of which was discovered in 2000. Although there is a ‘standard’ theoretical model for how magnetic pairing might bring about such a state, why it has only been seen in a few materials that at first sight appear to be very closely related has yet to be fully explained. This review covers the current state of knowledge of the magnetic and superconducting properties of these materials with emphasis on how they conform and differ from the behaviour expected from the ‘standard’ model and from each other.

  12. The polar Kerr effect in superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Robbins, Joshua; Annett, James F.; Gradhand, Martin [University of Bristol (United Kingdom)

    2016-07-01

    The polar Kerr effect is an optical phenomenon which arises in states with broken time-reversal symmetry. This effect has recently been observed in a series of unconventional superconductors, including the layered perovskite compound Sr{sub 2}RuO{sub 4}. Confirmation of a Kerr signal below T{sub c} supports the hypothesis of chiral p-wave superconductivity in this material. However, the nature of the unconventional superconducting state remains a source of controversy. Here, we present calculations for the chiral superconducting state including spin-orbit coupling (SOC) by extending the three dimensional, multiband model considered previously. SOC was found to induce strong mixing of the orbital characters within the bandstructure. This mixing is essential for the existence of the polar Kerr effect and the large increase due to SOC has a significant influence on the frequency dependence of the predicted Kerr signal. We will extend and apply the model to other unconventional superconductors which have displayed the Kerr effect in recent years. This will allow a detailed study of the symmetry properties of these systems and will provide valuable insight into the pairing mechanism of superconductors.

  13. Ferromagnetic superconductors

    Science.gov (United States)

    Huxley, Andrew D.

    2015-07-01

    The co-existence of superconductivity and ferromagnetism is of potential interest for spintronics and high magnetic field applications as well as a fascinating fundamental state of matter. The recent focus of research is on a family of ferromagnetic superconductors that are superconducting well below their Curie temperature, the first example of which was discovered in 2000. Although there is a 'standard' theoretical model for how magnetic pairing might bring about such a state, why it has only been seen in a few materials that at first sight appear to be very closely related has yet to be fully explained. This review covers the current state of knowledge of the magnetic and superconducting properties of these materials with emphasis on how they conform and differ from the behaviour expected from the 'standard' model and from each other.

  14. Topology of nonsymmorphic crystalline insulators and superconductors

    Science.gov (United States)

    Shiozaki, Ken; Sato, Masatoshi; Gomi, Kiyonori

    2016-05-01

    Topological classification in our previous paper [K. Shiozaki and M. Sato, Phys. Rev. B 90, 165114 (2014), 10.1103/PhysRevB.90.165114] is extended to nonsymmorphic crystalline insulators and superconductors. Using the twisted equivariant K theory, we complete the classification of topological crystalline insulators and superconductors in the presence of additional order-two nonsymmorphic space-group symmetries. The order-two nonsymmorphic space groups include half-lattice translation with Z2 flip, glide, twofold screw, and their magnetic space groups. We find that the topological periodic table shows modulo-2 periodicity in the number of flipped coordinates under the order-two nonsymmorphic space group. It is pointed out that the nonsymmorphic space groups allow Z2 topological phases even in the absence of time-reversal and/or particle-hole symmetries. Furthermore, the coexistence of the nonsymmorphic space group with time-reversal and/or particle-hole symmetries provides novel Z4 topological phases, which have not been realized in ordinary topological insulators and superconductors. We present model Hamiltonians of these new topological phases and analytic expressions of the Z2 and Z4 topological invariants. The half-lattice translation with Z2 spin flip and glide symmetry are compatible with the existence of boundaries, leading to topological surface gapless modes protected by the order-two nonsymmorphic symmetries. We also discuss unique features of these gapless surface modes.

  15. 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.

  16. 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.

  17. 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...

  18. High-temperature superconductors

    CERN Document Server

    Saxena, Ajay Kumar

    2010-01-01

    The present book aims at describing the phenomenon of superconductivity and high-temperature superconductors discovered by Bednorz and Muller in 1986. The book covers the superconductivity phenomenon, structure of high-Tc superconductors, critical currents, synthesis routes for high Tc materials, superconductivity in cuprates, the proximity effect and SQUIDs, theories of superconductivity and applications of superconductors.

  19. The cost of providing combined prevention and treatment services, including ART, to female sex workers in Burkina Faso.

    Directory of Open Access Journals (Sweden)

    Fiona Cianci

    Full Text Available BACKGROUND: Female Sex workers (FSW are important in driving HIV transmission in West Africa. The Yerelon clinic in Burkina Faso has provided combined preventative and therapeutic services, including anti-retroviral therapy (ART, for FSWs since 1998, with evidence suggesting it has decreased HIV prevalence and incidence in this group. No data exists on the costs of such a combined prevention and treatment intervention for FSW. This study aims to determine the mean cost of service provision per patient year for FSWs attending the Yerelon clinic, and identifies differences in costs between patient groups. METHODS: Field-based retrospective cost analyses were undertaken using top-down and bottom-up costing approaches for 2010. Expenditure and service utilisation data was collated from primary sources. Patients were divided into groups according to full-time or occasional sex-work, HIV status and ART duration. Patient specific service use data was extracted. Costs were converted to 2012 US$. Sensitivity analyses considered removal of all research costs, different discount rates and use of different ART treatment regimens and follow-up schedules. RESULTS: Using the top-down costing approach, the mean annual cost of service provision for FSWs on or off ART was US$1098 and US$882, respectively. The cost for FSWs on ART reduced by 29%, to US$781, if all research-related costs were removed and national ART monitoring guidelines were followed. The bottom-up patient-level costing showed the cost of the service varied greatly across patient groups (US$505-US$1117, primarily due to large differences in the costs of different ART regimens. HIV-negative women had the lowest annual cost at US$505. CONCLUSION: Whilst FSWs may require specialised services to optimise their care and hence, the public health benefits, our study shows that the cost of ART provision within a combined prevention and treatment intervention setting is comparable to providing ART to

  20. High temperature superconductor current leads

    Energy Technology Data Exchange (ETDEWEB)

    Hull, John R. (Hinsdale, IL); Poeppel, Roger B. (Glen Ellyn, IL)

    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.

  1. Magnetic Signals of High-Temperature Superconductor Bulk During the Levitation Force Measurement Process

    Science.gov (United States)

    Huang, Huan; Zheng, Jun; Qian, Nan; Che, Tong; Zheng, Botian; Jin, Liwei; Deng, Zigang

    2017-05-01

    In order to study the commonly neglected magnetic field information in the course of levitation force measurement process in a superconducting maglev system, a multipoint magnetic field measurement platform was employed to acquire magnetic signals of a bulk high-Tc superconductor on both the top and the bottom surface. Working conditions including field cooling (FC) and zero field cooling were investigated for these vertical down and up motions above a permanent magnet guideway performed on a HTS maglev measurement system. We have discussed the magnetic flux variation process based on the Bean model. A magnetic hysteresis effect similar to the levitation force hysteresis loop of the bulk superconductor was displayed and analyzed in this paper. What is more valuable, there exists some available magnetic flux on the top surface of the bulk superconductor, and the proportion is as high as 62.42% in the FC condition, which provides an experimental hint to design the superconductor bulk and the applied field for practical use in a more efficient way. In particular, this work reveals real-time magnetic flux variation of the bulk superconductor in the levitation application, which is the other important information in contrast to the macroscopic levitation and guidance force investigations in previous studies, and it enriches the existing research methods. The results are significant for understanding the magnetic characteristic of superconductors, and they can contribute to optimize the present HTS maglev system design.

  2. Magnetic Signals of High-Temperature Superconductor Bulk During the Levitation Force Measurement Process

    Science.gov (United States)

    Huang, Huan; Zheng, Jun; Qian, Nan; Che, Tong; Zheng, Botian; Jin, Liwei; Deng, Zigang

    2017-02-01

    In order to study the commonly neglected magnetic field information in the course of levitation force measurement process in a superconducting maglev system, a multipoint magnetic field measurement platform was employed to acquire magnetic signals of a bulk high-Tc superconductor on both the top and the bottom surface. Working conditions including field cooling (FC) and zero field cooling were investigated for these vertical down and up motions above a permanent magnet guideway performed on a HTS maglev measurement system. We have discussed the magnetic flux variation process based on the Bean model. A magnetic hysteresis effect similar to the levitation force hysteresis loop of the bulk superconductor was displayed and analyzed in this paper. What is more valuable, there exists some available magnetic flux on the top surface of the bulk superconductor, and the proportion is as high as 62.42% in the FC condition, which provides an experimental hint to design the superconductor bulk and the applied field for practical use in a more efficient way. In particular, this work reveals real-time magnetic flux variation of the bulk superconductor in the levitation application, which is the other important information in contrast to the macroscopic levitation and guidance force investigations in previous studies, and it enriches the existing research methods. The results are significant for understanding the magnetic characteristic of superconductors, and they can contribute to optimize the present HTS maglev system design.

  3. 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.

  4. 29 CFR 778.214 - Benefit plans; including profit-sharing plans or trusts providing similar benefits.

    Science.gov (United States)

    2010-07-01

    ... fide plan for providing old age, retirement, life, accident, or health insurance or similar benefits... such employees. Accordingly, reference should be made to § 5.32 of this title as well as to § 778.215... satisfaction of his obligation to provide the specified benefits are also excludable from the regular rate...

  5. 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).

  6. 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.

  7. 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.

  8. Nature of the superconductor-insulator transition in disordered superconductors.

    Science.gov (United States)

    Dubi, Yonatan; Meir, Yigal; Avishai, Yshai

    2007-10-18

    The interplay of superconductivity and disorder has intrigued scientists for several decades. Disorder is expected to enhance the electrical resistance of a system, whereas superconductivity is associated with a zero-resistance state. Although superconductivity has been predicted to persist even in the presence of disorder, experiments performed on thin films have demonstrated a transition from a superconducting to an insulating state with increasing disorder or magnetic field. The nature of this transition is still under debate, and the subject has become even more relevant with the realization that high-transition-temperature (high-T(c)) superconductors are intrinsically disordered. Here we present numerical simulations of the superconductor-insulator transition in two-dimensional disordered superconductors, starting from a microscopic description that includes thermal phase fluctuations. We demonstrate explicitly that disorder leads to the formation of islands where the superconducting order is high. For weak disorder, or high electron density, increasing the magnetic field results in the eventual vanishing of the amplitude of the superconducting order parameter, thereby forming an insulating state. On the other hand, at lower electron densities or higher disorder, increasing the magnetic field suppresses the correlations between the phases of the superconducting order parameter in different islands, giving rise to a different type of superconductor-insulator transition. One of the important predictions of this work is that in the regime of high disorder, there are still superconducting islands in the sample, even on the insulating side of the transition. This result, which is consistent with experiments, explains the recently observed huge magneto-resistance peak in disordered thin films and may be relevant to the observation of 'the pseudogap phenomenon' in underdoped high-T(c) superconductors.

  9. Photothermal measurements of superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Kino, G.S.; Studenmund, W.R.; Fishman, I.M. [Stanford Univ., Stanford, CA (United States)

    1996-12-31

    A photothermal technique has been used to measure diffusion and critical temperature in high temperature superconductors. The technique is particularly suitable for determining material quality and inhomogeneity.

  10. 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.

  11. Shielding superconductors with thin films

    CERN Document Server

    Posen, Sam; Catelani, Gianluigi; Liepe, Matthias U; Sethna, James P

    2015-01-01

    Determining the optimal arrangement of superconducting layers to withstand large amplitude AC magnetic fields is important for certain applications such as superconducting radiofrequency cavities. In this paper, we evaluate the shielding potential of the superconducting film/insulating film/superconductor (SIS') structure, a configuration that could provide benefits in screening large AC magnetic fields. After establishing that for high frequency magnetic fields, flux penetration must be avoided, the superheating field of the structure is calculated in the London limit both numerically and, for thin films, analytically. For intermediate film thicknesses and realistic material parameters we also solve numerically the Ginzburg-Landau equations. It is shown that a small enhancement of the superheating field is possible, on the order of a few percent, for the SIS' structure relative to a bulk superconductor of the film material, if the materials and thicknesses are chosen appropriately.

  12. Large area bulk superconductors

    Science.gov (United States)

    Miller, Dean J.; Field, Michael B.

    2002-01-01

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

  13. Superconductor terahertz metamaterial

    CERN Document Server

    Gu, Jianqiang; 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 cracks, voids and secondary phases which play dominant role in partially impeding the flow of current causing dissipation of energy and electrical resistance to appear in the superconductor film.

  14. 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.

  15. 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

  16. Topological superconductors: a review.

    Science.gov (United States)

    Sato, Masatoshi; Ando, Yoichi

    2017-04-03

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

  17. Layered nickel based superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Ronning, Filip [Los Alamos National Laboratory; Bauer, Eric D [Los Alamos National Laboratory; Park, Tuson [Los Alamos National Laboratory; Kurita, Nobuyuki [Los Alamos National Laboratory; Klimczuk, T [Los Alamos National Laboratory; Movshovich, R [Los Alamos National Laboratory; Thompson, J D [Los Alamos National Laboratory; Sefat, A S [ORNL; Mandrus, D [ORNL

    2009-01-01

    We review the properties of Ni-based superconductors which contain Ni{sub 2}X{sub 2} (X=As, P, Bi, Si, Ge, B) planes, a common structural element to the recently discovered FeAs superconductors. We also compare the properties ofthe Ni-and Fe-based systems from a perspective ofelectronic structure as well as structure-property relations.

  18. Continuous lengths of oxide superconductors

    Science.gov (United States)

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

    2000-01-01

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

  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 dev

  20. 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.

  1. Crack problem in a long cylindrical superconductor

    Science.gov (United States)

    Yong, Hua-Dong; Zhou, You-He; Zeng, Jun

    2008-12-01

    In this work, the general problem of a center crack in a long cylindrical superconductor is studied. The dependence of the stress intensity factor on the parameters, including the crack length and the applied field, is investigated. We presented a simple model in which the effect of the crack on the critical current is taken into account. It is assumed that the crack forms a perfect barrier to the flow of current. The Bean model and the Kim model are considered for the critical state. Based on the complex potential and boundary collocation methods, the stress intensity factor under the magnetic field is obtained for a long cylindrical superconductor containing a central crack. The results show that the crack length and the applied field have significant effects on the fracture behavior of the superconductor.

  2. 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.

  3. 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.

  4. 373 K Superconductors

    CERN Document Server

    Kostadinov, Ivan Zahariev

    2016-01-01

    Experimental evidence of superconductors with critical temperatures above $373\\:K$ is presented. In a family of different compounds we demonstrate the superconductor state, the transition to normal state above $387\\:K$, an intermediate $242\\:K$ superconductor, susceptibility up to $350\\:K$, $I-V$ curves at $4.2\\:K$ in magnetic field of $12\\:T$ and current up to $60\\:A$, $300\\:K$ Josephson Junctions and Shapiro steps with radiation of $5\\:GHz$ to $21\\:THz$, $300\\:K$ tapes tests with high currents up to $3000\\:A$ and many $THz$ images of coins and washers. Due to a pending patent, the exact chemical characterization and technological processes for these materials are temporarily withheld and will be presented elsewhere.

  5. In vitro studies of cells grown on the superconductor PrO(x)FeAs.

    Science.gov (United States)

    Yang, Shaoguang; Xie, Yuxuan; Yang, Wenrong; Zheng, Rongkun; Stevens, Frankie; Korkmaz, Emine; Weiss, Anthony S; Ringer, Simon P; Braet, Filip

    2009-06-01

    The recent discovery of arsenic-based high temperature superconductors has reignited interest in the study of superconductor: biological interfaces. However, the new superconductor materials involve the chemistry of arsenic and their toxicity remains unclear [Hand, E., 2008. Nature 452 (24), 922]. In this study the possible adverse effects of this new family of superconductors on cells have been examined. Cell culture studies in conjunction with microscopy and viability assays were employed to examine the influence of arsenic-based superconductor PrO(x)FeAs (x=0.75) material in vitro. Imaging data revealed that cells were well adhered and spread on the surface of the superconductor. Furthermore, cytotoxicity studies showed that cells were unaffected during the time-course of the experiments, providing support for the biocompatibility aspects of PrO(x)FeAs-based superconductor material.

  6. Enhancing critical current density of cuprate superconductors

    Science.gov (United States)

    Chaudhari, Praveen

    2015-06-16

    The present invention concerns the enhancement of critical current densities in cuprate superconductors. Such enhancement of critical current densities include using wave function symmetry and restricting movement of Abrikosov (A) vortices, Josephson (J) vortices, or Abrikosov-Josephson (A-J) vortices by using the half integer vortices associated with d-wave symmetry present in the grain boundary.

  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...

  8. Bi-based superconductor

    Directory of Open Access Journals (Sweden)

    S E Mousavi

    2009-08-01

    Full Text Available   In this paper, Bi-Sr-Ca-Cu-O (BCSCCO system superconductor is made by the solid state reaction method. The effect of doping Pb, Cd, Sb, Cu and annealing time on the critical temperature and critical current density have been investigated. The microstructure and morphology of the samples have been studied by X-ray diffraction, scanning electron microscope and energy dispersive X-ray. The results show that the fraction of Bi-2223 phase in the Bi- based superconductor, critical temperature and critical current density depend on the annealing temperature, annealing time and the kind and amount of doping .

  9. Physical Vacuum in Superconductors

    CERN Document Server

    de Matos, Clovis Jacinto

    2009-01-01

    Although experiments carried out by Jain et al. showed that the Cooper pairs obey the strong equivalence principle, The measurement of the Cooper pairs inertial mass by Tate et al. revealed an anomalous excess of mass. In the present paper we interpret these experimental results in the framework of an electromagnetic model of dark energy for the superconductors' vacuum. We argue that this physical vacuum is associated with a preferred frame. Ultimately from the conservation of energy for Cooper pairs we derive a model for a variable vacuum speed of light in the superconductors physical vacuum in relation with a possible breaking of the weak equivalence principle for Cooper pairs.

  10. Manufacturing of Superconductors

    DEFF Research Database (Denmark)

    Bech, Jakob Ilsted; Bay, Niels

    Superconducting tapes based on the ceramic high temperature superconductor (HTS) is a new promising product for high current applications such as electro-magnets and current transmission cables. The tapes are made by the oxide powder in tube (OPIT) method implying drawing and rolling of silver tu...

  11. Quantized conductance doubling and hard gap in a two-dimensional semiconductor–superconductor heterostructure

    Science.gov (United States)

    Kjaergaard, M.; Nichele, F.; Suominen, H. J.; Nowak, M. P.; Wimmer, M.; Akhmerov, A. R.; Folk, J. A.; Flensberg, K.; Shabani, J.; Palmstrøm, C. J.; Marcus, C. M.

    2016-01-01

    Coupling a two-dimensional (2D) semiconductor heterostructure to a superconductor opens new research and technology opportunities, including fundamental problems in mesoscopic superconductivity, scalable superconducting electronics, and new topological states of matter. One route towards topological matter is by coupling a 2D electron gas with strong spin–orbit interaction to an s-wave superconductor. Previous efforts along these lines have been adversely affected by interface disorder and unstable gating. Here we show measurements on a gateable InGaAs/InAs 2DEG with patterned epitaxial Al, yielding devices with atomically pristine interfaces between semiconductor and superconductor. Using surface gates to form a quantum point contact (QPC), we find a hard superconducting gap in the tunnelling regime. When the QPC is in the open regime, we observe a first conductance plateau at 4e2/h, consistent with theory. The hard-gap semiconductor–superconductor system demonstrated here is amenable to top-down processing and provides a new avenue towards low-dissipation electronics and topological quantum systems. PMID:27682268

  12. 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...

  13. Electronic transport in unconventional superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Graf, M.J.

    1998-12-31

    The author investigates the electron transport coefficients in unconventional superconductors at low temperatures, where charge and heat transport are dominated by electron scattering from random lattice defects. He discusses the features of the pairing symmetry, Fermi surface, and excitation spectrum which are reflected in the low temperature heat transport. For temperatures {kappa}{sub B}T {approx_lt} {gamma} {much_lt} {Delta}{sub 0}, where {gamma} is the bandwidth of impurity induced Andreev states, certain eigenvalues become universal, i.e., independent of the impurity concentration and phase shift. Deep in the superconducting phase ({kappa}{sub B}T {approx_lt} {gamma}) the Wiedemann-Franz law, with Sommerfeld`s value of the Lorenz number, is recovered. He compares the results for theoretical models of unconventional superconductivity in high-{Tc} and heavy fermion superconductors with experiment. The findings show that impurities are a sensitive probe of the low-energy excitation spectrum, and that the zero-temperature limit of the transport coefficients provides an important test of the order parameter symmetry.

  14. 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.

  15. Transverse acousto-electric effect in superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Lipavský, P., E-mail: lipavsky@karlov.mff.cuni.cz [Faculty of Mathematics and Physics, Charles University, Ke Karlovu 3, Prague 2 121 16 (Czech Republic); Koláček, J., E-mail: kolacek@fzu.cz [Institute of Physics, Academy of Sciences, Cukrovarnická 10, Prague 6 162 00 (Czech Republic); Lin, P.-J., E-mail: fareh.lin@gmail.com [Research Department, Universal Analytics Inc., RR2 Airdrie, AB T4B 2A4 (Canada)

    2016-06-15

    Highlights: • A description of an acousto-electric effect of superconductors is formulated, continuous over the phase transition. • Interactions among a sound wave, normal and superconducting electrons are included. • Response radiation attains a maximum before transition to the normal state. • Effects should be observable in clean niobium. - Abstract: We formulate a theory based on the time-dependent Ginzburg–Landau (TDGL) theory and Newtonian vortex dynamics to study the transverse acousto-electric response of a type-II superconductor with Abrikosov vortex lattice. When exposed to a transverse acoustic wave, Cooper pairs emerge from the moving atomic lattice and moving electrons. As in the Tolman–Stewart effect in a normal metal, an electromagnetic field is radiated from the superconductor. We adapt the equilibrium-based TDGL theory to this non-equilibrium system by using a floating condensation kernel. Due to the interaction between normal and superconducting components, the radiated electric field as a function of magnetic field attains a maximum value occurring below the upper critical magnetic field. This local increase in electric field has weak temperature dependence and is suppressed by the presence of impurities in the superconductor.

  16. The experiences of clients and healthcare providers regarding the provision of reproductive health services including the prevention of HIV and AIDS in an informal settlement in Tshwane

    Directory of Open Access Journals (Sweden)

    M.L.S. Mataboge

    2016-12-01

    Full Text Available Globally challenges regarding healthcare provision are sometimes related to a failure to estimate client numbers in peri-urban areas due to rapid population growth. About one-sixth of the world's population live in informal settlements which are mostly characterised by poor healthcare service provision. Poor access to primary healthcare may expose residents of informal settlement more to the human immunodeficiency virus (HIV and to acquired immunodeficiency syndrome (AIDS than their rural and urban counterparts due to a lack of access to information on prevention, early diagnosis and treatment. The objective of this study was to explore and describe the experiences of both the reproductive health services' clients and the healthcare providers with regard to the provision of reproductive health services including the prevention of HIV and AIDS in a primary healthcare setting in Tshwane. A qualitative, exploratory and contextual design using a phenomenological approach to enquire about the participants' experiences was implemented. Purposive sampling resulted in the selection of 23 clients who used the reproductive healthcare services and ten healthcare providers who were interviewed during individual and focus group interviews respectively. Tesch's method for qualitative data analysis was used. Ethical principles guided the study, and certain strategies were followed to ensure trustworthiness. The findings revealed that females who lived in informal settlements were aware of the inability of the PHC setting to provide adequate reproductive healthcare to meet their needs. The HCPs acknowledged that healthcare provision was negatively affected by policies. It was found that the community members could be taught how to coach teenagers and support each other in order to bridge staff shortages and increase health outcomes including HIV/AIDS prevention.

  17. 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.

  18. Introduction to Holographic Superconductor Models

    CERN Document Server

    Cai, Rong-Gen; Li, Li-Fang; Yang, Run-Qiu

    2015-01-01

    In the last years it has been shown that some properties of strongly coupled superconductors can be potentially described by classical general relativity living in one higher dimension, which is known as holographic superconductors. This paper gives a quick and introductory overview of some holographic superconductor models with s-wave, p-wave and d-wave orders in the literature from point of view of bottom-up, and summarizes some basic properties of these holographic models in various regimes. The competition and coexistence of these superconductivity orders are also studied in these superconductor models.

  19. Ground state, collective mode, phase soliton and vortex in multiband superconductors.

    Science.gov (United States)

    Lin, Shi-Zeng

    2014-12-10

    This article reviews theoretical and experimental work on the novel physics in multiband superconductors. Multiband superconductors are characterized by multiple superconducting energy gaps in different bands with interaction between Cooper pairs in these bands. The discovery of prominent multiband superconductors MgB2 and later iron-based superconductors, has triggered enormous interest in multiband superconductors. The most recently discovered superconductors exhibit multiband features. The multiband superconductors possess novel properties that are not shared with their single-band counterpart. Examples include: the time-reversal symmetry broken state in multiband superconductors with frustrated interband couplings; the collective oscillation of number of Cooper pairs between different bands, known as the Leggett mode; and the phase soliton and fractional vortex, which are the main focus of this review. This review presents a survey of a wide range of theoretical exploratory and experimental investigations of novel physics in multiband superconductors. A vast amount of information derived from these studies is shown to highlight unusual and unique properties of multiband superconductors and to reveal the challenges and opportunities in the research on the multiband superconductivity.

  20. Isotope and multiband effects in layered superconductors.

    Science.gov (United States)

    Bussmann-Holder, Annette; Keller, Hugo

    2012-06-13

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

  1. Superconductor Materials-A Revolutionary Value Addition to Space Electronics

    Directory of Open Access Journals (Sweden)

    Rathindra Nath Biswas

    2004-04-01

    Full Text Available An early success in low temperature superconductor technology has led to the development of a number of high temperature superconductor (H TS materials, which have critical temperature above 77 K. When the temperature of a solid is lowered below critical temperature, the material loses its electrical resistivity. Because resistance is almost zero, superconductors can carry very high current, generating very large homogeneous magnetic fields. Due to these features, it is possible to design electronic devices with extremely thin profile, offering less weight and low manufacturing cost. Such exceptional properties have made HTS materials useful in military and space sectors, wherc airborne systems have already provided with cryogenic infrastructure which can he used for cooling a high temperature superconductor at no extra cost.

  2. 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.

  3. The intercalation chemistry of layered iron chalcogenide superconductors

    Science.gov (United States)

    Vivanco, Hector K.; Rodriguez, Efrain E.

    2016-10-01

    The iron chalcogenides FeSe and FeS are superconductors composed of two-dimensional sheets held together by van der Waals interactions, which makes them prime candidates for the intercalation of various guest species. We review the intercalation chemistry of FeSe and FeS superconductors and discuss their synthesis, structure, and physical properties. Before we review the latest work in this area, we provide a brief background on the intercalation chemistry of other inorganic materials that exhibit enhanced superconducting properties upon intercalation, which include the transition metal dichalcogenides, fullerenes, and layered cobalt oxides. From past studies of these intercalated superconductors, we discuss the role of the intercalates in terms of charge doping, structural distortions, and Fermi surface reconstruction. We also briefly review the physical and chemical properties of the host materials-mackinawite-type FeS and β-FeSe. The three types of intercalates for the iron chalcogenides can be placed in three categories: 1.) alkali and alkaline earth cations intercalated through the liquid ammonia technique; 2.) cations intercalated with organic amines such as ethylenediamine; and 3.) layered hydroxides intercalated during hydrothermal conditions. A recurring theme in these studies is the role of the intercalated guest in electron doping the chalcogenide host and in enhancing the two-dimensionality of the electronic structure by spacing the FeSe layers apart. We end this review discussing possible new avenues in the intercalation chemistry of transition metal monochalcogenides, and the promise of these materials as a unique set of new inorganic two-dimensional systems.

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

    Science.gov (United States)

    Hosono, Hideo; Ren, Zhi-An

    2009-02-01

    pace of research within the last year, iron-based superconductors have revealed several unique properties such as a high upper critical field and a robustness to impurities. Participation of five 3d-orbitals in the Fermi levels also means that the electronic structure is complex compared with the cuprates. So, we now have a new family of superconductors and it is worth stressing that we have only just begun looking at the many varieties of candidate materials containing an iron square lattice. At this time we do not know whether a material with a critical temperature greater than 100 K exists, or if completely new properties are to be found. However, as a research community we should go ahead with hope and 'strike while the iron is hot'—this saying is always true! This focus issue of New Journal of Physics was put together to provide a broad-based, free-to-read snapshot of the current state of research in this rapidly emerging field. The papers included cover many aspects related to material exploration, physical analysis, and the theory of these materials, and, as editors, we thank the authors for their fine contributions, and the many referees for their considerable efforts that have ensured fast publication. As an aside, the first special issue on this SUBject was published in November 2008 in the Journal of the Physical Society of Japan (vol 77, supplement c) as the proceedings of the International Symposium on Iron-Pnictide Superconductors held in Tokyo on 29-30 June 2008. We would like to encourage the community to read both issues. On a final note we would like to acknowledge the staff of New Journal of Physics for all of their efficient work in bringing this collection to fruition. Focus on Iron-Based Superconductors Contents Microwave response of superconducting pnictides: extended s+/- scenario O V Dolgov, A A Golubov and D Parker Orbital and spin effects for the upper critical field in As-deficient disordered Fe pnictide superconductors G Fuchs, S

  5. 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

  6. Epitaxial heterojunctions of oxide semiconductors and metals on high temperature superconductors

    Science.gov (United States)

    Vasquez, Richard P. (Inventor); Hunt, Brian D. (Inventor); Foote, Marc C. (Inventor)

    1994-01-01

    Epitaxial heterojunctions formed between high temperature superconductors and metallic or semiconducting oxide barrier layers are provided. Metallic perovskites such as LaTiO3, CaVO3, and SrVO3 are grown on electron-type high temperature superconductors such as Nd(1.85)Ce(0.15)CuO(4-x). Alternatively, transition metal bronzes of the form A(x)MO(3) are epitaxially grown on electron-type high temperature superconductors. Also, semiconducting oxides of perovskite-related crystal structures such as WO3 are grown on either hole-type or electron-type high temperature superconductors.

  7. Coupling spin qubits via superconductors

    DEFF Research Database (Denmark)

    Leijnse, Martin; Flensberg, Karsten

    2013-01-01

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

  8. 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.

  9. Searching for the Genes of Unconventional High Temperature Superconductors

    Science.gov (United States)

    Hu, Jiangping

    In the past, both curates and iron-based superconductors were discovered accidentally. Lacking of successful predictions on new high Tc materials is one of major obstacles to reach a consensus on the high Tc mechanism. In this talk, we discuss two emergent principles, which are called as the correspondence principle and the selective magnetic pairing rule, to unify the understanding of both cuprates and iron-based superconductors. These two principles provide an unified explanation why the d-wave pairing symmetry and the s-wave pairing symmetry are robust respectively in cuprates and iron-based superconductors. In the meanwhile, the above two principles explain the rareness of unconventional high Tc superconductivity, identify necessary electronic environments required for high Tc superconductivity and finally serve as direct guiding rules to search new high Tc materials. We predict that the third family of unconventional high Tc superconductors exist in the compounds which carry two dimensional hexagonal lattices formed by cation-anion trigonal bipyramidal complexes with a d filling configuration on the cation ions. Their superconducting states are expected to be dominated by the d+id pairing symmetry and their maximum Tc should be higher than those of iron-based superconductors. Verifying the prediction can convincingly establish the high Tc superconducting mechanism and pave a way to design new high Tc superconductors

  10. High Temperature Superconductors for the Electric Power Grid

    Science.gov (United States)

    Malozemoff, Alexis P.

    2011-03-01

    High Temperature Superconductor power equipment is positioned to play a key role in addressing our national and global energy challenges. While the most obvious benefit is efficiency by using the superconductor's lossless current flow to cut the 10% power lost in the grid, other benefits are likely to be even more impactful. These benefits arise from the high current density of superconductor wire which enables design of highly power-dense and compact equipment including high capacity cables and rotating machinery -- generators and motors. Vast and dense urban areas are becoming home to an increasingly large proportion of world population, and high capacity ac superconductor cables offer a non-interfering and easily installed solution to increasing urban power needs. Longer term, the ultra-low loss of long-distance dc superconductor cables offers strengthened links and power sharing across wide geographical areas. Compact superconductor generators are the key to high power off-shore wind turbines, a major source of renewable energy. Some of these applications have reached a sophisticated level of demonstration, initiating commercial use.

  11. 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

  12. 'Beautiful' unconventional synthesis and processing technologies of superconductors and some other materials

    Directory of Open Access Journals (Sweden)

    Petre Badica, Adrian Crisan, Gheorghe Aldica, Kazuhiro Endo, Hanna Borodianska, Kazumasa Togano, Satoshi Awaji, Kazuo Watanabe, Yoshio Sakka and Oleg Vasylkiv

    2011-01-01

    Full Text Available Superconducting materials have contributed significantly to the development of modern materials science and engineering. Specific technological solutions for their synthesis and processing helped in understanding the principles and approaches to the design, fabrication and application of many other materials. In this review, we explore the bidirectional relationship between the general and particular synthesis concepts. The analysis is mostly based on our studies where some unconventional technologies were applied to different superconductors and some other materials. These technologies include spray-frozen freeze-drying, fast pyrolysis, field-assisted sintering (or spark plasma sintering, nanoblasting, processing in high magnetic fields, methods of control of supersaturation and migration during film growth, and mechanical treatments of composite wires. The analysis provides future research directions and some key elements to define the concept of 'beautiful' technology in materials science. It also reconfirms the key position and importance of superconductors in the development of new materials and unconventional synthesis approaches.

  13. 'Beautiful' unconventional synthesis and processing technologies of superconductors and some other materials.

    Science.gov (United States)

    Badica, Petre; Crisan, Adrian; Aldica, Gheorghe; Endo, Kazuhiro; Borodianska, Hanna; Togano, Kazumasa; Awaji, Satoshi; Watanabe, Kazuo; Sakka, Yoshio; Vasylkiv, Oleg

    2011-02-01

    Superconducting materials have contributed significantly to the development of modern materials science and engineering. Specific technological solutions for their synthesis and processing helped in understanding the principles and approaches to the design, fabrication and application of many other materials. In this review, we explore the bidirectional relationship between the general and particular synthesis concepts. The analysis is mostly based on our studies where some unconventional technologies were applied to different superconductors and some other materials. These technologies include spray-frozen freeze-drying, fast pyrolysis, field-assisted sintering (or spark plasma sintering), nanoblasting, processing in high magnetic fields, methods of control of supersaturation and migration during film growth, and mechanical treatments of composite wires. The analysis provides future research directions and some key elements to define the concept of 'beautiful' technology in materials science. It also reconfirms the key position and importance of superconductors in the development of new materials and unconventional synthesis approaches.

  14. Zeeman-Field-Tuned Topological Phase Transitions in a Two-Dimensional Class-DIII Superconductor.

    Science.gov (United States)

    Deng, W Y; Geng, H; Luo, W; Sheng, L; Xing, D Y

    2016-01-01

    We investigate the topological phase transitions in a two-dimensional time-reversal invariant topological superconductor in the presence of a Zeeman field. Based on the spin Chern number theory, we find that the system exhibits a number of topologically distinct phases with changing the out-of-plane component of the Zeeman field, including a quantum spin Hall-like phase, quantum anomalous Hall-like phases with total Chern number C = -2, -1, 1 and 2, and a topologically trivial superconductor phase. The BdG band gap closes at each boundary of the phase transitions. Furthermore, we demonstrate that the zero bias conductance provides clear transport signatures of the different topological phases, which are robust against symmetry-breaking perturbations.

  15. Antenna applications of superconductors

    Science.gov (United States)

    Hansen, R. C.

    1991-09-01

    The applicability of superconductors to antennas is examined. Potential implementations that are examined are superdirective arrays; electrically small antennas; tuning and matching of these two; high-gain millimeter-wavelength arrays; and kinetic inductance slow wave structures for array phasers and traveling wave array feeds. It is thought that superdirective arrays and small antennas will not benefit directly, but their tuning/matching networks will undergo major improvements. Miniaturization of antennas will not be aided, but much higher gain millimeter-wave arrays will be realizable. Kinetic inductance slow-wave lines appear advantageous for improved array phasers and time delay, as well as for traveling-wave array feeds.

  16. Rotor assembly including superconducting magnetic coil

    Energy Technology Data Exchange (ETDEWEB)

    Snitchler, Gregory L. (Shrewsbury, MA); Gamble, Bruce B. (Wellesley, MA); Voccio, John P. (Somerville, MA)

    2003-01-01

    Superconducting coils and methods of manufacture include a superconductor tape wound concentrically about and disposed along an axis of the coil to define an opening having a dimension which gradually decreases, in the direction along the axis, from a first end to a second end of the coil. Each turn of the superconductor tape has a broad surface maintained substantially parallel to the axis of the coil.

  17. Theoretical study of pair density wave superconductors

    Science.gov (United States)

    Zheng, Zhichao

    In conventional superconductors, the Cooper pairs are formed from quasiparticles. We explore another type of superconducting state, a pair density wave (PDW) order, which spontaneously breaks some of the translational and point group symmetries. In a PDW superconductor, the order parameter is a periodic function of the center-of-mass coordinate, and the spatial average value of the superconducting order parameter vanishes. In the early 1960s, following the success of the BCS theory of superconductivity, Fulde and Ferrell and Larkin and Ovchinnikov (FFLO) developed theories of inhomogeneous superconducting states. Because of this Zeeman splitting in a magnetic field, the Cooper pairs having a nonzero center-of-mass momentum are more stable than the normal pairing, leading to the FFLO state. Experiments suggest possible occurrence of the FFLO state in the heavy-fermion compound CeCoIn5, and in quasi-low-dimensional organic superconductors. FFLO phases have also been argued to be of importance in understanding ultracold atomic Fermi gases and in the formation of color superconductivity in high density quark matter. In all Fermi superfluids known at the present time, Cooper pairs are composed of particles with spin 1/2. The spin component of a pair wave function can be characterized by its total spin S = 0 (singlet) and S = 1 (triplet). In the discovered broken inversion superconductors CePt3Si, Li2Pt3B, and Li2Pd3B, the magnetic field leads to novel inhomogeneous superconducting states, namely the helical phase and the multiple-q phase. Its order parameter exhibits periodicity similar to FFLO phase, and the consequences of both phases are same: the enhancement of transition temperature as a function of magnetic field. We have studied the PDW phases in broken parity superconductors with vortices included. By studying PDW vortex states, we find the usual Abrikosov vortex solution is unstable against a new solution with fractional vortex pairs. We have also studied the

  18. Energy efficiency of adiabatic superconductor logic

    Science.gov (United States)

    Takeuchi, Naoki; Yamanashi, Yuki; Yoshikawa, Nobuyuki

    2015-01-01

    Adiabatic superconductor logic (ASL), including adiabatic quantum-flux-parametron (AQFP) logic, exhibits high energy efficiency because its bit energy can be decreased below the thermal energy through adiabatic switching operations. In the present paper, we present the general scaling laws of ASL and compare the energy efficiency of ASL with those of other energy-efficient logics. Also, we discuss the minimum energy-delay product (EDP) of ASL at finite temperature. Our study shows that there is a maximum temperature at which the EDP can reach the quantum limit given by ħ/2, which is dependent on the superconductor material and the Josephson junction quality, and that it is reasonable to operate ASL at cryogenic temperatures in order to achieve an EDP that approaches ħ/2.

  19. Sewerage Treatment Plants, Treatment plants included in sanitary sewer layer above, Published in Not Provided, 1:600 (1in=50ft) scale, Town of Franklin.

    Data.gov (United States)

    NSGIC GIS Inventory (aka Ramona) — This Sewerage Treatment Plants dataset, published at 1:600 (1in=50ft) scale, was produced all or in part from Field Survey/GPS information as of Not Provided. It is...

  20. Water Towers, Included in water system layer above, Published in Not Provided, 1:600 (1in=50ft) scale, Town of Franklin.

    Data.gov (United States)

    NSGIC GIS Inventory (aka Ramona) — This Water Towers dataset, published at 1:600 (1in=50ft) scale, was produced all or in part from Field Survey/GPS information as of Not Provided. It is described as...

  1. Water Pipelines, Major, Included in water system layer above, Published in Not Provided, 1:600 (1in=50ft) scale, Town of Franklin.

    Data.gov (United States)

    NSGIC GIS Inventory (aka Ramona) — This Water Pipelines, Major dataset, published at 1:600 (1in=50ft) scale, was produced all or in part from Field Survey/GPS information as of Not Provided. It is...

  2. Water Pumping Stations, Included in water system layer above, Published in Not Provided, 1:600 (1in=50ft) scale, Town of Franklin.

    Data.gov (United States)

    NSGIC GIS Inventory (aka Ramona) — This Water Pumping Stations dataset, published at 1:600 (1in=50ft) scale, was produced all or in part from Field Survey/GPS information as of Not Provided. It is...

