WorldWideScience

Sample records for superconductors etsub 2x

  1. Effects of magnetic field on the cuprate high-Tc superconductor La2-xSrxCuO4

    DEFF Research Database (Denmark)

    Lake, B.; Aeppli, G.; Christensen, N.B.

    2004-01-01

    This article discusses neutron scattering measurements on the cuprate, high transition temperature superconductor La2-xSrxCuO4 (LSCO) in an applied magnetic field. LSCO is a type-II superconductor and magnetic flux can penetrate the material via the formation of vorticies. Phase coherent...

  2. Topological superconductor in quasi-one-dimensional Tl2 -xMo6Se6

    Science.gov (United States)

    Huang, Shin-Ming; Hsu, Chuang-Han; Xu, Su-Yang; Lee, Chi-Cheng; Shiau, Shiue-Yuan; Lin, Hsin; Bansil, Arun

    2018-01-01

    We propose that the quasi-one-dimensional molybdenum selenide compound Tl2 -xMo6Se6 is a time-reversal-invariant topological superconductor induced by intersublattice pairing, even in the absence of spin-orbit coupling (SOC). No noticeable change in superconductivity is observed in Tl-deficient (0 ≤x ≤0.1 ) compounds. At weak SOC, the superconductor prefers the triplet d vector lying perpendicular to the chain direction and two-dimensional E2 u symmetry, which is driven to a nematic order by spontaneous rotation symmetry breaking. The locking energy of the d vector is estimated to be weak and hence the proof of its direction would rely on tunneling or phase-sensitive measurements.

  3. Structural phase transitions in Iron - based superconductors BaFe2-xCrxAs2 under high pressure

    International Nuclear Information System (INIS)

    Uhoya, W.O.; Montgomery, J.M.; Samudrala, G.K.; Tsoi, G.M.; Vohra, Y.K.; Sefar, A.S.

    2011-01-01

    Pure BaFe 2 As 2 with the ThCr 2 Si 2 -type crystal structure under ambient conditions is known to superconduct under high pressure and undergo an isostructural phase transition from tetragonal to collapsed tetragonal phase which is accompanied by anomalous compressibility effects. Presently, there is no reported work on the crystal structure on any of the chemically doped 122- iron based superconductors under high pressure. We have carried out the electrical resistance measurements and high pressure X-ray diffraction studies on Chromium doped samples of BaFe 2-x Cr x As 2 (x = 0, 0.05, 0.15, 0.4, 0.61) to a pressure of 75 GPa and a temperature of 10K using a synchrotron source and designer diamond anvils, so as to investigate the influence of chemical doping and high pressure on crystal structure and superconductivity

  4. Dispersive excitations in the high-temperature superconductor La2-xSrxCuO4

    DEFF Research Database (Denmark)

    Christensen, N.B.; McMorrow, D.F.; Rønnow, H.M.

    2004-01-01

    High-resolution neutron scattering experiments on optimally doped La(2-x)Sr(x)CuO(4) (x=0.16) reveal that the magnetic excitations are dispersive. The dispersion is the same as in YBa(2)Cu(3)O(6.85), and is quantitatively related to that observed with charge sensitive probes. The associated veloc...

  5. Role of the lattice dynamics in La2-xBaxCuO4 superconductor based on DFT method

    Directory of Open Access Journals (Sweden)

    A Tavana

    2010-09-01

    Full Text Available Electron-phonon coupling parameters are calculated for La2-x BaxCuO4 cuprate superconductor in a wide range of dopings, from undoped to overdoped compounds. In this study we aim to study the quality of such calculations based on DFT method so, the results of σ GGA+U electronic structure calculations are also investigated. The obtained value for electron-phonon coupling is in the same order of previous calculations but, the value obtained for the Hubbard U parameter shows that, such methods are poor in the estimation of electronic correlations to decide about the role of phonons in these compounds based on their results. Moreover, existence of several structural phase transitions with temperature and doping, lead to larger error in these calculations. Based on the calculated phonon dispersions, structural phase transitions can be resulted which shows the ability of DFT in the study of structural properties and the weakness of the strongly correlations in this properties.

  6. Nernst effect in the electron-doped cuprate superconductor L a2 -xC exCu O4

    Science.gov (United States)

    Mandal, P. R.; Sarkar, Tarapada; Higgins, J. S.; Greene, Richard L.

    2018-01-01

    We report a systematic study of the Nernst effect in films of the electron-doped cuprate superconductor L a2 -xC exCu O4 as a function of temperature and magnetic field (up to 14 T) over a range of doping from underdoped (x =0.08 ) to overdoped (x =0.16 ). We have determined the characteristic field scale HC2 * of superconducting fluctuation which is found to track the domelike dependence of superconductivity (TC). The fall of HC2 * and TC with underdoping is most likely due to the onset of long-range antiferromagnetic order. We also report the temperature onset, Tonset, of superconducting fluctuations above TC. For optimally doped x =0.11 Tonset (≅39 K ) is high compared to TC (26 K). For higher doping Tonset decreases and tends to zero along with the critical temperature at the end of the superconducting dome. The superconducting gap closely tracks HC2 * measured from the temperature- and field-dependent Nernst signal.

  7. New Intermetallic Ternary Phosphide Chalcogenide AP2-xXx (A = Zr, Hf; X = S, Se) Superconductors with PbFCl-Type Crystal Structure

    Science.gov (United States)

    Kitô, Hijiri; Yanagi, Yousuke; Ishida, Shigeyuki; Oka, Kunihiko; Gotoh, Yoshito; Fujihisa, Hiroshi; Yoshida, Yoshiyuki; Iyo, Akira; Eisaki, Hiroshi

    2014-07-01

    We have synthesized a series of intermetallic ternary phosphide chalcogenide superconductors, AP2-xXx (A = Zr, Hf; X = S, Se), using the high-pressure synthesis technique. These materials have a PbFCl-type crystal structure (space group P4/nmm) when x is greater than 0.3. The superconducting transition temperature Tc changes systematically with x, yielding dome-like phase diagrams. The maximum Tc is achieved at approximately x = 0.7, at which point the Tc is 6.3 K for ZrP2-xSex (x = 0.75), 5.5 K for HfP2-xSex (x = 0.7), 5.0 K for ZrP2-xSx (x = 0.675), and 4.6 K for Hfp2-xSx (x = 0.5). They are typical type-II superconductors and the upper and lower critical fields are estimated to be 2.92 T at 0 K and 0.021 T at 2 K for ZrP2-xSex (x = 0.75), respectively.

  8. Contact spectroscopy of high-temperature superconductors (Review). I - Physical and methodological principles of the contact spectroscopy of high-temperature superconductors. Experimental results for La(2-x)Sr(x)CuO4 and their discussion

    Science.gov (United States)

    Ianson, I. K.

    1991-03-01

    Research in the field of high-temperature superconductors based on methods of tunneling and microcontact spectroscopy is reviewed in a systematic manner. The theoretical principles of the methods are presented, and various types of contacts are described and classified. Attention is given to deviations of the measured volt-ampere characteristics from those predicted by simple theoretical models and those observed for conventional superconductors. Results of measurements of the energy gap and fine structure of volt ampere characteristic derivatives are presented for La(2-x)Sr(x)CuO4.

  9. Investigation of Pb doping on electrical, structural and superconducting properties of YBa2-xPbxCu3O7-δ superconductors

    Science.gov (United States)

    Ezzatpour, S.; Sharifzadegan, L.; Sarvari, F.; Sedghi, H.