  3. Water Tanks, Included in water system layer above, Published in Not Provided, 1:600 (1in=50ft) scale, Town of Franklin.

    Data.gov (United States)

    NSGIC GIS Inventory (aka Ramona) — This Water Tanks dataset, published at 1:600 (1in=50ft) scale, was produced all or in part from Field Survey/GPS information as of Not Provided. It is described as...

  4. Sewerage Pumping Stations, Pumping stations included in sanitary sewer system data above, Published in Not Provided, 1:600 (1in=50ft) scale, Town of Franklin.

    Data.gov (United States)

    NSGIC GIS Inventory (aka Ramona) — This Sewerage Pumping Stations dataset, published at 1:600 (1in=50ft) scale, was produced all or in part from Field Survey/GPS information as of Not Provided. It is...

  5. Flux pinning in superconductors

    CERN Document Server

    Matsushita, Teruo

    2014-01-01

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

  6. Flux Pinning in Superconductors

    CERN Document Server

    Matsushita, Teruo

    2007-01-01

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

  7. 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.

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

    Energy Technology Data Exchange (ETDEWEB)

    Tranquada,J.M.

    2008-09-01

    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.

  9. Neutron and synchrotron x-ray scattering studies of superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Tranquada, J.M.

    2008-10-15

    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. (au)

  10. Materials design for new superconductors.

    Science.gov (United States)

    Norman, M R

    2016-07-01

    Since the announcement in 2011 of the Materials Genome Initiative by the Obama administration, much attention has been given to the subject of materials design to accelerate the discovery of new materials that could have technological implications. Although having its biggest impact for more applied materials like batteries, there is increasing interest in applying these ideas to predict new superconductors. This is obviously a challenge, given that superconductivity is a many body phenomenon, with whole classes of known superconductors lacking a quantitative theory. Given this caveat, various efforts to formulate materials design principles for superconductors are reviewed here, with a focus on surveying the periodic table in an attempt to identify cuprate analogues.

  11. Spin manipulation in nanoscale superconductors.

    Science.gov (United States)

    Beckmann, D

    2016-04-27

    The interplay of superconductivity and magnetism in nanoscale structures has attracted considerable attention in recent years due to the exciting new physics created by the competition of these antagonistic ordering phenomena, and the prospect of exploiting this competition for superconducting spintronics devices. While much of the attention is focused on spin-polarized supercurrents created by the triplet proximity effect, the recent discovery of long range quasiparticle spin transport in high-field superconductors has rekindled interest in spin-dependent nonequilibrium properties of superconductors. In this review, the experimental situation on nonequilibrium spin injection into superconductors is discussed, and open questions and possible future directions of the field are outlined.

  12. Materials design for new superconductors

    Science.gov (United States)

    Norman, M. R.

    2016-07-01

    Since the announcement in 2011 of the Materials Genome Initiative by the Obama administration, much attention has been given to the subject of materials design to accelerate the discovery of new materials that could have technological implications. Although having its biggest impact for more applied materials like batteries, there is increasing interest in applying these ideas to predict new superconductors. This is obviously a challenge, given that superconductivity is a many body phenomenon, with whole classes of known superconductors lacking a quantitative theory. Given this caveat, various efforts to formulate materials design principles for superconductors are reviewed here, with a focus on surveying the periodic table in an attempt to identify cuprate analogues.

  13. The AC magnetic susceptibility of high temperature superconductors

    CERN Document Server

    Salim, M

    2001-01-01

    This research concerns the development of AC magnetic susceptometers and use of susceptometers in analysing high temperature superconductors. Two of the designs were a differential magnetic susceptometer (DMS) and a double coil screening susceptometer (DCSS) whose descriptions are given in detail including coil design, field measurements, susceptometer operation, experimental instrumentation, phase adjustment, susceptometer calibration and sensitivity for each design. Theoretical details are given regarding each design in order to calculate the complex external and internal susceptibility. Investigation concerning the demagnetisation factor of different geometries, and the significant features and limitation for each design are also provided. The susceptometers were applied to a wide range of YBCO samples, which includes bulk samples with different geometry (i.e. Slabs, disk, powder and thick film) and thin films with different oxygen contents. Several silver sheathed Bi-2223 tapes were also involved. This al...

  14. Studies of the gap structure of iron-based superconductors using magnetic penetration depth

    Science.gov (United States)

    Carrington, Antony

    2011-06-01

    This article reviews experiments to determine the structure of the superconducting gap in the iron-based superconductors. It focuses on insights provided by measurements of the temperature dependence of magnetic penetration depth but also discusses the information provided by other measurements especially thermal conductivity. The article includes background theory on the types of gap structure suggested for the iron-based superconductors as well as the general theory of penetration depth in conventional and unconventional superconductors. The effect of impurity scattering on each candidate gap structure is important for the interpretation of data and so will also be discussed. Penetration depth data for single crystals of the following compounds is reviewed: SmFeAsO 0.8F 0.2, FeTe 0.5Se 0.5, LaFePO, KFe 2As 2 and BaFe 2(As 0.67P 0.33) 2 along with discussion on related materials such as K- and Co-doped BaFe 2As 2.

  15. Combining Topological Hardware and Topological Software: Color-Code Quantum Computing with Topological Superconductor Networks

    Directory of Open Access Journals (Sweden)

    Daniel Litinski

    2017-09-01

    Full Text Available We present a scalable architecture for fault-tolerant topological quantum computation using networks of voltage-controlled Majorana Cooper pair boxes and topological color codes for error correction. Color codes have a set of transversal gates which coincides with the set of topologically protected gates in Majorana-based systems, namely, the Clifford gates. In this way, we establish color codes as providing a natural setting in which advantages offered by topological hardware can be combined with those arising from topological error-correcting software for full-fledged fault-tolerant quantum computing. We provide a complete description of our architecture, including the underlying physical ingredients. We start by showing that in topological superconductor networks, hexagonal cells can be employed to serve as physical qubits for universal quantum computation, and we present protocols for realizing topologically protected Clifford gates. These hexagonal-cell qubits allow for a direct implementation of open-boundary color codes with ancilla-free syndrome read-out and logical T gates via magic-state distillation. For concreteness, we describe how the necessary operations can be implemented using networks of Majorana Cooper pair boxes, and we give a feasibility estimate for error correction in this architecture. Our approach is motivated by nanowire-based networks of topological superconductors, but it could also be realized in alternative settings such as quantum-Hall–superconductor hybrids.

  16. High temperature superconductors applications in telecommunications

    Science.gov (United States)

    Kumar, A. Anil; Li, Jiang; Zhang, Ming Fang

    1995-01-01

    The purpose of this paper is twofold: (1) to discuss high temperature superconductors with specific reference to their employment in telecommunications applications; and (2) 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

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

    Science.gov (United States)

    Mukhanov, Oleg

    2011-03-01

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

  18. High temperature superconductors applications in telecommunications

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, A.A.; Li, J.; Zhang, M.F. [Prairie View A& M Univ., Texas (United States)

    1994-12-31

    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{sub c} superconductors.

  19. Free energy of a Lovelock holographic superconductor

    CERN Document Server

    Aranguiz, Ligeia

    2014-01-01

    We study black hole solutions in Lanczos-Lovelock AdS gravity in d+1 dimensions coupled to nonlinear electrodynamics and a Stueckelberg scalar field. This class of theories with [d/2] gravitational coupling constants and two arbitrary functions that govern the matter interaction is used in the context of gauge/gravity duality to describe a high-temperature superconductor in d dimensions. We regularize the gravitational action and find the finite conserved quantities for a planar black hole with scalar hair. Then we derive the quantum statistical relation in the Euclidean sector of the theory, and obtain the exact formula for the free energy of the superconductor in the holographic quantum field theory. Our result is exact, analytic and it includes the effects of back reaction of the gravitational field. We further discuss on how this formula could be used to analyze second order phase transitions through the discontinuities of the free energy, and classify holographic superconductors in terms of the parameter...

  20. Electronic evidence of an insulator-superconductor crossover in single-layer FeSe/SrTiO3 films.

    Science.gov (United States)

    He, Junfeng; Liu, Xu; Zhang, Wenhao; Zhao, Lin; Liu, Defa; He, Shaolong; Mou, Daixiang; Li, Fangsen; Tang, Chenjia; Li, Zhi; Wang, Lili; Peng, Yingying; Liu, Yan; Chen, Chaoyu; Yu, Li; Liu, Guodong; Dong, Xiaoli; Zhang, Jun; Chen, Chuangtian; Xu, Zuyan; Chen, Xi; Ma, Xucun; Xue, Qikun; Zhou, X J

    2014-12-30

    In high-temperature cuprate superconductors, it is now generally agreed that superconductivity is realized by doping an antiferromagnetic Mott (charge transfer) insulator. The doping-induced insulator-to-superconductor transition has been widely observed in cuprates, which provides important information for understanding the superconductivity mechanism. In the iron-based superconductors, however, the parent compound is mostly antiferromagnetic bad metal, raising a debate on whether an appropriate starting point should go with an itinerant picture or a localized picture. No evidence of doping-induced insulator-superconductor transition (or crossover) has been reported in the iron-based compounds so far. Here, we report an electronic evidence of an insulator-superconductor crossover observed in the single-layer FeSe film grown on a SrTiO3 substrate. By taking angle-resolved photoemission measurements on the electronic structure and energy gap, we have identified a clear evolution of an insulator to a superconductor with increasing carrier concentration. In particular, the insulator-superconductor crossover in FeSe/SrTiO3 film exhibits similar behaviors to that observed in the cuprate superconductors. Our results suggest that the observed insulator-superconductor crossover may be associated with the two-dimensionality that enhances electron localization or correlation. The reduced dimensionality and the interfacial effect provide a new pathway in searching for new phenomena and novel superconductors with a high transition temperature.

  1. Superconductor stripes move on

    Energy Technology Data Exchange (ETDEWEB)

    Tranquada, J. [Physics Department, Brookhaven National Laboratory, Upton, NY (United States)

    1999-11-01

    Differences in fundamental assumptions are behind much of the controversy among theorists over the cause of high-temperature superconductivity the absence of resistance to electrical current at temperatures as high as 130 K in layered copper-oxide compounds. One common assumption is that the charge carriers are distributed uniformly throughout the all-important CuO{sub 2} layers. However, there is growing experimental evidence that this is not the case and that 'stripes' of charge form in these puzzling materials. Now a significant step forward in the struggle to understand the behaviour of charge carriers in high-temperature superconductors has been made at the Oak Ridge National Laboratory in the US. (UK)

  2. Manufacturing of Superconductors

    DEFF Research Database (Denmark)

    Bech, Jakob Ilsted; Bay, Niels

    Superconducting tapes based on the ceramic high temperature superconductor (HTS) is a new promising product for high current applications such as electro-magnets and current transmission cables. The tapes are made by the oxide powder in tube (OPIT) method implying drawing and rolling of silver...... on the mechanical and thermal processes applied. One of the most crucial processes is probably the flat rolling process, where the round or square wire is rolled to form a thin tape (about 3 mm x 0.2 mm), while the density of the powder fibres increase and the fibres obtain their final geometry. For instance...... rolling a tape to a thickness of 250 µm may give a very high Je, whereas further reduction to 200 µm may be fatal. In the present work the flat rolling process is analysed systematically from a mechanical forming point of view. This work implies · Mechanical characterisation of the plastic parameters...

  3. Including the Copenhagen Adduction Exercise in the FIFA 11+ Provides Missing Eccentric Hip Adduction Strength Effect in Male Soccer Players: A Randomized Controlled Trial.

    Science.gov (United States)

    Harøy, Joar; Thorborg, Kristian; Serner, Andreas; Bjørkheim, André; Rolstad, Linn E; Hölmich, Per; Bahr, Roald; Andersen, Thor Einar

    2017-08-01

    The FIFA 11+ was developed as a complete warm-up program to prevent injuries in soccer players. Although reduced hip adduction strength is associated with groin injuries, none of the exercises included in the FIFA 11+ seem to specifically target hip adduction strength. To investigate the effect on eccentric hip adduction strength of the FIFA 11+ warm-up program with or without the Copenhagen adduction exercise. Randomized controlled trial; Level of evidence, 1. We recruited 45 eligible players from 2 U19 elite male soccer teams. Players were randomized into 2 groups; 1 group carried out the standard FIFA 11+ program, while the other carried out the FIFA 11+ but replaced the Nordic hamstring exercise with the Copenhagen adduction exercise. Both groups performed the intervention 3 times weekly for 8 weeks. Players completed eccentric strength and sprint testing before and after the intervention. Per-protocol analyses were performed, and 12 players were excluded due to low compliance (<67% of sessions completed). The main outcome was eccentric hip adduction strength (N·m/kg). Between-group analyses revealed a significantly greater increase in eccentric hip adduction strength of 0.29 Nm/kg (8.9%; P = .01) in favor of the group performing the Copenhagen adduction exercise, whereas no within-group change was noted in the group that used the standard FIFA 11+ program (-0.02 N·m/kg [-0.7%]; P = .69). Including the Copenhagen adduction exercise in the FIFA 11+ program increases eccentric hip adduction strength, while the standard FIFA 11+ program does not. Registration: Registration: ISRCTN13731446 (International Standard Randomised Controlled Trial Number registry).

  4. High-Temperature Cuprate Superconductors Experiment, Theory, and Applications

    CERN Document Server

    Plakida, Nikolay Maksimilianovich

    2010-01-01

    High-Temperature Cuprate Superconductors provides an up-to-date and comprehensive review of the properties of these fascinating materials. The essential properties of high-temperature cuprate superconductors are reviewed on the background of their theoretical interpretation. The experimental results for structural, magnetic, thermal, electric, optical and lattice properties of various cuprate superconductors are presented with respect to relevant theoretical models. A critical comparison of various theoretical models involving strong electron correlations, antiferromagnetic spin fluctuations, phonons and excitons provides a background for understanding of the mechanism of high-temperature superconductivity. Recent achievements in their applications are also reviewed. A large number of illustrations and tables gives valuable information for specialists. A text-book level presentation with formulation of a general theory of strong-coupling superconductivity will help students and researches to consolidate their...

  5. Computational Assessment of a 3-Stage Axial Compressor Which Provides Airflow to the NASA 11- by 11-Foot Transonic Wind Tunnel, Including Design Changes for Increased Performance

    Science.gov (United States)

    Kulkarni, Sameer; Beach, Timothy A.; Jorgenson, Philip C.; Veres, Joseph P.

    2017-01-01

    A 24 foot diameter 3-stage axial compressor powered by variable-speed induction motors provides the airflow in the closed-return 11- by 11-Foot Transonic Wind Tunnel (11-Foot TWT) Facility at NASA Ames Research Center at Moffett Field, California. The facility is part of the Unitary Plan Wind Tunnel, which was completed in 1955. Since then, upgrades made to the 11-Foot TWT such as flow conditioning devices and instrumentation have increased blockage and pressure loss in the tunnel, somewhat reducing the peak Mach number capability of the test section. Due to erosion effects on the existing aluminum alloy rotor blades, fabrication of new steel rotor blades is planned. This presents an opportunity to increase the Mach number capability of the tunnel by redesigning the compressor for increased pressure ratio. Challenging design constraints exist for any proposed design, demanding the use of the existing driveline, rotor disks, stator vanes, and hub and casing flow paths, so as to minimize cost and installation time. The current effort was undertaken to characterize the performance of the existing compressor design using available design tools and computational fluid dynamics (CFD) codes and subsequently recommend a new compressor design to achieve higher pressure ratio, which directly correlates with increased test section Mach number. The constant cross-sectional area of the compressor leads to highly diffusion factors, which presents a challenge in simulating the existing design. The CFD code APNASA was used to simulate the aerodynamic performance of the existing compressor. The simulations were compared to performance predictions from the HT0300 turbomachinery design and analysis code, and to compressor performance data taken during a 1997 facility test. It was found that the CFD simulations were sensitive to endwall leakages associated with stator buttons, and to a lesser degree, under-stator-platform flow recirculation at the hub. When stator button leakages were

  6. Applications of bulk high-temperature superconductors

    Science.gov (United States)

    Hull, J. R.

    The development of high-temperature superconductors (HTS's) can be broadly generalized into thin-film electronics, wire applications, and bulk applications. We consider bulk HTS's to include sintered or crystallized forms that do not take the geometry of filaments or tapes, and we discuss major applications for these materials. For the most part applications may be realized with the HTS's cooled to 77 K, and the properties of the bulk HTS's are often already sufficient for commercial use. A non-exhaustive list of applications for bulk HTS's includes trapped field magnets, hysteresis motors, magnetic shielding, current leads, and magnetic bearings. These applications are briefly discussed in this paper.

  7. Published assessments bearing on the future use of ceramic superconductors by the electric power sector

    Energy Technology Data Exchange (ETDEWEB)

    Giese, R.F.; Wolsky, A.M.

    1992-08-25

    Much has been written about ceramic superconductors since their discovery in 1986. Most of this writing reports and describes scientific research. However, some authors have sought to put this research in context: to assess where the field stands, what might be technically feasible, what might be economically feasible, and what potential impacts ceramic superconductors will bring to the electric power sector. This report's purpose is to make the results of already published assessments readily available. To that end, this report lists and provides abstracts for various technical and economic assessments related to applications of High-Temperature Superconductors (HTS) to the electric power sector. Those studies deemed most important are identified and summarized. These assessments were identified by two means. First, members of the Executive Committee identified some reports as worthy of consideration and forwarded them to Argonne National Laboratory. Twelve assessments were selected. Each of these is listed and summarized in the following section. Second, a bibliographic search was performed on five databases: INSPEC, NTIS, COMPENDEX, Energy Science Technology, and Electric Power Database. The search consisted of first selecting all papers related to High Temperature Superconductors. Then papers related to SMES, cables, generators, motors, fault current limiters, or electric utilities were selected. When suitable variants of the above terms were included, this resulted in a selection of 493 citations. These citations were subjected to review by the authors. A number of citations were determined to be inappropriate (e.g. a number referred to digital transmission lines for electronics and communications applications). The reduced list consisted of 200 entries. Each of these citations, with an abstract, is presented in the following sections.

  8. Published assessments bearing on the future use of ceramic superconductors by the electric power sector

    Energy Technology Data Exchange (ETDEWEB)

    Giese, R.F.; Wolsky, A.M.

    1992-08-25

    Much has been written about ceramic superconductors since their discovery in 1986. Most of this writing reports and describes scientific research. However, some authors have sought to put this research in context: to assess where the field stands, what might be technically feasible, what might be economically feasible, and what potential impacts ceramic superconductors will bring to the electric power sector. This report`s purpose is to make the results of already published assessments readily available. To that end, this report lists and provides abstracts for various technical and economic assessments related to applications of High-Temperature Superconductors (HTS) to the electric power sector. Those studies deemed most important are identified and summarized. These assessments were identified by two means. First, members of the Executive Committee identified some reports as worthy of consideration and forwarded them to Argonne National Laboratory. Twelve assessments were selected. Each of these is listed and summarized in the following section. Second, a bibliographic search was performed on five databases: INSPEC, NTIS, COMPENDEX, Energy Science & Technology, and Electric Power Database. The search consisted of first selecting all papers related to High Temperature Superconductors. Then papers related to SMES, cables, generators, motors, fault current limiters, or electric utilities were selected. When suitable variants of the above terms were included, this resulted in a selection of 493 citations. These citations were subjected to review by the authors. A number of citations were determined to be inappropriate (e.g. a number referred to digital transmission lines for electronics and communications applications). The reduced list consisted of 200 entries. Each of these citations, with an abstract, is presented in the following sections.

  9. Flux pinning in superconductors. 2. ed.

    Energy Technology Data Exchange (ETDEWEB)

    Matsushita, Teruo [Kyushu Institute of Technology, Iizuka, Fukuoka (Japan). Dept. of Computer Science and Electronics

    2014-04-01

    of flux bundle size which determines the irreversibility line under the flux creep. The new edition has been thoroughly updated, with new sections on the progress in enhancing the critical current density in high temperature superconductors by introduction of artificial pinning centers, the effect of packing density on the critical current density and irreversibility field in MgB2 and derivation of the force-balance equation from the minimization of the free energy including the pinning energy.

  10. Developments in the processing of bulk (RE)BCO superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Babu, N. Hari, E-mail: mtsthbn@brunel.ac.u [Brunel Centre for Advanced Solidification Technology (BCAST), Brunel University, West London UB8 3PH (United Kingdom); Shi, Y.-H.; Pathak, S.K.; Dennis, A.R.; Cardwell, D.A. [Bulk Superconductivity Group, Engineering Department, University of Cambridge, Cambridge CB2 1PZ (United Kingdom)

    2011-03-15

    Research highlights: {yields} (RE)-Ba-Cu-O bulk superconductors containing nano-scale inclusions are fabricated. {yields} Generic seed crystal development enabled batch process for Gd-Ba-Cu-O. {yields} Multi-grains with strongly coupled grain boundaries are fabricated. {yields} We propose recycling concept for bulk superconductors. - Abstract: The development of a practical processing method for the fabrication of high performance large, single grain bulk superconductors is essential for their cost-effective application in a variety of high field engineering devices. We discuss recent developments in the processing of these materials that enable high performance bulk superconductors to be fabricated in a practical way. These include the introduction of nano-scale second phase inclusions to the superconducting phase matrix, the development of a generic seed crystal, the development of practical, batch processing routes for the fabrication of light rare earth superconductors, the processing of complex shaped geometries via controlled multi-seeding and recycling of scrap bulk samples into high performance, single grains.

  11. 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.

  12. Odd-parity topological superconductors: theory and application to CuxBi2Se3.

    Science.gov (United States)

    Fu, Liang; Berg, Erez

    2010-08-27

    Topological superconductors have a full pairing gap in the bulk and gapless surface Andreev bound states. In this Letter, we provide a sufficient criterion for realizing time-reversal-invariant topological superconductors in centrosymmetric superconductors with odd-parity pairing. We next study the pairing symmetry of the newly discovered superconductor CuxBi2Se3 within a two-orbital model, and find that a novel spin-triplet pairing with odd parity is favored by strong spin-orbit coupling. Based on our criterion, we propose that CuxBi2Se3 is a good candidate for a topological superconductor. We close by discussing experimental signatures of this new topological phase.

  13. 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.

  14. Ferromagnet / superconductor oxide superlattices

    Science.gov (United States)

    Santamaria, Jacobo

    2006-03-01

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

  15. 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.

  16. Holographic entanglement entropy in general holographic superconductor models

    CERN Document Server

    Peng, Yan

    2014-01-01

    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.

  17. Phases of holographic superconductors with broken translational symmetry

    CERN Document Server

    Baggioli, Matteo

    2015-01-01

    We consider holographic superconductors in a broad class of massive gravity backgrounds. These theories provide a holographic description of a superconductor with broken translational symmetry. Such models exhibit a rich phase structure: depending on the values of the temperature and the doping the boundary system can be in superconducting, normal metallic or normal pseudo-insulating phases. Furthermore the system supports interesting collective excitations of the charge carriers, which appears in the normal phase, persists in the superconducting phase, but eventually gets destroyed by the superconducting condensate. We also show the possibility of building a phase diagram of a system with the superconducting phase occupying a dome-shaped region, therefore resembling more of a real-world doped high-Tc superconductor.

  18. Gravitoelectromagnetism and Dark Energy in Superconductors

    CERN Document Server

    De Matos, C J

    2006-01-01

    A gravitomagnetic analogue of the London moment in superconductors can explain the anomalous Cooper pair mass excess reported by Janet Tate. Ultimately the gravitomagnetic London moment is attributed to the breaking of the principle of general covariance in superconductors. This naturally implies non-conservation of classical energy-momentum. Possible relation with the manifestation of dark energy in superconductors is questioned.

  19. 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...

  20. Symmetry analysis of transport properties in helical superconductor junctions

    Science.gov (United States)

    Cheng, Qiang; Zhang, Yinhan; Zhang, Kunhua; Jin, Biao; Zhang, Changlian

    2017-03-01

    We study the discrete symmetries satisfied by helical p-wave superconductors with the d-vectors {{k}x}\\hat{x}+/- {{k}y}\\hat{y} or {{k}y}\\hat{x}+/- {{k}x}\\hat{y} and the transformations brought by symmetry operations to ferromagnet and spin-singlet superconductors, which show intimate associations with the transport properties in heterojunctions, including helical superconductors. In particular, the partial symmetries of the Hamiltonian under spin-rotation and gauge-rotation operations are responsible for the novel invariances of the conductance in tunnel junctions and the new selection rules for the lowest current and peculiar phase diagrams in Josephson junctions, which were reported recently. The symmetries of constructed free energies for Josephson junctions are also analyzed, and are consistent with the results from the Hamiltonian.

  1. Vortices in high-performance high-temperature superconductors

    Science.gov (United States)

    Kwok, Wai-Kwong; Welp, Ulrich; Glatz, Andreas; Koshelev, Alexei E.; Kihlstrom, Karen J.; Crabtree, George W.

    2016-11-01

    The behavior of vortex matter in high-temperature superconductors (HTS) controls the entire electromagnetic response of the material, including its current carrying capacity. Here, we review the basic concepts of vortex pinning and its application to a complex mixed pinning landscape to enhance the critical current and to reduce its anisotropy. We focus on recent scientific advances that have resulted in large enhancements of the in-field critical current in state-of-the-art second generation (2G) YBCO coated conductors and on the prospect of an isotropic, high-critical current superconductor in the iron-based superconductors. Lastly, we discuss an emerging new paradigm of critical current by design—a drive to achieve a quantitative correlation between the observed critical current density and mesoscale mixed pinning landscapes by using realistic input parameters in an innovative and powerful large-scale time dependent Ginzburg-Landau approach to simulating vortex dynamics.

  2. Vortices in high-performance high-temperature superconductors.

    Science.gov (United States)

    Kwok, Wai-Kwong; Welp, Ulrich; Glatz, Andreas; Koshelev, Alexei E; Kihlstrom, Karen J; Crabtree, George W

    2016-11-01

    The behavior of vortex matter in high-temperature superconductors (HTS) controls the entire electromagnetic response of the material, including its current carrying capacity. Here, we review the basic concepts of vortex pinning and its application to a complex mixed pinning landscape to enhance the critical current and to reduce its anisotropy. We focus on recent scientific advances that have resulted in large enhancements of the in-field critical current in state-of-the-art second generation (2G) YBCO coated conductors and on the prospect of an isotropic, high-critical current superconductor in the iron-based superconductors. Lastly, we discuss an emerging new paradigm of critical current by design-a drive to achieve a quantitative correlation between the observed critical current density and mesoscale mixed pinning landscapes by using realistic input parameters in an innovative and powerful large-scale time dependent Ginzburg-Landau approach to simulating vortex dynamics.

  3. The LHC's future, part 2: The High-Luminosity superconductor

    CERN Multimedia

    2017-01-01

    The goal of the HL-LHC project is to increase the total number of collisions of the LHC by a factor of 10 . Among the components to be upgraded are the interaction region quadrupole magnets in IP1 and IP5, which will implement a new superconducting technology based on Nb3Sn superconductor. This superconductor will allow reaching magnetic field of about 12 T, but it requires a complex fabrication process which includes heat treatment of the coils to about 650 C and vacuum impregnation with epoxy. In the Superconducting Model Magnets Laboratory (building 927), the Magnet, Superconductors and Cryostats (MSC) group is currently fabricating short models of the final Nb3Sn LHL-LHC quadrupole magnet to verify the magnet design and define fabrication and assembly procedures

  4. 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, Nb3Sn 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.

  5. Critical field enhancement near a superconductor-insulator transition.

    Science.gov (United States)

    Lee, I J; Chaikin, P M; Naughton, M J

    2002-05-20

    We have discovered a phenomenon where the orbital pair breaking effect is reduced, if not eliminated. It appears as a striking enhancement in the upper critical field H(c2) for (TMTSF)2PF6 and a strong upward curvature in the critical field versus temperature in the region of pressure-temperature phase space near the superconductor-spin density wave insulator boundary. A simple model based on self-consistently dividing the superconductor into layers explains the observations remarkably well and provides a unique way around orbital frustration and toward higher critical fields.

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

    CERN Document Server

    Deutscher, Guy

    2017-01-01

    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.

  7. Electrochemical synthesis of alkali-intercalated iron selenide superconductors

    Institute of Scientific and Technical Information of China (English)

    申士杰; 应天平; 王刚; 金士锋; 张韩; 林志萍; 陈小龙

    2015-01-01

    Electrochemical method has been used to insert K/Na into FeSe lattice to prepare alkali-intercalated iron selenides at room temperature. Magnetization measurement reveals that KxFe2Se2 and NaxFe2Se2 are superconductive at 31 K and 46 K, respectively. This is the first successful report of obtaining metal-intercalated FeSe-based high-temperature superconductors using electrochemical method. It provides an effective route to synthesize metal-intercalated layered compounds for new superconductor exploration.

  8. 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.

  9. 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.

  10. Photoemission study of iron-based superconductor

    Institute of Scientific and Technical Information of China (English)

    Liu Zhong-Hao; Cai Yi-Peng; Zhao Yan-Ge; Jia Lei-Lei; Wang Shan-Cai

    2013-01-01

    The iron-based superconductivity (IBSC) is a great challenge in correlated system.Angle-resolved photoemission spectroscopy (ARPES) provides electronic structure of the IBSCs,the pairing strength,and the order parameter symmetry.Here,we briefly review the recent progress in IBSCs and focus on the results from ARPES.The ARPES study shows the electronic structure of “122”,“111”,“11”,and “122*” families of IBSCs.It has been agreed that the IBSCs are unconventional superconductors in strong coupling region.The order parameter symmetry basically follows s± form with considerable out-of-plane contribution.

  11. Practical Low-Temperature Superconductors for Electromagnets

    CERN Document Server

    Devred, Arnaud

    2004-01-01

    After a brief history of the main discoveries in applied superconductivity, the structure and properties of NbTi and Nb3Sn are discussed. Then, we explain why low-critical-temperature superconductors are produced under the form of multifilament composites, and we review the manufacturing processes of NbTi and Nb3Sn wires. We follow by a description of the transition from the superconducting to the normal resistive state of multifilament composite wires and we detail their magnetization properties. Last, we present the most commonly used cable configurations and we provide simple formulae illustrating with a few examples the computation of losses generated under time-varying magnetic fields.

  12. 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.

  13. Terahertz Detection with Twin Superconductor-Insulator-Superconductor Tunnel Junctions

    Institute of Scientific and Technical Information of China (English)

    LI Jing; WANG Ming-Jye; SHI Sheng-Cai; Hiroshi Mat-suo

    2007-01-01

    Terahertz detection with twin superconductor-insulator-superconductor (SIS) tunnel junctions, which are connected in parallel via an inductive thin-film superconducting microstrip line, is mainly studied. Firstly, we investigate the direct-detection response of a superconducting twin-junction device by means of a Fourier transform spectrometer. Secondly, we construct a direct-detection model of twin SIS tunnel junctions. The superconducting twin-junction device is then simulated in terms of the constructed model. The simulation result is found to be in good agreement with the measured one. In addition, we observe that the direct-detection response of the device is consistent with the noise temperature behaviour.

  14. Modified Entropic Gravitation in Superconductors

    CERN Document Server

    de Matos, Clovis Jacinto

    2011-01-01

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

  15. Superconductor stability, 1983: a review

    Energy Technology Data Exchange (ETDEWEB)

    Dresner, L.

    1983-01-01

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

  16. Property and microstructural nonuniformity in the yttrium-barium-copper-oxide superconductor determined from electrical, magnetic, and ultrasonic measurements. Ph.D. Thesis - Case Western Reserve Univ.

    Science.gov (United States)

    Roth, Don J.

    1991-01-01

    The purpose of this dissertation was the following: (1) to characterize the effect of pore fraction on a comprehensive set of electrical and magnetic properties for the yttrium-barium-copper-oxide (YBCO) high temperature ceramic superconductor; and (2) to determine the viability of using a room-temperature, nondestructive characterization method to aid in the prediction of superconducting (cryogenic) properties. The latter involved correlating ultrasonic velocity measurements at room temperature with property-affecting pore fraction and oxygen content variations. The use of ultrasonic velocity for estimating pore fraction in YBCO is presented, and other polycrystalline materials are reviewed, modeled, and statistically analyzed. This provides the basis for using ultrasonic velocity to interrogate microstructure. The effect of pore fraction (0.10-0.25) on superconductor properties of YBCO samples was characterized. Spatial (within-sample) variations in microstructure and superconductor properties were investigated, and the effect of oxygen content on elastic behavior was examined. Experimental methods used included a.c. susceptibility, electrical, and ultrasonic velocity measurements. Superconductor properties measured included transition temperature, magnetic transition width, transport and magnetic critical current density, magnetic shielding, a.c. loss, and sharpness of the voltage-current characteristics. An ultrasonic velocity image constructed from measurements at 1mm increments across a YBCO sample revealed microstructural variations that correlated with variations in magnetic shielding and a.c. loss behavior. Destructive examination using quantitative image analysis revealed pore fraction to be the varying microstructural feature.

  17. Topological surface states in nodal superconductors.

    Science.gov (United States)

    Schnyder, Andreas P; Brydon, Philip M R

    2015-06-24

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

  18. Apparatus for fabricating continuous lengths of superconductor

    Science.gov (United States)

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

    2002-01-01

    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.

  19. Holographic superconductor in a deformed four-dimensional STU model

    CERN Document Server

    Pourhassan, B

    2016-01-01

    In this paper, we consider deformed STU model in four dimension including both electric and magnetic charges. Using AdS/CFT we study holographic superconductor and obtain transport properties. We find that presence of magnetic charge is necessary to have maximum electrical conductivity. Also we show that thermal conductivity increases with magnetic charge.

  20. Dissipative flux motion in high-temperature superconductors

    NARCIS (Netherlands)

    Palstra, T.T.M.; Batlogg, B.; Dover, R.B. van; Schneemeyer, L.F.; Waszczak, J.V.

    1990-01-01

    The dissipation below Tc has been studied for representatives of all classes of cuprate hightemperature superconductors, including Ba2YCu3O7–δ, and Bi and Tl compounds. The results are parametrized in the framework of flux creep, with the largest activation energies found in Ba2YCu3O7. It is argued

  1. Holographic Multi-Band Superconductor

    CERN Document Server

    Huang, Ching-Yu; Maity, Debaprasad

    2011-01-01

    We propose a gravity dual for the holographic superconductor with multi-band carriers. Moreover, the currents of these carriers are unified under a global non-Abelian symmetry, which is dual to the bulk non-Abelian gauge symmetry. We study the phase diagram of our model, and find it qualitatively agrees with the one for the realistic 2-band superconductor, such as MgB2. We also evaluate the holographic conductivities and find the expected mean-field like behaviors in some cases. However, for a wide range of the parameter space, we also find the non-mean-field like behavior with negative conductivities.

  2. 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.

  3. Topological Aspects of Triplet Superconductors

    Institute of Scientific and Technical Information of China (English)

    REN Ji-Rong; XU Dong-Hui; ZHANG Xin-Hui; LI Ran

    2007-01-01

    In this paper, using the φ-mapping theory, it is shown that two kinds of topological defects, i.e., the vortex lines and the monopoles exist in the helical configuration of magnetic field in triplet superconductors. And the inner topological structure of these defects is studied. Because the knot solitons in the triplet superconductors are characterized by the Hopf invariant, we also establish a relationship between the Hopf invariant and the linking number of knots family,and reveal the inner topological structure of the Hopf invariant.

  4. Holographic superconductors without translational symmetry

    CERN Document Server

    Zeng, Hua Bi

    2014-01-01

    A holographic superconductor is constructed in the background of a massive gravity theory. In the normal state without condensation, the conductivity exhibits a Drude peak that approaches a delta function in the massless gravity limit as studied by David Vegh. In the superconducting state, besides the infinite DC conductivity, the AC conductivity has Drude behavior at low frequency followed by a power law-fall. These results are in agreement with that found earlier by Horowitz and Santos, who studied a holographic superconductor with an implicit periodic potential beyond the probe limit. The results also agree with measurements on some cuprates.

  5. Exploring intertwined orders in cuprate superconductors

    Science.gov (United States)

    Tranquada, John M.

    2015-03-01

    The concept of intertwined orders has been introduced to describe the cooperative relationship between antiferromagnetic spin correlations and electron (or hole) pair correlations that develop in copper-oxide superconductors. This contrasts with systems in which, for example, charge-density-wave (CDW) order competes for Fermi surface area with superconductivity. La2-xBaxCuO4 with x=0.125 provides an example in which the ordering of spin stripes coincides with the onset of two-dimensional superconducting correlations. The apparent frustration of the interlayer Josephson coupling has motivated the concept of the pair-density-wave superconductor, a state that theoretical calculations show to be energetically competitive with the uniform d-wave superconductor. Even at x=0.095, where there is robust superconductivity below 32 K in zero field, the coexistence of strong, low-energy, incommensurate spin excitations implies a spatially modulated and intertwined pair wave function. Recent observations of CDW order in YBa2Cu3O6+x and other cuprate families have raised interesting questions regarding the general role of charge modulations and the relation to superconductivity. While there are differences in the doping dependence of the modulation wave vectors in YBa2Cu3O6+x and La2-xBaxCuO4, the maximum ordering strength is peaked at the hole concentration of 1/8 in both cases. There are also possible connections with the quantum oscillations that have been detected about the same hole concentration but at high magnetic fields. Resolving these relationships remains a research challenge.

  6. 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.

  7. 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...

  8. 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.

  9. Quaternary borocarbides: Relatively high T{sub c} intermetallic superconductors and magnetic superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Mazumdar, Chandan, E-mail: chandan.mazumdar@saha.ac.in [Saha Institute of Nuclear Physics, Kolkata 700064 (India); Nagarajan, R., E-mail: nagarajan@cbs.ac.in [University of Mumbai-Department of Atomic Energy Centre for Excellence in Basic Sciences, Santacruz (East), Mumbai 400 098 (India)

    2015-07-15

    Discovery of superconductivity in Y–Ni–B–C (T{sub c} ∼ 13 K) gave rise to the class of quaternary rare earth transition metal borocarbide superconductors. Before the discovery of Fe-based arsenide superconductors, this was the only class of materials containing a magnetic element, viz., Ni, yet exhibiting T{sub c}s > 5 K. Many members of this class have high T{sub c} (>10 K). T{sub c} of ∼23 K in Y–Pd–B–C system equaled the record T{sub c} known then, for intermetallics. Another feature that sets this class apart, is the occurrence of the exotic phenomenon of coexistence of superconductivity and magnetism at temperatures >5 K. Availability of large and electronically ‘clean’ single crystals and large Ginzburg-Landau (G–L) parameter, κ, have enabled detailed investigation of nonlocal effects of superconductivity. Intermediate value of upper critical field H{sub c2}, has enabled detailed investigation of superconductivity in this class, over the complete H–T plane. This has revealed details of anisotropy of superconductivity (e.g., a fourfold symmetry in the square a–b plane is found) and raised questions on the symmetry of order parameter. After a brief outline of the discovery, this article gives a summary of the materials and highlights of superconducting properties of this class of materials. Interesting results from studies, using various techniques, on YNi{sub 2}B{sub 2}C (T{sub c} ∼ 15 K) and LuNi{sub 2}B{sub 2}C (T{sub c} ∼ 16 K) are presented, including observation of unusual square vortex lattice and its structural transformation with H and T. With conduction electrons involved in the magnetic order of this class of superconductors, the interplay of superconductivity and magnetism is intimate in these magnetic superconductors. With T{sub c} (∼11 K) > T{sub N} (∼6 K) in ErNi{sub 2}B{sub 2}C, T{sub c} (∼8 K) = T{sub N} (∼8 K) in HoNi{sub 2}B{sub 2}C and T{sub c} (∼6 K) < T{sub N} (∼11 K) in DyNi{sub 2}B{sub 2}C, and

  10. Electronic phase separation and high temperature superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Kivelson, S.A. [Univ. of California, Los Angeles, CA (United States). Dept. of Physics; Emery, V.J. [Brookhaven National Lab., Upton, NY (United States)

    1994-01-11

    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.

  11. Magnetic Excitations from Stripes in Cuprate Superconductors

    Science.gov (United States)

    Tranquada, J. M.; Woo, H.; Perring, T. G.; Goka, H.; Gu, G. D.; Xu, G.; Fujita, M.; Yamada, K.

    2004-03-01

    While it is generally believed that antiferromagnetic spin excitations play a significant role in the pairing mechanism of copper-oxide superconductors [1], the nature of the magnetic excitations themselves remains a matter of controversy. Recent measurements of the dispersion of spin excitations in superconducting YBa_2Cu_3O_6+x (YBCO) have attracted much attention. Here we present the results of comprehensive inelastic neutron scattering measurements of the momentum- and energy-dependent spectra of the magnetic fluctuations in La_0.875Ba_0.125CuO_4, which exhibits inhomogeneous, charge-stripe order. We will also point out universalities and differences in the magnetic excitation spectra compared to related charge-stripe ordered compounds and high-temperature superconductors, including La_2-xSr_xNiO4 and YBCO. JMT, HW, GDG and GX are supported by U.S. Department of Energy contract # DE-AC02-98CH1088 [1] J. Orenstein and A. J. Millis, Science 288, 468 (2000).