    2018-06-01

    In this study the high temperature superconductor YBa2-xPbxCu3O7-δ with doping x = ,0.05,0.1,0.15 were prepared by the standard solid-state reaction method. The effect of Pb substitution on Ba site of YBCO superconducting system, structural, electrical and superconducting properties of Y-based superconductor has been investigated. The measurements of dc resisitivity were performed on all samples with four-probe method using low frequency/lowAC current (4 mA) . The superconducting temperature, Tc, were determined from the resistivity versus temperature (R-T) curves. Results show that Pb doping reduced the cirtical temperature(Tc) and superconductivity properties of our samples. The maximum and the minimum Tc were observed for the samples with x = 0.15 and x = 0.1 respectively. The structure and phase purity of samples were examined by the X-ray powder diffraction technique (XRD) performed by means of D8 Advance Bruker diffractometer with Cu kα radiation. The grain morphology of surface of the samples was analyzed by sacanning electron microscopy (SEM). XRD patterns of polycrystalline materials of composition YBa2-xPbxCu3O7-δ revealed that all prepared samples are orthorhombic. All of the peaks of YBCO and YBa2-xPbxCu3O7-δ have been used for the estimation of volume fractions of the phases and ignored the void peaks.

  10. Evidence for electron-electron correlations in La2CuO4 and Lasub(2-x)Srsub(x)CuO4 superconductors

    International Nuclear Information System (INIS)

    Greene, R.L.; Plaskett, T.S.; Maletta, H.; Bednorz, J.G.; Muller, K.A.

    1987-01-01

    We report a study of the magnetic susceptibility of Lasub(2-x)Srsub(x)CUO 4 for x = 0, 0.10, 0.15, 0.20 from 4-350K. Our data suggest that La 2 CuO 4 has a spin-density wave or antiferromagnetic transition near 250K. The Sr doped superconductors have a Pauli susceptibility above Tsub(c) 35-40K that is enhanced by electron-electron correlations. The variation in Tsub(c) with Sr doping is not directly correlated with the change in electron density of states. (author)

  11. Effects of calcium doping on the superconducting properties of top-seeded melt growth processed Y1.5Ba2-xCaxCu3Oy superconductors

    International Nuclear Information System (INIS)

    Park, S.D.; Kim, H.J.; Park, B.J.; Han, Y.H.; Jun, B.-H.; Lee, J.S.; Kim, C.-J.

    2011-01-01

    We study effects of calcium doping in melt processed Y123 superconductors. We examine a superconducting transition temperature and current density. A transition temperature and current density decreases by calcium doping. Calcium doping leads to coarseing of Y211 particles. Y211 refining effect by CeO 2 is disappreared by calcium doping. The effect of calcium doping on the superconducting properties of top seeded melt growth (TSMG) processed Y 1.5 Ba 2-x Ca x Cu 3 O y superconductors was studied in terms of calcium content (X ca ). YBa 2-x Ca x Cu 3 O 7-δ (X ca = 0, 0.005, 0.01, 0.02, 0.04, 0.1, 0.3) powders were synthesized by the powder calcination method. YBa 2-x Ca x Cu 3 O 7-δ powders were mixed with 0.25 mole Y 2 O 3 powder and 1 wt.% CeO 2 as Y 2 BaCuO 5 (Y211) refiner, and finally made into Y 1 . 5 Ba 2-x Ca x Cu 3 O y (Y1.5) + 1 wt.% CeO 2 composition. The single Y123 growth on the top surface was observed up to X ca = 0.1, while the multiple Y123 growth was observed at X ca ≥ 0.1. The superconducting transition temperature (T c ) and critical current density (J c ) of TSMG processed Y1.5 samples were inversely proportional to X ca . The Y211 size increased with increasing X ca due to the enhancement of Y211 coarsening by calcium doping. No Y211 refining effect by CeO 2 was observed in the calcium doped samples. The T c and J c decrease by calcium doping are likely to be due to the calcium incorporation with the Y123 lattice and formation of coarse Y211 particles.