  12. Josephson Current in Superconductor-Ferromagnet/Insulator/d-Wave Superconductor Junctions

    Institute of Scientific and Technical Information of China (English)

    LI Xiao-Wei; DONG Zheng-Chao

    2005-01-01

    Solving the Bogoliubov-de Gennes equation, the energy levels of bound states are obtained in the ferromagnetic superconductor. The Josephson currents in a ferromagnetic superconductor/Insulator/d-wave superconductor junction are calculated as a function of the exchange field, temperature, and insulating barrier strength. It is found that the Josephson critical current is always suppressed by the presence of exchange field h and depends on crystalline axis orientation of d-wave superconductor.

  13. Zoning Districts, Zoning for each area provided to us from all cities and Johnson County. The only city in Johnson County not included is Gardner at this time., Published in 2007, Johnson County Government.

    Data.gov (United States)

    NSGIC Local Govt | GIS Inventory — Zoning Districts dataset current as of 2007. Zoning for each area provided to us from all cities and Johnson County. The only city in Johnson County not included is...

  14. Universal lower limit on vortex creep in superconductors

    Science.gov (United States)

    Eley, S.; Miura, M.; Maiorov, B.; Civale, L.

    2017-04-01

    Superconductors are excellent testbeds for studying vortices, topological excitations that also appear in superfluids, liquid crystals and Bose-Einstein condensates. Vortex motion can be disruptive; it can cause phase transitions, glitches in pulsars, and losses in superconducting microwave circuits, and it limits the current-carrying capacity of superconductors. Understanding vortex dynamics is fundamentally and technologically important, and the competition between thermal energy and energy barriers defined by material disorder is not completely understood. Specifically, early measurements of thermally activated vortex motion (creep) in iron-based superconductors unveiled fast rates (S) comparable to measurements of YBa 2Cu3O7-δ (refs ,,,,,). This was puzzling because S is thought to somehow correlate with the Ginzburg number (Gi), and Gi is significantly lower in most iron-based superconductors than in YBa 2Cu3O7-δ. Here, we report very slow creep in BaFe 2(As0.67P0.33)2 films, and propose the existence of a universal minimum realizable S ~ Gi1/2(T/Tc) (Tc is the superconducting transition temperature) that has been achieved in our films and few other materials, and is violated by none. This limitation provides new clues about designing materials with slow creep and the interplay between material parameters and vortex dynamics.

  15. 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.

  16. Comparison of Tunneling in Fe-based Superconductors with Multi-band MgB2

    Science.gov (United States)

    Zasadzinski, John; Iavarone, Maria

    MgB2 is an s-wave, phonon coupled, multiband superconductor that exhibits novel tunneling spectra including a subtle dip feature due to quasiparticle transfer between bands. Since this feature mimics the above-gap spectral dip feature observed in Fe-based superconductors, typically attributed to a strong coupling boson, it is worthwhile to consider whether quasiparticle transfer is relevant. We first show that the dip in MgB2 appears in the π-band, DOS (Δ = 2.4 meV) and is due to quasiparticle transfer to the σ-band with Δ = 7.2 meV. Reviewing the spectral dip in Fe-based superconductors, including new data on FeSe crystals, there are inconsistencies with quasiparticle transfer as the origin. The conclusion is that the spectral dip is more likely due to a boson, the resonance spin excitation, as found in cuprate superconductors.

  17. Current status of iron-based superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Kamihara, Yoichi, E-mail: kamihara_yoichi@appi.keio.ac.jp [Keio University, Department of Applied Physics and Physico-Informatics, Faculty of Science and Technology (Japan)

    2012-03-15

    Current status of iron-based superconductors is summarized. Although short range magnetic ordering and magnetic phase separation of Fe are controversial, (long range) magnetic and electronic phase diagrams of iron based superconductors can be classified into two-type. Antiferromagnetic ordering of itinerant Fe does not coexist with superconducting phase of SmFeAsO{sub 1 - x}F{sub x}. The very large H{sub c2} of iron-based superconductors attract us to attempts at applications.

  18. Current status of iron-based superconductors

    Science.gov (United States)

    Kamihara, Yoichi

    2012-03-01

    Current status of iron-based superconductors is summarized. Although short range magnetic ordering and magnetic phase separation of Fe are controversial, (long range) magnetic and electronic phase diagrams of iron based superconductors can be classified into two-type. Antiferromagnetic ordering of itinerant Fe does not coexist with superconducting phase of SmFeAsO1 - xFx. The very large H c2 of iron-based superconductors attract us to attempts at applications.

  19. A Road Towards High Temperature Superconductors

    Science.gov (United States)

    2013-08-01

    AFRL-AFOSR-UK-TR-2013-0040 A Road Towards High Temperature Superconductors Guy Deutscher Tel Aviv University Research... Superconductors 5a. CONTRACT NUMBER FA8655-10-1-3011 5b. GRANT NUMBER Grant 10-3011 5c. PROGRAM ELEMENT NUMBER 61102F 6. AUTHOR(S...issue in trying to make useful high temperature superconductors is obviously to discover superconductivity at higher temperatures. But there is also

  20. 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

  1. Phase transition via entanglement entropy in $AdS_3/CFT_2$ superconductors

    CERN Document Server

    Momeni, Davood; Myrzakulov, Ratbay

    2016-01-01

    The purpose of this report is to provide a framework for defining phase transition processes in two dimensional holographic superconductors, and to illustrate how they are useful to be described by holographic entanglement entropy. We study holographic entanglement entropy in a two dimensional fully backrected model for holographic superconductors. We prove that phase transition could be observe using a discontinuty in the first order of entropy.

  2. Biomimetic synthesis of high-t{sub c}, type-II superconductor nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Hall, S.R. [Centre for Organized Matter Chemistry, School of Chemistry, University of Bristol, Cantock' s Close, Bristol BS8 1TS (United Kingdom)

    2006-02-17

    Chitosan from crab shells is used to control the synthesis of superconductors. The morphological control over crystallization provided by the chitosan matrix during calcination allows the production of nanowires of the high-T{sub c} superconductor Y124 (YBa{sub 2}Cu{sub 4}O{sub 8}). SQUID magnetometry of these nanowires indicates that the high T{sub c} is successfully retained in this highly anisotropic and technologically important morphology. (Abstract Copyright [2006], Wiley Periodicals, Inc.)

  3. 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

  4. Thermal Analysis for the Recovery and Quenching of Disturbed Composite Superconductors.

    Science.gov (United States)

    Seol, Seoung Yun

    Thermal stability is one of the major issues in the design and operation of superconducting devices. Due to a thermal disturbance, the superconductor may experience a transition from the superconducting state to the normal resistive state, a phenomenon known as quenching. The high electrical resistivity of normal state superconductor contribute to an excessive amount of heat generation which may cause an irrecoverable damage. In a composite superconductor, a stabilizer is provided to alleviate the problem through a current sharing process. For a low disturbance energy, the conductor can reinstate its superconducting state. However for a large disturbance energy, irrecoverable quenching still occurs. The critical energy is referred to a maximum energy required to initiate quenching. The one-dimensional heat balance equation based on the assumption of uniform cross-sectional temperature distribution has been used to calculate the critical energy in previous studies. Cryogenic stability criterion and the Minimum Propagation Zone (MPZ) theory have been typical tools to analyze the stability of composite superconductors. The present study investigates the effect of non -uniform temperature distribution in a cross-section of a composite superconductor. Mathematical models of current sharing and Joule heat generation in the superconductor and the stabilizer are formulated. The transient solution by finite-difference method reveals the scenario of the behavior of the conductor, starting from the deposition of initial disturbance energy, current sharing, quenching, and possible recovery of superconductivity. The analytical solutions of the critical energies in the superconductor and the stabilizer are also obtained for special geometries, such as a tape/film superconductor sandwiched between two stabilizers, and a wire superconductor imbedded in a stabilizer. Based on the analytical calculation of the critical energies, a new stability criterion for the composite

  5. Coherent and correlated spin transport in nanoscale superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Morten, Jan Petter

    2008-03-15

    the system varies from e.g. ballistic conductors or tunnel barriers. In the tunneling case, we calculate the magnetization-dependent full counting statistics, which determines all noise properties including the cross-correlations that can resolve the contributions due to crossed Andreev reflection and direct electron transport. We evaluate the magnetization-dependent two-particle probability that the constituents of spin-entangled pairs from crossed Andreev reflection flow into different ferromagnetic contacts. This probability implies violation of a Bell inequality, and determines the performance of a superconductor-ferromagnet entangler. (author). 105 refs., 13 figs

  6. 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

  7. 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.

  8. Generalized Superconductors and Holographic Optics

    CERN Document Server

    Mahapatra, Subhash; Sarkar, Tapobrata

    2013-01-01

    We study generalized holographic s-wave superconductors in four dimensional R-charged black hole backgrounds, in the probe limit. We first establish the superconducting nature of the boundary theory, and then study its optical properties. Numerical analysis indicates that a negative index of refraction appears at low frequencies in the theory, for certain temperature ranges, for specific values of the charge parameter. The corresponding cut-off values for these are numerically established in several cases.

  9. Holographic superconductors with Weyl corrections

    Science.gov (United States)

    Momeni, Davood; Raza, Muhammad; Myrzakulov, Ratbay

    2016-10-01

    A quick review on the analytical aspects of holographic superconductors (HSCs) with Weyl corrections has been presented. Mainly, we focus on matching method and variational approaches. Different types of such HSC have been investigated — s-wave, p-wave and Stúckelberg ones. We also review the fundamental construction of a p-wave type, in which the non-Abelian gauge field is coupled to the Weyl tensor. The results are compared from numerics to analytical results.

  10. Wetting, prewetting and surface transitions in type-I superconductors

    Science.gov (United States)

    Indekeu, J. O.; van Leeuwen, J. M. J.

    1995-02-01

    Within the Ginzburg-Landau theory, which is quantitatively correct for classical superconductors, it is shown that a type-I superconductor can display an interface delocalization or “wetting” transition, in which a macroscopically thick superconducting layer intrudes from the surface into the bulk normal phase. The condition for this transition to occur is that the superconducting order parameter | ψ| 2 is enhanced at the surface. This corresponds to a negative surface extrapolation length b. The wetting transition takes place at bulk two-phase coexistence of normal and superconducting phases, at a temperature TD below the critical temperature Tc, and at magnetic field HD = Hc( TD). The field is applied parallel to the surface. Surprisingly, the order of the wetting transition is controlled by a bulk material constant, the Ginzburg-Landau parameter κ. This is very unusual, since in other systems (fluids, Ising magnets,…) the order of the wetting transition depends on surface parameters that are difficult to determine or control. For superconductors, first-order wetting is predicted for 0 ≤ κ wetting for 0.374 wetting, the prewetting extension is also found. Unlike in standard wetting problems, the prewetting line does not terminate at a critical point but changes from first to second order at a tricritical point. Twinning-plane superconductivity (TPS) is reinterpreted as a prewetting phenomenon. The possibility of critical wetting in superconductors is especially interesting because this phenomenon has largely eluded experimental verification in any system until now. Furthermore, superconductors provide a realization of wetting in systems with short-range (exponentially decaying) interactions. This is very different from the usual long-range (algebraically decaying) interactions, such as van der Waals forces, and has important consequences for the wetting characteristics.

  11. Edge instabilities of topological superconductors

    Science.gov (United States)

    Hofmann, Johannes S.; Assaad, Fakher F.; Schnyder, Andreas P.

    2016-05-01

    Nodal topological superconductors display zero-energy Majorana flat bands at generic edges. The flatness of these edge bands, which is protected by time-reversal and translation symmetry, gives rise to an extensive ground-state degeneracy. Therefore, even arbitrarily weak interactions lead to an instability of the flat-band edge states towards time-reversal and translation-symmetry-broken phases, which lift the ground-state degeneracy. We examine the instabilities of the flat-band edge states of dx y-wave superconductors by performing a mean-field analysis in the Majorana basis of the edge states. The leading instabilities are Majorana mass terms, which correspond to coherent superpositions of particle-particle and particle-hole channels in the fermionic language. We find that attractive interactions induce three different mass terms. One is a coherent superposition of imaginary s -wave pairing and current order, and another combines a charge-density-wave and finite-momentum singlet pairing. Repulsive interactions, on the other hand, lead to ferromagnetism together with spin-triplet pairing at the edge. Our quantum Monte Carlo simulations confirm these findings and demonstrate that these instabilities occur even in the presence of strong quantum fluctuations. We discuss the implications of our results for experiments on cuprate high-temperature superconductors.

  12. Is a color superconductor topological?

    CERN Document Server

    Nishida, Yusuke

    2010-01-01

    A fully gapped state of matter, whether insulator or superconductor, can be asked if it is topologically trivial or nontrivial. Here we investigate topological properties of superconducting Dirac fermions in 3D having a color superconductor as an application. In the chiral limit, when the pairing gap is parity even, the right-handed and left-handed sectors of the free space Hamiltonian have nontrivial topological charges with opposite signs. Accordingly, a vortex line in the superconductor supports localized gapless right-handed and left-handed fermions with the dispersion relations E=+/-vp_z (v is a parameter dependent velocity) and thus propagating in opposite directions along the vortex line. However, the presence of the fermion mass immediately opens up a mass gap for such localized fermions and the dispersion relations become E=+/-v(m^2+p_z^2)^(1/2). When the pairing gap is parity odd, the situation is qualitatively different. The right-handed and left-handed sectors of the free space Hamiltonian in the ...

  13. Modified entropic gravitation in superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Matos, Clovis Jacinto de, E-mail: clovis.de.matos@esa.int [European Space Agency, 8-10 rue Mario Nikis, 75015 Paris (France)

    2012-01-15

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

  14. Fault current limiters using superconductors

    Science.gov (United States)

    Norris, W. T.; Power, A.

    Fault current limiters on power systems are to reduce damage by heating and electromechanical forces, to alleviate duty on switchgear used to clear the fault, and to mitigate disturbance to unfaulted parts of the system. A basic scheme involves a super-resistor which is a superconductor being driven to high resistance when fault current flows either when current is high during a cycle of a.c. or, if the temperature of the superconductive material rises, for the full cycle. Current may be commuted from superconductor to an impedance in parallel, thus reducing the energy dispersed at low temperature and saving refrigeration. In a super-shorted transformer the ambient temperature primary carries the power system current; the superconductive secondary goes to a resistive condition when excessive currents flow in the primary. A super-transformer has the advantage of not needing current leads from high temperature to low temperature; it behaves as a parallel super-resistor and inductor. The supertransductor with a superconductive d.c. bias winding is large and has small effect on the rate of fall of current at current zero; it does little to alleviate duty on switchgear but does reduce heating and electromechanical forces. It is fully active after a fault has been cleared. Other schemes depend on rapid recooling of the superconductor to achieve this.

  15. Giant Mesoscopic Fluctuations and Long-Range Superconducting Correlations in Superconductor-Ferromagnet Structures.

    Science.gov (United States)

    Mel'nikov, A S; Buzdin, A I

    2016-08-12

    The fluctuating superconducting correlations emerging in dirty hybrid structures under the conditions of the strong proximity effect are demonstrated to affect the validity range of the widely used formalism of Usadel equations at mesoscopic scales. In superconductor-ferromagnet structures these giant mesoscopic fluctuations originating from the interference effects for the Cooper pair wave function in the presence of the exchange field can be responsible for an anomalously slow decay of superconducting correlations in a ferromagnet even when the noncollinear and spin-orbit effects are negligible. The resulting sample-to-sample fluctuations of the Josephson current in superconductor-ferromagnetic-superconductor junctions and the local density of states in superconductor-ferromagnetic hybrid structures can provide an explanation of the long-range proximity phenomena observed in mesoscopic samples with collinear magnetization.

  16. Lifshitz Scaling Effects on Holographic Superconductors

    CERN Document Server

    Lu, Jun-Wang; Qian, Peng; Zhao, Yue-Yue; Zhang, Xue

    2014-01-01

    Via numerical and analytical methods, the effects of the Lifshitz dynamical exponent $z$ on holographic superconductors are studied in some detail, including $s$ wave and $p$ wave models. Working in the probe limit, we find that the behaviors of holographic models indeed depend on concrete value of $z$. We obtain the condensation and conductivity in both Lifshitz black hole and soliton backgrounds with general $z$. For both $s$ wave and $p$ wave models in the black hole backgrounds, as $z$ increases, the phase transition becomes more difficult and the growth of conductivity is suppressed. For the Lifshitz soliton backgrounds, when $z$ increases ($z=1,~2,~3$), the critical chemical potential decreases in the $s$ wave cases but increases in the $p$ wave cases. For $p$ wave models in both Lifshitz black hole and soliton backgrounds, the anisotropy between the AC conductivity in different spatial directions is suppressed when $z$ increases. The analytical results uphold the numerical results.

  17. Quench properties of high current superconductors

    Energy Technology Data Exchange (ETDEWEB)

    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/sub 3/Sn braids which have critical currents in excess of 10 kA at 5 T, 4.2 K.

  18. A novel heat engine for magnetizing superconductors

    Science.gov (United States)

    Coombs, T. A.; Hong, Z.; Zhu, X.; Krabbes, G.

    2008-03-01

    The potential of bulk melt-processed YBCO single domains to trap significant magnetic fields (Tomita and Murakami 2003 Nature 421 517-20 Fuchs et al 2000 Appl. Phys. Lett. 76 2107-9) at cryogenic temperatures makes them particularly attractive for a variety of engineering applications including superconducting magnets, magnetic bearings and motors (Coombs et al 1999 IEEE Trans. Appl. Supercond. 9 968-71 Coombs et al 2005 IEEE Trans. Appl. Supercond. 15 2312-5). It has already been shown that large fields can be obtained in single domain samples at 77 K. A range of possible applications exist in the design of high power density electric motors (Jiang et al 2006 Supercond. Sci. Technol. 19 1164-8). Before such devices can be created a major problem needs to be overcome. Even though all of these devices use a superconductor in the role of a permanent magnet and even though the superconductor can trap potentially huge magnetic fields (greater than 10 T) the problem is how to induce the magnetic fields. There are four possible known methods: (1) cooling in field; (2) zero field cooling, followed by slowly applied field; (3) pulse magnetization; (4) flux pumping. Any of these methods could be used to magnetize the superconductor and this may be done either in situ or ex situ. Ideally the superconductors are magnetized in situ. There are several reasons for this: first, if the superconductors should become demagnetized through (i) flux creep, (ii) repeatedly applied perpendicular fields (Vanderbemden et al 2007 Phys. Rev. B 75 (17)) or (iii) by loss of cooling then they may be re-magnetized without the need to disassemble the machine; secondly, there are difficulties with handling very strongly magnetized material at cryogenic temperatures when assembling the machine; thirdly, ex situ methods would require the machine to be assembled both cold and pre-magnetized and would offer significant design difficulties. Until room temperature superconductors can be prepared, the

  19. A novel heat engine for magnetizing superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Coombs, T A; Hong, Z; Zhu, X [Cambridge University Engineering Department, Trumpington Street, CB2 1PZ (United Kingdom); Krabbes, G [IFW Dresden, Helmholtzstrasse 20, 01069 Dresden (Germany)

    2008-03-01

    The potential of bulk melt-processed YBCO single domains to trap significant magnetic fields (Tomita and Murakami 2003 Nature 421 517-20; Fuchs et al 2000 Appl. Phys. Lett. 76 2107-9) at cryogenic temperatures makes them particularly attractive for a variety of engineering applications including superconducting magnets, magnetic bearings and motors (Coombs et al 1999 IEEE Trans. Appl. Supercond. 9 968-71; Coombs et al 2005 IEEE Trans. Appl. Supercond. 15 2312-5). It has already been shown that large fields can be obtained in single domain samples at 77 K. A range of possible applications exist in the design of high power density electric motors (Jiang et al 2006 Supercond. Sci. Technol. 19 1164-8). Before such devices can be created a major problem needs to be overcome. Even though all of these devices use a superconductor in the role of a permanent magnet and even though the superconductor can trap potentially huge magnetic fields (greater than 10 T) the problem is how to induce the magnetic fields. There are four possible known methods: (1) cooling in field; (2) zero field cooling, followed by slowly applied field; (3) pulse magnetization; (4) flux pumping. Any of these methods could be used to magnetize the superconductor and this may be done either in situ or ex situ. Ideally the superconductors are magnetized in situ. There are several reasons for this: first, if the superconductors should become demagnetized through (i) flux creep, (ii) repeatedly applied perpendicular fields (Vanderbemden et al 2007 Phys. Rev. B 75 (17)) or (iii) by loss of cooling then they may be re-magnetized without the need to disassemble the machine; secondly, there are difficulties with handling very strongly magnetized material at cryogenic temperatures when assembling the machine; thirdly, ex situ methods would require the machine to be assembled both cold and pre-magnetized and would offer significant design difficulties. Until room temperature superconductors can be prepared, the

  20. Enhancement of mechanical properties of 123 superconductors

    Science.gov (United States)

    Balachandran, Uthamalingam

    1995-01-01

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

  1. Electromagnetic Dark Energy and Gravitoelectrodynamics of Superconductors

    CERN Document Server

    de Matos, Clovis Jacinto

    2007-01-01

    It is shown that Beck's electromagnetic model of dark energy in superconductors can account for the gravitomagnetic London moment, which has been conjectured by the author to explain the Cooper pair's mass excess reported by Cabrera and Tate. A new Einstein-Planck regime for gravitation in condensed matter is proposed as a natural scale to host the gravitoelectrodynamic properties of superconductors.

  2. Gravitational force between two electrons in superconductors

    CERN Document Server

    de Matos, Clovis Jacinto

    2007-01-01

    The attractive gravitational force between two electrons in superconductors is deduced from the Eddington-Dirac large number relation, together with Beck and Mackey electromagnetic model of vacuum energy in superconductors. This force is estimated to be weaker than the gravitational attraction between two electrons in the vacuum.

  3. 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.

  4. Iron-based superconductors via soft chemistry

    Energy Technology Data Exchange (ETDEWEB)

    Friederichs, Gina Maya

    2015-06-30

    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{sub 3}O{sub 4}) could be proven by low temperature O{sub 2}-annealing of Fe{sub 1+x}Te{sub 1-y}Se{sub y}. By using redox (de)intercalations K{sub 1-x}Fe{sub 2-y}Se{sub 2}, metastable Na{sub 1-x}Fe{sub 2-y}As{sub 2} and Na{sub 1-x}((Fe{sub 1-y}Co{sub y}){sub 1-z}As){sub 2} could successfully be obtained at room temperature. The mild synthesis conditions led to compounds like FeSe and K{sub 1-x}Fe{sub 2-y}Se{sub 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{sub 4/4} tetrahedral layers, however, are preserved. Soft chemistry syntheses have been shown to allow the formation of a variety of phases, like Na{sub 1-x}Fe{sub 2-y}As{sub 2}, Na{sub 1-x}((Fe{sub 1-y}Co{sub y}){sub 1-z}As){sub 2} and K{sub 1-x}Fe{sub 2-y}Se{sub 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.

  5. Signatures of time reversal symmetry breaking in multiband superconductors

    Science.gov (United States)

    Maiti, Saurabh

    Multiband superconductors serve as natural host to several possible gound states that compete with each other. At the boundaries of such competing phases, the system usually compromises and settles for `mixed' phases that can show intriguing properties like co-existence of magnetism and superconductiivty or even co-existence of different superconducting phases. The latter is particularly interesting as it can lead to non-magnetic ground states that spontaneously break Time-Reversal symmetry. While the experimental verification of such states has proved to been challenging, the theoretical investigations have provided exciting new insights into the nature of the ground state and its excitations all of which have experimental consequences of some sort. These include extrinsic properties like spontaneous currents around impurity sites, and intrinsic properties in the form of collective excitations. These collective modes bear a unique signature and should provide clear evidence for time reversal symmetry broken state. While the results are general, in light of recent Raman scattering experiments, its direct relevance to extremely hole doped Ba(1-x)K(FeAs)2 will be presented where a strong competition of s-wave and d-wave ground state is expected.

  6. Process for producing fine and ultrafine filament superconductor wire

    Energy Technology Data Exchange (ETDEWEB)

    Kanithi, Hem C. (15 Briar Ct., Chesire, CT 06410)

    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.

  7. Melting of the Abrikosov flux lattice in anisotropic superconductors

    Science.gov (United States)

    Beck, R. G.; Farrell, D. E.; Rice, J. P.; Ginsberg, D. M.; Kogan, V. G.

    1992-01-01

    It has been proposed that the Abrikosov flux lattice in high-Tc superconductors is melted over a significant fraction of the phase diagram. A thermodynamic argument is provided which establishes that the angular dependence of the melting temperature is controlled by the superconducting mass anisotropy. Using a low-frequency torsional-oscillator technique, this relationship has been tested in untwinned single-crystal YBa2Cu3O(7-delta). The results offer decisive support for the melting proposal.

  8. 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.

  9. 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.

  10. Noncentrosymmetric superconductors in one dimension

    Science.gov (United States)

    Samokhin, K. V.

    2017-02-01

    We study the fermionic boundary modes (Andreev bound states) in a time-reversal invariant one-dimensional superconductor. In the presence of a substrate, spatial inversion symmetry is broken and the electronic properties are strongly affected by an antisymmetric spin-orbit coupling. We assume an arbitrary even number of nondegenerate bands crossing the Fermi level. We show that there is only one possible pairing symmetry in one dimension, an analog of s -wave pairing. The zero-energy Andreev bound states are present if the sign of the gap function in an odd number of the bands is different from all other bands.

  11. Passivation of high temperature superconductors

    Science.gov (United States)

    Vasquez, Richard P. (Inventor)

    1991-01-01

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

  12. Microgravity Processing of Oxide Superconductors

    Science.gov (United States)

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

    2000-01-01

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

  13. Holographic superconductors with hyperscaling violation

    CERN Document Server

    Fan, ZhongYing

    2013-01-01

    We investigate holographic superconductors in asympototically geometries with hyperscaling violation. The mass of the scalar field decouples from the UV dimension of the dual scalar operator and can be chosen as negative as we want, without disturbing the Breitenlohner-Freedman bound. We first numerically find that the scalar condenses below a critical temperature and a gap opens in the real part of the conductivity, indicating the onset of superconductivity. We further analytically explore the effects of the hyperscaling violation on the superconducting transition temperature. We find that the critical temperature increases with the increasing of hyperscaling violation.

  14. 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.

  15. Generalized superconductors and holographic optics

    Energy Technology Data Exchange (ETDEWEB)

    Mahapatra, Subhash; Phukon, Prabwal; Sarkar, Tapobrata [Department of Physics, Indian Institute of Technology,Kanpur 208016 (India)

    2014-01-24

    We study generalized holographic s-wave superconductors in four dimensional R-charged black hole and Lifshitz black hole backgrounds, in the probe limit. We first establish the superconducting nature of the boundary theories, and then study their optical properties. Numerical analysis indicates that a negative Depine-Lakhtakia index may appear at low frequencies in the theory dual to the R-charged black hole, for certain temperature ranges, for specific values of the charge parameter. The corresponding cut-off values for these are numerically established in several cases. Such effects are seen to be absent in the Lifshitz background where this index is always positive.

  16. Reverse process of usual optical analysis of boson-exchange superconductors: impurity effects on s- and d-wave superconductors.

    Science.gov (United States)

    Hwang, Jungseek

    2015-03-04

    We performed a reverse process of the usual optical data analysis of boson-exchange superconductors. We calculated the optical self-energy from two (MMP and MMP+peak) input model electron-boson spectral density functions using Allen's formula for one normal and two (s- and d-wave) superconducting cases. We obtained the optical constants including the optical conductivity and the dynamic dielectric function from the optical self-energy using an extended Drude model, and finally calculated the reflectance spectrum. Furthermore, to investigate impurity effects on optical quantities we added various levels of impurities (from the clean to the dirty limit) in the optical self-energy and performed the same reverse process to obtain the optical conductivity, the dielectric function, and reflectance. From these optical constants obtained from the reverse process we extracted the impurity-dependent superfluid densities for two superconducting cases using two independent methods (the Ferrel-Glover-Tinkham sum rule and the extrapolation to zero frequency of -ϵ1(ω)ω(2)); we found that a certain level of impurities is necessary to get a good agreement on results obtained by the two methods. We observed that impurities give similar effects on various optical constants of s- and d-wave superconductors; the greater the impurities the more distinct the gap feature and the lower the superfluid density. However, the s-wave superconductor gives the superconducting gap feature more clearly than the d-wave superconductor because in the d-wave superconductors the optical quantities are averaged over the anisotropic Fermi surface. Our results supply helpful information to see how characteristic features of the electron-boson spectral function and the s- and d-wave superconducting gaps appear in various optical constants including raw reflectance spectrum. Our study may help with a thorough understanding of the usual optical analysis process. Further systematic study of experimental

  17. Superconductive articles including cerium oxide layer

    Science.gov (United States)

    Wu, Xin D.; Muenchausen, Ross E.

    1993-01-01

    A ceramic superconductor comprising a metal oxide substrate, a ceramic high temperature superconductive material, and a intermediate layer of a material having a cubic crystal structure, said layer situated between the substrate and the superconductive material is provided, and a structure for supporting a ceramic superconducting material is provided, said structure comprising a metal oxide substrate, and a layer situated over the surface of the substrate to substantially inhibit interdiffusion between the substrate and a ceramic superconducting material deposited upon said structure.

  18. Disc Motor: Conventional and Superconductor Simulated Results Analysis

    Science.gov (United States)

    Inácio, David; Martins, João; Neves, Mário Ventim; Álvarez, Alfredo; Rodrigues, Amadeu Leão

    Taking into consideration the development and integration of electrical machines with lower dimensions and higher performance, this paper presents the design and development of a three-phase axial flux disc motor, with 50 Hz frequency supply. It is made with two conventional semi-stators and a rotor, which can be implemented with a conventional aluminum disc or a high temperature-superconducting disc. The analysis of the motor characteristics is done with a 2D commercial finite elements package, being the modeling performed as a linear motor. The obtained results allow concluding that the superconductor motor provides a higher force than the conventional one. The conventional disc motor presents an asynchronous behavior, like a conventional induction motor, while the superconductor motor presents both synchronous and asynchronous behaviors.

  19. Electrochemical synthesis of alkali-intercalated iron selenide superconductors

    Science.gov (United States)

    Shen, Shi-Jie; Ying, Tian-Ping; Wang, Gang; Jin, Shi-Feng; Zhang, Han; Lin, Zhi-Ping; Chen, Xiao-Long

    2015-11-01

    Electrochemical method has been used to insert K/Na into FeSe lattice to prepare alkali-intercalated iron selenides at room temperature. Magnetization measurement reveals that KxFe2Se2 and NaxFe2Se2 are superconductive at 31 K and 46 K, respectively. This is the first successful report of obtaining metal-intercalated FeSe-based high-temperature superconductors using electrochemical method. It provides an effective route to synthesize metal-intercalated layered compounds for new superconductor exploration. Project supported by the National Natural Science Foundation of China (Grant Nos. 51322211and 91422303), the Strategic Priority Research Program (B) of the Chinese Academy of Sciences (Grant No. XDB07020100), Beijing Nova Program of China (Grant No. 2011096), and K. C. Wong Education Foundation, Hong Kong, China.

  20. Campbell penetration depth in Fe-based superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Prommapan, Plegchart [Iowa State Univ., Ames, IA (United States)

    2011-01-01

    A 'true' critical current density, jc, as opposite to commonly measured relaxed persistent (Bean) current, jB, was extracted from the Campbell penetration depth, Λc(T,H) measured in single crystals of LiFeAs, and optimally electron-doped Ba(Fe0.954Ni0.046)2As2 (FeNi122). In LiFeAs, the effective pinning potential is nonparabolic, which follows from the magnetic field - dependent Labusch parameter α. At the equilibrium (upon field - cooling), α(H) is non-monotonic, but it is monotonic at a finite gradient of the vortex density. This behavior leads to a faster magnetic relaxation at the lower fields and provides a natural dynamic explanation for the fishtail (second peak) effect. We also find the evidence for strong pinning at the lower fields.The inferred field dependence of the pinning potential is consistent with the evolution from strong pinning, through collective pinning, and eventually to a disordered vortex lattice. The value of jc(2 K) ≅ 1.22 x 106 A/cm2 provide an upper estimate of the current carrying capability of LiFeAs. Overall, vortex behavior of almost isotropic, fully-gapped LiFeAs is very similar to highly anisotropic d-wave cuprate superconductors, the similarity that requires further studies in order to understand unconventional superconductivity in cuprates and pnictides. In addition to LiFeAs, we also report the magnetic penetration depth in BaFe2As2 based superconductors including irradiation of FeNi122. In unirradiated FeNi122, the maximum critical current value is, jc(2K) ≅ 3.3 x 106 A/cm2. The magnetic-dependent feature was observed near the transition temperature in FeTe0.53Se0.47 and irradiated FeNi122. Because of this feature, further studies are required in order to properly calibrate the Campbell penetration depth. Finally, we detected the

  1. Holographic Superfluids and Superconductors in Dilaton-Gravity

    CERN Document Server

    Salvio, Alberto

    2012-01-01

    We investigate holographic models of superfluids and superconductors in which the gravitational theory includes a dilatonic field. Dilaton extensions are interesting as they allow us to obtain a better description of low temperature condensed matter systems. We focus on asymptotically AdS black hole configurations, which are dual to field theories with conformal ultraviolet behavior. A nonvanishing value of the dilaton breaks scale invariance in the infrared and is therefore compatible with the normal phase being insulating (or a solid in the fluid mechanical interpretation); indeed we find that this is the case at low temperatures and if one appropriately chooses the parameters of the model. Not only the superfluid phase transitions, but also the response to external gauge fields is analyzed. This allows us to study, among other things, the vortex phase and to show that these holographic superconductors are also of Type II. However, at low temperatures they can behave in a qualitatively different way compare...

  2. Complete Phase Diagrams for a Holographic Superconductor/Insulator System

    CERN Document Server

    Horowitz, Gary T

    2010-01-01

    The gravitational dual of an insulator/superconductor transition driven by increasing the chemical potential has recently been constructed. However, the system was studied in a probe limit and only a part of the phase diagram was obtained. We include the backreaction and construct the complete phase diagram for this system. For fixed chemical potential there are typically two phase transitions as the temperature is lowered. Surprisingly, for a certain range of parameters, the system first becomes a superconductor and then becomes an insulator as the temperature approaches zero. As a byproduct of our analysis, we also construct the gravitational dual of a Bose-Einstein condensate of glueballs in a confining gauge theory.

  3. 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.

  4. Ultrafast spectroscopy of quasiparticle dynamics in cuprate superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Li, Wei [National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, Nanjing 210093 (China); Zhang, Chunfeng, E-mail: cfzhang@nju.edu.cn [National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, Nanjing 210093 (China); Wang, Xiaoyong [National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, Nanjing 210093 (China); Chakhalian, Jak, E-mail: jchakhal@uark.edu [Department of Physics, University of Arkansas, Fayetteville, AR 72701 (United States); Xiao, Min, E-mail: mxiao@uark.edu [National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, Nanjing 210093 (China); Department of Physics, University of Arkansas, Fayetteville, AR 72701 (United States)

    2015-02-15

    Ultrafast pump-probe spectroscopy is a powerful tool to study the nonequilibrium dynamics in high-Tc cuprate superconductors. The photo-induced quasiparticle (QP) dynamics revealed by pump-probe spectroscopy are sensitive to the near-Fermi level electronic structures. Here we review several selected examples to illustrate the enduring challenges including pairing glue, phase separation, and phase transitions in cuprate superconductors. We also present the data obtained on thin films of YBa{sub 2}Cu{sub 3}O{sub 7−δ} in connection to these issues. - Highlights: • This paper reviews recent ultrafast spectroscopic study on cuprates. • Dynamics related to pairing glues and phase separations are summarized. • Mid-IR pulses enhance the coherent transport in underdoped cuprates. • Pump-probe data on the quasiparticle dynamics in YBCO films are presented.

  5. Elliptical hole in a bulk superconductor under electromagnetic forces

    Energy Technology Data Exchange (ETDEWEB)

    Yong Huadong; Zhou Youhe [Key Laboratory of Mechanics on Western Disaster and Environment, Ministry of Education, Lanzhou 730000 (China); Department of Mechanics, Lanzhou University, Lanzhou 730000 (China)

    2009-02-15

    A simple model is presented for the distribution of flux-pinning-induced stress in a superconductor around an elliptical hole and the singular stress field near crack tips. The magnetic behavior is described by the critical state, the original Bean model. It is assumed that the perturbation brought upon by the elliptical hole on the critical current density is not significant. Explicit expressions for the stress field in the vicinity of an elliptical hole are derived based on the complex variable method. Furthermore, the stress intensity factor at the tip of a slender crack is determined. An exact solution is found during the decreasing field and field-cooling process. Dependence of the stress field on the parameters including the applied field, shape of the elliptical hole or superconductor slab is investigated. The results show that the applied field and geometry parameter have obvious effects on the distribution of the stress.

  6. Elliptical hole in a bulk superconductor under electromagnetic forces

    Science.gov (United States)

    Yong, Hua-Dong; Zhou, You-He

    2009-02-01

    A simple model is presented for the distribution of flux-pinning-induced stress in a superconductor around an elliptical hole and the singular stress field near crack tips. The magnetic behavior is described by the critical state, the original Bean model. It is assumed that the perturbation brought upon by the elliptical hole on the critical current density is not significant. Explicit expressions for the stress field in the vicinity of an elliptical hole are derived based on the complex variable method. Furthermore, the stress intensity factor at the tip of a slender crack is determined. An exact solution is found during the decreasing field and field-cooling process. Dependence of the stress field on the parameters including the applied field, shape of the elliptical hole or superconductor slab is investigated. The results show that the applied field and geometry parameter have obvious effects on the distribution of the stress.

  7. Symmetry-Enforced Line Nodes in Unconventional Superconductors

    Science.gov (United States)

    Micklitz, T.; Norman, M. R.

    2017-05-01

    We classify line nodes in superconductors with strong spin-orbit interactions and time-reversal symmetry, where the latter may include nonprimitive translations in the magnetic Brillouin zone to account for coexistence with antiferromagnetic order. We find four possible combinations of irreducible representations of the order parameter on high-symmetry planes, two of which allow for line nodes in pseudospin-triplet pairs and two that exclude conventional fully gapped pseudospin-singlet pairs. We show that the former can only be realized in the presence of band-sticking degeneracies, and we verify their topological stability using arguments based on Clifford algebra extensions. Our classification exhausts all possible symmetry protected line nodes in the presence of spin-orbit coupling and a (generalized) time-reversal symmetry. Implications for existing nonsymmorphic and antiferromagnetic superconductors are discussed.

  8. Emerging Diluted Ferromagnetism in High-Tc Superconductors Driven by Point Defect Clusters.

    Science.gov (United States)

    Gazquez, Jaume; Guzman, Roger; Mishra, Rohan; Bartolomé, Elena; Salafranca, Juan; Magén, Cesar; Varela, Maria; Coll, Mariona; Palau, Anna; Valvidares, S Manuel; Gargiani, Pierluigi; Pellegrin, Eric; Herrero-Martin, Javier; Pennycook, Stephen J; Pantelides, Sokrates T; Puig, Teresa; Obradors, Xavier

    2016-06-01

    Defects in ceramic materials are generally seen as detrimental to their functionality and applicability. Yet, in some complex oxides, defects present an opportunity to enhance some of their properties or even lead to the discovery of exciting physics, particularly in the presence of strong correlations. A paradigmatic case is the high-temperature superconductor YBa2Cu3O7-δ (Y123), in which nanoscale defects play an important role as they can immobilize quantized magnetic flux vortices. Here previously unforeseen point defects buried in Y123 thin films that lead to the formation of ferromagnetic clusters embedded within the superconductor are unveiled. Aberration-corrected scanning transmission microscopy has been used for exploring, on a single unit-cell level, the structure and chemistry resulting from these complex point defects, along with density functional theory calculations, for providing new insights about their nature including an unexpected defect-driven ferromagnetism, and X-ray magnetic circular dichroism for bearing evidence of Cu magnetic moments that align ferromagnetically even below the superconducting critical temperature to form a dilute system of magnetic clusters associated with the point defects.