  12. Superconductivity, critical current density, and flux pinning in MgB2-x(SiC)x/2 superconductor after SiC nanoparticle doping

    Science.gov (United States)

    Dou, S. X.; Pan, A. V.; Zhou, S.; Ionescu, M.; Wang, X. L.; Horvat, J.; Liu, H. K.; Munroe, P. R.

    2003-08-01

    We investigated the effect of SiC nanoparticle doping on the crystal lattice structure, critical temperature Tc, critical current density Jc, and flux pinning in MgB2 superconductor. A series of MgB2-x(SiC)x/2 samples with x=0-1.0 were fabricated using an in situ reaction process. The contraction of the lattice and depression of Tc with increasing SiC doping level remained rather small most likely due to the counterbalancing effect of Si and C co-doping. The high level Si and C co-doping allowed the creation of intragrain defects and highly dispersed nanoinclusions within the grains which can act as effective pinning centers for vortices, improving Jc behavior as a function of the applied magnetic field. The enhanced pinning is mainly attributable to the substitution-induced defects and local structure fluctuations within grains. A pinning mechanism is proposed to account for different contributions of different defects in MgB2-x(SiC)x/2 superconductors.

  13. Superconductors

    International Nuclear Information System (INIS)

    1988-01-01

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

  14. Superconductors

    CERN Document Server

    Narlikar, A V

    2014-01-01

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

  15. Effect of lead content on nonstoichiometric Bi2-xPbySr2Ca2Cu3Oδ ceramic superconductors

    International Nuclear Information System (INIS)

    Diaz-Valdes, E.; Pacheco-Malagon, G.; Contreras-Puente, G.; Mejia-Garcia, C.; Andrade-Garay, G.; Ortiz-Lopez, J.; Conde-Gallardo, A.; Falcony, C.

    1993-01-01

    Ceramic superconducting samples of the type Bi 2-x Pb y Sr 2 Ca 2 Cu 3 O δ were processed with a nonstoichiometric content of Bi and Pb (x≠y) with respect to the 2223 phase in this system. The resistance vs. temperature characteristics and the presence of the 2223 and 2212 phases as a function of the sample preparation conditions and the lead content (Bi/Pb ratio) are reported. The growth of unwanted phases such as PbO was observed for those samples with a high content of Pb (y=0.9) and Bi (x=0.1). (orig.)

  16. Angle Resolved Photoemission Spectroscopy Studies of the Mott Insulator to Superconductor Evolution in Ca2-xNaxCuO2Cl2

    Energy Technology Data Exchange (ETDEWEB)

    Shen, Kyle Michael

    2005-09-02

    It is widely believed that many of the exotic physical properties of the high-T{sub c} cuprate superconductors arise from the proximity of these materials to the strongly correlated, antiferromagnetic Mott insulating state. Therefore, one of the fundamental questions in the field of high-temperature superconductivity is to understand the insulator-to-superconductor transition and precisely how the electronic structure of Mott insulator evolves as the first holes are doped into the system. This dissertation presents high-resolution, doping dependent angle-resolved photoemission (ARPES) studies of the cuprate superconductor Ca{sub 2-x}Na{sub x}CuO{sub 2}Cl{sub 2}, spanning from the undoped parent Mott insulator to a high-temperature superconductor with a T{sub c} of 22 K. A phenomenological model is proposed to explain how the spectral lineshape, the quasiparticle band dispersion, and the chemical potential all progress with doping in a logical and self-consistent framework. This model is based on Franck-Condon broadening observed in polaronic systems where strong electron-boson interactions cause the quasiparticle residue, Z, to be vanishingly small. Comparisons of the low-lying states to different electronic states in the valence band strongly suggest that the coupling of the photohole to the lattice (i.e. lattice polaron formation) is the dominant broadening mechanism for the lower Hubbard band states. Combining this polaronic framework with high-resolution ARPES measurements finally provides a resolution to the long-standing controversy over the behavior of the chemical potential in the high-T{sub c} cuprates. This scenario arises from replacing the conventional Fermi liquid quasiparticle interpretation of the features in the Mott insulator by a Franck-Condon model, allowing the reassignment of the position of the quasiparticle pole. As a function of hole doping, the chemical potential shifts smoothly into the valence band while spectral weight is transferred

  17. Superconductors

    International Nuclear Information System (INIS)

    Ekin, J.W.