  9. Emerging Diluted Ferromagnetism in High‐T c Superconductors Driven by Point Defect Clusters

    Science.gov (United States)

    Guzman, Roger.; Mishra, Rohan; Bartolomé, Elena; Salafranca, Juan; Magén, Cesar; Varela, Maria; Coll, Mariona; Palau, Anna; Valvidares, S. Manuel; Gargiani, Pierluigi; Pellegrin, Eric; Herrero‐Martin, Javier.; Pennycook, Stephen J.; Pantelides, Sokrates T.; Puig, Teresa; Obradors, Xavier

    2016-01-01

    Defects in ceramic materials are generally seen as detrimental to their functionality and applicability. Yet, in some complex oxides, defects present an opportunity to enhance some of their properties or even lead to the discovery of exciting physics, particularly in the presence of strong correlations. A paradigmatic case is the high‐temperature superconductor YBa2Cu3O7‐δ (Y123), in which nanoscale defects play an important role as they can immobilize quantized magnetic flux vortices. Here previously unforeseen point defects buried in Y123 thin films that lead to the formation of ferromagnetic clusters embedded within the superconductor are unveiled. Aberration‐corrected scanning transmission microscopy has been used for exploring, on a single unit‐cell level, the structure and chemistry resulting from these complex point defects, along with density functional theory calculations, for providing new insights about their nature including an unexpected defect‐driven ferromagnetism, and X‐ray magnetic circular dichroism for bearing evidence of Cu magnetic moments that align ferromagnetically even below the superconducting critical temperature to form a dilute system of magnetic clusters associated with the point defects. PMID:27812469

  10. Characterisation of practical high temperature superconductors in pulsed magnetic fields and development of associated technology

    CERN Document Server

    Saleh, P M

    2000-01-01

    including a innovative design of a 100ms pulsed magnet solenoid. Critical current measurements on state of the art practical high temperature superconductors are presented. Bi sub 2 Sr sub 2 CaCu sub 2 O silver-alloy matrix powder-in-tube and silver-alloy substrate dip-coated tapes, formed into various geometries, have been tested in pulsed magnetic fields of various pulse lengths. These measurements have been compared to tests performed in continuous magnetic fields. A distinct discrepancy between pulsed and continuous measurements has been observed in these silver-alloy, high temperature superconductor composites. The critical current measured in pulsed fields is depressed compared to those measured in continuous fields. Evidence is provided to strongly suggest that eddy current heating in the silver-alloy substrate/sheath of the conductor is responsible for this discrepancy. A model is presented to predict the temperature rise due to eddy current heating. This model shows good agreement with observations. ...

  11. Nanoengineering of Flux Pinning Sites in High-Tc Superconductors

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    Volume pinning forces were determined for a variety of bulk high-Tcsuperconductors of the 123-type from magnetization measurements. By means of scaling of the pinning forces, the acting pinning mechanisms in various temperature ranges were identified. The Nd-based superconductors and some YBCO crystalsexhibited a dominating pinning of the δTc-type (i.e., small, superconducting pinning sites). In contrast to this, the addition of insulating 211 particles provided pinning of the δl-type; providing effective pinning in the entire temperature range acting as a "background" pinning mechanism for the peak effect. Due to the small coherence lengths of the high-Tc compounds, effective pinning sites are defects or particles of nanometer size relative to ξ3. Integral magnetic measurements of the magnetization as a function of temperature in large applied magnetic fields (up to 7 T) revealed that practically all high-Tc compounds were spatially inhomogeneous, which could be caused byoxygen deficiency (YBCO), solid solutions of Nd/Ba (NdBCO and other light rare earth compounds), intergrowths (Bi-based superconductors), and doping by pair-breaking dopants like Zn, Pr. This implies that the superconducting sample consists of stronger and weaker superconducting areas, coupled together. In large appliedfields, this coupling gets broken and the magnetization versus temperature curves revealed more than one superconducting transition. In contrast, irradiation experiments by neutrons, protons, and heavy-ions enabled the artificial introduction of very effective pinning sites into the high-Tc superconductors, thus creating a large variety of different observations using magnetic data. From all these observations, we construct a pinning diagram for bulk high-Tc superconductors explaining many features observed in high-Tc samples.

  12. Losses of Superconductor Journal Bearing

    Science.gov (United States)

    Han, Y. H.; Hull, J. R.; Han, S. C.; Jeong, N. H.; Oh, J. M.; Sung, T. H.

    2004-06-01

    A high-temperature superconductor (HTS) journal bearing was studied for rotational loss. Two HTS bearings support the rotor at top and bottom. The rotor weight is 4 kg and the length is about 300 mm. Both the top and bottom bearings have two permanent magnet (PM) rings with an iron pole piece separating them. Each HTS journal bearing is composed of six pieces of superconductor blocks of size 35×25×10 mm. The HTS blocks are encased in a cryochamber through which liquid nitrogen flows. The inner spool of the cryochamber is made from G-10 to reduce eddy current loss, and the rest of the cryochamber is stainless steel. The magnetic field from the PM rings is < 10 mT on the stainless part. The rotational drag was measured over the same speed range at several chamber pressures. Results indicate that a chamber pressure of 0.4 mtorr is sufficiently low to minimize windage loss, and the 10 mT design criterion for the magnetic field on the stainless part of the cryochamber is too high.

  13. 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.

  14. 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.

  15. Position-sensitive superconductor detectors

    Science.gov (United States)

    Kurakado, M.; Taniguchi, K.

    2016-12-01

    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.

  16. Photoemission and magnetic response in the bipolaronic superconductor

    CERN Document Server

    Dent, C

    2001-01-01

    in the cuprates is extended to explain the crossing point in the curves of induced magnetization divided by the square root of field against temperature in the less anisotropic cuprates. This model has already been shown to provide a parameter-free expression for T sub c in a wide range of cuprates. We compare our results with experiment in YBa sub 2 Cu sub 3 O sub 7 sub - subdelta. A theory of angle-resolved photoemission (ARPES) in doped charge-transfer Mott insulators is developed taking into account the realistic band structure, (bi)polaron formation due to the strong electron-phonon interaction, and a random field potential. We derive the coherent part of the ARPES spectra with the oxygen hole spectral function calculated in the non-crossing (ladder) approximation and with the exact spectral function of a one-dimensional hole in a random potential. On the basis of this theory, explanations are proposed for several features of the ARPES spectra taken from the cuprate superconductors. These include the pol...

  17. Synthesis of highly phase pure BSCCO superconductors

    Science.gov (United States)

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

    1995-11-21

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

  18. Tuning non-equilibrium superconductors with lasers

    Energy Technology Data Exchange (ETDEWEB)

    Sentef, Michael A.; Kollath, Corinna [HISKP, University of Bonn, Nussallee 14-16, D-53115 Bonn (Germany); Kemper, Alexander F. [LBL Berkeley (United States); Georges, Antoine [Ecole Polytechnique and College de France, Paris (France)

    2015-07-01

    The study of the real-time dynamics dynamics of solids perturbed by short laser pulses is an intriguing opportunity of ultrafast materials science. Previous theoretical work on pump-probe photoemission spectroscopy revealed spectroscopic signatures of electron-boson coupling, which are reminiscent of features observed in recent pump-probe photoemission experiments on cuprate superconductors. Here we investigate the ordered state of electron-boson mediated superconductors subject to laser driving using Migdal-Eliashberg theory on the Kadanoff-Baym-Keldysh contour. We extract the characteristic time scales on which the non-equilibrium superconductor reacts to the perturbation, and their relation to the coupling boson and the underlying order.

  19. An overview of the Fe-chalcogenide superconductors

    Science.gov (United States)

    Wu, M. K.; Wu, P. M.; Wen, Y. C.; Wang, M. J.; Lin, P. H.; Lee, W. C.; Chen, T. K.; Chang, C. C.

    2015-08-01

    This review intends to summarize recent advancements in FeSe and related systems. The FeSe and related superconductors are currently receiving considerable attention for the high critical temperature (T C) observed and for many similar features to the high T C cuprate superconductors. These similarities suggest that understanding the FeSe-based compounds could potentially help our understanding of the cuprates. We begin the review by presenting common features observed in the FeSe- and FeAs-based systems. Then we discuss the importance of careful control of the material preparation allowing for a systematic structure characterization. With this control, numerous rich phases have been observed. Importantly, we suggest that the Fe-vacancy ordered phases found in the FeSe-based compounds, which are non-superconducting magnetic Mott insulators, are the parent compounds of the superconductors. Superconductivity can emerge from the parent phases by disordering the Fe vacancy order, often by a simple annealing treatment. Then we review physical properties of the Fe chalcogenides, specifically the optical properties and angle-resolved photoemission spectroscopy (ARPES) results. From the literature, strong evidence points to the existence of orbital modification accompanied by a gap-opening, prior to the structural phase transition, which is closely related to the occurrence of superconductivity. Furthermore, strong lattice to spin coupling are important for the occurrence of superconductivity in FeSe. Therefore, it is believed that the iron selenides and related compounds will provide essential information to understand the origin of superconductivity in the iron-based superconductors, and possibly the superconducting cuprates.

  20. Higgs mode excitation in superconductors by intense terahertz pulse

    Science.gov (United States)

    Matsunaga, Ryusuke; Shimano, Ryo

    2016-05-01

    Recent development of intense terahertz (THz) pulse generation technique has offered novel opportunities to reveal ultrafast phenomena in a variety of materials on tabletop experiments and provided a new pathway toward ultrafast control of quantum phases. Here we present our recent study of nonequilibrium dynamics in metallic superconductors NbN excited by intense THz pulse. Since the superconducting gap energy is located in the THz frequency range, the intense THz pulse excitation makes it possible to instantaneously excite high-density quasiparticles at the gap edge without injecting excess energies. It has also become possible to coherently drive the superconducting ground state without exciting incoherent quasiparticles by tuning the pump frequency below the gap energy. The ultrafast dynamics of the order parameter induced by such an intense low energy excitation is directly probed, and the nature of a collective excitation, namely the Higgs amplitude mode, is revealed. Efficient THz higher-harmonic generation from a superconductor is discovered, manifesting the nonlinear coupling between the THz wave and the Higgs mode. We also report the experimental results in a multi-gap superconductor MgB2.

  1. Kramer Pesch Effect in Chiral p-Wave Superconductors

    Science.gov (United States)

    Kato, Yusuke; Hayashi, Nobuhiko

    2001-11-01

    The pair-potential and current density around a single vortex of the two-dimensional chiral p-wave superconductor with \\mbi{d}=\\hat{\\mbi{z}}(px ± i py) are determined self-consistently within the quasiclassical theory of superconductivity. Shrinking of the vortex core at low temperatures are considered numerically and analytically. Temperature-dependences of the spatial variation of pair-potential and circular current around the core and density of states at zero energy are the same as those in the isotropic s-wave case. When the senses of vorticity and chirality are opposite, however, we find two novel results; 1) the scattering rate due to non-magnetic impurities is considerably suppressed, compared to that in the s-wave vortex. From this observation, we expect that the chiral p-wave superconductors provide the best chance to observe the shrinking of the vortex (“Kramer Pesch effect”) experimentally. 2) The pair-potential of chiral p-wave superconductors inside vortex core recovers a combined time-reversal-Gauge symmetry, although this symmetry is broken in the region far from the vortex core. This local recovery of symmetry leads to the suppression of the impurity effect inside vortex core.

  2. A superconductor to superfluid phase transition in liquid metallic hydrogen.

    Science.gov (United States)

    Babaev, Egor; Sudbø, Asle; Ashcroft, N W

    2004-10-07

    Although hydrogen is the simplest of atoms, it does not form the simplest of solids or liquids. Quantum effects in these phases are considerable (a consequence of the light proton mass) and they have a demonstrable and often puzzling influence on many physical properties, including spatial order. To date, the structure of dense hydrogen remains experimentally elusive. Recent studies of the melting curve of hydrogen indicate that at high (but experimentally accessible) pressures, compressed hydrogen will adopt a liquid state, even at low temperatures. In reaching this phase, hydrogen is also projected to pass through an insulator-to-metal transition. This raises the possibility of new state of matter: a near ground-state liquid metal, and its ordered states in the quantum domain. Ordered quantum fluids are traditionally categorized as superconductors or superfluids; these respective systems feature dissipationless electrical currents or mass flow. Here we report a topological analysis of the projected phase of liquid metallic hydrogen, finding that it may represent a new type of ordered quantum fluid. Specifically, we show that liquid metallic hydrogen cannot be categorized exclusively as a superconductor or superfluid. We predict that, in the presence of a magnetic field, liquid metallic hydrogen will exhibit several phase transitions to ordered states, ranging from superconductors to superfluids.

  3. Application Fields of High-Temperature Superconductors

    OpenAIRE

    Hott, Roland

    2003-01-01

    Potential application fields for cuprate high-temperature superconductors (HTS) and the status of respective projects are reviewed. The availability of a reliable and inexpensive cooling technique will be essential for a future broad acceptance of HTS applications.

  4. 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.

  5. De-Sitter spacetime as a superconductor

    CERN Document Server

    Momeni, D

    2016-01-01

    A superconductor is a material with infinite electric conductivity. Superconductivity and magnetism are happening as two opposite phenomena: superconductors need weak external magnetic fields (the Meissner effect) while generally with a strong external magnetic field we loose superconductivity. In \\cite{ref:I}-\\cite{Chernodub:2011tv} , the author showed that a very strong magnetic field can turn an empty space into a superconductor. We extended this idea to the constant curvature spaces, de Sitter (dS) spacetime and by a careful analysis of the modes for a spinor with arbitrary spin, we show that in a very similar condensation scenario as was proposed for flat space, we could transform dS to a superconductor.

  6. Thermoelectric effect in a nonequilibrium superconductor

    Energy Technology Data Exchange (ETDEWEB)

    Falco, C. M.

    1977-01-01

    Initial results are reported showing experimental evidence for a pair-quasiparticle electrochemical potential difference in a superconductor in a temperature gradient. This potential diverges at low temperature and, within the resolution of the data, seems to approach a constant value at T/sub c/. The data can be used to extract a value for the thermal transport current of normal excitations in the superconductor.

  7. Majorana Fermions and Topology in Superconductors

    OpenAIRE

    Sato, Masatoshi; Fujimoto, Satoshi

    2016-01-01

    Topological superconductors are novel classes of quantum condensed phases, characterized by topologically nontrivial structures of Cooper pairing states. On the surfaces of samples and in vortex cores of topological superconductors, Majorana fermions, which are particles identified with their own anti-particles, appear as Bogoliubov quasiparticles. The existence and stability of Majorana fermions are ensured by bulk topological invariants constrained by the symmetries of the systems. Majorana...

  8. Holographic entanglement entropy in imbalanced superconductors

    CERN Document Server

    Dutta, Arghya

    2014-01-01

    We study the behavior of holographic entanglement entropy (HEE) for imbalanced holographic superconductor. It is found that HEE for this imbalanced system decreases with the increase of imbalance in chemical potentials. Also for an arbitrary mismatch between two chemical potentials, below the critical temperature, superconducting phase has a lower HEE in comparison to the AdS-Reissner-Nordstrom black hole phase. This suggests entanglement entropy to be a useful physical probe for understanding the imbalanced holographic superconductors.

  9. 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.

  10. 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)

  11. Charge order in cuprate superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Bulut, Sinan; Kampf, Arno P. [Theoretical Physics III, Center for Electronic Correlations and Magnetism, Institute of Physics, University of Augsburg (Germany); Atkinson, Bill A. [Department of Physics and Astronomy, Trent University, Peterborough, Ontario (Canada)

    2015-07-01

    Motivated by widespread experimental evidence of charge orders in underdoped cuprate superconductors, we study a three band model of a cuprate plane. Our calculations start from a pseudogap-like normal system with a reconstructed Fermi surface, and we search for charge instabilities. From the charge susceptibilities, we identify a charge ordering instability with an ordering wavevector, q*, that matches experimental results not only with respect to the doping dependence but more importantly regarding its magnitude and direction. Namely, q* points along the Brillouin zone axes. Thus, our results clarify the discrepancy between many recent theoretical calculations and the experiments. We extend this calculation towards possible loop current instabilities and the charge ordering pattern in bilayer systems.

  12. Ultrasonic attenuation in cuprate superconductors

    Indian Academy of Sciences (India)

    T Gupta; D M Gaitonde

    2002-05-01

    We calculate the longitudinal ultrasonic attenuation rate (UAR) in clean d-wave superconductors in the Meissner and the mixed phases. In the Meissner phase we calculate the contribution of previously ignored processes involving the excitation of a pair of quasi-holes or quasi-particles. There is a contribution ∝ in the regime B ≪ F ≪ 0 and a contribution ∝ 1/ in the regime F ≪ B ≪ 0. We find that these contributions to the UAR are large and cannot be ignored. In the mixed phase, using a semi-classical description, we calculate the electronic quasi-particle contribution to the UAR which at very low , has a independent term proportional to $\\sqrt{H}$.

  13. Moessbauer studies of ternary superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Kimball, C.W.; Van Landuyt, G.L.; Barnet, C.D.; Shenoy, G.K.; Dunlap, B.D.; Fradin, F.Y.

    1978-01-01

    Moessbauer studies of the ternary Chevrel phase and rare earth rhodium boride superconductors have been made. Anomalous phonon properties at the Sn site in SnMo/sub 6/S/sub 8/, SnMo/sub 6/Se/sub 8/, and La/sub 0/ /sub 98/Sn/sub 0/ /sub 02/Mo/sub 6/Se/sub 8/ have been investigated. Studies of polarization of conduction electrons at the site of the magnetic ion have been made by means of the /sup 151/Eu Moessbauer effect in Eu/sub x/Sn/sub 1-x/Mo/sub 6/S/sub 8/ and the effects of such polarization on superconducting properties discussed. The Moessbauer effect in /sup 166/Er has been used to investigate the electronic ground state in the ternary compound ErRh/sub 4/B/sub 4/ both in the superconducting and magnetically ordered states.

  14. Subgap states in disordered superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Skvortsov, M. A., E-mail: skvor@itp.ac.ru; Feigel' man, M. V., E-mail: feigel@landau.ac.ru [Russian Academy of Sciences, Landau Institute for Theoretical Physics (Russian Federation)

    2013-09-15

    We revise the problem of the density of states in disordered superconductors. Randomness of local sample characteristics translates to the quenched spatial inhomogeneity of the spectral gap, smearing the BCS coherence peak. We show that various microscopic models of potential and magnetic disorder can be reduced to a universal phenomenological random order parameter model, whereas the details of the microscopic description are encoded in the correlation function of the order parameter fluctuations. The resulting form of the density of states is generally described by two parameters: the width {Gamma} measuring the broadening of the BCS peak and the energy scale {Gamma}{sub tail} that controls the exponential decay of the density of subgap states. We refine the existing instanton approaches for determination of {Gamma}{sub tail} and show that they appear as limiting cases of a unified theory of optimal fluctuations in a nonlinear system. The application to various types of disorder is discussed.

  15. 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).

  16. Superconductors

    Science.gov (United States)

    Newkirk, Lawrence R.; Valencia, Flavio A.

    1977-02-01

    The structural quality of niobium germanide as a high-transition-temperature superconducting material is substantially improved by the presence of about 5 at. % oxygen. Niobium germanide having this oxygen content may readily be prepared as a bulk coating bonded to a metallic substrate by chemical vapor deposition techniques.

  17. 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...

  18. Geometric heat trapping in niobium superconductor-insulator-superconductor mixers due to niobium titanium nitride leads

    NARCIS (Netherlands)

    Leone, B; Jackson, BD; Gao, [No Value; Klapwijk, TM

    2000-01-01

    We analyze the current-voltage characteristics of a Nb superconductor-insulator-superconductor mixer with NbTiN leads to identify the heating processes in this device. We argue that the electron-electron interaction is much faster than the electron-phonon interaction, and show that the heat flow to

  19. Strong nonequilibrium coherent states in mesoscopic superconductor-semiconductor-superconductor junctions

    DEFF Research Database (Denmark)

    Kutchinsky, Jonatan; Wildt, Morten; Taboryski, Rafael Jozef;

    1999-01-01

    A biased superconductor-normal metal-superconductor junction is known to be a strong nonequilibrium system, where Andreev scattering at the interfaces creates a quasiparticle distribution function far from equilibrium, a manifestation of this is the well-known subgap structure in the I...

  20. 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

  1. 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 circ

  2. Josephson current in a normal-metal nanowire coupled to a superconductor/ferromagnet/superconductor junction

    NARCIS (Netherlands)

    Ebisu, H.; Lu, B.; Taguchi, K.; Golubov, Alexandre Avraamovitch; Tanaka, Y.

    2016-01-01

    We consider a superconducting nanowire proximity coupled to a superconductor/ferromagnet/superconductor (S/F/S) junction, where the magnetization penetrates into a superconducting segment in a nanowire decaying as ∼exp[−∣n∣ξ], where n is the site index and the ξ is the decay length. We tune chemical

  3. A star role for stripes[Charge order in high-temperature superconductors in magnetic fields

    Energy Technology Data Exchange (ETDEWEB)

    Tranquada, John [Physics Department, Brookhaven National Laboratory (United States)

    2002-06-01

    New images of magnetic and charge order in copper-oxide compounds are providing important clues about the nature of high-temperature superconductors. Visual images can have a powerful impact on the viewer, and this is certainly the case when the images are atomic-scale pictures of the surface of a high-temperature copper-oxide superconductor. The unusual properties of these materials have vexed condensed-matter theorists for the last 15 years. Now a new flurry of theoretical papers has been stimulated by the latest images of a cuprate superconductor, which reveal that an applied magnetic field can induce 'stripes' of charge. The experimental results provide intriguing and important clues to the nature of these ever-surprising materials - although the theorists have still to agree on their meaning. (U.K.)

  4. Repulsive Casimir force between silicon dioxide and superconductor

    Energy Technology Data Exchange (ETDEWEB)

    Phan, Anh D. [Department of Physics, University of South Florida, Tampa, Florida (United States); Viet, N.A. [Institute of Physics, Badinh, Hanoi (Viet Nam)

    2012-06-15

    We present a detailed investigation of the Casimir interaction between the superconductor Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8+{delta}} (BSCCO) and silicon dioxide with bromobenzene present in between. We found that the dispersion force is repulsive and the magnitude of the force can be changed by varying the thickness of the object and the temperature. The repulsive force would provide a method to deal with stiction problems and provide much significant from the practical point of view. (copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  5. LDA+DCA calculations of cuprate superconductors

    Science.gov (United States)

    Kent, Paul; Macridin, Alexandru; Schulthess, Thomas; Krogh Andersen, Ole

    2005-03-01

    We present calculations of the properties of realistic models of single-layer cuprate superconductors. A multi-band Hubbard model is obtained from downfolded material specific local density approximation (LDA) density functional theory (DFT) calculations. The on-site U is obtained from constrained DFT calculations. The resulting model is solved using the dynamic cluster approximation (DCA) and quantum Monte Carlo, for small clusters. Some of us have previously shown that DCA calculations of the single band Hubbard model, with empirical parameters, reproduce key features of the experimental phase diagram, including the d-wave superconducting region and pseudogap. In the multi-band model, we find a superconducting region, and discuss how the computed transition temperature depends on the downfolded band structure. In model calculations, we test the sensitivity of the transition temperature to changes in the individual hopping terms, including the copper-oxygen and oxygen-oxygen hybridization. Work supported by the Division of Materials Science and Engineering, U.S. Department of Energy, under Contract DE-AC05-00OR22725 with UT-Battelle LLC.

  6. Epitaxial layers of 2122 BCSCO superconductor thin films having single crystalline structure

    Science.gov (United States)

    Pandey, Raghvendra K. (Inventor); Raina, Kanwal K. (Inventor); Solayappan, Narayanan (Inventor)

    1995-01-01

    A substantially single phase, single crystalline, highly epitaxial film of Bi.sub.2 CaSr.sub.2 Cu.sub.2 O.sub.8 superconductor which has a T.sub.c (zero resistance) of 83K is provided on a lattice-matched substrate with no intergrowth. This film is produced by a Liquid Phase Epitaxy method which includes the steps of forming a dilute supercooled molten solution of a single phase superconducting mixture of oxides of Bi, Ca, Sr, and Cu having an atomic ratio of about 2:1:2:2 in a nonreactive flux such as KCl, introducing the substrate, e.g., NdGaO.sub.3, into the molten solution at 850.degree. C., cooling the solution from 850.degree. C. to 830.degree. C. to grow the film and rapidly cooling the substrate to room temperature to maintain the desired single phase, single crystalline film structure.

  7. The string universe high T$_{c}$ superconductor or quantum Hall conductor?

    CERN Document Server

    Ellis, Jonathan Richard; Nanopoulos, Dimitri V

    1992-01-01

    Our answer is the latter. Space-time singularities, including the initial one, are described by world-sheet topological Abelian gauge theories with a Chern-Simons term. Their effective $N=2$ supersymmetry provides an initial fixed point where the Bogomolny bound is saturated on the world-sheet, corresponding to an extreme Reissner-Nordstrom solution in space-time. Away from the singularity the gauge theory has world-sheet matter fields, bosons and fermions, associated with the generation of target space-time. Because the fermions are complex (cf the Quantum Hall Effect) rather than real (cf high-$T_c$ superconductors) the energetically-preferred vacuum is not parity or time-reversal invariant, and the associated renormalization group flow explains the cosmological arrow of time, as well as the decay of real or virtual black holes, with a monotonic increase in entropy.

  8. Test Status for Proposed Coupling of a Gravitational Force to Extreme Type II YBCO Ceramic Superconductors

    Science.gov (United States)

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

    1999-01-01

    As a Bose condensate, superconductors provide novel conditions for revisiting previously proposed couplings between electromagnetism and gravity. Strong variations in Cooper pair electron density, large conductivity and low magnetic permeability define superconductive and degenerate condensates without the traditional density limits imposed by the Fermi energy (about 10-6 g/cu cm). 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(exp 4) was reported above a stationary (non-rotating) superconductor. In the present experiments reported using a sensitive gravimeter (resolution superconductors were stably levitated in a DC magnetic field (0.6 Tesla) subject to lateral AC fields (60 Gauss at 60 Hz) and rotation. With magnetic shielding, thermal control and buoyancy compensation, changes in acceleration were measured to be less than 2 parts in 10(exp 8) of the normal gravitational acceleration. This result puts new limits on the strength and range of the proposed coupling between high-Tc superconductors and gravity. Latest test results will be reported, along with status for future improvements and prospects.

  9. Test Status for Proposed Coupling of a Gravitational Force to Extreme Type II YBCO Ceramic Superconductors

    Science.gov (United States)

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

    1999-01-01

    As a Bose condensate, superconductors provide novel conditions for revisiting previously proposed couplings between electromagnetism and gravity. Strong variations in Cooper pair electron density, large conductivity and low magnetic permeability define superconductive and degenerate condensates without the traditional density limits imposed by the Fermi energy (about 10-6 g/cu cm). 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(exp 4) was reported above a stationary (non-rotating) superconductor. In the present experiments reported using a sensitive gravimeter (resolution YBCO superconductors were stably levitated in a DC magnetic field (0.6 Tesla) subject to lateral AC fields (60 Gauss at 60 Hz) and rotation. With magnetic shielding, thermal control and buoyancy compensation, changes in acceleration were measured to be less than 2 parts in 10(exp 8) of the normal gravitational acceleration. This result puts new limits on the strength and range of the proposed coupling between high-Tc superconductors and gravity. Latest test results will be reported, along with status for future improvements and prospects.

  10. High-resolution dichroic imaging of magnetic flux distributions in superconductors with scanning x-ray microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Ruoss, Stephen; Stahl, Claudia; Weigand, Markus; Schuetz, Gisela [Max-Planck-Institut fuer Intelligente Systeme, Stuttgart (Germany); Albrecht, Joachim [Research Institute for Innovative Surfaces, FINO, Aalen University (Germany)

    2015-07-01

    The penetration of magnetic flux into the high-temperature superconductor YBCO has been observed using a new high-resolution technique based on X-ray magnetic circular dichroism (XMCD). Superconductors coated with thin soft magnetic layers of CoFeB are observed in a scanning x-ray microscope providing cooling of the sample down to 83 K under the influence of external magnetic fields. Resulting electrical currents create an inhomogeneous magnetic field distribution above the superconductor which leads to a local reorientation of the ferromagnetic layer. X-ray absorption measurements with circular polarized radiation allows the analysis of the magnetic flux distribution in the superconductor via the ferromagnetic layer. In this work we present first images taken at 83K with high spatial resolution in the nanoscale.

  11. Application of superconductor-semiconductor Schottky barrier for electron cooling

    Energy Technology Data Exchange (ETDEWEB)

    Savin, Alexander; Prunnila, Mika; Ahopelto, Jouni; Kivinen, Pasi; Toermae, Paeivi; Pekola, Jukka

    2003-05-01

    Electronic cooling in superconductor-semiconductor-superconductor structures at sub kelvin temperatures has been demonstrated. Effect of the carrier concentration in the semiconductor on performance of the micro-cooler has been investigated.

  12. Critical Current Test of Liquid Hydrogen Cooled HTC Superconductors under External Magnetic Field

    Science.gov (United States)

    Shirai, Yasuyuki; Shiotsu, Masahiro; Tatsumoto, Hideki; Kobayashi, Hiroaki; Naruo, Yoshihiro; Nonaka, Satoshi; Inatani, Yoshifumi

    High-Tc (HTC) superconductors including MgB2 will show excellent properties under temperature of Liquid Hydrogen (LH2:20K), which has large latent heat and low viscosity coefficient. In order to design and fabricate the LH2 cooled superconducting energy devices, we must clear the cooling property of LH2 for superconductors, the cooling system and safety design of LH2 cooled superconducting devices and electro-magnetic property evaluation of superconductors (BSCCO, REBCO and MgB2) and their magnets cooled by LH2. As the first step of the study, an experimental setup which can be used for investigating heat transfer characteristics of LH2 in a pool and also in forced flow (circulation loop with a pump), and also for evaluation of electro-magnetic properties of LH2 cooled superconductors under external magnetic field (up to 7 T). In this paper, we will show a short sketch of the experimental set-up, practical experiences in safety operation of liquid hydrogen cooling system and example test results of critical current evaluation of HTC superconductors cooled by LH2.

  13. Superconductors, analysis and applications, with special reference to the utilisation of bulk (Re)BCO materials

    Energy Technology Data Exchange (ETDEWEB)

    Coombs, T.A., E-mail: tac1000@cam.ac.u [University of Cambridge, Department of Engineering, Trumpington Street, Cambridge CB2 1PZ (United Kingdom)

    2010-11-01

    The Electrical Power and Energy Conversion (EPEC) superconductivity group at Cambridge University has been working on the application of superconductivity to large scale devices. This work is taking place over a range of areas which cover FCLs, motors and generators, SMES, accelerator magnets and MRI. The research is underpinned by advanced modelling techniques using both pure Critical State models and E-J models to analyse the behaviour of the superconductors. As part of the device design we are concentrating on the analysis of AC losses in complicated geometries such as are found in motor windings and the magnetisation of bulk superconductors to enable their full potential to be realised. We are interested in the full range of high-temperature superconductors and have measured and predicted the performance of YBCO, MgB{sub 2} and BSCCO at a range of temperatures and in wire, tape and bulk forms. This paper concentrates on recent work which includes: modelling of coils using formulations based on H and A. A critical state model for the analysis of coils in SMES; crossed field effects in bulk superconductors; a magnetic model together with experimental results which explain and describe the method of flux pumping whereby a bulk superconductor can be magnetised to a high flux density using a repeatedly applied field of low flux density and finally a new configuration for MRI magnets

  14. Quantum oscillations in organic metals and superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Clayton, N

    2000-12-01

    De Haas-van Alphen (dHvA) oscillations have been observed in the organic superconductor {kappa}-(BEDT-TTF){sub 2}Cu(NCS){sub 2} at temperatures down to 30 mK, and the oscillations are found to suffer an additional attenuation, R{sub s}, in the mixed state. None of the theoretical models, coupled with the mean-field expression for the field-dependence of the superconducting energy gap, {delta}, offer a good fit to the data. By including the effects of thermal fluctuations in the field-dependence of {delta}, a reasonable fit to the data can be made at the lowest temperatures. However, the form of the damping does not change appreciably as the temperature is increased up to 560 mK, which is inconsistent with the thermal fluctuation model. Angle resolved dHvA measurements on {kappa}-(BEDT-TTF){sub 2}Cu(NCS){sub 2} have allowed R{sub s} curves to be measured as a function of the orientation of the applied magnetic field. These R{sub s}({theta}) curves may be scaled onto one another by taking the components of the magnetic fields perpendicular to the layers. The scale of the fluctuations is independent of angle within experimental errors. This, and an angle-independent normal state Dingle temperature, suggests that the quasiparticle orbits are confined to the two-dimensional layers for all angles of applied magnetic field. An angle resolved dHvA study has been performed on the organic metal {alpha}-(BEDT-TTF){sub 2}KHg(NCS){sub 4}. At low temperatures and low fields, the Fermi surface is reconstructed in this material, and the dHvA signal is dominated by an a frequency and its second harmonic, 2{alpha}. The amplitude of the 2{alpha} frequency is shown to deviate from the predictions of the Lifshitz-Kosevich expression, but is found to be consistent with a 'frequency doubling' mechanism. In this scheme, the 2{alpha} frequency arises from a new type of quantum oscillatory phenomenon, due to the susceptibility of the quasi one-dimensional sheets, driven by

  15. Performance of ceramic superconductors in magnetic bearings

    Science.gov (United States)

    Kirtley, James L., Jr.; Downer, James R.

    1993-01-01

    Magnetic bearings are large-scale applications of magnet technology, quite similar in certain ways to synchronous machinery. They require substantial flux density over relatively large volumes of space. Large flux density is required to have satisfactory force density. Satisfactory dynamic response requires that magnetic circuit permeances not be too large, implying large air gaps. Superconductors, which offer large magnetomotive forces and high flux density in low permeance circuits, appear to be desirable in these situations. Flux densities substantially in excess of those possible with iron can be produced, and no ferromagnetic material is required. Thus the inductance of active coils can be made low, indicating good dynamic response of the bearing system. The principal difficulty in using superconductors is, of course, the deep cryogenic temperatures at which they must operate. Because of the difficulties in working with liquid helium, the possibility of superconductors which can be operated in liquid nitrogen is thought to extend the number and range of applications of superconductivity. Critical temperatures of about 98 degrees Kelvin were demonstrated in a class of materials which are, in fact, ceramics. Quite a bit of public attention was attracted to these new materials. There is a difficulty with the ceramic superconducting materials which were developed to date. Current densities sufficient for use in large-scale applications have not been demonstrated. In order to be useful, superconductors must be capable of carrying substantial currents in the presence of large magnetic fields. The possible use of ceramic superconductors in magnetic bearings is investigated and discussed and requirements that must be achieved by superconductors operating at liquid nitrogen temperatures to make their use comparable with niobium-titanium superconductors operating at liquid helium temperatures are identified.

  16. Electron tunneling and point contact Andreev reflection studies of superconductors

    Science.gov (United States)

    Dai, Wenqing

    The energy gap is the most fundamental property of a superconductor. Electron tunneling spectroscopy and point contact spectroscopy (PCS) are powerful techniques for studying the density of states and energy gap features of superconductors. Two different superconducting systems, multiband superconductor MgB2 and proximity induced topological superconductor NbSe2/Bi 2Se3 heterostructures were studied using either quasiparticle tunneling in planar tunnel junctions or PCS in this work. (Abstract shortened by ProQuest.).

  17. Studies on Magnetization Technique of High Temperature Superconductors

    OpenAIRE

    大橋, 忠巌; 荻原, 宏康

    1999-01-01

    It is known that permanent magnets produce magnetic fields up to 1T. On the other hand, magnetized high temperature superconductors can be used as "super"-permanent magnets which produce magnetic fields higher than 1T, because superconductors can trap higher magnetic fluxes than usual permanent magnets. In order to magnetize a YBCO bulk superconductor, there are two ways; a field cooling (FC) method and a zero field cooling (ZFC) method. FC is the way of magnetizing the superconductor by appl...

  18. Antiferromagnetic phase diagram of the cuprate superconductors

    Science.gov (United States)

    Nunes, L. H. C. M.; Teixeira, A. W.; Marino, E. C.

    2017-02-01

    Taking the spin-fermion model as the starting point for describing the cuprate superconductors, we obtain an effective nonlinear sigma-field hamiltonian, which takes into account the effect of doping in the system. We obtain an expression for the spin-wave velocity as a function of the chemical potential. For appropriate values of the parameters we determine the antiferromagnetic phase diagram for the YBa2Cu3O6+x compound as a function of the dopant concentration in good agreement with the experimental data. Furthermore, our approach provides a unified description for the phase diagrams of the hole-doped and the electron doped compounds, which is consistent with the remarkable similarity between the phase diagrams of these compounds, since we have obtained the suppression of the antiferromagnetic phase as the modulus of the chemical potential increases. The aforementioned result then follows by considering positive values of the chemical potential related to the addition of holes to the system, while negative values correspond to the addition of electrons.

  19. Design of superconductor frame compression circuits

    Science.gov (United States)

    Sakurai, T.; Miyaho, N.; Miyahara, K.

    2007-10-01

    We proposed previously a novel interface circuit which was used between semiconductor data-input circuits and superconductor high-speed routers. The frame length of data packets is compressed in the interface circuit. Our proposed interface circuit has rather narrow timing margin. The problem was that our control circuit of the interface circuit could allow only very small timing delay. In this paper we propose a modified control circuit. We have improved the timing margin of the control circuit using RS-flip flop (RS-FF), where two shift registers and one control circuit are driven by clock pulses provided from a master clock-pulse generator. In this circuit, we have assumed fixed frame length packets. Our final target of master clock frequency is 100 GHz which will be realized with the device-parameter set of future advanced process. As the first step of realizing this target value, we aimed at 40 GHz clock operation with the conventional device-parameter set of NECs standard I process. The behavior of the whole frame compression circuit was simulated by a computer, and it was confirmed that it operated properly up to the master clock frequency of 23 GHz.

  20. 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...

  1. 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?

  2. 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

  3. 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

  4. Block copolymer self-assembly-directed synthesis of mesoporous gyroidal superconductors.

    Science.gov (United States)

    Robbins, Spencer W; Beaucage, Peter A; Sai, Hiroaki; Tan, Kwan Wee; Werner, Jörg G; Sethna, James P; DiSalvo, Francis J; Gruner, Sol M; Van Dover, Robert B; Wiesner, Ulrich

    2016-01-01

    Superconductors with periodically ordered mesoporous structures are expected to have properties very different from those of their bulk counterparts. Systematic studies of such phenomena to date are sparse, however, because of a lack of versatile synthetic approaches to such materials. We demonstrate the formation of three-dimensionally continuous gyroidal mesoporous niobium nitride (NbN) superconductors from chiral ABC triblock terpolymer self-assembly-directed sol-gel-derived niobium oxide with subsequent thermal processing in air and ammonia gas. Superconducting materials exhibit a critical temperature (T c) of about 7 to 8 K, a flux exclusion of about 5% compared to a dense NbN solid, and an estimated critical current density (J c) of 440 A cm(-2) at 100 Oe and 2.5 K. We expect block copolymer self-assembly-directed mesoporous superconductors to provide interesting subjects for mesostructure-superconductivity correlation studies.

  5. Observation of Majorana fermions in ferromagnetic atomic chains on a superconductor

    Science.gov (United States)

    Nadj-Perge, Stevan; Drozdov, Ilya K.; Li, Jian; Chen, Hua; Jeon, Sangjun; Seo, Jungpil; MacDonald, Allan H.; Bernevig, B. Andrei; Yazdani, Ali

    2014-10-01

    Majorana fermions are predicted to localize at the edge of a topological superconductor, a state of matter that can form when a ferromagnetic system is placed in proximity to a conventional superconductor with strong spin-orbit interaction. With the goal of realizing a one-dimensional topological superconductor, we have fabricated ferromagnetic iron (Fe) atomic chains on the surface of superconducting lead (Pb). Using high-resolution spectroscopic imaging techniques, we show that the onset of superconductivity, which gaps the electronic density of states in the bulk of the Fe chains, is accompanied by the appearance of zero-energy end-states. This spatially resolved signature provides strong evidence, corroborated by other observations, for the formation of a topological phase and edge-bound Majorana fermions in our atomic chains.

  6. Topological matter. Observation of Majorana fermions in ferromagnetic atomic chains on a superconductor.

    Science.gov (United States)

    Nadj-Perge, Stevan; Drozdov, Ilya K; Li, Jian; Chen, Hua; Jeon, Sangjun; Seo, Jungpil; MacDonald, Allan H; Bernevig, B Andrei; Yazdani, Ali

    2014-10-31

    Majorana fermions are predicted to localize at the edge of a topological superconductor, a state of matter that can form when a ferromagnetic system is placed in proximity to a conventional superconductor with strong spin-orbit interaction. With the goal of realizing a one-dimensional topological superconductor, we have fabricated ferromagnetic iron (Fe) atomic chains on the surface of superconducting lead (Pb). Using high-resolution spectroscopic imaging techniques, we show that the onset of superconductivity, which gaps the electronic density of states in the bulk of the Fe chains, is accompanied by the appearance of zero-energy end-states. This spatially resolved signature provides strong evidence, corroborated by other observations, for the formation of a topological phase and edge-bound Majorana fermions in our atomic chains.

  7. Block copolymer self-assembly–directed synthesis of mesoporous gyroidal superconductors

    Science.gov (United States)

    Robbins, Spencer W.; Beaucage, Peter A.; Sai, Hiroaki; Tan, Kwan Wee; Werner, Jörg G.; Sethna, James P.; DiSalvo, Francis J.; Gruner, Sol M.; Van Dover, Robert B.; Wiesner, Ulrich

    2016-01-01

    Superconductors with periodically ordered mesoporous structures are expected to have properties very different from those of their bulk counterparts. Systematic studies of such phenomena to date are sparse, however, because of a lack of versatile synthetic approaches to such materials. We demonstrate the formation of three-dimensionally continuous gyroidal mesoporous niobium nitride (NbN) superconductors from chiral ABC triblock terpolymer self-assembly–directed sol-gel–derived niobium oxide with subsequent thermal processing in air and ammonia gas. Superconducting materials exhibit a critical temperature (Tc) of about 7 to 8 K, a flux exclusion of about 5% compared to a dense NbN solid, and an estimated critical current density (Jc) of 440 A cm−2 at 100 Oe and 2.5 K. We expect block copolymer self-assembly–directed mesoporous superconductors to provide interesting subjects for mesostructure-superconductivity correlation studies. PMID:27152327

  8. 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.

  9. Physics and chemistry review of layered chalcogenide superconductors

    OpenAIRE

    Deguchi, Keita; Takano, Yoshihiko; Mizuguchi, Yoshikazu

    2012-01-01

    Structural and physical properties of layered chalcogenide superconductors are summarized. In particular, we review the remarkable properties of the Fe-chalcogenide superconductors, FeSe and FeTe-based materials. Furthermore, we introduce the recently-discovered new BiS2-based layered superconductors and discuss its prospects.

  10. Quantized conductance doubling and hard gap in a two-dimensional semiconductor-superconductor heterostructure

    DEFF Research Database (Denmark)

    Kjærgaard, Morten; Nichele, F; Suominen, Henri Juhani;

    2016-01-01

    Coupling a two-dimensional (2D) semiconductor heterostructure to a superconductor opens new research and technology opportunities, including fundamental problems in mesoscopic superconductivity, scalable superconducting electronics, and new topological states of matter. One route towards...... topological matter is by coupling a 2D electron gas with strong spin-orbit interaction to an s-wave superconductor. Previous efforts along these lines have been adversely affected by interface disorder and unstable gating. Here we show measurements on a gateable InGaAs/InAs 2DEG with patterned epitaxial Al......, yielding devices with atomically pristine interfaces between semiconductor and superconductor. Using surface gates to form a quantum point contact (QPC), we find a hard superconducting gap in the tunnelling regime. When the QPC is in the open regime, we observe a first conductance plateau at 4e(2)/h...

  11. Tunneling Conductance in Ferromagnetic Metal/Normal Metal/Spin-Singlet -Wave Ferromagnetic Superconductor Junctions

    Directory of Open Access Journals (Sweden)

    Hamidreza Emamipour

    2013-01-01

    Full Text Available In the framework of scattering theory, we study the tunneling conductance in a system including two junctions, ferromagnetic metal/normal metal/ferromagnetic superconductor, where ferromagnetic superconductor is in spin-singlet -wave pairing state. The non-magnetic normal metal is placed in the intermediate layer with the thickness ( which varies from 1 nm to 10000 nm. The interesting result which we have found is the existence of oscillations in conductance curves. The period of oscillations is independent of FS and FN exchange field while it depends on . The obtained results can serve as a useful tool to determine the kind of pairing symmetry in ferromagnetic superconductors.

  12. Low-temperature rapid synthesis and superconductivity of Fe-based oxypnictide superconductors.

    Science.gov (United States)

    Fang, Ai-Hua; Huang, Fu-Qiang; Xie, Xiao-Ming; Jiang, Mian-Heng

    2010-03-17

    Fe-based oxypnictide superconductors were successfully synthesized at lower reaction temperatures and with shorter reaction times made possible by starting with less stable compounds, which provide a larger driving force for reactions. Using ball-milled powders of intermediate compounds, phase-pure superconductors with T(c) above 50 K were synthesized at 1173 K in 20 min. This method is particularly advantageous for retaining F, a volatile dopant that enhances superconductivity. Bulk superconductivity and high upper critical fields up to 392 T in Sm(0.85)Nd(0.15)FeAsO(0.85)F(0.15) were demonstrated.

  13. Thermoelectric power and transport entropy of dirty type-II superconductors

    Science.gov (United States)

    de Lange, O. L.; Gridin, V. V.

    1992-09-01

    The relation FT0c2S(B,T)dT~=Bħ/(2mc) presented recently for the thermoelectric power S of a dirty high-Tc superconductor [V. V. Gridin et al., Phys. Rev. B 40, 8814 (1989)] is considered. It is shown that measurements which have been reported for the thermomagnetic coefficients of nearly reversible conventional type-II superconductors provide additional support for this relation. The result obtained from time-dependent microscopic theory for vortex motion (time-dependent Ginzburg-Landau theory and linear-response theory) is also discussed.

  14. Using core-shell metamaterial engineering to triple the critical temperature of a superconductor

    CERN Document Server

    Smolyaninova, Vera N; Gresock, Thomas; Jensen, Christopher; Prestigiacomo, Joseph C; Osofsky, M S; Smolyaninov, Igor I

    2015-01-01

    Recent experiments have shown the viability of the metamaterial approach to dielectric response engineering for moderately enhancing the transition temperature, Tc, of a superconductor. In this report, we demonstrate the use of Al2O3-coated aluminium nanoparticles to form the recently proposed epsilon near zero (ENZ) core-shell metamaterial superconductor with a Tc that is three times that of pure aluminium. IR reflectivity measurements confirm the predicted metamaterial modification of the dielectric function thus demonstrating the efficacy of the ENZ metamaterial approach to Tc engineering. These results provide an explanation for the long known, but not understood, enhancement of the Tc of granular aluminum films.

  15. Quantized conductance doubling and hard gap in a two-dimensional semiconductor-superconductor heterostructure

    DEFF Research Database (Denmark)

    Kjærgaard, Morten; Nichele, F; Suominen, Henri Juhani

    2016-01-01

    topological matter is by coupling a 2D electron gas with strong spin-orbit interaction to an s-wave superconductor. Previous efforts along these lines have been adversely affected by interface disorder and unstable gating. Here we show measurements on a gateable InGaAs/InAs 2DEG with patterned epitaxial Al......, consistent with theory. The hard-gap semiconductor-superconductor system demonstrated here is amenable to top-down processing and provides a new avenue towards low-dissipation electronics and topological quantum systems....

  16. Chiral CP2 skyrmions in three-band superconductors and layered superconducting structures

    Science.gov (United States)

    Garaud, Julien; Carlstrom, Johan; Babaev, Egor; Speight, Martin

    2013-03-01

    Recently discovered iron-based superconductors and well as multilayer structures involving s+/- superconductors can exhibit a spontaneous breaking of the time reversal symmetry. This raises the question of experimental manifestations of this additional broken symmetry. We demonstrate that it can result in formation of experimentally detectable nontrivial flux-carrying excitations which are topologically different conventional vortices. This new kind of solitons can provide an experimental signature of the breaking of time reversal symmetry. Supported by NSF CAREER Award DMR-0955902, Knut and Alice Wallenberg Foundation through the Royal Swedish Academy of Sciences and Swedish Research Council. And Swedish National Infrastructure for Computing (SNIC) at National Supercomputer Center.

  17. Force balance on two-dimensional superconductors with a single moving vortex

    Science.gov (United States)

    Chung, Chun Kit; Arahata, Emiko; Kato, Yusuke

    2014-03-01

    We study forces on two-dimensional superconductors with a single moving vortex based on a recent fully self-consistent calculation of DC conductivity in an s-wave superconductor (E. Arahata and Y. Kato, arXiv:1310.0566). By considering momentum balance of the whole liquid, we attempt to identify various contributions to the total transverse force on the vortex. This provides an estimation of the effective Magnus force based on the quasiclassical theory generalized by Kita [T. Kita, Phys. Rev. B, 64, 054503 (2001)], which allows for the Hall effect in vortex states.

  18. 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 (Tc; ref. 7), revealing a dome-shaped phase diagram reminiscent of high-Tc 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.

  19. Zero-Bias Conductance versus Potential Strength of Interface in Ferromagnetic Superconductors

    Institute of Scientific and Technical Information of China (English)

    Hamidreza Emamipour; Jafar Emamipour

    2012-01-01

    We study zero-bias conductance (ZBC) spectra of a normal-metal/insulator/singlet (and triplet) ferromagnetic superconductor as a function of potential strength of interface in the Blonder-Tinkham Klapwijk (BTK) theory framework.We consider possible pairing states including spin singlet s-wave pairing (SWP),spin triplet opposite spin pairing (OSP) and spin triplet equal spin pairing (ESP).It is found that ZBC as a function of potential strength of interface shows a clear difference between SWP,OSP and ESP states.These results may serve as a useful tool for discriminating pairing states in ferromagnetic superconductors.

  20. Theory of specific heat of vortex liquid of high T c superconductors

    Science.gov (United States)

    Bai, Chen; Chi, Cheng; Wang, Jiangfan

    2016-10-01

    Superconducting thermal fluctuation (STF) plays an important role in both thermodynamic and transport properties in the vortex liquid phase of high T c superconductors. It was widely observed in the vicinity of the critical transition temperature. In the framework of Ginzburg-Landau-Lawrence-Doniach theory in magnetic field, a self-consistent analysis of STF including all Landau levels is given. Besides that, we calculate the contribution of STF to specific heat in vortex liquid phase for high T c cuprate superconductors, and the fitting results are in good agreement with experimental data. Project supported by the National Natural Science Foundation of China (Grant No. 11274018).

  1. 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

  2. Random-matrix theory of Majorana fermions and topological superconductors

    Science.gov (United States)

    Beenakker, C. W. J.

    2015-07-01

    The theory of random matrices originated half a century ago as a universal description of the spectral statistics of atoms and nuclei, dependent only on the presence or absence of fundamental symmetries. Applications to quantum dots (artificial atoms) followed, stimulated by developments in the field of quantum chaos, as well as applications to Andreev billiards—quantum dots with induced superconductivity. Superconductors with topologically protected subgap states, Majorana zero modes, and Majorana edge modes, provide a new arena for applications of random-matrix theory. These recent developments are reviewed, with an emphasis on electrical and thermal transport properties that can probe the Majorana fermions.

  3. 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.

  4. Thermo-electromagnetic properties of a magnetically shielded superconductor strip: theoretical foundations and numerical simulations

    Science.gov (United States)

    Ma, G. T.; Rauh, H.

    2013-10-01

    Numerical simulations of thermo-electromagnetic properties of a thin type-II superconductor strip surrounded by open cavity soft-magnetic shields and exposed to an oscillating transverse magnetic field are performed by resorting to the quasistatic approximation of a vector potential approach in conjunction with the classical description of conduction of heat. The underlying definition of the superconducting constituent makes use of an extended ‘smoothed’ Bean model of the critical state, which includes the field and temperature dependence of the induced supercurrent as well. The delineation of the magnetic shields exploits the reversible-paramagnet approximation in the Langevin form, as appropriate for magnetizations with narrow Z-type loops, and considers induced eddy currents too. The coolant is envisaged as acting like a bath that instantly takes away surplus heat. Based on the Jacobian-free Newton-Krylov approach and the backward Euler scheme, the numerical analysis at hand is tailored to the problem of a high width/thickness aspect ratio of the superconductor strip. Assigning representative materials characteristics and conditions of the applied magnetic field, the main findings for a practically relevant magnet configuration include: (i) an overall rise of the maximum temperature of the superconductor strip tending to saturation in a superconducting thermo-electromagnetic steady state above the operating temperature, magnetic shielding lending increased stability and smoothing the temperature profile along the width of the superconductor strip; (ii) a washing out of the profile of the magnetic induction and a lowering of its strength, a relaxation of the profile of the supercurrent density and an increase of its strength, a tightening of the power loss density and a reduction of its strength, all inside the superconductor strip. The hysteretic ac loss suffered by the superconductor strip is seen to be cut back or, at most, to converge on that of an

  5. Infrared properties of high T{sub c} superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Schlesinger, Z.; Rotter, L.D.; Collins, R.T.; Holtzberg, F.; Feild, C. [International Business Machines Corp., Yorktown Heights, NY (United States). Thomas J. Watson Research Center; Welp, U.; Crabtree, G.W.; Liu, J.Z.; Fang, Y.; Vandervoort, K.G. [Argonne National Lab., IL (United States)

    1991-12-31

    Over the past several years a coherent phenomenology of the high {Tc} 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 {omega}>T, and of order {omega}, (2) a characteristic energy scale in the superconducting state of 500 cm{sup {minus}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 {Tc}. An attempt to describe these aspects of the data is presented here.

  6. Infrared properties of high T sub c superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Schlesinger, Z.; Rotter, L.D.; Collins, R.T.; Holtzberg, F.; Feild, C. (International Business Machines Corp., Yorktown Heights, NY (United States). Thomas J. Watson Research Center); Welp, U.; Crabtree, G.W.; Liu, J.Z.; Fang, Y.; Vandervoort, K.G. (Argonne National Lab., IL (United States))

    1991-01-01

    Over the past several years a coherent phenomenology of the high {Tc} 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 {omega}>T, and of order {omega}, (2) a characteristic energy scale in the superconducting state of 500 cm{sup {minus}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 {Tc}. An attempt to describe these aspects of the data is presented here.

  7. Rugged Low-Resistance Contacts To High-Tc Superconductors

    Science.gov (United States)

    Caton, Randall; Selim, Raouf; Byvik, Charles E.; Buoncristiani, A. Martin

    1992-01-01

    Newly developed technique involving use of gold makes possible to fabricate low-resistance contacts with rugged connections to high-Tc superconductors. Gold diffused into specimen of superconducting material by melting gold beads onto surface of specimen, making strong mechanical contacts. Shear strength of gold bead contacts greater than epoxy or silver paste. Practical use in high-current-carrying applications of new high-Tc materials, including superconducting magnets, long-wavelength sensors, electrical ground planes at low temperatures, and efficient transmission of power.

  8. Hacia el motor superconductor: estudio de las interacciones entre un rotor superconductor y un estator convencional

    OpenAIRE

    Pallarès Viña, Miquel Joan

    2002-01-01

    de la tesis:Hacia el motor superconductor: estudio de las interacciones entre un estator convencional y un rotor superconductorEl desarrollo de superconductores de alta temperatura (HTSC) de gran corriente crítica ha permitido la fabricación de dispositivos en varias áreas de la ingeniería electromecánica. En particular, los HTSC pueden mejorar el rendimiento de los motores eléctricos, ya sea sustituyendo el cobre en el rotor de los mismos o con la realización de nuevos diseños.El particular...

  9. dc Josephson Effect in s-Wave Superconductor/Ferromagnet Insulator/p-Wave Superconductor Junctions

    Institute of Scientific and Technical Information of China (English)

    LI Xiao-Wei

    2007-01-01

    The Josephson currents in s-wave superconductor/ferromagnet insulator/p-wave superconductor(s/FI/p)junctions are calculated as a function of temperature and the phase taking into account the roughness scattering effect at interface.The phase dependence of the Josephson current I ( φ) between s-wave and px-wave superconductor is predicted to be sin(2φ).The ferromagnet scattering effect,the barrier strength,and the roughness strength at interface suppress the dc currents in s/FI/p junction.

  10. Shock compaction of high- Tc superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Weir, S.T.; Nellis, W.J.; McCandless, P.C.; Brocious, W.F. (Lawrence Livermore National Lab., CA (USA)); Seaman, C.L.; Early, E.A.; Maple, M.B. (California Univ., San Diego, La Jolla, CA (USA). Dept. of Physics); Kramer, M.J. (Ames Lab., IA (USA)); Syono, Y.; Kikuchi, M. (Tohoku Univ., Sendai (Japan))

    1990-09-01

    We present the results of shock compaction experiments on high-{Tc} superconductors and describe the way in which shock consolidation addresses critical problems concerning the fabrication of high J{sub c} bulk superconductors. In particular, shock compaction experiments on YBa{sub 2}Cu{sub 3}O{sub 7} show that shock-induced defects can greatly increase intragranular critical current densities. The fabrication of crystallographically aligned Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8} samples by shock-compaction is also described. These experiments demonstrate the potential of the shock consolidation method as a means for fabricating bulk high-{Tc} superconductors having high critical current densities.

  11. Radiation shielding effectiveness of newly developed superconductors

    Science.gov (United States)

    Singh, Vishwanath P.; Medhat, M. E.; Badiger, N. M.; Saliqur Rahman, Abu Zayed Mohammad

    2015-01-01

    Gamma ray shielding effectiveness of superconductors with a high mass density has been investigated. We calculated the mass attenuation coefficients, the mean free path (mfp) and the exposure buildup factor (EBF). The gamma ray EBF was computed using the Geometric Progression (G-P) fitting method at energies 0.015-15 MeV, and for penetration depths up to 40 mfp. The fast-neutron shielding effectiveness has been characterized by the effective neutron removal cross-section of the superconductors. It is shown that CaPtSi3, CaIrSi3, and Bi2Sr2Ca1Cu2O8.2 are superior shielding materials for gamma rays and Tl0.6Rb0.4Fe1.67Se2 for fast neutrons. The present work should be useful in various applications of superconductors in fusion engineering and design.

  12. 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.

  13. High-temperature superconductor antenna investigations

    Science.gov (United States)

    Karasack, Vincent G.

    1990-10-01

    The use of superconductors to increase antenna radiation efficiency and gain is examined. Although the gain of all normal-metal antennas can be increased through the use of superconductors, some structures have greater potential for practical improvement than others. Some structures suffer a great degradation in bandwidth when replaced with superconductors, while for others the improvement in efficiency is trivial due to the minimal contribution of the conductor loss mechanism to the total losses, or the already high efficiency of the structure. The following antennas and related structures are discussed: electrically small antennas, impedance matching of antennas, microstrip antennas, microwave and millimeter-wave antenna arrays, and superdirective arrays. The greatest potential practical improvements occur for large microwave and millimeter-wave arrays and the impedance matching of antennas.

  14. Practical superconductor development for electrical power applications

    Energy Technology Data Exchange (ETDEWEB)

    Goretta, K.C. (comp.)

    1992-10-01

    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 the technical progress of research and development efforts aimed at producing superconducting components that are based on the Y-Ba-Cu, Bi-Sr-Ca-Cu, Bi-Pb-Sr-Ca-Cu, and (TI,Pb)-(Ba,Sr)-Ca-Cu oxide 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, fabrication and properties of thin films, and development of prototype components. Collaborations with industry and academia are documented.

  15. On n-quantum vortices in superconductors

    CERN Document Server

    Marchenko, V I

    2002-01-01

    The conditions of the n-quantum vortices observation in the superconductors are discussed. It is established in the course of calculating the coefficient by the |psi| sup 6 (psi - the order parameter) in the Ginzburg-Landau theory for the BCS standard model that the sign of this coefficient is negative. This favours the possibility of observing the n-quantum vortices in the superconductors, wherein the vortex lattice with gravitation is formed. The existence of gravitation is manifested in the magnetization finite jump in the H sub 0 = H sub c sub sup 1 field. When by the temperature change the superconductor behavior changes in such a way, that its magnetization in the H sub 0 = H sub c field reduces to the zero, than the observation of the n-quantum vortices near this transition is possible

  16. 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.

  17. AC susceptibilities of grain-textured superconductors

    Science.gov (United States)

    Sakamoto, N.; Fukuda, Y.; Koga, M.; Akune, T.; Khan, H. R.; Lüders, K.

    2008-09-01

    In-phase χ n‧ and out-phase χ n″ components of nth harmonics of AC susceptibility with measuring parameters of a DC magnetic field Bdc, an amplitude Ba and a frequency f of the superimposed AC magnetic fields give substantial information of the superconducting properties. In low- Tc metallic superconductors, χ1‧ shows smooth transition and χ1″ does single peak. High- Tc oxide superconductors with anisotropic and grain-textured structures show deformed complex characteristics. Double peaks in χ1″ and shoulders in χ1‧ appear in AC susceptibility of Hg-1223 superconductors. Instead of simple Bean model, a grained model, where the superconducting grains are immersed in weak superconducting matrix, are proposed. The susceptibilities numerically analyzed using the model show varied and deformed curves and are successfully compared with the measured results.

  18. Superconductivity-induced phononic effects in high-temperature superconductors: Raman study

    Energy Technology Data Exchange (ETDEWEB)

    Limonov, M. [Ioffe Physico-Technical Institute, Politekhnicheskaya 26, 194021 St. Petersburg (Russian Federation); Superconductivity Research Laboratory, International Superconductivity Technology Center, 10-13, Shinonome 1-Chome, Koto-ku, Tokyo 135-0062 (Japan); Lee, S.; Masui, T.; Uchiyama, H.; Tajima, S. [Superconductivity Research Laboratory, International Superconductivity Technology Center, 10-13, Shinonome 1-Chome, Koto-ku, Tokyo 135-0062 (Japan); Yamanaka, A. [Chitose Institute of Science and Technology, Chitose, Hokkaido 066-8655 (Japan)

    2004-11-01

    Raman scattering spectra of (123) and Bi-based high-temperature superconductors (HTSC) with different doping levels have been investigated. It is demonstrated that phonons in HTSC can provide unique information on energy, symmetry, temperature- and doping-dependencies of the superconducting gap and pseudogap. (copyright 2004 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  19. On the transition to the normal phase for superconductors surrounded by normal conductors

    DEFF Research Database (Denmark)

    Fournais, Søren; Kachmar, Ayman

    2009-01-01

    For a cylindrical superconductor surrounded by a normal material, we discuss transition to the normal phase of stable, locally stable and critical configurations. Associated with those phase transitions, we define critical magnetic fields and we provide a sufficient condition for which those...

  20. Neutron diffraction from the vortex lattice in the heavy-fermion superconductor UPt3

    DEFF Research Database (Denmark)

    Kleiman, R.N.; Broholm, C.; Aeppli, G.

    1992-01-01

    We have used neutron diffraction to observe the vortex lattice of UPt3. This is the first such measurement in a heavy-fermion system, a superconductor below 1 K, or in a system with such a long magnetic penetration depth (6000 +/- 75 angstrom). It also provides the first value for the pair...

  1. Atomic-scale studies of impurities in superconductors with a scanning tunneling microscope

    Energy Technology Data Exchange (ETDEWEB)

    Yazdani, A. [Illinois Univ., Urbana, IL (United States). Dept. of Physics and Materials Research Lab.

    2001-04-01

    Imaging and spectroscopy with a cryogenic scanning tunneling microscope (STM) have been used to study the local variation of electronic states on the atomic scale in both low-T{sub c} and high-T{sub c} superconductors. These experiments provide an atomic-scale perspective of impurity scattering by directly probing the localized excitations that are induced by individual impurities. (orig.)

  2. Small angle neutron diffraction studies of vortex structures in high temperature superconductors

    DEFF Research Database (Denmark)

    Cubitt, R.; Forgan, E.M.; Wylie, M.T.

    1994-01-01

    We have used neutron scattering to provide direct information about flux structures in the bulk of crystals of the superconductor Bi2Sr2CaCu2O8. Its extremely high effective mass anisotropy, makes the flux lattice susceptable to melting and also to decomposition into 'pancake' vortices, which would...

  3. Thermomagnetic phenomena in the mixed state of high temperature superconductors

    Science.gov (United States)

    Meilikhov, E. Z.

    1995-01-01

    Galvano- and thermomagnetic-phenomena in high temperature superconductors, based on kinetic coefficients, are discussed, along with a connection between the electric field and the heat flow in superconductor mixed state. The relationship that determines the transport coefficients of high temperature superconductors in the mixed state based on Seebeck and Nernst effects is developed. It is shown that this relationship is true for a whole transition region of the resistive mixed state of a superconductor. Peltier, Ettingshausen and Righi-Leduc effects associated with heat conductivity as related to high temperature superconductors are also addressed.

  4. 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.

  5. Magnetic-flux dynamics of high-Tc superconductors in weak magnetic fields

    DEFF Research Database (Denmark)

    Il’ichev, E. V.; Jacobsen, Claus Schelde

    1994-01-01

    Aspects of magnetic-flux dynamics in different types of samples of the high-temperature superconductor YBa2Cu3Ox have been investigated in magnetic fields below 1 Oe and at 77 K. The experiments were carried out in an arrangement including a field coil, a flat sample perpendicular to the field...

  6. A high-Tc superconductor bolometer for remote sensing of atmospheric OH

    NARCIS (Netherlands)

    Nivelle, de M.J.M.E.; Bruijn, M.P.; Vries, de R.; Wijnbergen, J.J.; Korte, de P.A.J.; Sanchez, S.; Elwenspoek, M.; Heidenblut, T.; Schwierzi, B.; Michalke, W.; Steinbeiss, E.; Frericks, M.

    1996-01-01

    The technological feasibility is being investigated of a high-Tc superconductor transition edge bolometer for far-infrared detection, which can meet the requirements of a Fabry-Perot based satellite instrument designed for remote sensing of atmospheric OH. These include a time constant τ<0.3 s, an o

  7. Analysis of a Superconductor: Development of a Practical Exam for the International Chemistry Olympiad

    Science.gov (United States)

    Nick, Sabine; Nather, Christian

    2007-01-01

    In July 2004 the 36th International Chemistry Olympiad was held in Kiel, Germany. Competition for medals included 236 students from 61 countries, accompanied by about 150 teachers and other mentors. During this Olympiad the students performed qualitative and quantitative analyses of a superconductor, based on lanthanum barium cuprate. In the…

  8. 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.

  9. Order parameter fluctuations in the holographic superconductor

    CERN Document Server

    Plantz, N W M; Vandoren, S

    2015-01-01

    We investigate the effect of order parameter fluctuations in the holographic superconductor. In particular, the fully backreacted spectral functions of the order parameter in both the normal and the superconducting phase are computed. We also present a vector-like large-$N$ version of the Ginzburg-Landau model that accurately describes our long-wavelength results in both phases. The large-$N$ limit of the latter model explains why the Higgs mode and the second-sound mode are not present in the spectral functions. Our results indicate that the holographic superconductor describes a relativistic multi-component superfluid in the universal regime of the BEC-BCS crossover.

  10. 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.

  11. Building blocks for correlated superconductors and magnets

    Directory of Open Access Journals (Sweden)

    J. L. Sarrao

    2015-04-01

    Full Text Available Recent efforts at Los Alamos to discover strongly correlated superconductors and hard ferromagnets are reviewed. While serendipity remains a principal engine of materials discovery, design principles and structural building blocks are beginning to emerge that hold potential for predictive discovery. Successes over the last decade with the so-called “115” strongly correlated superconductors are summarized, and more recent efforts to translate these insights and principles to novel hard magnets are discussed. While true “materials by design” remains a distant aspiration, progress is being made in coupling empirical design principles to electronic structure simulation to accelerate and guide materials design and synthesis.

  12. Building blocks for correlated superconductors and magnets

    Energy Technology Data Exchange (ETDEWEB)

    Sarrao, J. L.; Ronning, F.; Bauer, E. D.; Batista, C. D.; Zhu, J.-X.; Thompson, J. D. [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)

    2015-04-01

    Recent efforts at Los Alamos to discover strongly correlated superconductors and hard ferromagnets are reviewed. While serendipity remains a principal engine of materials discovery, design principles and structural building blocks are beginning to emerge that hold potential for predictive discovery. Successes over the last decade with the so-called “115” strongly correlated superconductors are summarized, and more recent efforts to translate these insights and principles to novel hard magnets are discussed. While true “materials by design” remains a distant aspiration, progress is being made in coupling empirical design principles to electronic structure simulation to accelerate and guide materials design and synthesis.

  13. Electromagnetic Effects in Superconductors in Gravitational Field

    CERN Document Server

    Ahmedov, B J

    2005-01-01

    The general relativistic modifications to the resistive state in superconductors of second type in the presence of a stationary gravitational field are studied. Some superconducting devices that can measure the gravitational field by its red-shift effect on the frequency of radiation are suggested. It has been shown that by varying the orientation of a superconductor with respect to the earth gravitational field, a corresponding varying contribution to AC Josephson frequency would be added by gravity. A magnetic flux (being proportional to angular velocity of rotation $\\Omega$) through a rotating hollow superconducting cylinder with the radial gradient of temperature $\

  14. Long-range spin transport in superconductors

    Energy Technology Data Exchange (ETDEWEB)

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

    2012-07-01

    Recently, there has been some controversy about spin-polarized quasiparticle transport and relaxation in superconductors, with reports of both anomalously short or anomalously long relaxation times as compared to the normal state. Here, we report on non-local transport in multiterminal superconductor-ferromagnet structures. We find signatures of spin transport over distances much larger than the normal-state spin-diffusion length in the presence of a large Zeeman splitting of the quasiparticle states. The relaxation length shows a nearly linear increase with magnetic field, hinting at a freeze-out of spin relaxation by the Zeeman splitting.

  15. Order parameter fluctuations in the holographic superconductor

    Science.gov (United States)

    Plantz, N. W. M.; Stoof, H. T. C.; Vandoren, S.

    2017-03-01

    We investigate the effect of order parameter fluctuations in the holographic superconductor. In particular, following an introduction to the concept of intrinsic dynamics and its implementation within holographic models, we compute the intrinsic spectral functions of the order parameter in both the normal and the superconducting phase, using a fully backreacted bulk geometry. We also present a vector-like large-N version of the Ginzburg–Landau model that accurately describes our long-wavelength results in both phases. Our results indicate that the holographic superconductor describes a relativistic multi-component superfluid in the universal regime of the BEC–BCS crossover.

  16. Giant supercurrent states in a superconductor-InAs/GaSb-superconductor junction

    Energy Technology Data Exchange (ETDEWEB)

    Shi, Xiaoyan, E-mail: xshi@sandia.gov; Pan, W.; Hawkins, S. D.; Klem, J. F. [Sandia National Laboratories, Albuquerque, New Mexico 87185 (United States); Yu, Wenlong; Jiang, Zhigang [School of Physics, Georgia Institute of Technology, Atlanta, Georgia 30332 (United States); Andrei Bernevig, B. [Department of Physics, Princeton University, Princeton, New Jersey 08544 (United States)

    2015-10-07

    Superconductivity in topological materials has attracted a great deal of interest in both electron physics and material sciences since the theoretical predictions that Majorana fermions can be realized in topological superconductors. Topological superconductivity could be realized in a type II, band-inverted, InAs/GaSb quantum well if it is in proximity to a conventional superconductor. Here, we report observations of the proximity effect induced giant supercurrent states in an InAs/GaSb bilayer system that is sandwiched between two superconducting tantalum electrodes to form a superconductor-InAs/GaSb-superconductor junction. Electron transport results show that the supercurrent states can be preserved in a surprisingly large temperature-magnetic field (T – H) parameter space. In addition, the evolution of differential resistance in T and H reveals an interesting superconducting gap structure.

  17. Analytical Result on the Supercurrent Through a Superconductor/Quantum-Dot/Superconductor Junction

    Institute of Scientific and Technical Information of China (English)

    LI Wei; ZHU Yu; LIN Tsung-Han

    2002-01-01

    We present an analytical result for the supercurrent across a superconductor/quantum-dot/superconductor junction. By converting the current integration into a special contour integral, we can express the current as a sum of the residues of poles. These poles are real and give a natural definition of the Andreev bound states. We also use the exact result to explain some features of the supercurrent transport behavior.

  18. Water Distribution Lines, Water distribution system details Including pumps, storage tanks, valves, and mains, Published in Not Provided, 1:600 (1in=50ft) scale, Town of Franklin.

    Data.gov (United States)

    NSGIC GIS Inventory (aka Ramona) — This Water Distribution Lines dataset, published at 1:600 (1in=50ft) scale, was produced all or in part from Field Survey/GPS information as of Not Provided. It is...

  19. Park Land and Nature Preserves, Park facilities are maintained by Johnson County Parks and Recreation Department and includes all parks with in Johnson County, Published in Not Provided, Johnson County Government.

    Data.gov (United States)

    NSGIC Local Govt | GIS Inventory — Park Land and Nature Preserves dataset current as of unknown. Park facilities are maintained by Johnson County Parks and Recreation Department and includes all parks...

  20. Fabrication mechanism of FeSe superconductors with high-energy ball milling aided sintering process

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Shengnan, E-mail: snzhang@c-nin.com [Northwest Institute for Non-Ferrous Metal Research, 710016, Xi' an (China); Liu, Jixing [Northwest Institute for Non-Ferrous Metal Research, 710016, Xi' an (China); School of Materials and Metallurgical, Northeast University, Shenyang, 110016 (China); Feng, Jianqing; Wang, Yao; Ma, Xiaobo; Li, Chengshan; Zhang, Pingxiang [Northwest Institute for Non-Ferrous Metal Research, 710016, Xi' an (China)

    2015-08-01

    FeSe Superconducting bulks with high content of superconducting PbO-type β-FeSe phase were prepared with high-energy ball milling (HEBM) aided sintering process. During this process, precursor powders with certain Fe/Se ratio were ball milled first then sintered. The influences of HEBM process as well as initial Fe/Se ratio on the phase evolution process were systematically discussed. With HEBM process and proper initial Fe/Se ratio, the formation of non-superconducting hexagonal δ-FeSe phase were effectively avoided. FeSe bulk with the critical temperature of 9.0 K was obtained through a simple one-step sintering process with lower sintering temperature. Meanwhile, the phase evolution mechanism of the HEBM precursor powders during sintering was deduced based on both the thermodynamic analysis and step-by-step sintering results. The key function of the HEBM process was to provide a high uniformity of chemical composition distribution, thus to successfully avoide the formation of intermediate product during sintering, including FeSe{sub 2} and Fe{sub 7}Se{sub 8}. Therefore, the fundamental principal for the synthesis of FeSe superconductors were concluded as: HEBM aided sintering process, with the sintering temperature of >635 °C and a slow cooling process. - Highlights: • A novel synthesis technique was developed for FeSe based superconductors. • FeSe bulks with high Tc and high β-FeSe phase content has been obtained. • Phase evolution process for the HEBM aided sintering process was proposed.

  1. p-wave superconductors in dilaton gravity

    CERN Document Server

    Fan, ZhongYing

    2013-01-01

    In this paper, we study peculiar properties of p-wave superconductors in dilaton gravity. The scale invariance of the bulk geometry is effectively broken due to the existence of dilaton. By coupling the dilaton to the non-Abelian gauge field, i.e., $-\\frac14 e^{-\\beta \\Phi} F^a_{\\mu\

  2. Stripe phases in high-temperature superconductors.

    Science.gov (United States)

    Emery, V J; Kivelson, S A; Tranquada, J M

    1999-08-03

    Stripe phases are predicted and observed to occur in a class of strongly correlated materials describable as doped antiferromagnets, of which the copper-oxide superconductors are the most prominent representatives. The existence of stripe correlations necessitates the development of new principles for describing charge transport and especially superconductivity in these materials.

  3. 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

  4. Stripe Phases in High-Temperature Superconductors

    Science.gov (United States)

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

    1999-08-01

    Stripe phases are predicted and observed to occur in a class of strongly correlated materials describable as doped antiferromagnets, of which the copper-oxide superconductors are the most prominent representatives. The existence of stripe correlations necessitates the development of new principles for describing charge transport and especially superconductivity in these materials.

  5. 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...

  6. Noncontact Measurement Of Critical Current In Superconductor

    Science.gov (United States)

    Israelsson, Ulf E.; Strayer, Donald M.

    1992-01-01

    Critical current measured indirectly via flux-compression technique. Magnetic flux compressed into gap between superconductive hollow cylinder and superconductive rod when rod inserted in hole in cylinder. Hall-effect probe measures flux density before and after compression. Method does not involve any electrical contact with superconductor. Therefore, does not cause resistive heating and consequent premature loss of superconductivity.

  7. 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.).

  8. Technological Evolution of High Temperature Superconductors

    Science.gov (United States)

    2015-12-01

    power level would reach 250 kilowatts in a joint Navy-Advanced Research Projects Agency (the fore- runner to the Defense Advanced Research Projects...A1 2/22/2007 Method and apparatus for cooling a blade server H01L 021/66 US- 20060283620 A1 American Superconductor Corporation (United States

  9. Towards Structural Testing of Superconductor Electronics

    NARCIS (Netherlands)

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

    2003-01-01

    Many of the semiconductor technologies are already facing limitations while new-generation data and telecommunication systems are implemented. Although in its infancy, superconductor electronics (SCE) is capable of handling some of these high-end tasks. We have started a defect-oriented test

  10. Phonon dispersions and Fermi surfaces nesting explaining the variety of charge ordering in titanium-oxypnictides superconductors

    Science.gov (United States)

    Nakano, Kousuke; Hongo, Kenta; Maezono, Ryo

    2016-01-01

    There has been a puzzle between experiments and theoretical predictions on the charge ordering of layered titanium-oxypnictides superconductors. Unconventional mechanisms to explain this discrepancy have been argued so far, even affecting the understanding of superconductivity on the compound. We provide a new theoretical prediction, by which the discrepancy itself is resolved without any complicated unconventional explanation. Phonon dispersions and changes of nesting vectors in Fermi surfaces are clarified to lead to the variety of superlattice structures even for the common crystal structures when without CDW, including orthorhombic 2 × 2 × 1 one for BaTi2As2O, which has not yet been explained successfully so far, being different from tetragonal for BaTi2Sb2O and BaTi2Bi2O. The electronic structure analysis can naturally explain experimental observations about CDW including most latest ones without any cramped unconventional mechanisms. PMID:27430418

  11. Angle-Resolved Photoemission Spectroscopy on Electronic Structure and Electron-Phonon Coupling in Cuprate Superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, X.J.

    2010-04-30

    In addition to the record high superconducting transition temperature (T{sub c}), high temperature cuprate superconductors are characterized by their unusual superconducting properties below T{sub c}, and anomalous normal state properties above T{sub c}. In the superconducting state, although it has long been realized that superconductivity still involves Cooper pairs, as in the traditional BCS theory, the experimentally determined d-wave pairing is different from the usual s-wave pairing found in conventional superconductors. The identification of the pairing mechanism in cuprate superconductors remains an outstanding issue. The normal state properties, particularly in the underdoped region, have been found to be at odd with conventional metals which is usually described by Fermi liquid theory; instead, the normal state at optimal doping fits better with the marginal Fermi liquid phenomenology. Most notable is the observation of the pseudogap state in the underdoped region above T{sub c}. As in other strongly correlated electrons systems, these unusual properties stem from the interplay between electronic, magnetic, lattice and orbital degrees of freedom. Understanding the microscopic process involved in these materials and the interaction of electrons with other entities is essential to understand the mechanism of high temperature superconductivity. Since the discovery of high-T{sub c} superconductivity in cuprates, angle-resolved photoemission spectroscopy (ARPES) has provided key experimental insights in revealing the electronic structure of high temperature superconductors. These include, among others, the earliest identification of dispersion and a large Fermi surface, an anisotropic superconducting gap suggestive of a d-wave order parameter, and an observation of the pseudogap in underdoped samples. In the mean time, this technique itself has experienced a dramatic improvement in its energy and momentum resolutions, leading to a series of new discoveries not

  12. Analytical Computation of Critical Exponents in Several Holographic Superconductors

    CERN Document Server

    Zeng, Hua-Bi; Jiang, Yu; Zong, Hong-Shi

    2010-01-01

    It is very interesting that all holographic superconductors like $s$-wave, $p$-wave and $d$-wave holographic superconductors shows the universal mean-field critical exponent $1/2$ at the critical temperature just like Gindzburg-Landau (G-L) theory for second order phase transitions. Now it is believed that the universal critical exponents appear since the dual gravity theory is classic in the large $N$ limit. However, there is an exception called "non-mean-field theory" even in the large $N$ limit: An extension of the $s$-wave model with a cubic term of the charged scalar field provides a different critical exponent $1$. In this paper, we try to use analytical calculation to get the critical exponents for these models to see how these properties of the gravity action decides the appearance of the mean-field or "non-mean-field" behaviors. It will be seen that like the G-L theory, it is the fundamental symmetries rather than the detail parameters of the bulk theory result in the universal properties of the holo...

  13. Bringing Superconductor Digital Technology to the Market Place

    Science.gov (United States)

    Nisenoff, Martin

    The unique properties of superconductivity can be exploited to provide the ultimate in electronic technology for systems such as ultra-precise analogue-to-digital and digital-to-analogue converters, precise DC and AC voltage standards, ultra high speed logic circuits and systems (both digital and hybrid analogue-digital systems), and very high throughput network routers and supercomputers which would have superior electrical performance at lower overall electrical power consumption compared to systems with comparable performance which are fabricated using conventional room temperature technologies. This potential for high performance electronics with reduced power consumption would have a positive impact on slowing the increase in the demand for electrical utility power by the information technology community on the overall electrical power grid. However, before this technology can be successfully brought to the commercial market place, there must be an aggressive investment of resources and funding to develop the required infrastructure needed to yield these high performance superconductor systems, which will be reliable and available at low cost. The author proposes that it will require a concerted effort by the superconductor and cryogenic communities to bring this technology to the commercial market place or make it available for widespread use in scientific instrumentation.

  14. Infrared pseudogap in cuprate and pnictide high-temperature superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Moon, S. J. [University of California; Lee, Y. S. [University of California; Schafgans, A. A. [University of California; Chubukov, A. V. [Universsity of Wisconsin - Madison; Kasahara, S. [Kyoto University; Shibauchi, T. [Kyoto University; Terashima, T. [Kyoto University; Matsuda, Y. [Kyoto University; Tanatar, M. A. [Ames Laboratory; Prozorov, R. [Ames Laboratory; Thaler, A. [Ames Laboratory; Canfield, Paul C. [Ames Laboratory; Bud' ko, Sergey L. [Ames Laboratory; Sefat, A. S. [Oak Ridge National Laboratory; Mandrus, D. [Oak Ridge National Laboratory; Segawa, K. [Osaka University; Ando, Y. [Osaka University; Basov, D. N. [University of California

    2014-07-01

    We investigate infrared manifestations of the pseudogap in the prototypical cuprate and pnictide superconductors, YBa2Cu3Oy and BaFe2As2 (Ba122) systems. We find remarkable similarities between the spectroscopic features attributable to the pseudogap in these two classes of superconductors. The hallmarks of the pseudogap state in both systems include a weak absorption feature at about 500cm-1 followed by a featureless continuum between 500 and 1500cm-1 in the conductivity data and a significant suppression in the scattering rate below 700–900 cm-1. The latter result allows us to identify the energy scale associated with the pseudogap ΔPG. We find that in the Ba122-based materials the superconductivity-induced changes of the infrared spectra occur in the frequency region below 100–200 cm-1, which is much lower than the energy scale of the pseudogap. We performed theoretical analysis of the scattering rate data of the two compounds using the same model, which accounts for the effects of the pseudogap and electron-boson coupling. We find that the scattering rate suppression in Ba122-based compounds below ΔPG is solely due to the pseudogap formation, whereas the impact of the electron-boson coupling effects is limited to lower frequencies. The magnetic resonance modes used as inputs in our modeling are found to evolve with the development of the pseudogap, suggesting an intimate correlation between the pseudogap and magnetism

  15. Emerging Trends in Topological Insulators and Topological Superconductors

    Indian Academy of Sciences (India)

    A M Jayannavar; Arijit Saha

    2017-08-01

    Topological insulators are new class of materials which arecharacterized by a bulk band gap like ordinary band insulatorsbut have protected conducting states on their edgesor surfaces. These states emerge due to the combination ofspin-orbit coupling and time reversal symmetry. Also, thesestates are insensitive to scattering by non-magnetic impurities.A two-dimensional topological insulator has one dimensionaledge states in which the spin-momentum locking ofthe electrons give rise to quantum spin Hall effect. A threedimensionaltopological insulator supports novel spin-polarized2D Dirac fermions on its surface. These topological insulatormaterials have been theoretically predicted and experimentallyobserved in a variety of 2D and 3D systems, includingHgTe quantum wells, BiSb alloys, and Bi2Te3, Bi2Se3 crystals.Moreover, proximity induced superconductivity in these systemscan lead to a state that supports zero energy Majoranafermions, and the phase is known as topological superconductors.In this article, the basic idea of topological insulatorsand topological superconductors are presented alongwith their experimental development.

  16. Conformal phase transition as a new perspective on conventional superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Nogueira, Flavio [Theoretische Physik III, Ruhr-Universitaet Bochum (Germany); Sudbo, Asle [Dept. of Physics, Norwegian University of Science and Technology (Norway)

    2015-07-01

    We argue that the phase transition in strong type I superconductors features charged fluctuations, meaning that it is essentially driven by thermal fluctuations of the magnetic field. This is simply a consequence of the small value of the Ginzburg parameter in the deep type I regime. We substantiate this conclusion by a generalization of the Ginzburg criterion to include charged fluctuations. Finally, we demonstrate by means of a renormalization group analysis that the correlation length actually does not obey a power law as function of T-T{sub c}. Rather it features an essential singularity at T{sub c}, which is characteristic of a so called conformal phase transition, one known example of it being the Berezinski-Kosterliz-Thouless (BKT) phase transition in two-dimensional superfluids. We argue that a similar behavior happens in three-dimensional strongly type I superconductors. One important prediction from our theory that may be tested experimentally by microwave measurement is a universal discontinuous jump in the superfluid density.

  17. Gate-tuned Superconductor-Insulator transition in (Li,Fe)OHFeSe

    OpenAIRE

    Lei, B; Xiang, Z. J.; Lu, X. F.; Wang, N. Z.; Chang, J. R.; Shang, C.; Luo, X. G.; Wu, T.; Z. Sun; Chen, X. H.

    2015-01-01

    The antiferromagnetic(AFM) insulator-superconductor transition has been always a center of interest in the underlying physics of unconventional superconductors. The quantum phase transition between Mott insulator with AFM and superconductor can be induced by doping charge carriers in high-Tc cuprate superconductors. For the best characterized organic superconductors of k-(BEDT-TTF)2X (X=anion), a first order transition between AFM insulator and superconductor can be tuned by applied external ...

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

    Directory of Open Access Journals (Sweden)

    Yeping Jiang

    2016-04-01

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

  19. Superconductor Magnetization Modeling for the Numerical Calculation of Field Errors in Accelerator Magnets

    CERN Document Server

    Völlinger, C

    2002-01-01

    Superconducting magnets are obligatory today in order to provide the high magnetic fields that are needed for the acceleration of heavy particles in particle accelerators. The coils of such magnets are made of type II superconducting material and are exposed to a changing magnetic field which induces a so-called persistent current. Persistent currents are bipolar screening currents that do not decay, but persist due to the lack of resistivity in the superconductor. This way, they are the source of a superconductor magnetization in the coil which disturbs the field quality in the magnet aperture. In the framework of this thesis, a macroscopic superconductor model for the calculation of the magnetization of a thin superconducting cylinder of type II material has been developed. The model considers the dependency of the induced current density on the applied field as well as the local distribution of the magnetic induction within the superconductor. Both, the one-dimensional case of a homogeneous change of an ex...

  20. Electronic structure Fermi liquid theory of high T(sub c) superconductors: Comparison with experiments

    Science.gov (United States)

    Freeman, A. J.; Yu, Jaejun

    1990-01-01

    For years, there has been controversy on whether the normal state of the Cu-oxide superconductors is a Fermi liquid or some other exotic ground state. However, some experimentalists are clarifying the nature of the normal state of the high T(sub c) superconductors by surmounting the experimental difficulties in producing clean, well characterized surfaces so as to obtain meaningful high resolved photoemission data, which agrees with earlier positron-annihilation experiments. The experimental work on high resolution angle resolved photoemission by Campuzano et al. and positron-annihilation studies by Smedskjaer et al. has verified the calculated Fermi surfaces in YBa2Cu3O7 superconductors and has provided evidence for the validity of the energy band approach. Similar good agreement was found for Bi2Sr2CaCu2O8 by Olson et al. As a Fermi liquid (metallic) nature of the normal state of the high T(sub c) superconductors becomes evident, these experimental observations have served to confirm the predictions of the local density functional calculations and hence the energy band approach as a valid natural starting point for further studies of their superconductivity.

  1. EDITORIAL: Focus on Superconductors with Exotic Symmetries FOCUS ON SUPERCONDUCTORS WITH EXOTIC SYMMETRIES

    Science.gov (United States)

    Rice, T. Maurice; Sigrist, Manfred; Maeno, Yoshiteru

    2009-05-01

    Superconductors can usefully be divided into two classes, those that are well described by the classic Bardeen-Cooper-Schrieffer (BCS) theory and its extensions and those which require a different microscopic description. The BCS theory of superconductivity solved the long standing mystery of this spectacular phenomenon and described all superconductors that were known when it was formulated in the 1950s. The key ingredient is an attractive interaction generated by the exchange of phonons between electrons which overcomes a Coulomb repulsion weakened by screening, to give a net attractive force on the low energy scale. In this case the simplest s-wave pairing always maximises the energy gain. There were speculations a little later that other types of electron pairing could be possible, but it took a quarter of a century until the first signs of superconductors with different and exotic pairing appeared. In the intervening thirty years many superconductors with exotic pairing have been and continue to be discovered and the study of their superconductivity has grown into a major subfield of condensed matter physics today. The importance of these exotic superconductors with unconventional symmetry is that their pairing is of electronic origin. As a result they are freed from the restrictions of low transition temperatures that go along with the phonon driven conventional superconductors. However in two of the main classes of the exotic superconductors, namely heavy fermion and organic superconductors, the intrinsic energy scales are very small leading to low temperature scales. The third class contains the small number of superconducting transition metal compounds with exotic pairing symmetry. The most studied of these are the high-Tc cuprates, the newly discovered iron pnictides and strontium ruthenate which is closely related to superfluid 3He. Although the basic electronic structure of these materials is well understood, the origin of the pairing is more complex

  2. Ginzburg-Landau theory of dirty two band s(+/-) superconductors.

    Science.gov (United States)

    Ng, Tai-Kai

    2009-12-04

    In this Letter, we study the effect of nonmagnetic impurities on two-band superconductors by deriving the corresponding Ginzburg-Landau equation. Depending on the strength of (impurity-induced) interband scattering, we find that there are two distinctive regions where the superconductors behave very differently. In the strong impurity-induced interband scattering regime T(c) band, the two-band superconductor behaves as an effective one-band dirty superconductor. In the other limit T(c) > or = tau(t)(-1), the dirty two-band superconductor is described by a network of frustrated two-band superconductor grains connected by Josephson tunneling junctions, and the Anderson theorem breaks down.

  3. Shiba chains of scalar impurities on unconventional superconductors

    Science.gov (United States)

    Neupert, Titus; Yazdani, A.; Bernevig, B. Andrei

    2016-03-01

    We show that a chain of nonmagnetic impurities deposited on a fully gapped two- or three-dimensional superconductor can become a topological one-dimensional superconductor with protected Majorana bound states at its end. A prerequisite is that the pairing potential of the underlying superconductor breaks the spin-rotation symmetry, as it is generically the case in systems with strong spin-orbit coupling. We illustrate this mechanism for a spinless triplet-superconductor (px+i py ) and a time-reversal symmetric Rashba superconductor with a mixture of singlet and triplet pairing. For the latter, we show that the impurity chain can be topologically nontrivial even if the underlying superconductor is topologically trivial.

  4. Striped superconductors: how spin, charge and superconducting orders intertwine in the cuprates

    Energy Technology Data Exchange (ETDEWEB)

    Berg, Erez; Kivelson, Steven A [Department of Physics, Stanford University, Stanford, CA 94305-4060 (United States); Fradkin, Eduardo [Department of Physics, University of Illinois at Urbana-Champaign, Urbana, IL 61801-3080 (United States); Tranquada, John M [Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, NY 11973-5000 (United States)], E-mail: kivelson@stanford.edu

    2009-11-15

    Recent transport experiments in the original cuprate high temperature superconductor, La{sub 2-x}Ba{sub x}CuO{sub 4}, have revealed a remarkable sequence of transitions and crossovers that give rise to a form of dynamical dimensional reduction, in which a bulk crystal becomes essentially superconducting in two directions while it remains poorly metallic in the third. We identify these phenomena as arising from a distinct new superconducting state, the 'striped superconductor', in which the superconducting order is spatially modulated, so that its volume average value is zero. Here, in addition to outlining the salient experimental findings, we sketch the order parameter theory of the state, stressing some of the ways in which a striped superconductor differs fundamentally from an ordinary (uniform) superconductor, especially concerning its response to quenched randomness. We also present the results of density matrix renormalization group calculations on a model of interacting electrons in which sign oscillations of the superconducting order are established. Finally, we speculate concerning the relevance of this state to experiments in other cuprates, including recent optical studies of La{sub 2-x}Sr{sub x}CuO{sub 4} in a magnetic field, neutron scattering experiments in underdoped YBa{sub 2}Cu{sub 3}O{sub 6+x} and a host of anomalies seen in STM and ARPES studies of Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8+{delta}}.

  5. Striped superconductors: how spin, charge and superconducting orders intertwine in the cuprates

    Science.gov (United States)

    Berg, Erez; Fradkin, Eduardo; Kivelson, Steven A.; Tranquada, John M.

    2009-11-01

    Recent transport experiments in the original cuprate high temperature superconductor, La2-xBaxCuO4, have revealed a remarkable sequence of transitions and crossovers that give rise to a form of dynamical dimensional reduction, in which a bulk crystal becomes essentially superconducting in two directions while it remains poorly metallic in the third. We identify these phenomena as arising from a distinct new superconducting state, the 'striped superconductor', in which the superconducting order is spatially modulated, so that its volume average value is zero. Here, in addition to outlining the salient experimental findings, we sketch the order parameter theory of the state, stressing some of the ways in which a striped superconductor differs fundamentally from an ordinary (uniform) superconductor, especially concerning its response to quenched randomness. We also present the results of density matrix renormalization group calculations on a model of interacting electrons in which sign oscillations of the superconducting order are established. Finally, we speculate concerning the relevance of this state to experiments in other cuprates, including recent optical studies of La2-xSrxCuO4 in a magnetic field, neutron scattering experiments in underdoped YBa2Cu3O6+x and a host of anomalies seen in STM and ARPES studies of Bi2Sr2CaCu2O8+δ.

  6. Peculiar long-range supercurrent in superconductor-ferromagnet-superconductor junction containing a noncollinear magnetic domain in the ferromagnetic region

    Energy Technology Data Exchange (ETDEWEB)

    Meng, Hao, E-mail: menghao1982@shu.edu.cn [School of Physics and Telecommunication Engineering, Shaanxi University of Technology, Hanzhong 723001 (China); National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, Nanjing 210093 (China); Wu, Xiuqiang [National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, Nanjing 210093 (China); Ren, Yajie [School of Physics and Telecommunication Engineering, Shaanxi University of Technology, Hanzhong 723001 (China)

    2015-01-14

    We study the supercurrent in clean superconductor-ferromagnet-superconductor heterostructure containing a noncollinear magnetic domain in the ferromagnetic region. It is demonstrated that the magnetic domain can lead to a spin-flip scattering process, which reverses the spin orientations of the singlet Cooper pair and simultaneously changes the sign of the corresponding electronic momentum. If the ferromagnetic layers on both sides of magnetic domain have the same features, the long-range proximity effect will take place. That is because the singlet Cooper pair will create an exact phase-cancellation effect and gets an additional π phase shift as it passes through the entire ferromagnetic region. Then, the equal spin triplet pair only exists in the magnetic domain region and can not diffuse into the other two ferromagnetic layers. So, the supercurrent mostly arises from the singlet Cooper pairs, and the equal spin triplet pairs are not involved. This result can provide a approach for generating the long-range supercurrent.

  7. 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.

  8. 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.

  9. Search for New and Better High Temperature Superconductors

    Science.gov (United States)

    2014-03-30

    AFRL-OSR-VA-TR-2015-0096 (MURI 09) TOWARDS NEW AND BETTER HIGH TEMPERATURE SUPERCONDUCTORS Malcolm Beasley LELAND STANFORD JUNIOR UNIV CA Final...Search for New and Better High Temperature Superconductors 5a. CONTRACT NUMBER 5b. GRANT NUMBER FA9550-09-1-0583 5c. PROGRAM ELEMENT NUMBER 6...SUPPLEMENTARY NOTES 14. ABSTRACT This program was focused on an integrated search for new superconductors in material systems with perceived

  10. Andreev Spectra and Subgap Bound States in Multiband Superconductors

    OpenAIRE

    Golubov, A. A.; Brinkman, A.; Tanaka, Yukio; Mazin, I.I.; Dolgov, O. V.

    2009-01-01

    The theory of Andreev conductance is formulated for junctions involving normal metals (N) and multiband superconductors (S) and applied to the case of superconductors with nodeless extended $s_{\\pm}$-wave order parameter symmetry, as possibly realized in the recently discovered ferro pnictides. We find qualitative differences from tunneling into s-wave or d-wave superconductors that may help to identify such a state. First, interband interference leads to a suppression of Andreev reflection i...

  11. Conductance of d-wave superconductor/normal metal/d-wave superconductor junctions

    Science.gov (United States)

    Pesin, Dmytro; Andreev, Anton; Spivak, Boris

    2008-03-01

    We develop a theory of the low-temperature conductance of superconductor/normal metal/superconductor junctions in which the superconductors have d-wave pairing symmetry. We show that at low temperatures the conductance of the junction is determined by the inelastic relaxation time of quasiparticles in the bulk of d-wave superconductors, GDND√&(d)circ;ɛ. Thus it greatly exceeds the conductance of the normal metal part of the junction, which is controlled by the elastic mean free path. This dependence of GDND on the inelastic relaxation time should be contrasted with that of the low-temperature conductance of the junction in the case of the s- wave superconductor leads, GSNS. In the latter case the conductance is proportional to the first power of the inelastic electron relaxation time in the normal metal part of the junction, GSNSτɛ^(n) [1]. [1] S. V. Lempitskii, Sov. Phys. JETP 58, 624 (1983); U. Gunsenheimer and A. D. Zaikin, Phys. Rev. B50, 6317 (1994); F. Zhou and B. Spivak, JETP Lett. 65, 369 (1997).

  12. A modified beam stiffness matrix for superconductor elements

    Energy Technology Data Exchange (ETDEWEB)

    Gori, R.; Schrefler, B.A. (Padua Univ. (Italy). Ist. di Scienza e Tecnica delle Costruzioni)

    1989-10-01

    The components of the stiffness matrix of superconductor elements are derived taking into account the effects of the wrapping of superconductor strands around the internal insulating strip and of possible stabilizing profiles around conductor core. It is already known that the inclination of the strands referred to the longitudinal axis of the superconductor produces a reduction of the axial stiffness and a considerable increase in torsional stiffness. Here also the effects of bending are taken into account, completing hence the previous investigation. Examples relating to superconductors proposed for the Toroidal Field Coil of the Next European Torus are shown. In that instance the strand transposition is carried out by roebling. (orig.).

  13. Structural and Chemical Diversity of Tl-Based Cuprate Superconductors

    Institute of Scientific and Technical Information of China (English)

    信赢

    2003-01-01

    The Tl-based cuprate superconductor family is the largest family in crystal structure and chemical composition among all high Tc cuprate superconductors. The Tl family can be divided into two sub-families, the Tl single layer family and the Tl double layer family, based on their crystal structural characteristics. The Tl single layer family is an ideal material for investigating the evolution of crystalline formation, charge carrier density, chemical composition, transport properties, superconductivity and their relationships. The Tl family contains almostall possible crystal structures discovered in high-Tc cuprate superconductors. Tl cuprate superconductors are of great importance not only in studying high-temperature superconductivity but also in commercial applications.

  14. 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.

  15. Application of High Temperature Superconductors to Accelerators

    CERN Document Server

    Ballarino, A

    2000-01-01

    Since the discovery of high temperature superconductivity, a large effort has been made by the scientific community to investigate this field towards a possible application of the new oxide superconductors to different devices like SMES, magnetic bearings, flywheels energy storage, magnetic shielding, transmission cables, fault current limiters, etc. However, all present day large scale applications using superconductivity in accelerator technology are based on conventional materials operating at liquid helium temperatures. Poor mechanical properties, low critical current density and sensitivity to the magnetic field at high temperature are the key parameters whose improvement is essential for a large scale application of high temperature superconductors to such devices. Current leads, used for transferring currents from the power converters, working at room temperature, into the liquid helium environment, where the magnets are operating, represent an immediate application of the emerging technology of high t...

  16. Method for fabrication of high temperature superconductors

    Science.gov (United States)

    Balachandran, Uthamalingam; Ma, Beihai; Miller, Dean

    2009-07-14

    A layered article of manufacture and a method of manufacturing same is disclosed. A substrate has a biaxially textured MgO crystalline layer having the c-axes thereof inclined with respect to the plane of the substrate deposited thereon. A layer of one or more of YSZ or Y.sub.2O.sub.3 and then a layer of CeO.sub.2 is deposited on the MgO. A crystalline superconductor layer with the c-axes thereof normal to the plane of the substrate is deposited on the CeO.sub.2 layer. Deposition of the MgO layer on the substrate is by the inclined substrate deposition method developed at Argonne National Laboratory. Preferably, the MgO has the c-axes thereof inclined with respect to the normal to the substrate in the range of from about 10.degree. to about 40.degree. and YBCO superconductors are used.

  17. A Fifth Force: Generalized through Superconductors

    Science.gov (United States)

    Robertson, Glen A.

    1999-01-01

    The connection between the Biefield-Brown Effect, the recent repeat of the 1902 Trouton-Noble (TN) experiments, and the gravity shielding experiments was explored. This connection is visualized through high capacitive electron concentrations. From this connection, a theory is proposed that connects mass energy to gravity and a fifth force. The theory called the Gravi-Atomic Energy theory presents two new terms: Gravi-atomic energy and quantum vacuum pressure (QVP). Gravi-atomic energy is defined as the radiated mass energy, which acts on vacuum energy to create a QVP about a mass, resulting in gravity and the fifth force. The QVP emission from a superconductor was discussed followed by the description of a test for QVP from a superconductor using a Cavendish balance.

  18. Abrikosov Gluon Vortices in Color Superconductors

    CERN Document Server

    Ferrer, Efrain J

    2010-01-01

    In this talk I will discuss how the in-medium magnetic field can influence the gluon dynamics in a three-flavor color superconductor. It will be shown how at field strengths comparable to the charged gluon Meissner mass a new phase can be realized, giving rise to Abrikosov's vortices of charged gluons. In that phase, the inhomogeneous gluon condensate anti-screens the magnetic field due to the anomalous magnetic moment of these spin-1 particles. This paramagnetic effect can be of interest for astrophysics, since due to the gluon vortex antiscreening mechanism, compact stars with color superconducting cores could have larger magnetic fields than neutron stars made up entirely of nuclear matter. I will also discuss a second gluon condensation phenomenon connected to the Meissner instability attained at moderate densities by two-flavor color superconductors. In this situation, an inhomogeneous condensate of charged gluons emerges to remove the chromomagnetic instability created by the pairing mismatch, and as a ...

  19. Phases of holographic d-wave superconductor

    CERN Document Server

    Krikun, Alexander

    2015-01-01

    We study different phases in the holographic model of d-wave superconductor. These are described by solutions to the classical equations of motion found in different ansatze. Apart from the known homogeneous d-wave superconducting phase we find three new solutions. Two of them represent two distinct families of the spatially modulated solutions, which realize the charge density wave phases in the dual theory. The third one is the new homogeneous phase with nonzero anapole moment. These phases are relevant to the physics of cuprate high-Tc superconductor in pseudogap region. While the d-wave phase preserves translation, parity and time reversal symmetry, the striped phases break translations spontaneously. Parity and time-reversal are preserved when combined with discrete half-periodic shift of the wave. In anapole phase translation symmetry is preserved, but parity and time reversal are spontaneously broken. All of the considered solutions brake the global $U(1)$. Thermodynamical treatment shows that in the s...

  20. Electronic structure of Fe-based superconductors

    Indian Academy of Sciences (India)

    Kalobaran Maiti

    2015-06-01

    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 role of states in their electronic properties, which is significantly different from the cuprate superconductors. In this article, some of our studies of the electronic structure of these fascinating systems employing high-resolution photoemission spectroscopy is reviewed. The combined effect of electron correlation and covalency reveals an interesting scenario in their electronic structure. The contribution of ligand states at the Fermi level is found to be much more significant than indicated in earlier studies. Temperature evolution of the energy bands reveals the signature of transition akin to Lifshitz transition in these systems.

  1. Shot Noise in Ferromagnetic Superconductor Tunnel Junctions

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    In this paper, the superconducting order parameter and the energy spectrum of the Bogoliubov excitations are obtained from the Bogoliubov-de Gennes (BdG) equation for a ferromagnetic superconductor (FS). Taking into account the rough interface scattering effect, we calculate the shot noise and the differential conductance of the normal- metal insulator ferromagnetic superconductor junction. It is shown that the exchange energy Eh in FS can lead to splitting of the differential shot noise peaks and the conductance peaks. The energy difference between the two splitting peaks is equal to 2Eh. The rough interface scattering strength results in descent of conductance peaks and the shot noise-to-current ratio but increases the shot noise.

  2. Magnetic chains on a triplet superconductor.

    Science.gov (United States)

    Sacramento, P D

    2015-11-11

    The topological state of a two-dimensional triplet superconductor may be changed by an appropriate addition of magnetic impurities. A ferromagnetic magnetic chain at the surface of a superconductor with spin-orbit coupling may eliminate the edge states of a finite system giving rise to localized zero modes at the edges of the chain. The coexistence/competition between the two types of zero modes is considered. The reduction of the system to an effective 1d system gives partial information on the topological properties but the study of the two sets of zero modes requires a two-dimensional treatment. Increasing the impurity density from a magnetic chain to magnetic islands leads to a finite Chern number. At half-filling small concentrations are enough to induce chiral modes.

  3. Asymmetric Ferromagnet-Superconductor-Ferromagnet Switch

    Energy Technology Data Exchange (ETDEWEB)

    Cadden-Zimansky, P.; Bazaliy, Ya.B.; Litvak, L.M.; Jiang, J.S.; Pearson, J.; Gu, J.Y.; You, Chun-Yeol; Beasley, M.R.; Bader, S.D.

    2011-11-04

    In layered ferromagnet-superconductor-ferromagnet F{sub 1} /S/F{sub 2} structures, the critical temperature T{sub c} of the superconductors depends on the magnetic orientation of the ferromagnetic layers F{sub 1} and F{sub 2} relative to each other. So far, the experimentally observed magnitude of change in T{sub c} for structures utilizing weak ferromagnets has been 2 orders of magnitude smaller than is expected from calculations. We theoretically show that such a discrepancy can result from the asymmetry of F/S boundaries, and we test this possibility by performing experiments on structures where F{sub 1} and F{sub 2} are independently varied. Our experimental results indicate that asymmetric boundaries are not the source of the discrepancy. If boundary asymmetry is causing the suppressed magnitude of T{sub c} changes, it may only be possible to detect in structures with thinner ferromagnetic layers.

  4. Unconventional Disorder Effects in Correlated Superconductors

    Science.gov (United States)

    Gastiasoro, Maria N.; Bernardini, Fabio; Andersen, Brian M.

    2016-12-01

    We study the effects of disorder on unconventional superconductors in the presence of correlations, and explore a novel correlated disorder paradigm dominated by strong deviations from standard Abrikosov-Gor'kov theory due to generation of local bound states and cooperative impurity behavior driven by Coulomb interactions. Specifically we explain under which circumstances magnetic disorder acts as a strong poison destroying high-Tc superconductivity at the sub-1% level, and when nonmagnetic disorder, counterintuitively, hardly affects the unconventional superconducting state while concomitantly inducing an inhomogeneous full-volume magnetic phase. Recent experimental studies of Fe-based superconductors have discovered that such unusual disorder behavior seems to be indeed present in those systems.

  5. Very General Holographic Superconductors and Entanglement Thermodynamics

    CERN Document Server

    Dey, Anshuman; Sarkar, Tapobrata

    2014-01-01

    We construct and analyze holographic superconductors with generalized higher derivative couplings, in single R-charged black hole backgrounds in four and five dimensions. These systems, which we call very general holographic superconductors, have multiple tuning parameters and are shown to exhibit a rich phase structure. We establish the phase diagram numerically as well as by computing the free energy, and then validated the results by calculating the entanglement entropy for these systems. The entanglement entropy is shown to be a perfect indicator of the phase diagram. The differences in the nature of the entanglement entropy in R-charged backgrounds compared to the AdS-Schwarzschild cases are pointed out. We also compute the analogue of the entangling temperature for a subclass of these systems and compare the results with non-hairy backgrounds.

  6. Revisiting holographic superconductors with hyperscaling violation

    Energy Technology Data Exchange (ETDEWEB)

    Pan, Qiyuan [Universidade de Sao Paulo, Instituto de Fisica, C.P. 66318, Sao Paulo (Brazil); Hunan Normal University, Department of Physics, Key Laboratory of Low Dimensional Quantum Structures and Quantum Control of Ministry of Education, Changsha, Hunan (China); Institute of Theoretical Physics, Chinese Academy of Sciences, State Key Laboratory of Theoretical Physics, Beijing (China); Zhang, Shao-Jun [Universidade de Sao Paulo, Instituto de Fisica, C.P. 66318, Sao Paulo (Brazil)

    2016-03-15

    We investigate the effect of the hyperscaling violation on the holographic superconductors. In the s-wave model, we find that the critical temperature decreases first and then increases as the hyperscaling violation increases, and the mass of the scalar field will not modify the value of the hyperscaling violation which gives the minimum critical temperature. We analytically confirm the numerical results by using the Sturm-Liouville method with the higher order trial function and improve the previous findings in Fan (J High Energy Phys 09:048, 2013). However, different from the s-wave case, we note that the critical temperature decreases with the increase of the hyperscaling violation in the p-wave model. In addition, we observe that the hyperscaling violation affects the conductivity of the holographic superconductors and changes the expected relation in the gap frequency in both s-wave and p-wave models. (orig.)

  7. Spin and quadrupolar orders in the spin-1 bilinear-biquadratic model for iron-based superconductors

    Science.gov (United States)

    Luo, Cheng; Datta, Trinanjan; Yao, Dao-Xin

    2016-06-01

    Motivated by the recent experimental and theoretical progress of the magnetic properties in iron-based superconductors, we provide a comprehensive analysis of the extended spin-1 bilinear-biquadratic (BBQ) model on the square lattice. Using a variational approach at the mean-field level, we identify the existence of various magnetic phases, including conventional spin dipolar orders (ferro- and antiferromagnet), novel quadrupolar orders (spin nematic), and mixed dipolar-quadrupolar orders. In contrast to the regular Heisenberg model, the elementary excitations of the spin-1 BBQ model are described by the SU(3) flavor-wave theory. By fitting the experimental spin-wave dispersion, we determine the refined exchange couplings corresponding to the collinear antiferromagnetic iron pnictides. We also present the dynamic structure factors of both spin dipolar and quadrupolar components with connections to the future experiments.

  8. Flywheel energy storage with superconductor magnetic bearings

    Energy Technology Data Exchange (ETDEWEB)

    Weinberger, Bernard R. (Avon, CT); Lynds, Jr., Lahmer (Glastonbury, CT); Hull, John R. (Hinsdale, IL)

    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.

  9. Scale dependent superconductor-insulator transition

    OpenAIRE

    D. Kowal; Ovadyahu, Z.

    2007-01-01

    We study the disorder driven superconductor to insulator transition in amorphous films of high carrier-concentration indium-oxide. Using thin films with various sizes and aspect ratios we show that the `critical' sheet-resistance $R_{{\\small \\square}}$ depends systematically on sample geometry; superconductivity disappears when $R_{{\\small \\square}}$ exceeds $\\approx6 $k$\\Omega$ in large samples. On the other hand, wide and sufficiently short samples of the same batch exhibit superconductivit...

  10. Magnetic impurities in spin-split superconductors

    Science.gov (United States)

    van Gerven Oei, W.-V.; Tanasković, D.; Žitko, R.

    2017-02-01

    Hybrid semiconductor-superconductor quantum dot devices are tunable physical realizations of quantum impurity models for a magnetic impurity in a superconducting host. The binding energy of the localized subgap Shiba states is set by the gate voltages and external magnetic field. In this work we discuss the effects of the Zeeman spin splitting, which is generically present both in the quantum dot and in the (thin-film) superconductor. The unequal g factors in semiconductor and superconductor materials result in respective Zeeman splittings of different magnitude. We consider both classical and quantum impurities. In the first case we analytically study the spectral function and the subgap states. The energy of bound states depends on the spin-splitting of the Bogoliubov quasiparticle bands as a simple rigid shift. For the case of collinear magnetization of impurity and host, the Shiba resonance of a given spin polarization remains unperturbed when it overlaps with the branch of the quasiparticle excitations of the opposite spin polarization. In the quantum case, we employ numerical renormalization group calculations to study the effect of the Zeeman field for different values of the g factors of the impurity and of the superconductor. We find that in general the critical magnetic field for the singlet-doublet transition changes nonmonotonically as a function of the superconducting gap, demonstrating the existence of two different transition mechanisms: Zeeman splitting of Shiba states or gap closure due to Zeeman splitting of Bogoliubov states. We also study how in the presence of spin-orbit coupling, modeled as an additional noncollinear component of the magnetic field at the impurity site, the Shiba resonance overlapping with the quasiparticle continuum of the opposite spin gradually broadens and then merges with the continuum.

  11. Phases of holographic d-wave superconductor

    OpenAIRE

    Krikun, A.

    2015-01-01

    We study different phases in the holographic model of d-wave superconductor. These are described by solutions to the classical equations of motion found in different ansatze. Apart from the known homogeneous d-wave superconducting phase we find three new solutions. Two of them represent two distinct families of the spatially modulated solutions, which realize the charge density wave phases in the dual theory. The third one is the new homogeneous phase with nonzero anapole moment. These phases...

  12. Soft wall model for a holographic superconductor

    Energy Technology Data Exchange (ETDEWEB)

    Afonin, S.S.; Pusenkov, I.V. [Saint Petersburg State University, St.Petersburg (Russian Federation)

    2016-06-15

    We consider the soft wall holographic approach for description of the high-T{sub c} superconductivity. In comparison with the existing bottom-up holographic superconductors, the proposed approach is more phenomenological and does not describe the superconducting phase transition. On the other hand, technically it is simpler and has more freedom for fitting the conductivity properties of the real high-T{sub c} materials in the superconducting phase. Some examples of emerging models are analyzed. (orig.)

  13. Review of holographic superconductors with Weyl corrections

    CERN Document Server

    Momeni, Davood; Myrzakulov, Ratbay

    2014-01-01

    A quick review on the analytical aspects of holographic superconductors (HSC) with Weyl corrections has been presented. Mainly we focus on matching method and variations approaches. Different types of such HSC have been investigated, s-wave, p-wave and St\\'{u}ckelberg ones. We also review the fundamental construction of a p-wave type , in which the non-Abelian gauge field is coupled to the Weyl tensor. The results are compared from numerics to analytical results.

  14. Soft wall model for a holographic superconductor

    CERN Document Server

    Afonin, S S

    2015-01-01

    We apply the soft wall holographic model from hadron physics to a description of the high-$T_c$ superconductivity. In comparison with the existing bottom-up holographic superconductors, the proposed approach is more phenomenological. On the other hand, it is much simpler and has more freedom for fitting the conductivity properties of the real high-$T_c$ materials. We demonstrate some examples of emerging models and discuss a possible origin of the approach.

  15. Towards Structural Testing of Superconductor Electronics

    OpenAIRE

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

    2003-01-01

    Many of the semiconductor technologies are already facing limitations while new-generation data and telecommunication systems are implemented. Although in its infancy, superconductor electronics (SCE) is capable of handling some of these high-end tasks. We have started a defect-oriented test methodology for SCE, so that reliable systems can be implemented in this technology. In this paper, the details of the study on the Rapid Single-Flux Quantum (RSFQ) process are presented. We present commo...

  16. Chemical stability of high-temperature superconductors

    Science.gov (United States)

    Bansal, Narottam P.

    1992-01-01

    A review of the available studies on the chemical stability of the high temperature superconductors (HTS) in various environments was made. The La(1.8)Ba(0.2)CuO4 HTS is unstable in the presence of H2O, CO2, and CO. The YBa2Cu3O(7-x) superconductor is highly susceptible to degradation in different environments, especially water. The La(2-x)Ba(x)CuO4 and Bi-Sr-Ca-Cu-O HTS are relatively less reactive than the YBa2Cu3O(7-x). Processing of YBa2Cu3O(7-x) HTS in purified oxygen, rather than in air, using high purity noncarbon containing starting materials is recommended. Exposure of this HTS to the ambient atmosphere should also be avoided at all stages during processing and storage. Devices and components made out of these oxide superconductors would have to be protected with an impermeable coating of a polymer, glass, or metal to avoid deterioration during use.

  17. Electronic structure investigation of novel superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Buling, Anna

    2014-05-15

    The discovery of superconductivity in iron-based pnictides in 2008 gave rise to a high advance in the research of high-temperature superconductors. But up to now there is no generally admitted theory of the non-BCS mechanism of these superconductors. The electron and hole doped Ba122 (BaFe{sub 2}As{sub 2}) compounds investigated in this thesis are supposed to be suitable model systems for studying the electronic behavior in order to shed light on the superconducting mechanisms. The 3d-transition metal doped Ba122 compounds are investigated using the X-ray photoelectron spectroscopy (XPS), X-ray absorption spectroscopy (XAS), X-ray emission spectroscopy (XES) and X-ray magnetic circular dichroism (XMCD), while the completely hole doped K122 is observed using XPS. The experimental measurements are complemented by theoretical calculations. A further new class of superconductors is represented by the electride 12CaO*7Al{sub 2}O{sub 3}: Here superconductivity can be realized by electrons accommodated in the crystallographic sub-nanometer-sized cavities, while the mother compound is a wide band gap insulator. Electronic structure investigations, represented by XPS, XAS and resonant X-ray photoelectron spectroscopy (ResPES), carried out in this work, should help to illuminate this unconventional superconductivity and resolve a debate of competing models for explaining the existence of superconductivity in this compound.

  18. Charge of a quasiparticle in a superconductor.

    Science.gov (United States)

    Ronen, Yuval; Cohen, Yonatan; Kang, Jung-Hyun; Haim, Arbel; Rieder, Maria-Theresa; Heiblum, Moty; Mahalu, Diana; Shtrikman, Hadas

    2016-02-16

    Nonlinear charge transport in superconductor-insulator-superconductor (SIS) Josephson junctions has a unique signature in the shuttled charge quantum between the two superconductors. In the zero-bias limit Cooper pairs, each with twice the electron charge, carry the Josephson current. An applied bias VSD leads to multiple Andreev reflections (MAR), which in the limit of weak tunneling probability should lead to integer multiples of the electron charge ne traversing the junction, with n integer larger than 2Δ/eVSD and Δ the superconducting order parameter. Exceptionally, just above the gap eVSD ≥ 2Δ, with Andreev reflections suppressed, one would expect the current to be carried by partitioned quasiparticles, each with energy-dependent charge, being a superposition of an electron and a hole. Using shot-noise measurements in an SIS junction induced in an InAs nanowire (with noise proportional to the partitioned charge), we first observed quantization of the partitioned charge q = e*/e = n, with n = 1-4, thus reaffirming the validity of our charge interpretation. Concentrating next on the bias region eVSD ~ 2Δ, we found a reproducible and clear dip in the extracted charge to q ~ 0.6, which, after excluding other possibilities, we attribute to the partitioned quasiparticle charge. Such dip is supported by numerical simulations of our SIS structure.

  19. AC susceptibilities of grain-textured superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Sakamoto, N. [Department of Electrical Engineering, Kyushu Sangyo University, 2-3-1 Matsukadai, 813-8503 Fukuoka (Japan)], E-mail: saka@te.kyusan-u.ac.jp; Fukuda, Y.; Koga, M.; Akune, T. [Department of Electrical Engineering, Kyushu Sangyo University, 2-3-1 Matsukadai, 813-8503 Fukuoka (Japan); Khan, H.R. [Institut von Ionenstrahl und Vakuum Technologie, 73728 Esslingen (Germany); Lueders, K. [Freie Universitaet Berlin, Arnimallee, Fac.Physik, D-14195 Berlin (Germany)

    2008-09-15

    In-phase {chi}{sub n}' and out-phase {chi}{sub n}'' components of nth harmonics of AC susceptibility with measuring parameters of a DC magnetic field B{sub dc}, an amplitude B{sub a} and a frequency f of the superimposed AC magnetic fields give substantial information of the superconducting properties. In low-T{sub c} metallic superconductors, {chi}{sub 1}' shows smooth transition and {chi}{sub 1}'' does single peak. High-T{sub c} oxide superconductors with anisotropic and grain-textured structures show deformed complex characteristics. Double peaks in {chi}{sub 1}'' and shoulders in {chi}{sub 1}' appear in AC susceptibility of Hg-1223 superconductors. Instead of simple Bean model, a grained model, where the superconducting grains are immersed in weak superconducting matrix, are proposed. The susceptibilities numerically analyzed using the model show varied and deformed curves and are successfully compared with the measured results.

  20. Meissner holes in iron-based superconductors

    Science.gov (United States)

    Tamegai, Tsuyoshi; Mohan, Shyam; Tsuchiya, Yuji; Nakajima, Yasuyuki

    2012-02-01

    Magnetic flux penetrates into a superconductor in the form of quantized vortices. This process is usually described by the Bean model, and the flux front forms a regular pattern reflecting the shape of the sample. However, a novel form of flux penetration accompanying wiggling fronts between vortices and antivortices has been observed in YBa2Cu3O7-δ upon remagnetization [1]. Such a phenomenon is ascribed to the presence of special arrangements of vortices at the front accompanying flux free regions and excess current around it. The flux free region is called as `Mesissner hole'. We have performed extensive magneto-optical imagings of iron-based superconductor single crystals and found similar anomalous features for the first time in superconductors other than 123-type cuprates [2]. Implications of this finding will be discussed with possible origins of the anomalous vortex arrangements. [1] V. K. Vlasko-Vlasov et al., Phys. Rev. B 56, 5622 (1997). [2] S. Mohan, Y. Tsuchiya, Y. Nakajima, and T. Tamegai, Phys. Rev. B 84, 18050X (2011).

  1. A Simple Holographic Superconductor with Momentum Relaxation

    CERN Document Server

    Kim, Keun-Young; Park, Miok

    2015-01-01

    We study a holographic superconductor model with momentum relaxation due to massless scalar fields linear to spatial coordinates($\\psi_I = \\beta \\delta_{Ii} x^i$), where $\\beta$ is the strength of momentum relaxation. In addition to the original superconductor induced by the chemical potential($\\mu$) at $\\beta=0$, there exists a new type of superconductor induced by $\\beta$ even at $\\mu=0$. It may imply a new `pairing' mechanism of particles and antiparticles interacting with $\\beta$, which may be interpreted as `impurity'. Two parameters $\\mu$ and $\\beta$ compete in forming superconducting phase. As a result, the critical temperature behaves differently depending on $\\beta/\\mu$. It decreases when $\\beta/\\mu$ is small and increases when $\\beta/\\mu$ is large, which is a novel feature compared to other models. After analysing ground states and phase diagrams for various $\\beta/\\mu$, we study optical electric($\\sigma$), thermoelectric($\\alpha$), and thermal($\\bar{\\kappa}$) conductivities. When the system undergo...

  2. Visualizing Majorana fermions in a chain of magnetic atoms on a superconductor

    Science.gov (United States)

    Yazdani, Ali

    2015-12-01

    A chain of magnetic atoms on the surface of a superconductor provides a versatile platform for realizing a one-dimensional topological superconductivity phase with edge-bounded Majorana fermions zero modes. This platform lends itself to spatial resolved measurements with scanning tunneling microscope (STM) that enables direct visualization of the presence of a localized Majorana zero mode. Experiments on self-assembled chains of Fe atoms on the surface of Pb show that such a system can be experimentally fabricated and studied using various high-resolution STM measurement techniques. Spatial and energy resolved STM experiments provide strong evidence for Majorana bound states that emerge due to the combination of Fe’s ferromagnetism and spin-orbit coupling of the superconducting Pb substrate. These studies provide a roadmap for optimizing topological superconductivity in this one-dimensional platform and its extension to realize chiral two-dimensional superconductors.

  3. McMillan-Rowell like oscillations in a superconductor-InAs/GaSb-superconductor junction

    Energy Technology Data Exchange (ETDEWEB)

    Shi, Xiaoyan, E-mail: xshi@sandia.gov; Yu, Wenlong; Hawkins, S. D.; Klem, J. F.; Pan, W. [Sandia National Laboratories, Albuquerque, New Mexico 87185 (United States)

    2015-08-03

    We have fabricated a superconductor (Ta)-InAs/GaSb bilayer-superconductor (Ta) junction device that has a long mean free path and can preserve the wavelike properties of particles (electrons and holes) inside the junction. Differential conductance measurements were carried out at low temperatures in this device, and McMillan-Rowell like oscillations (MROs) were observed. Surprisingly, a much larger Fermi velocity, compared to that from Shubnikov-de Haas oscillations, was obtained from the frequency of MROs. Possible mechanisms are discussed for this discrepancy.

  4. McMillan-Rowell Like Oscillations in a Superconductor-InAs/GaSb-Superconductor Junction

    Energy Technology Data Exchange (ETDEWEB)

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

    2015-08-04

    We fabricated a superconductor (Ta)-InAs/GaSb bilayer-superconductor (Ta) junction device that has a long mean free path and can preserve the wavelike properties of particles (electrons and holes) inside the junction. Differential conductance measurements were also carried out at low temperatures in this device, and McMillan-Rowell like oscillations (MROs) were observed. A much larger Fermi velocity, compared to that from Shubnikov-de Haas oscillations, was obtained from the frequency of MROs. Possible mechanisms are discussed for this discrepancy.

  5. McMillan-Rowell like oscillations in a superconductor-InAs/GaSb-superconductor junction

    Science.gov (United States)

    Shi, Xiaoyan; Yu, Wenlong; Hawkins, S. D.; Klem, J. F.; Pan, W.

    2015-08-01

    We have fabricated a superconductor (Ta)-InAs/GaSb bilayer-superconductor (Ta) junction device that has a long mean free path and can preserve the wavelike properties of particles (electrons and holes) inside the junction. Differential conductance measurements were carried out at low temperatures in this device, and McMillan-Rowell like oscillations (MROs) were observed. Surprisingly, a much larger Fermi velocity, compared to that from Shubnikov-de Haas oscillations, was obtained from the frequency of MROs. Possible mechanisms are discussed for this discrepancy.

  6. Magnetic excitations in iron chalcogenide superconductors.

    Science.gov (United States)

    Kotegawa, Hisashi; Fujita, Masaki

    2012-10-01

    Nuclear magnetic resonance and neutron scattering experiments in iron chalcogenide superconductors are reviewed to make a survey of the magnetic excitations in FeSe, FeSe1-x Te x and alkali-metal-doped Ax Fe2-y Se2 (A = K, Rb, Cs, etc). In FeSe, the intimate relationship between the spin fluctuations and superconductivity can be seen universally for the variations in the off-stoichiometry, the Co-substitution and applied pressure. The isovalent compound FeTe has a magnetic ordering with different wave vector from that of other Fe-based magnetic materials. The transition temperature Tc of FeSe increases with Te substitution in FeSe1-x Te x with small x, and decreases in the vicinity of the end member FeTe. The spin fluctuations are drastically modified by the Te substitution. In the vicinity of the end member FeTe, the low-energy part of the spin fluctuation is dominated by the wave vector of the ordered phase of FeTe; however, the reduction of Tc shows that it does not support superconductivity. The presence of same wave vector as that of other Fe-based superconductors in FeSe1-x Te x and the observation of the resonance mode demonstrate that FeSe1-x Te x belongs to the same group as most of other Fe-based superconductors in the entire range of x, where superconductivity is mediated by the spin fluctuations whose wave vector is the same as the nesting vector between the hole pockets and the electron pockets. On the other hand, the spin fluctuations differ for alkali-metal-doped Ax Fe2-y Se2 and FeSe or other Fe-based superconductors in their wave vector and strength in the low-energy part, most likely because of the different Fermi surfaces. The resonance mode with different wave vector suggests that Ax Fe2-y Se2 has an exceptional superconducting symmetry among Fe-based superconductors.

  7. Phase fluctuations in a strongly disordered s-wave NbN superconductor close to the metal-insulator transition.

    Science.gov (United States)

    Mondal, Mintu; Kamlapure, Anand; Chand, Madhavi; Saraswat, Garima; Kumar, Sanjeev; Jesudasan, John; Benfatto, L; Tripathi, Vikram; Raychaudhuri, Pratap

    2011-01-28

    We explore the role of phase fluctuations in a three-dimensional s-wave superconductor, NbN, as we approach the critical disorder for destruction of the superconducting state. Close to critical disorder, we observe a finite gap in the electronic spectrum which persists at temperatures well above T(c). The superfluid density is strongly suppressed at low temperatures and evolves towards a linear-T variation at higher temperatures. These observations provide strong evidence that phase fluctuations play a central role in the formation of a pseudogap state in a disordered s-wave superconductor.

  8. Method for preparation of textured YBa.sub.2 Cu.sub.3 O.sub.x superconductor

    Science.gov (United States)

    Selvamanickam, Venkat; Goyal, Amit; Kroeger, Donald M.

    1998-01-01

    The present invention relate to textured YBa.sub.2 Cu.sub.3 O.sub.x (Y-123) superconductors and a process of preparing them by directional recrystallization of compacts fabricated from quenched YBCO powders at temperatures about 100.degree. C. below the peritectic temperature to provide a superconductor where more than 75% of the YBa.sub.2 Cu.sub.3 O.sub.x phase is obtained without any Y.sub.2 BaCuO.sub.5 .

  9. The Origin of Tc Enhancement in Heterostructure Cuprate Superconductors

    Directory of Open Access Journals (Sweden)

    Doron L. Bergman

    2011-10-01

    Full Text Available Recent experiments on heterostructures composed of two or more films of cuprate superconductors of different oxygen doping levels have shown a remarkable Tc enhancement (up to 50% relative to single compound films. We provide a simple explanation of the enhancement which arises naturally from a collection of experimental works. We show that the enhancement could be caused by a structural change in the lattice, namely an increase in the distance of the apical oxygen from the copper-oxygen plane. This increase modifies the effective off-site interaction in the plane which in turn enhances the d-wave superconductivity order parameter. To illustrate this point we study the extended Hubbard model using the fluctuation exchange approximation.

  10. International Discussion Meeting on High-Tc Superconductors

    CERN Document Server

    1988-01-01

    In the past two years conferences on superconductivity have been characterized by the attendance of hundreds of scientists. Consequently, the organizers were forced to schedule numerous parallel sessions and poster presentations with an almost unsurveyable amount of information. It was, therefore, felt that a more informal get-together, providing ample time for a thourough discussion of some topics of current interest in high-temperature superconductivity, was timely and benefitial for leading scientists as well as for newcomers in the field. The present volume contains the majority of papers presented at the International Discussion Meeting on High-Tc Superconductors held at the Mauterndorf Castle in the Austrian Alps from February 7 to 11, 1988. Each subject was introduced in review form by a few invited speakers and then discussed together with the contributed poster presentations. These discussion sessions chaired by selected scientists turned out to be the highlights of the meeting, not only because all ...

  11. Optimized Coplanar Waveguide Resonators for a Superconductor-Atom Interface

    CERN Document Server

    Beck, M A; Booth, D; Pritchard, J D; Saffman, M; McDermott, R

    2016-01-01

    We describe the design and characterization of superconducting coplanar waveguide cavities tailored to facilitate strong coupling between superconducting quantum circuits and single trapped Rydberg atoms. For initial superconductor-atom experiments at 4.2 K, we show that resonator quality factors above $10^4$ can be readily achieved. Furthermore, we demonstrate that the incorporation of thick-film copper electrodes at a voltage antinode of the resonator provides a route to enhance the zero-point electric fields of the resonator in a trapping region that is 40 $\\mu$m above the chip surface, thereby minimizing chip heating from scattered trap light. The combination of high resonator quality factor and strong electric dipole coupling between the resonator and the atom should make it possible to achieve the strong coupling limit of cavity quantum electrodynamics with this system.

  12. High field superconductor development and understanding project, Final Report

    Energy Technology Data Exchange (ETDEWEB)

    Larbalestier, David C.; Lee, Peter J.

    2009-07-15

    Over 25 years the Applied Superconductivity Center at the University of Wisconsin-Madison provided a vital technical resource to the High Energy Physics community covering development in superconducting strand for HEP accelerator magnet development. In particular the work of the group has been to develop the next generation of high field superconductors for high field application. Grad students Mike Naus, Chad Fischer, Arno Godeke and Matt Jewell improved our understanding of the microstructure and microchemistry of Nb3Sn and their impact on the physical and mechanical properties. The success of this work has led to the continued funding of this work at the ASC after it moved to the NHMFL and also to direct funding from BNL for some aspects of Nb3Sn cable evaluation.

  13. Charge orders, magnetism and pairings in the cuprate superconductors.

    Science.gov (United States)

    Kloss, T; Montiel, X; de Carvalho, V S; Freire, H; Pépin, C

    2016-08-01

    We review the recent developments in the field of cuprate superconductors with special focus on the recently observed charge order in the underdoped compounds. We introduce new theoretical developments following the study of the antiferromagnetic quantum critical point in two dimensions, in which preemptive orders in both charge and superconducting (SC) sectors emerge, that are in turn related by an SU(2) symmetry. We consider the implications of this proliferation of orders in the underdoped region, and provide a study of the type of fluctuations which characterize the SU(2) symmetry. We identify an intermediate energy scale where the SC fluctuations are dominant and argue that they are unstable towards the formation of a resonant excitonic state at the pseudogap temperature T (*). We discuss the implications of this scenario for a few key experiments.

  14. Medicare Provider Data - Hospice Providers

    Data.gov (United States)

    U.S. Department of Health & Human Services — The Hospice Utilization and Payment Public Use File provides information on services provided to Medicare beneficiaries by hospice providers. The Hospice PUF...

  15. Nodal effects on the electronic specific heat of anisotropic superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Perez, Luis A. [Departamento de Fisica Quimica, Instituto de Fisica, Universidad Nacional Autonoma de Mexico, C.P. 01000, Mexico D.F. (Mexico)], E-mail: lperez@fisica.unam.mx; Samuel Millan, J. [Facultad de Ingenieria, Universidad Autonoma del Carmen, C.P. 24180, Cd. del Carmen, Campeche (Mexico); Wang Chumin [Insituto de Investigaciones en Materiales, Universidad Nacional Autonoma de Mexico, C.P. 04510, Mexico D.F. (Mexico)

    2008-04-01

    Based on the BCS formalism, the electronic specific heat of d-symmetry superconducting states is studied. This study is performed on a square lattice described by a generalized Hubbard model, in which correlated-hopping interactions are included in addition to the repulsive Coulomb ones. Instead of the exponential temperature dependence for the s-channel, the results show second and higher power-law behaviors for d-wave superconducting specific heat, depending on the angular dependence of the single-excitation energy gap occurred at different carrier concentrations. The results of this study could help to understand a variety of power-law behaviors observed in La{sub 2-x}Sr{sub x}CuO{sub 4} superconductors.

  16. Potential impact of high temperature superconductors on MAGLEV transportation

    Science.gov (United States)

    Hull, J. R.

    1992-02-01

    This report describes the potential impact that high-temperature superconductors (HTS's) may have on transportation by magnetically levitated vehicles. It is not intended as a planning document, but rather as an overview of potential HTS applications to magnetic-levitation (maglev) transportation. The present maglev program in the United States is summarized, and the present status of development of HTS's is described. Areas identified for possible impact on maglev technology are: (1) liquid-nitrogen-cooled levitation magnets; (2) magnetic-field shielding of the passenger compartment; (3) superconducting magnetic energy storage for wayside power; (4) superconducting bearings for flywheel energy storage for wayside power; (5) downleads to continuously powered liquid-helium-cooled levitation magnets; and (6) liquid-hydrogen-cooled levitation magnets and linear motor propulsion windings. Major technical issues that remain to be resolved for the use of HTS's in maglev applications include thermal magnetic stability, mechanical properties, and critical current density at liquid-nitrogen temperatures.

  17. Anomalous density of states in hybrid normalmetal–superconductor bilayers

    Indian Academy of Sciences (India)

    A K Gupta; L Crétinon; B Pannetier; H Courtois

    2006-01-01

    In contact with a superconductor, the Andreev reflection of the electronslocally modifies the N metal electronic properties, including the local density of states(LDOS). We investigated the LDOS in superconductor–normal metal (Nb–Au) bilayersusing a very low temperature (60 mK) STM on the normal metal side. High resolutiontunneling spectra measured on the Au surface show a clear proximity effect with an energygap of reduced amplitude compared to the bulk Nb gap. The dependence of this mini-gap width with the normal metal thickness is discussed in terms of the Thouless energy. Within the mini-gap, the density of states does not reach zero and shows clear sub-gapfeatures. We compare the experimental spectra with the well-established quasi-classicaltheory.

  18. Topological Insulators and Superconductors from D-branes

    CERN Document Server

    Ryu, Shinsei

    2010-01-01

    Realization of topological insulators (TIs) and superconductors (TSCs), such as the quantum spin Hall effect and the Z_2 topological insulator, in terms of D-branes in string theory is proposed. We establish a one-to-one correspondence between the K-theory classification of TIs/TSCs and D-brane charges. The string theory realization of TIs and TSCs comes naturally with gauge interactions, and the Wess-Zumino term of the D-branes gives rise to a gauge field theory of topological nature. This sheds light on TIs and TSCs beyond non-interacting 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.

  19. Microstructure and Properties of High-Temperature Superconductors

    CERN Document Server

    Parinov, Ivan A

    2007-01-01

    The main features of high-temperature superconductors (HTSC) that define their properties are intrinsic brittleness of oxide cuprates, the layered anisotropic structure and the supershort coherence length. Taking into account these features, this treatise presents research into HTSC microstructure and properties, and also explores the possibilities of optimization of the preparation techniques and superconducting compositions. The "composition-technique-experiment-theory-model," employed here, assumes considerable HTSC defectiveness and structure heterogeneity and helps to draw a comprehensive picture of modern representations of the microstructure, strength and the related structure-sensitive properties of the materials considered. Special attention is devoted to the Bi-Sr-Ca-Cu-O and Y-Ba-Cu-O families, which currently offer the most promising applications. Including a great number of illustrations and references, this monograph addresses students, post-graduate students and specialists, taking part in the ...

  20. Microstructure and Properties of High-Temperature Superconductors

    CERN Document Server

    Parinov, I A

    2012-01-01

    The main features of high-temperature superconductors (HTSC) that define their properties are intrinsic brittleness of oxide cuprates, the layered anisotropic structure and the supershort coherence length. Taking into account these features, this treatise presents research into HTSC microstructure and properties, and also explores the possibilities of optimization of the preparation techniques and superconducting compositions. The "composition-technique-experiment-theory-model," employed here, assumes considerable HTSC defectiveness and structure heterogeneity and helps to draw a comprehensive picture of modern representations of the microstructure, strength and the related structure-sensitive properties of the materials considered. Special attention is devoted to the Bi-Sr-Ca-Cu-O and Y-Ba-Cu-O families, which currently offer the most promising applications. Including a great number of illustrations and references, this monograph addresses students, post-graduate students and specialists, taking part in the ...

  1. Magnetic stripes in the UCoGe superconductor

    Energy Technology Data Exchange (ETDEWEB)

    Mora, Pablo de la [Departemento de Fisica, Facultad de Ciencias, Universidad Nacional Autonoma de Mexico, Apartado Postal 70-542, 04510 Mexico DF, Mexico and Institute de Investigacion en Materiales, Universidad Nacional Autonoma de Mexico, Campus Morelia (Mexico); Navarro, O, E-mail: delamora@unam.m [Instituto de Investigacion en Materiales, Universidad Nacional Autonoma de Mexico, Apartado Postal 70-360, 04510 Mexico DF (Mexico)

    2009-05-01

    The magnetic superconductor UCoGe is analyzed with an electronic structure package, spin-orbit coupling and intra-atomic repulsion (via Hubbard U{sub H}) were included. The possibility of an antiferromagnetic configuration is studied, but it is found to be unstable, also the non-collinear magnetization seems to be ruled out. The magnetization is given mainly by the Co-atoms with M = 0.6 mu{sub B}/f.u. The U-atoms have two magnetic moments; M = 0.07 and 0.32 mu{sub B}/f.u. arranged in an alternated planes along the b-direction forming magnetic stripes.

  2. Potential impact of high temperature superconductors on maglev transportation

    Energy Technology Data Exchange (ETDEWEB)

    Hull, J.R.

    1992-02-01

    This report describes the potential impact that high-temperature superconductors (HTSs) may have on transportation by magnetically levitated vehicles. It is not intended as a planning document, but rather as an overview of potential HTS applications to magnetic-levitation (maglev) transportation. The present maglev program in the United States is summarized, and the present status of development of HTSs is described. Areas identified for possible impact on maglev technology are (1) liquid-nitrogen-cooled levitation magnets, (2) magnetic-field shielding of the passenger compartment, (3) superconducting magnetic energy storage for wayside power, (4) superconducting bearings for flywheel energy storage for wayside power, (5) downleads to continuously powered liquid-helium-cooled levitation magnets, and (6) liquid-hydrogen-cooled levitation magnets and linear motor propulsion windings. Major technical issues that remain to be resolved for the use of HTSs in maglev applications include thermal magnetic stability, mechanical properties, and critical current density at liquid-nitrogen temperatures.

  3. Fluxons in thin-film superconductor-insulator superlattices

    DEFF Research Database (Denmark)

    Sakai, S.; Bodin, P.; Pedersen, Niels Falsig

    1993-01-01

    films; in the limit of ultrathin superconductor films it may give a model for describing fluxon motion in layered high-Tc superconductors. Numerical examples of current versus voltage curves to be expected in such an experiment are presented. Journal of Applied Physics is copyrighted by The American...... Institute of Physics....

  4. Peltier effect in the mixed state of high- Tc superconductors

    Science.gov (United States)

    Logvenov, G. Yu.; Ryazanov, V. V.; Ustinov, A. V.; Huebener, R. P.

    1991-04-01

    The Peltier and Seebeck effects in the mixed state of high- Tc superconductors are proportional to the resistivity due to flux motion. Therefore, both effects also show the broadening of the transition regime characteristic for these superconductors. The origin of the Peltier effect is discussed in detail, and the validity of the Thomson relation is confirmed, as expected.

  5. BCS-Hubbard model applied to anisotropic superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Millan, J.S., E-mail: smillan@pampano.unacar.mx [Facultad de Ingenieria, Universidad Autonoma del Carmen, Cd. del Carmen, 24180 Campeche (Mexico); Perez, L.A. [Instituto de Fisica, Universidad Nacional Autonoma de Mexico, A.P. 20-364, 01000, Mexico D.F. (Mexico); Wang, C. [Instituto de Investigaciones en Materiales, Universidad Nacional Autonoma de Mexico, A.P. 70-360, 04510, Mexico D.F. (Mexico)

    2011-11-15

    The BCS formalism applied to a Hubbard model, including correlated hoppings, is used to study d-wave superconductors. The theoretical T{sub c} vs. n relationship is compared with experimental data from BiSr{sub 2-x}La{sub x}CuO{sub 6+{delta}} and La{sub 2-x}Sr{sub x}CuO{sub 4}. The results suggest a nontrivial correlation between the hole and the doping concentrations. Based on the BCS formalism, we study the critical temperature (T{sub c}) as a function of electron density (n) in a square lattice by means of a generalized Hubbard model, in which first ({Delta}t) and second neighbors ({Delta}t{sub 3}) correlated-hopping interactions are included in addition to the repulsive Coulomb ones. We compare the theoretical T{sub c} vs. n relationship with experimental data of cuprate superconductors BiSr{sub 2-x}La{sub x}CuO{sub 6+{delta}} (BSCO) and La{sub 2-x}Sr{sub x}CuO{sub 4}, (LSCO). The theory agrees very well with BSCO data even though the complicated association between Sr concentration (x) and hole doping (p). For the LSCO system, it is observed that in the underdoped regime, the T{sub c} vs. n behavior can be associated to different systems with small variations of t'. For the overdoped regime, a more complicated dependence n = 1 - p/2 fits better than n = 1 - p. On the other hand, it is proposed that the second neighbor hopping ratio (t'/t) should be replaced by the effective mean field hopping ratio t{sub MF}{sup '}/t{sub MF}, which can be very sensitive to small changes of t' due to the doping.

  6. Holographic insulator/superconductor phase transition model with dark matter sector away from the probe limit

    CERN Document Server

    Peng, Yan; Liu, Yunqi

    2015-01-01

    We generalize the holographic phase transitions affected by the dark matter sector in the AdS soliton background by including backreaction. We observe the unstable retrograde condensation appears due to the dark matter sector and also derive the general stable conditions expressed by the coupling parameters $\\alpha$ and $\\xi/\\mu$. Moreover, we find that the larger coupling parameter $\\alpha$ makes the gap of condensation lower but the ratio $\\xi/\\mu$ does not affect it. In contrast, the critical chemical potential always keeps as a constant for different values of $\\alpha$ and $\\xi/\\mu$ even including backreaction. In all, there is a lot of difference between the properties of dark matter sector in insulator/superconductor transitions and those reported in metal/superconductor systems. We also arrive at the same conclusion from the effective mass and holographic topological entanglement entropy approach. In particular, we state that the entanglement entropy is powerful in studying the effects of the dark matt...

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

    Science.gov (United States)

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

    2012-12-07

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

  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. Stop of magnetic flux movement in levitating superconductor

    Energy Technology Data Exchange (ETDEWEB)

    Smolyak, B.M., E-mail: b-smolyak@yandex.ru; Zakharov, M.S., E-mail: maksim.s.zakharov@gmail.com

    2017-01-15

    Highlights: • A direct experimental study of magnetic flux creep in the levitating superconductor. • When a levitating object is in a fixed position, magnetic flux movement is observed. • Levitation stops flux creep process. - Abstract: A phenomenon of magnetic relaxation stopping in a levitating superconductor was studied. It was experimentally shown that magnetic flux creep (diffusion of flux lines to regions with lower vortex density) is absent in magnetic suspension of the superconductor. Magnetic relaxation arises, when a rigid constraint that fixes a position of the superconductor relative to a magnet is imposed on a levitating object. It is assumed that oscillations of magnetic structure, which is due to free oscillations of the levitating superconductor, stop magnetic relaxation.

  10. Optical studies of crystalline organic superconductors under extreme conditions

    CERN Document Server

    McDonald, R D

    2001-01-01

    the aim being to make an optical measurement of the pressure dependence of the charge carrier effective mass. Chapter 4 concentrates on the vibrational modes of kappa-(BEDT-TTF) sub 2 Cu(SCN) sub 2. This chapter reports the first Raman scattering experiments on an organic superconductor at high pressure. Comparison of the infrared reflectance and Raman scattering measurements are used to elucidate the role of electron-phonon coupling in this material's superconductivity. Chapter 5 reports the first non-resonant measurements of the GHz conductivity of an organic molecular superconductor. These experiments probe the unconventional metallic properties of an organic superconductor during the onset of superconductivity. This thesis reports experiments which involve the interaction of light and matter to probe the properties of crystalline organic superconductors. The organic superconductors of the BEDT-TTF family are prototypical correlated electron systems; their low-temperature ground states are dominated by man...

  11. Stable and unstable thermo -current states of high temperature superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Romanovskii, V; Lavrov, N; Ozhogina, V [Russian Research Center ' Kurchatov Institute' , Moscow 123182 (Russian Federation)], E-mail: vromanovskii@netscape.net

    2008-02-01

    Formation peculiarities of the stable and unstable states of high-T{sub c} superconductors are discussed. To understand the basic physical trends, which are characteristic for the current penetration mechanism in high temperature superconductors, the operating states of Bi2212 slab without stabilizing matrix placed in DC external magnetic fields at low coolant temperature are theoretically investigated. It is proved that the temperature of a high-T{sub c} superconductor is not equals to the coolant temperature before instability onset. Therefore, the voltage-current characteristic of a high-T{sub c} superconductor has only a positive slope during continuous current charging. As a result, it does not allow one to find the boundary between stable and unstable thermo - current states. This peculiarity has to be considered during experiments at which the critical current of high-T{sub c} superconductors is defined.

  12. 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.

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

    Energy Technology Data Exchange (ETDEWEB)

    Han, Y.H., E-mail: yhhan@kepri.re.kr [KEPCO Research Institute, 105 Munji-Ro, Yuseong-Gu, Daejeon 305-760 (Korea, Republic of); Park, B.J.; Jung, S.Y.; Han, S.C.; Lee, W.R.; Bae, Y.C. [KEPCO Research Institute, 105 Munji-Ro, Yuseong-Gu, Daejeon 305-760 (Korea, Republic of)

    2013-02-14

    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.

  14. A Double-Decker Levitation Experiment Using a Sandwich of Superconductors.

    Science.gov (United States)

    Jacob, Anthony T.; And Others

    1988-01-01

    Shows that the mutual repulsion that enables a superconductor to levitate a magnet and a magnet to levitate a superconductor can be combined into a single demonstration. Uses an overhead projector, two pellets of "1-2-3" superconductor, Nd-Fe-B magnets, liquid nitrogen, and paraffin. Offers superconductor preparation, hazards, and disposal…

  15. Mixed state of a dirty two-band superconductor: application to MgB2.

    Science.gov (United States)

    Koshelev, A E; Golubov, A A

    2003-05-01

    We investigate the vortex state in a two-band superconductor with strong intraband and weak interband electronic scattering rates. Coupled Usadel equations are solved numerically, and the distributions of the pair potentials and local densities of states are calculated for two bands at different values of magnetic fields. The existence of two distinct length scales corresponding to different bands is demonstrated. The results provide qualitative interpretation of recent scanning tunneling microscopy experiments on vortex structure imaging in MgB2.

  16. Concepts for using trapped-flux bulk high-temperature superconductor in motors and generators

    Science.gov (United States)

    Hull, John R.; Strasik, Michael

    2010-12-01

    We review previous concepts for using bulk high-temperature superconductors (HTSs) in motors and generators and discuss methods for using trapped-flux (TF) HTSs in motors and generators that have been recently investigated in our laboratory. We examine the expected performance of a brushless motor/generator that uses TF bulk HTSs to provide magnetomotive force, where the stator windings are used to create the TF. A key feature is the use of dysprosium for the stator and rotor cores.

  17. Concepts for using trapped-flux bulk high-temperature superconductor in motors and generators

    Energy Technology Data Exchange (ETDEWEB)

    Hull, John R; Strasik, Michael [Boeing Research and Technology, PO Box 3707, MC 2T-50, Seattle, WA 98124-2207 (United States)

    2010-12-15

    We review previous concepts for using bulk high-temperature superconductors (HTSs) in motors and generators and discuss methods for using trapped-flux (TF) HTSs in motors and generators that have been recently investigated in our laboratory. We examine the expected performance of a brushless motor/generator that uses TF bulk HTSs to provide magnetomotive force, where the stator windings are used to create the TF. A key feature is the use of dysprosium for the stator and rotor cores.

  18. New concept of current switch based on high-temperature superconductor

    CERN Document Server

    Ovchinnikov, S G; Balaev, D A; Gokhfel'd, D M; Kharlamova, S A; Shajkhutdinov, K A; Kirko, V I; Ivanov, V V; Militsyn, S V; Mamalis, A G

    2001-01-01

    A new concept of alternating current circuit protection device on the basis of combination of a superconducting short circuit (SC) current limiter and an electric circuit breaker was suggested. High-temperature superconductor as a stack of plane rings was used as active element in the superconducting current limiter. Test results of the limiter mock-up under stationary short circuit conditions are provided. Characteristics of composite materials, that do not contain silver, which are used for current breaker designing, are presented

  19. Coherent diffusive transport mediated by Andreev reflections at V=Delta/e in a mesoscopic superconductor/semiconductor/superconductor junction

    DEFF Research Database (Denmark)

    Kutchinsky, Jonatan; Taboryski, Rafael Jozef; Kuhn, Oliver

    1997-01-01

    We present experiments revealing a singularity in the coherent current across a superconductor/semiconductor/superconductor (SSmS) junction at the bias voltage corresponding to the superconducting energy gap V=Delta/e. The SSmS structure consists of highly doped GaAs with superconducting electrodes...

  20. Triplet Cooper pairs induced in diffusive s-wave superconductors interfaced with strongly spin-polarized magnetic insulators or half-metallic ferromagnets.

    Science.gov (United States)

    Ouassou, Jabir Ali; Pal, Avradeep; Blamire, Mark; Eschrig, Matthias; Linder, Jacob

    2017-05-16

    Interfacing superconductors with strongly spin-polarized magnetic materials opens the possibility to discover new spintronic devices in which spin-triplet Cooper pairs play a key role. Motivated by the recent derivation of spin-polarized quasiclassical boundary conditions capable of describing such a scenario in the diffusive limit, we consider the emergent physics in hybrid structures comprised of a conventional s-wave superconductor (e.g. Nb, Al) and either strongly spin-polarized ferromagnetic insulators (e.g. EuO, GdN) or halfmetallic ferromagnets (e.g. CrO2, LCMO). In contrast to most previous works, we focus on how the superconductor itself is influenced by the proximity effect, and how the generated triplet Cooper pairs manifest themselves in the self-consistently computed density of states (DOS) and the superconducting critical temperature T c . We provide a comprehensive treatment of how the superconductor and its properties are affected by the triplet pairs, demonstrating that our theory can reproduce the recent observation of an unusually large zero-energy peak in a superconductor interfaced with a half-metal, which even exceeds the normal-state DOS. We also discuss the recent observation of a large superconducting spin-valve effect with a T c change ~1 K in superconductor/half-metal structures, in which case our results indicate that the experiment cannot be explained fully by a long-ranged triplet proximity effect.

  1. Raman and infrared studies of the Sharp 890 cm{sup -1} mode in organic superconductors.

    Energy Technology Data Exchange (ETDEWEB)

    Eldridge, J. E.; Lin, Y.; Schlueter, J. A.; Wang, H. H.; Kini, A. M.

    2000-11-28

    Raman and infrared spectra of several organic superconductors are presented, showing some unusual behaviors of a sharp line at 890 cm{sup {minus}} in both spectra. These include a frequency shift below T{sub c}, a positive deuterium isotope shift, frequency softening at low temperatures and sensitivity to lattice superstructure. It is proposed that either the ion or the neutral molecule has a distortion with a strong v{sub 60}(B{sub 3g}) mode component.

  2. High-Temperature Ceramic Superconductors

    Science.gov (United States)

    1989-07-15

    error quoted above, since the solid state synthesis did not include any standard- ization of the component oxides. When a similar standardization is...included, the errors are about the same, about 1 to 2% for the solid state synthesis . In looking at the error analysis above, it first appears that...while 0.3% total error is required, the solution method and solid state synthesis methods will both fail. This conclusion is not entirely warranted

  3. Optical modulator including grapene

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Ming; Yin, Xiaobo; Zhang, Xiang

    2016-06-07

    The present invention provides for a one or more layer graphene optical modulator. In a first exemplary embodiment the optical modulator includes an optical waveguide, a nanoscale oxide spacer adjacent to a working region of the waveguide, and a monolayer graphene sheet adjacent to the spacer. In a second exemplary embodiment, the optical modulator includes at least one pair of active media, where the pair includes an oxide spacer, a first monolayer graphene sheet adjacent to a first side of the spacer, and a second monolayer graphene sheet adjacent to a second side of the spacer, and at least one optical waveguide adjacent to the pair.

  4. 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)

  5. Ginzburg-Landau theory of noncentrosymmetric superconductors

    OpenAIRE

    Mukherjee, Soumya P.; Mandal, Sudhansu S.

    2007-01-01

    The data of temperature dependent superfluid density $n_s(T)$ in Li$_2$Pd$_3$B and Li$_2$Pt$_3$B [Yuan {\\it et al.}, \\phrl97, 017006 (2006)] show that a sudden change of the slope of $n_s (T)$ occur at slightly lower than the critical temperature. Motivated by this observation, we microscopically derive the Ginzburg-Landau (GL) equations for noncentrosymmetric superconductors with Rashba type spin orbit interaction. Cooper pairing is assumed to occur between electrons only in the same spin sp...

  6. Quantum oscillations in superconductors in magnetic field

    Science.gov (United States)

    Gvozdikov, Vladimir M.; Gvozdikova, Mariya V.

    2000-07-01

    The Aharonov-Bohm oscillations (ABO) of the free energy, the critical temperature, and the magnetic susceptibility in a stack of hollow mesoscopic cylinders are calculated. It is shown that sinusoidal (in flux) ABO crosses over to the parabolic Little-Parks oscillations (LPO) when the diameter of cylinders exceeds the coherence length. The exponential temperature behaviour of the magnetic susceptibility is like that found in Ag cylinders with thin Nb coating [Czech. J. Physics 46 (1996) 2317]. The formal analogy between oscillations of the free energy in the Aharonov-Bohm system in question and the de Haas-van Alphen oscillations (dHvAO) in layered superconductors is discussed.

  7. Topological Aspects of Superconductors at Dual Point

    Institute of Scientific and Technical Information of China (English)

    REN Ji-Rong; XU Dong-Hui; ZHANG Xin-Hui; DUAN Yi-Shi

    2008-01-01

    We study the properties of the Ginzburg-Landau model at the dual point for the superconductors. By making use of the U(1) gauge potential decomposition and the C-mapping theory, we investigate the topological inner structure of the Bogomol'nyi equations and deduce a modified deeoupled Bogomol'nyi equation with a nontrivial topo-logical term, which is ignored in conventional model. We find that the nontrivial topological term is closely related tothe N-vortex, which arises from the zero points of the complex scalar field. Furthermore, we establish a relationship between Ginzburg-Landau free energy and the winding number.

  8. Potential aerospace applications of high temperature superconductors

    Science.gov (United States)

    Selim, Raouf

    1994-01-01

    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

  9. 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-

  10. 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.

  11. Detection of infrared photons with a superconductor

    Institute of Scientific and Technical Information of China (English)

    ZHANG LaBao; ZHONG YangYin; KANG Lin; CHEN Jian; JI ZhengMing; XU WeiWei; CAO ChunHai

    2009-01-01

    A superconductor single photon detector based on NbN nanowire was fabricated using electron beam lithography (EBL) and reactive ion etching (RIE) for infrared photon detection. When biased well below its critical current at 4.2 K, NbN nanowire is very sensitive to the incident photons. Typical telecommunication photons with a wavelength of 1550 nm were detected by this detector. Data analysis indicates the repeating rate of the device with 200 nm NbN nanowire may be up to 100 MHz, and the quantum efficiency is about 0.01% when biased at 0.95Ic.

  12. High-Tc superconductor coplanar waveguide filter

    Science.gov (United States)

    Chew, Wilbert; Bajuk, Louis J.; Cooley, Thomas W.; Foote, Marc C.; Hunt, Brian D.; Rascoe, Daniel L.; Riley, A. L.

    1991-01-01

    Coplanar waveguide (CPW) low-pass filters made of YBa2Cu3O(7-delta) (YBCO) on LaAlO3 substrates, with dimensions suited for integrated circuits, were fabricated and packaged. A complete filter gives a true idea of the advantages and difficulties in replacing thin-film metal with a high-temperature superconductor in a practical circuit. Measured insertion losses in liquid nitrogen were superior to the loss of a similar thin-film copper filter throughout the 0- to 9.5-GHz passband. These results demonstrate the performance of fully patterned YBCO in a practical CPW structure after sealing in a hermetic package.

  13. Paramagnetic excited vortex states in superconductors

    Science.gov (United States)

    Gomes, Rodolpho Ribeiro; Doria, Mauro M.; Romaguera, Antonio R. de C.

    2016-06-01

    We consider excited vortex states, which are vortex states left inside a superconductor once the external applied magnetic field is switched off and whose energy is lower than of the normal state. We show that this state is paramagnetic and develop here a general method to obtain its Gibbs free energy through conformal mapping. The solution for any number of vortices in any cross-section geometry can be read off from the Schwarz-Christoffel mapping. The method is based on the first-order equations used by Abrikosov to discover vortices.

  14. 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

    2013-10-01

    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.

  15. Coulomb blockade in fractional topological superconductors

    Science.gov (United States)

    Kim, Younghyun; Clarke, David J.; Lutchyn, Roman M.

    2017-07-01

    We study charge transport through a floating mesoscopic superconductor coupled to counterpropagating fractional quantum Hall edges at filling fraction ν =2 /3 . We consider a superconducting island with finite charging energy and investigate its effect on transport through the device. We calculate conductance through such a system as a function of temperature and gate voltage applied to the superconducting island. We show that transport is strongly affected by the presence of parafermionic zero modes, leading at zero temperature to a zero-bias conductance quantized in units of ν e2/h independent of the applied gate voltage.

  16. High temperature superconductor bulk materials fundamentals, processing, properties control, applications aspects

    CERN Document Server

    Krabbes, Gernot; Canders, Wolf-Rüdiger; May, Hardo; Palka, Ryszard

    2005-01-01

    With its comprehensive review of the current knowledge and the future requirements in the field, this book presents all the features of bulk high temperature superconducting materials. Starting from physical and chemical fundamentals, the authors move on to portray methods and problems of materials processing, thoroughly working out the characteristic properties of bulk superconductors in contrast to long conductors and films. They provide a wide range of specific materials characteristics with respect to the latest developments and future applications guiding from fundamentals to practical engineering examples. The authors are all leading international specialists involved in the field of high TC superconductor bulk materials since the beginning. Of utmost interest to engineers, scientists, and PhD students working in this field

  17. Dynamics of skyrmions and edge states in the resistive regime of mesoscopic p-wave superconductors

    Science.gov (United States)

    Fernández Becerra, V.; Milošević, M. V.

    2017-02-01

    In a mesoscopic sample of a chiral p-wave superconductor, novel states comprising skyrmions and edge states have been stabilized in out-of-plane applied magnetic field. Using the time-dependent Ginzburg-Landau equations we shed light on the dynamic response of such states to an external applied current. Three different regimes are obtained, namely, the superconducting (stationary), resistive (non-stationary) and normal regime, similarly to conventional s-wave superconductors. However, in the resistive regime and depending on the external current, we found that moving skyrmions and the edge state behave distinctly different from the conventional kinematic vortex, thereby providing new fingerprints for identification of p-wave superconductivity.

  18. A comparison of graphene, superconductors and metals as conductors for metamaterials and plasmonics

    Energy Technology Data Exchange (ETDEWEB)

    Tassin, Philippe; Koschny, Thomas; Kafesaki, Maria; Soukoulis, Costas

    2012-03-30

    Recent advancements in metamaterials and plasmonics have promised a number of exciting applications, in particular at terahertz and optical frequencies. Unfortunately, the noble metals used in these photonic structures are not particularly good conductors at high frequencies, resulting in significant dissipative loss. Here, we address the question of what is a good conductor for metamaterials and plasmonics. For resonant metamaterials, we develop a figure-of-merit for conductors that allows for a straightforward classification of conducting materials according to the resulting dissipative loss in the metamaterial. Application of our method predicts that graphene and high-T{sub c} superconductors are not viable alternatives for metals in metamaterials. We also provide an overview of a number of transition metals, alkali metals and transparent conducting oxides. For plasmonic systems, we predict that graphene and high-T{sub c} superconductors cannot outperform gold as a platform for surface plasmon polaritons, because graphene has a smaller propagation length-to-wavelength ratio.

  19. Interior seeding combined with top seeding for the fabrication of single grain REBCO bulk superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Hee Gyoun [Korea Polytechnic University, Siheung (Korea, Republic of)

    2017-06-15

    This study presents three dimensional (3-D) seeding technique which is a modification of interior seeding. 3-D seeding is beneficial for shortening the processing period and enhancing the magnetic properties of REBCO bulk superconductors fabricated by melt growth. Oxygen channels were provided by using divided powder compacts instead of by using a rubber insert. Microstructure observations revealed that the grains grown from the seeds impinged each other and formed low angle grain boundaries of (001)/(001). It has been shown that the 3-D seeding technique reduces the volume fraction of a-c growth sector and thereby maximizes the area of a-b growth sector which attribute to the high magnetic characteristics of single grain REBCO bulk superconductors.

  20. Transmittance properties in a magnetized cold plasma-superconductor periodic multilayer.

    Science.gov (United States)

    Aghajamali, Alireza

    2016-08-10

    This study theoretically investigates the transmittance properties of a one-dimensional photonic crystal containing magnetized cold plasma and high-temperature superconductor materials. The cutoff frequency, as a function of the magnetic field, electron density of the plasma layer, and temperature, will be investigated. The results illustrate that the temperature, electron density, and variations of the magnetic field affect the cutoff frequency. In addition, the shift trend in the cutoff frequency proves to be dependent on the polarization due to the presence of polarization-dependent magnetized cold plasma. Moreover, in temperature-dependent transmittance, weak oscillation and intensity can be seen at higher temperatures, which is in sharp contrast to low-temperature superconductor-dielectric structures. The proposed structure could certainly provide helpful information for the design of new types of antennas, reflectors, and high-pass filters at microwave frequency.

  1. Anisotropy Effect on Levitation Performance of Bulk High-Tc Superconductors Above a Permanent Magnet Guideway

    Science.gov (United States)

    Zheng, Jun; Liao, Xinglin; Jing, Hailian; Lin, Qunxu; Ma, Guangtong; Yen, Fei; Wang, Suyu; Wang, Jiasu

    The anisotropy properties of bulk high-temperature superconductors (HTSCs) are taken into consideration for the application of high-temperature superconducting (HTS) Maglev systems, which are especially based on the different flux-trapping capabilities as well as critical current density, Jc, values between the growth section boundary (GSB) and the growth sections (GS) in bulk superconductors. By adjusting the angle between the GSB of bulk HTSCs and the strongest magnetic field position of a permanent magnet guideway (PMG), the levitation force and its relaxation processes are compared at different field-cooling conditions. Experimental results show that the levitation capability and the suppression of levitation force decay can be enhanced by optimizing the GS/GSB alignment of every bulk HTSC above the PMG. Meanwhile, our conclusions may provide references to other HTS maglev systems with small levitation gaps, i.e., superconducting magnetic bearings.

  2. Antiferromagnetic fluctuations in a quasi-two-dimensional organic superconductor detected by Raman spectroscopy.

    Energy Technology Data Exchange (ETDEWEB)

    Drichko, Natalia; Hackl, Rudi; Schlueter, John A.

    2015-10-15

    Using Raman scattering, the quasi-two-dimensional organic superconductor kappa-(BEDT-TTF)(2)Cu[N(CN)(2)]Br (T-c = 11.8 K) and the related antiferromagnet kappa-(BEDT-TTF)(2)Cu[N(CN)(2)]Cl are studied. Raman scattering provides unique spectroscopic information about magnetic degrees of freedom that has been otherwise unavailable on such organic conductors. Below T = 200 K a broad band at about 500 cm(-1) develops in both compounds. We identify this band with two-magnon excitation. The position and the temperature dependence of the spectral weight are similar in the antiferromagnet and in the metallic Fermi liquid. We conclude that antiferromagnetic correlations are similarly present in the magnetic insulator and the Fermi-liquid state of the superconductor.

  3. The magnetostriction in a superconductor-magnet system under non-uniform magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Li, Xueyi; Jiang, Lang; Wu, Hao [Key Laboratory of Mechanics on Disaster and Environment in Western China attached to the Ministry of Education of China, Lanzhou University, Lanzhou, Gansu 730000 (China); Gao, Zhiwen, E-mail: gaozhw@lzu.edu.cn [Department of Mechanics and Engineering Science, College of Civil Engineering and Mechanics, Lanzhou University, Lanzhou, Gansu 730000 (China)

    2017-03-15

    Highlights: • We studied firstly magnetostriction in HTS under non-uniform magnetic field. • The superconductors may be homogeneous and nonhomogeneous. • The magnetostrictions response of the HTS is sensitive to the critical current density and amplitude of the applied magnetic field. • The magnetostriction of nonhomogeneous HTS is larger than that of homogeneous HTS. - Abstract: This paper describes a numerical model to examine the magnetostriction of bulk high-temperature superconductor (HTS) under non-uniform magnetic field in conjunction with finite element analysis. Through this model, the magnetostriction of homogeneous and nonhomogeneous HTS can be implemented under non-uniform magnetic field. Further, the effects of critical current density, applied field frequency and amplitude are also considered. The computational study can provide a fundamental mechanistic understanding the effects of non-uniform magnetic field on magnetostriction of HTS.

  4. Fracture problem of a nonhomogeneous high temperature superconductor slab based on real fundamental solutions

    Science.gov (United States)

    Gao, Zhiwen; Zheng, Zhiye; Li, Xueyi

    2015-12-01

    To analyze the fracture problem of the nonhomogeneous high temperature superconductor (HTS) slab under electromagnetic force, we derive the real fundamental solutions based on eigenvalue and eigenvector analyses. The superconductor E-J constitutive law is characterized by the Bean model where the critical current density is independent of the flux density. Fracture analysis is performed by the methods of singular integral equations which are solved numerically by Lobatto-Chybeshev collocation method. Numerical results of the stress intensity factor (SIF) are obtained. Moreover, the crack opening displacement (COD) can be obtained by numerical integration dislocation density functions. The effects of the thickness ratio, HTS material nonhomogeneous parameters, applied magnetic field and critical current density on SIF and COD are discussed. The present work could theoretically provide quantitative predictions of the fracture mechanism of the nonhomogeneous HTS.

  5. Tunneling of quasiparticles in the normal-insulator-superconductor-insulator-normal geometry

    Science.gov (United States)

    Hidaka, Mutsuo; Ishizaka, Satoshi; Sone, Jun'ichi

    1993-12-01

    The probability of quasiparticle transmission going through a normal-insulator- superconductor-insulator-normal (NISIN) geometry is theoretically calculated using Bogoliubov-de Gennes equations to investigate the feasibility of electron devices utilizing this geometry. This new calculation is able to include a current carried by Cooper pairs by employing hole injections from the outlet which destroy Cooper pairs at the outlet super- conductor-insulator boundary. Resonant tunneling phenomena occur even if the electron kinetic energy is less than the superconducting energy gap and electron tunneling probabilities are greatly modified by the resonance. When the unevenness of the superconductor (S) width thickness is large compared with the electron wavelength in the S layer, the resonance is smeared out in averaged tunneling probabilities. Then the tunneling probabilities can be controlled by the electron kinetic energy. Applications of the NISIN geometry for superconducting transistors are also discussed.

  6. Method of manufacturing superconductor wire

    Science.gov (United States)

    Motowidlo, Leszek

    2014-09-16

    A method for forming Nb.sub.3Sn superconducting wire is provided. The method employs a powder-in-tube process using a high-tin intermetallic compound, such as MnSn.sub.2, for producing the Nb.sub.3Sn. The use of a high-tin intermetallic compound enables the process to perform hot extrusion without melting the high-tin intermetallic compound. Alternatively, the method may entail drawing the wire without hot extrusion.

  7. 0 -π phase transition in hybrid superconductor-InSb nanowire quantum dot devices

    Science.gov (United States)

    Li, Sen; Kang, N.; Caroff, P.; Xu, H. Q.

    2017-01-01

    Hybrid superconductor-semiconducting nanowire devices provide an ideal platform to investigating interesting intragap bound states, such as the Andreev bound states (ABSs), Yu-Shiba-Rusinov (YSR) states, and the Majorana bound states. The competition between Kondo correlations and superconductivity in Josephson quantum dot (QD) devices results in two different ground states and the occurrence of a 0 -π quantum phase transition. Here we report on transport measurements on hybrid superconductor-InSb nanowire QD devices with different device geometries. We demonstrate a realization of continuous gate-tunable ABSs with both 0-type levels and π -type levels. This allow us to manipulate the transition between the 0 and π junction and explore charge transport and spectrum in the vicinity of the quantum phase transition regime. Furthermore, we find a coexistence of 0-type ABS and π -type ABS in the same charge state. By measuring temperature and magnetic field evolution of the ABSs, the different natures of the two sets of ABSs are verified, being consistent with the scenario of phase transition between the singlet and doublet ground state. Our study provides insight into Andreev transport properties of hybrid superconductor-QD devices and sheds light on the crossover behavior of the subgap spectrum in the vicinity of the 0 -π transition.

  8. Provider Info

    Data.gov (United States)

    U.S. Department of Health & Human Services — General information on currently active nursing homes, including number of certified beds, quality measure scores, staffing and other information used in the...

  9. Investigation on stresses of superconductors under pulsed magnetic fields based on multiphysics model

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Xiaobin, E-mail: yangxb@lzu.edu.cn; Li, Xiuhong; He, Yafeng; Wang, Xiaojun; Xu, Bo

    2017-04-15

    Highlights: • The differential equation including temperature and magnetic field was derived for a long cylindrical superconductor. • Thermal stress and electromagnetic stress were studied at the same time under pulse field magnetizing. • The distributions of the magnetic field, the temperature and stresses are studied and compared for two pulse fields of the different duration. • The Role thermal stress and electromagnetic stress play in the process of pulse field magnetizing is discussed. - Abstract: A multiphysics model for the numerical computation of stresses, trapped field and temperature distribution of a infinite long superconducting cylinder is proposed, based on which the stresses, including the thermal stresses and mechanical stresses due to Lorentz force, and trapped fields in the superconductor subjected to pulsed magnetic fields are analyzed. By comparing the results under pulsed magnetic fields with different pulse durations, it is found that the both the mechanical stress due to the electromagnetic force and the thermal stress due to temperature gradient contribute to the total stress level in the superconductor. For pulsed magnetic field with short durations, the thermal stress is the dominant contribution to the total stress, because the heat generated by AC-loss builds up significant temperature gradient in such short durations. However, for a pulsed field with a long duration the gradient of temperature and flux, as well as the maximal tensile stress, are much smaller. And the results of this paper is meaningful for the design and manufacture of superconducting permanent magnets.

  10. Nodal Liquid Theory of the Pseudo-Gap Phase of High-Tc Superconductors

    Science.gov (United States)

    Balents, Leon; Fisher, Matthew P. A.; Nayak, Chetan

    We introduce and study the nodal liquid, a novel zero-temperature quantum phase obtained by quantum-disordering a d-wave superconductor. It has numerous remarkable properties which lead us to suggest it as an explanation of the pseudo-gap state in underdoped high-temperature superconductors. In the absence of impurities, these include power-law magnetic order, a T-linear spin susceptibility, nontrivial thermal conductivity, and two- and one-particle charge gaps, the latter evidenced, e.g. in transport and electron photoemission (which exhibits pronounced fourfold anisotropy inherited from the d-wave quasiparticles). We use a (2+1)-dimensional duality transformation to derive an effective field theory for this phase. The theory is comprised of gapless neutral Dirac particles living at the former d-wave nodes, weakly coupled to the fluctuating gauge field of a dual Ginzburg-Landau theory. The nodal liquid interpolates naturally between the d-wave superconductor and the insulating antiferromagnet, and our effective field theory is powerful enough to permit a detailed analysis of a panoply of interesting phenomena, including charge ordering, antiferromagnetism, and d-wave superconductivity. We also discuss the zero-temperature quantum phase transitions which separate the nodal liquid from various ordered phases.

  11. 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...

  12. Charge of a quasiparticle in a superconductor

    Science.gov (United States)

    Ronen, Yuval; Cohen, Yonatan; Kang, Jung-Hyun; Haim, Arbel; Rieder, Maria-Theresa; Heiblum, Moty; Mahalu, Diana; Shtrikman, Hadas

    2016-01-01

    Nonlinear charge transport in superconductor–insulator–superconductor (SIS) Josephson junctions has a unique signature in the shuttled charge quantum between the two superconductors. In the zero-bias limit Cooper pairs, each with twice the electron charge, carry the Josephson current. An applied bias VSD leads to multiple Andreev reflections (MAR), which in the limit of weak tunneling probability should lead to integer multiples of the electron charge ne traversing the junction, with n integer larger than 2Δ/eVSD and Δ the superconducting order parameter. Exceptionally, just above the gap eVSD ≥ 2Δ, with Andreev reflections suppressed, one would expect the current to be carried by partitioned quasiparticles, each with energy-dependent charge, being a superposition of an electron and a hole. Using shot-noise measurements in an SIS junction induced in an InAs nanowire (with noise proportional to the partitioned charge), we first observed quantization of the partitioned charge q = e*/e=n, with n = 1–4, thus reaffirming the validity of our charge interpretation. Concentrating next on the bias region eVSD∼2Δ, we found a reproducible and clear dip in the extracted charge to q ∼0.6, which, after excluding other possibilities, we attribute to the partitioned quasiparticle charge. Such dip is supported by numerical simulations of our SIS structure. PMID:26831071

  13. Demagnetisation by crossed fields in superconductors

    Science.gov (United States)

    Campbell, Archie; Baghdadi, Mehdi; Patel, Anup; Zhou, Difan; Huang, K. Y.; Shi, Yunhua; Coombs, Tim

    2017-03-01

    A study has been made of the decay of the trapped magnetisation in superconductors when exposed to a crossed field. Numerical results have been compared with the theory of Brandt and Mikitik (2002 Phys. Rev. Lett. 89 027002) which solves the problem for a thin strip superconductor. FlexPDE with the A formulation and COMSOL with the H formulation were both used. Simulations of a strip with a cross section aspect ratio of 20 showed good agreement with theory both for the case of a transverse field larger than the transverse penetration field and for one smaller. In the latter case the magnetisation saturates as predicted, however the simulations show a slow decay after many cycles. In the case of stacked YBCO tapes the movement of flux lines is very small and the effects of the reversible motion were investigated. This can decrease the decay initially for very thin decoupled tapes, but cause a steady decay after very large numbers of cycles. Simulations on stacked strips showed that the decay constant increased approximately linearly with the number of strips. When combined with the theory for one tape this can explain the very slow decay observed in previous experiments. Experimental results were qualitatively in agreement with theory and simulations but showed some discrepancies. However there are a number of differences between the experimental situation and theory so good agreement is not expected.

  14. Development of Strengthened Bundle High Temperature Superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Lue, J.W.; Lubell, M.S. [Oak Ridge National Lab., TN (United States); Demko, J.A. [Oak Ridge Inst. for Science and Education, TN (United States); Tomsic, M. [Plastronic, Inc., Troy, OH (United States); Sinha, U. [Southwire Company, Carollton, GA (United States)

    1997-12-31

    In the process of developing high temperature superconducting (HTS) transmission cables, it was found that mechanical strength of the superconducting tape is the most crucial property that needs to be improved. It is also desirable to increase the current carrying capacity of the conductor so that fewer layers are needed to make the kilo-amp class cables required for electric utility usage. A process has been developed by encapsulating a stack of Bi-2223/Ag tapes with a silver or non-silver sheath to form a strengthened bundle superconductor. This process was applied to HTS tapes made by the Continuous Tube Forming and Filling (CTFF) technique pursued by Plastronic Inc. and HTS tapes obtained from other manufacturers. Conductors with a bundle of 2 to 6 HTS tapes have been made. The bundled conductor is greatly strengthened by the non-silver sheath. No superconductor degradation as compared to the sum of the original critical currents of the individual tapes was seen on the finished conductors.

  15. Percolation effect in thick film superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Sali, R.; Harsanyi, G. [Technical Univ. of Budapest (Hungary)

    1994-12-31

    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{sub 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{sup 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.

  16. Optical Spectroscopy of Strongly Correlated (MOTT-HUBBARD, Heavy-Fermion, Unconventional Superconductor) Materials Tuned Pressure

    Energy Technology Data Exchange (ETDEWEB)

    Goncharov, A; Struzhkin, V V

    2003-11-12

    During the past years, the Co-PI's have been responsible for the development and operation of optical techniques (Raman, IR, fluorescence, absorption and reflectance spectroscopy at ultrahigh pressures and high and low temperatures) which have proven to be extremely powerful for studying low-Z, molecular solids including hydrogen, ice, etc. (see results below). Meanwhile, it has become increasingly clear that optical spectroscopy has an equally extraordinary potential for studying metals and superconductors at ultrahigh pressures, thus the result will have a major impact on material research. However, because of the extreme difference in optical properties of opaque metals and transparent insulating molecular solids, successful accomplishment of the present project will require substantial effort in improving the present equipment and developing new techniques, and funds for this are requested here. Below we provide a short description of the work done and techniques developed during the last years. We also propose to explore new frontiers in compressed materials close to the insulator-metal boundaries, spin-crossover, and other quantum critical points.

  17. Incoherent vs. coherent behavior in the normal state of copper oxide superconductors

    Science.gov (United States)

    Tesanovic, Zlatko

    1991-01-01

    The self-consistent quantum fluctuations around the mean-field Hartree-Fock state of the Hubbard model provide a very good description of the ground state and low temperature properties of a 2-D itinerant antiferromagnet. Very good agreement with numerical calculations and experimental data is obtained by including the one- and two-loop spin wave corrections to various physical quantities. In particular, the destruction of the long-range order above the Neel temperature can be understood as a spontaneous generation of a length-scale epsilon(T), which should be identified as the spin correlation length. For finite doping, the question of the Hartree-Fock starting point becomes a more complex one since an extra hole tends to self-trap in antiferromagnetic background. Such quantum defects in an underlying antiferromagnetic state can be spin-bags or vortex-like structures and tend to suppress the long-range order. If motion of the holes occurs on a time-scale shorter than the one associated with the motion of these quantum defects of a spin background, one obtains several important empirical features of the normal state of CuO superconductors like linear T-dependence of resistivity, the cusp in the tunneling density of states, etc. As opposed to a familiar Fermi-liquid behavior, the phenomenology of the above system is dominated by a large incoherent piece of a single hole propagator, resulting in many unusual normal state properties.

  18. Electronic fine structure in the nickel carbide superconductor Th2NiC2

    Science.gov (United States)

    Quan, Y.; Pickett, W. E.

    2013-07-01

    The recently reported nickel carbide superconductor body centered tetragonal I4/mmm Th2NiC2 with Tc=8.5 K increasing to 11.2 K upon alloying Th with Sc is found to have very fine structure in its electronic spectrum, according to density functional based first-principles calculations. The filled Ni 3d band complex is hybridized with C 2p and Th character to and through the Fermi level (EF), and a sharply structured density of states arises only when spin-orbit coupling is included, which splits a zone-center degeneracy, leaving a very flat band edge lying at the Fermi level. The flat part of the band corresponds to an effective mass mz*→∞ with large and negative mx*=my*. Although the region over which the effective mass characterization applies is less than 1% of the zone volume, it supplies on the order of half the states at (or just above) the Fermi level. The observed increase of Tc by hole doping is accounted for if the reference as-synthesized sample is minutely hole doped, which decreases the Fermi level density of states and will provide some stabilization. In this scenario, electron doping will increase the Fermi level density of states and the superconducting critical temperature. Vibrational properties are presented, and enough coupling to the C-Ni-C stretch mode at 70 meV is obtained to imply that superconductivity is electron-phonon mediated.

  19. Electrical manipulation of Majorana fermions in an interdigitated superconductor-ferromagnet device.

    Science.gov (United States)

    Lee, Shu-Ping; Alicea, Jason; Refael, Gil

    2012-09-21

    We show that a topological phase supporting Majorana fermions can form in a two-dimensional electron gas (2DEG) adjacent to an interdigitated superconductor-ferromagnet structure. An advantage of this setup is that the 2DEG can induce the required Zeeman splitting and superconductivity from a single interface, allowing one to utilize a wide class of 2DEGs including the surface states of bulk InAs. We demonstrate that the interdigitated device supports a robust topological phase when the finger spacing λ is smaller than half of the Fermi wavelength λ(F). In this regime, the electrons effectively see a "smeared" Zeeman splitting and pairing field despite the interdigitation. The topological phase survives even in the opposite limit λ > λ(F)/2, although with a reduced bulk gap. We describe how to electrically generate a vortex in this setup to trap a Majorana mode, and predict an anomalous Fraunhofer pattern that provides a sharp signature of chiral Majorana edge states.

  20. Design features of internal tin superconductors for ITER magnetic system

    Energy Technology Data Exchange (ETDEWEB)

    Pantsyrnyi, V.I.; Shikov, A.K.; Nikulin, A.D.; Silaev, A.G.; Bel`akov, N.A.; Vdovin, V.F.; Semin, M.J. [Bochvar All-Russia Inst. of Inorganic Materials, Moscow (Russian Federation)

    1996-07-01

    The influence of parameters of internal tin superconductor design on the main working characteristics such as critical current density and hysteresis losses were analyzed. It was shown that having the value of hysteresis losses at the acceptable level of 400--600 mJ/cm{sup 3} the critical current density 20--30% higher than the value typical for bronze route processed superconductors was attainable in principle. The results of experimental work on the design of new types of internal tin superconductors for ITER magnetic system are given.

  1. Study of the glass formation of high temperature superconductors

    Science.gov (United States)

    Ethridge, Edwin C.; Kaukler, William F.; Rolin, Terry

    1992-01-01

    A number of compositions of ceramic oxide high T(sub c) superconductors were elevated for their glass formation ability by means of rapid thermal analysis during quenching, optical, and electron microscopy of the quenched samples, and with subsequent DSC measurements. Correlations between experimental measurements and the methodical composition changes identified the formulations of superconductors that can easily form glass. The superconducting material was first formed as a glass; then, with subsequent devitrification, it was formed into a bulk crystalline superconductor by a series of processing methods.

  2. Vortex loops entry into type-II superconductors

    CERN Document Server

    Samokhvalov, A V

    1996-01-01

    The magnetic field distribution, the magnetic flux, and the free energy of an Abrikosov vortex loop near a flat surface of type--II superconductors are calculated in the London approximation. The shape of such a vortex line is a semicircle of arbitrary radius. The interaction of the vortex half--ring and an external homogeneous magnetic field applied along the surface is studied. The magnitude of the energy barrier against the vortex expansion into superconductor is found. The possibilities of formation of an equilibrium vortex line determined by the structure of the applied magnetic field by creating the expanding vortex loops near the surface of type--II superconductor are discussed.

  3. Effects of chiral helimagnets on vortex states in a superconductor

    Science.gov (United States)

    Fukui, Saoto; Kato, Masaru; Togawa, Yoshihiko

    2016-12-01

    We have investigated vortex states in chiral helimagnet/superconductor bilayer systems under an applied external magnetic field {H}{appl}, using the Ginzburg-Landau equations. Effect of the chiral helimagnet on the superconductor is taken as a magnetic field {H}{CHM}, which is perpendicular to the superconductor and oscillates spatially. For {H}{appl}=0 and weak {H}{CHM}, there appear pairs of up- and down-vortices. Increasing {H}{appl}, down-vortices gradually disappear, and the number of up-vortices increases in the large magnetic field region. Then, up-vortices form parallel, triangular, or square structures.

  4. Magnetization of two-dimensional superconductors with defects

    CERN Document Server

    Kashurnikov, V A; Zyubin, M V

    2002-01-01

    The new method for modeling the layered high-temperature superconductors magnetization with defects, based on the Monte-Carlo algorithm, is developed. Minimization of the free energy functional of the vortex two-dimensional system made it possible to obtain the equilibrium vortex density configurations and calculate the magnetization of the superconductor with the arbitrary defects distribution in the wide range of temperatures. The magnetic induction profiles and magnetic flux distribution inside the superconductor, proving the applicability of the Bean model, are calculated

  5. 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.

  6. Unbalanced Holographic Superconductors and Spintronics

    CERN Document Server

    Bigazzi, Francesco; Musso, Daniele; Fokeeva, Natalia Pinzani; Seminara, Domenico

    2011-01-01

    We present a minimal holographic model for s-wave superconductivity with unbalanced Fermi mixtures, in 2+1 dimensions at strong coupling. The breaking of a U(1)_A "charge" symmetry is driven by a non-trivial profile for a charged scalar field in a charged asymptotically AdS_4 black hole. The chemical potential imbalance is implemented by turning on the temporal component of a U(1)_B "spin" field under which the scalar field is uncharged. We study the phase diagram of the model and comment on the eventual (non) occurrence of LOFF-like inhomogeneous superconducting phases. Moreover, we study "charge" and "spin" transport, implementing a holographic realization (and a generalization thereof to superconducting setups) of Mott's two-current model which provides the theoretical basis of modern spintronics. Finally we comment on possible string or M-theory embeddings of our model and its higher dimensional generalizations, within consistent Kaluza-Klein truncations and brane-anti brane setups.

  7. Experiments on non-equilibrium superconductor-normal metal-superconductor Josephson junctions

    Science.gov (United States)

    Crosser, Michael S.

    By controlling the distribution function within the normal metal of a superconductor/normal metal/superconductor (SNS) Josephson junction, one can reverse the supercurrent-phase relation in the normal wire, creating a pi-junction. This manipulation is done by injecting normal quasiparticle current into the wire, via one or more leads attached at the middle of the junction. Two experiments evolve from this concept. First, in a sample of four reservoirs, two normal and two superconducting, all connected by a wire cross of normal metal, one may inject current either antisymmetrically (AS) or symmetrically (S). In the AS case, current is injected into one normal lead and extracted from the other, creating normal current flow that does not interact with the supercurrent except at the junction. In the S case, current is injected into both normal leads and extracted from the superconductors. Theory predicts that, in the absence of electron energy relaxation in the normal part of the junction, these two situations should result in identical behavior of the Josephson junction. However, due to Joule heating, the S case shows a slightly larger maximum pi-current than the AS case. The second experiment considers a more subtle effect resulting from normal current being injected symmetrically into a SNS Josephson junction. One side of the SNS junction has both normal current and supercurrent flowing in the same direction while the other side has opposing current flows. This situation creates an effective energy gradient across the SNS junction that can appear in the distribution function of the normal wire. Using superconductor/insulator/normal metal tunnelling spectroscopy, it is possible to extract these changes to the distribution function.

  8. Physics picture from neutron scattering study on Fe-based superconductors

    Institute of Scientific and Technical Information of China (English)

    Bao Wei

    2013-01-01

    Neutron scattering,with its ability to measure the crystal structure,the magnetic order,and the structural and magnetic excitations,plays an active role in investigating various families of Fe-based high-Tc superconductors.Three different types of antiferromagnetic orders have been discovered in the Fe plane,but two of them cannot be explained by the spin-densitywave (SDW) mechanism of nesting Fermi surfaces.Noticing the close relation between antiferromagnetic order and lattice distortion in orbital ordering from previous studies on manganites and other oxides,we have advocated orbital ordering as the underlying common mechanism for the structural and antiferromagnetic transitions in the 1111,122,and 11 parent compounds.We observe the coexistence of antiferromagnetic order and superconductivity in the (Ba,K)Fe2As2 system,when its phase separation is generally accepted.Optimal Tc is proposed to be controlled by the local FeAs4 tetrahedron from our investigation on the 1111 materials.The Bloch phase coherence of the Fermi liquid is found crucial to the occurrence of bulk superconductivity in iron chalcogenides of both the 11 and the 245 families.Iron chalcogenides carry a larger staggered magnetic moment (> 2 μB/Fe) than that in iron pnictides (< 1 μB/Fe) in the antiferromagnetic order.Normal state magnetic excitations in the 11 superconductor are of the itinerant nature while in the 245 superconductor the spin-waves of localized moments.The observation of superconducting resonance peak provides a crucial piece of information in current deliberation of the pairing symmetry in Fe-based superconductors.

  9. Development and exploration of potential routes of discovery of new superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Lin, Xiao [Iowa State Univ., Ames, IA (United States)

    2013-01-01

    This thesis summarizes our efforts to develop and explore potential routes for the discovery of new superconductors. The development of viable solutions for sulfur-bearing compounds is presented. It also provides the details of searching for quantum critical points (QCPs) and possible superconductors by suppressing ferromagnetic states via chemical substitution and the application of pressure. The ferromagnetism in La(VxCr1-x)Ge3 was successfully suppressed by pressure, and, in addition, a potential QCP at ambient pressure was discovered for x = 0.16. On the other hand, the La(VxCr1-x)Sb3 series is likely to evolve into new magnetic state with V-substitution with the Cr-based magnetism appearing to be more local-moment like than for the case of LaCrGe3. We also performed detailed characterization on BaSn5 superconductor, giving further understanding of its superconducting state, and on R3Ni2-xSn7 and RNi1-xBi2±y series putting to rest spurious claims of superconductivity.

  10. Progress in American Superconductor's HTS wire and optimization for fault current limiting systems

    Science.gov (United States)

    Malozemoff, Alexis P.

    2016-11-01

    American Superconductor has developed composite coated conductor tape-shaped wires using high temperature superconductor (HTS) on a flexible substrate with laminated metal stabilizer. Such wires enable many applications, each requiring specific optimization. For example, coils for HTS rotating machinery require increased current density J at 25-50 K. A collaboration with Argonne, Brookhaven and Los Alamos National Laboratories and several universities has increased J using an optimized combination of precipitates and ion irradiation defects in the HTS. Major commercial opportunities also exist to enhance electric power grid resiliency by linking substations with distribution-voltage HTS power cables [10]. Such links provide alternative power sources if one substation's transmission-voltage power is compromised. But they must also limit fault currents which would otherwise be increased by such distribution-level links. This can be done in an HTS cable, exploiting the superconductor-to-resistive transition when current exceeds the wires' critical J. A key insight is that such transitions are usually nonuniform; so the wire must be designed to prevent localized hot spots from damaging the wire or even generating gas bubbles in the cable causing dielectric breakdown. Analysis shows that local heating can be minimized by increasing the composite tape's total thickness, decreasing its total resistance in the normal state and decreasing its critical J. This conflicts with other desirable wire characteristics. Optimization of these conflicting requirements is discussed.

  11. Develop and test an internally cooled, cabled superconductor (ICCS) for large scale MHD magnets

    Energy Technology Data Exchange (ETDEWEB)

    Marston, P.G.; Hale, J.R.; Dawson, A.M.

    1990-04-30

    The work conducted under DOE/PETC Contract DE-AC22-84PC70512 has included four principal tasks, (1) development of a Design Requirements Definition for a retrofit MHD magnet system, (2) analysis of an internally cooled, cabled superconductor (ICCS) to use in that design, (3) design of an experiment to test a subscale version of that conductor, which is a NbTi, copper stabilized superconductor, and (4) proof-of-concept testing of the conductor. The program was carried forth through the third task with very successful development and test of a conventional ICCS conductor with 27 multifilamentary copper-superconductor composite strands and a new concept conductor in which, in each triplet, two strands were pure copper and the third strand was a multifilamentary composite. In reviewing the magnet design and the premises for the conductor design it became obvious that, since the principal source of perturbation in MHD magnets derives from slippage between coils, or between turns in a coil, thereby producing frictional heat which must flow through the conductor sheath and the helium to the superconductor strands, an extra barrier might be highly effective in enhancing magnet stability and protection. This concept was developed and a sample conductor manufactured and tested in comparison with an identical conductor lacking such an additional barrier. Results of these conductor tests confirm the potential value of such a barrier. As the work of tasks 1 through 3 has been reported in detail in quarterly and semiannual reports, as well as in special reports prepared throughout the course of this project, this report reviews early work briefly and then discusses this last phase in great detail. 8 refs., 36 figs.

  12. Magnetic studies in organic superconductors bis(tetramethyltetraselenafulvalene) perchlorate: Upper critical fields and vortex matters

    Science.gov (United States)

    Oh, Jeong Il

    A thermodynamic determination of the upper critical field Hc2 in the quasi-one dimensional molecular organic superconductor (TMTSF) 2ClO4 has been obtained for magnetic field accurately aligned along the in-plane, inter-chain direction by utilizing silicon cantilever magnetometer technology. This magnetically-measured upper critical field, simultaneously confirmed by electrical transport measurements, was found to well-exceed all paramagnetic limits known to date for spin singlet superconductors, strongly indicating that (TMTSF)2ClO4 is a spin triplet superconductor. Also, we were able to investigate novel structure in the upper critical field, where we observed that Hc2(T) has three different temperature regimes, characterized by an usual upturn at a temperature T* ˜ 0.2 K and a very unusual kink at a temperature T0 ˜ 1.04 K. In addition, the magnetic field-temperature superconducting vortex phase diagram of (TMTSF)2ClO4 has been obtained. The phase diagram showed a variety of vortex phases, including solid (Bragg lattice and disordered glass) and liquid (liquid-1 and liquid-2) subphases. A distinct irreversibility line was found, likely separating the solid from the liquid phase. Within the solid phase, we observed an unusual inverse transition driven by the pinning force, splitting the solid phase into a disordered glass and a Bragg lattice. Also, within the Bragg lattice, we observed a temperature-independent magnetic crossover line at low field (˜0.05 T), interpreted as possibly indicating the existence of multiple Tc's in (TMTSF)2X, further evidence for claiming this system to be a triplet superconductor.

  13. Hard-Wired Dopant Networks and the Prediction of High Transition Temperatures in Ceramic Superconductors

    Directory of Open Access Journals (Sweden)

    J. C. Phillips

    2010-01-01

    Full Text Available I review the multiple successes of the discrete hard-wired dopant network model ZZIP, and comment on the equally numerous failures of continuum models, in describing and predicting the properties of ceramic superconductors. The prediction of transition temperatures can be regarded in several ways, either as an exacting test of theory, or as a tool for identifying theoretical rules for defining new homology models. Popular “first principle” methods for predicting transition temperatures in conventional crystalline superconductors have failed for cuprate HTSC, as have parameterized models based on CuO2 planes (with or without apical oxygen. Following a path suggested by Bayesian probability, it was found that the glassy, self-organized dopant network percolative model is so successful that it defines a new homology class appropriate to ceramic superconductors. The reasons for this success in an exponentially complex (non-polynomial complete, NPC problem are discussed, and a critical comparison is made with previous polynomial (PC theories. The predictions are successful for the superfamily of all ceramics, including new non-cuprates based on FeAs in place of CuO2.

  14. Nematic quantum critical point without magnetism in FeSe1-xSx superconductors

    Science.gov (United States)

    Hosoi, Suguru; Matsuura, Kohei; Ishida, Kousuke; Wang, Hao; Mizukami, Yuta; Watashige, Tatsuya; Kasahara, Shigeru; Matsuda, Yuji; Shibauchi, Takasada

    2016-07-01

    In most unconventional superconductors, the importance of antiferromagnetic fluctuations is widely acknowledged. In addition, cuprate and iron-pnictide high-temperature superconductors often exhibit unidirectional (nematic) electronic correlations, including stripe and orbital orders, whose fluctuations may also play a key role for electron pairing. In these materials, however, such nematic correlations are intertwined with antiferromagnetic or charge orders, preventing the identification of the essential role of nematic fluctuations. This calls for new materials having only nematicity without competing or coexisting orders. Here we report systematic elastoresistance measurements in FeSe1-xSx superconductors, which, unlike other iron-based families, exhibit an electronic nematic order without accompanying antiferromagnetic order. We find that the nematic transition temperature decreases with sulfur content x; whereas, the nematic fluctuations are strongly enhanced. Near ≈0.17, the nematic susceptibility diverges toward absolute zero, revealing a nematic quantum critical point. The obtained phase diagram for the nematic and superconducting states highlights FeSe1-xSx as a unique nonmagnetic system suitable for studying the impact of nematicity on superconductivity.

  15. Develop and test an Internally Cooled, Cabled Superconductor (ICCS) for large scale MHD magnets

    Science.gov (United States)

    Marston, P. G.; Hale, J. R.; Dawson, A. M.

    1990-04-01

    The work included four principal tasks: (1) development of a design requirements definition for a retrofit MHD magnet system; (2) analysis of an internally cooled, cabled superconductor (ICCS) to use in that design; (3) design of an experiment to test a subscale version of that conductor, which is a NbTi, copper stabilized superconductor; and (4) proof-of-concept testing of the conductor. The program was carried forth through the third task with very successful development and test of a conventional ICCS conductor with 27 multifilamentary copper-superconductor composite strands and a new concept conductor in which, in each triplet, two strands were pure copper and the third strand was a multifilamentary composite. In reviewing the magnet design and the premises for the conductor design it became obvious that an extra barrier might be highly effective in enhancing magnet stability and protection. This concept was developed and a sample conductor manufactured and tested in comparison with an identical conductor lacking such an additional barrier. Results of these conductor tests confirm the potential value of such a barrier. Since the work of tasks 1 through 3 has been reported in detail in quarterly and semiannual reports, as well as in special reports prepared throughout the course of this project, this report reviews early work briefly and then discusses this last phase in great detail.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2016-09-15

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

  17. Nematic quantum critical point without magnetism in FeSe1-xSx superconductors.

    Science.gov (United States)

    Hosoi, Suguru; Matsuura, Kohei; Ishida, Kousuke; Wang, Hao; Mizukami, Yuta; Watashige, Tatsuya; Kasahara, Shigeru; Matsuda, Yuji; Shibauchi, Takasada

    2016-07-19

    In most unconventional superconductors, the importance of antiferromagnetic fluctuations is widely acknowledged. In addition, cuprate and iron-pnictide high-temperature superconductors often exhibit unidirectional (nematic) electronic correlations, including stripe and orbital orders, whose fluctuations may also play a key role for electron pairing. In these materials, however, such nematic correlations are intertwined with antiferromagnetic or charge orders, preventing the identification of the essential role of nematic fluctuations. This calls for new materials having only nematicity without competing or coexisting orders. Here we report systematic elastoresistance measurements in FeSe1-xSx superconductors, which, unlike other iron-based families, exhibit an electronic nematic order without accompanying antiferromagnetic order. We find that the nematic transition temperature decreases with sulfur content x; whereas, the nematic fluctuations are strongly enhanced. Near [Formula: see text], the nematic susceptibility diverges toward absolute zero, revealing a nematic quantum critical point. The obtained phase diagram for the nematic and superconducting states highlights FeSe1-xSx as a unique nonmagnetic system suitable for studying the impact of nematicity on superconductivity.

  18. Scanning tunneling microscopy and spectroscopy measurements of superconductor/ferromagnet hybrids

    Science.gov (United States)

    Moore, Steven A.

    The focus of this thesis work is the study of the nanoscale electronic properties of magnetically coupled superconductor/ferromagnet hybrid structures using low-temperature scanning tunneling microscopy and spectroscopy (LT-STM/STS) under ultra-high vacuum conditions. There are a number of novel effects that can occur due to the non-homogenous magnetic field from the ferromagnet, which directly influence the global and local superconducting properties. These effects include the generation of vortices/anti-vortices by the non-uniform magnetic stray field, local modulations in the critical temperature, filamentary superconductivity close to the transition temperature, and superconducting channels that can be controlled by external magnetic fields. Prior to this dissertation the subject of superconductor/ferromagnet hybrid structures has been mainly studied using global measurements (such as transport and magnetization) or scanning probe techniques that are sensitive to the magnetic field. Scanning tunneling microscopy probes the local electronic density of states with atomic resolution, and therefore is the only technique that can study the emergence of superconductivity on the length scale of the coherence length. The novel results presented in this dissertation show that magnetically coupled superconductor/ferromagnet heterostructures offer the possibility to control and tune the strength and location of superconductivity and superconducting vortices, which has potential for promising technological breakthroughs in computing and power applications.

  19. High-temperature superconductor applications development at Argonne National Laboratory

    Science.gov (United States)

    Hull, J. R.; Poeppel, R. B.

    1992-02-01

    Developments at Argonne National Laboratory of near and intermediate term applications using high-temperature superconductors are discussed. Near-term applications of liquid-nitrogen depth sensors, current leads, and magnetic bearings are discussed in detail.

  20. The Discovery of a Class of High-Temperature Superconductors.

    Science.gov (United States)

    Muller, K. Alex; Bednorz, J. Georg

    1987-01-01

    Describes the new class of oxide superconductors, the importance of these materials, and the concepts that led to its discovery. Summarizes the discovery itself and its early confirmation. Discusses the observation of a superconductive glass state in percolative samples. (TW)