    1983-01-01

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

  18. Study of magnetic excitations in the high critical temperature La2-xSrxCuO4 superconductor with neutrons inelastic scattering

    International Nuclear Information System (INIS)

    Petit, S.

    1997-01-01

    In this work, we question the relevance of spin correlations in the problem of high-T c superconductivity. To characterize these correlations, we present a detailed inelastic neutron scattering study of the magnetic excitations spectrum, in the high T c La 2-x Sr x CuO 4 copper oxide superconductor, as a function of temperature and strontium content x. Our study demonstrates the existence of two distinct types of fluctuations. The first type corresponds to two-dimensional isotropic fluctuations peaked at incommensurate points around the antiferromagnetic wavevector. These fluctuations show a gap below T c . The second type of fluctuations corresponds to two-dimensional very low energy, typically 1 MeV, antiferromagnetic correlations. They arise at low temperatures, for T ≤T f ∼ 10 K ≤T c . Different scenarios are discussed, namely particle-hole excitation arising because of nesting properties of the Fermi surface, stripes, and localized carriers in the CuO 2 plane because of the La/Sr substitution disorder. Next, aiming to study the interrelation between magnetism and superconductivity, we present a theoretical perturbative treatment of the t-t'-J model. This model is believed to describe the physics of the CuO 2 plane. The considered quasiparticles describe the motion of a doped hole, followed by localized spins on the copper sites. For a given doping x, two phases can exist, containing either x or 1 + x of these quasiparticles. We show at in the second phase, the exchange interaction between localized spins, combined to the intrinsic anharmonicity of these quasiparticles leads to an attractive interaction between them. We study the stability and the symmetry of a superconducting phase based on this mechanism. (author)

  19. Effect of mixing RE elements (Nd, Sm, Gd, Eu, Y, Yb) on the RE2BaCuO5/Nd4-2xBa2+2xCu2-xO10-2x phases in RE cuprate high-Tc superconductors

    International Nuclear Information System (INIS)

    Langhorn, J.B.; Black, M.A.; McGinn, P.J.

    1999-01-01

    The phases RE 2 BaCuO 5 /RE 4 Ba 2 Cu 2 O 10 phases (where RE is a mixture of Nd, Sm, Gd, Eu, Y and Yb) have been synthesized in an oxygen atmosphere and subsequently characterized. The mixing of RE elements which inherently form the RE 2 BaCuO 5 phase through the peritectic decomposition of REBa 2 Cu 3 O 7-x (RE123) (i.e. Sm, Gd, Eu, Y, Yb), was observed to give homogeneous mixing of the elements in the 211 phase. In contrast it was found that on mixing Nd with other RE elements a mixture of the Nd 4-2x Ba 2+2x Cu 2-x O 10-2x (Nd422) and RE 2 BaCuO 5 (RE211) phases resulted. It was also observed that on mixing Nd with other REs a finite amount of the RE is substituted into the Nd422 phase and Nd into the RE211. (author)

  20. New organic superconductors beta-(BDA-TTP)2X [BDA-TTP + 2,5-bis(1,3-dithian-2ylidene)-1,3,4,6-tetrathiapentalene; X(-) = SbF6(-), AsF6(-), and PF6(-)].

    Science.gov (United States)

    Yamada, J; Watanabe, M; Akutsu, H; Nakatsuji, S; Nishikawa, H; Ikemoto, I; Kikuchi, K

    2001-05-09

    The synthesis, electrochemical properties, and molecular structure of a new pi-electron donor, 2,5-bis(1,3-dithian-2-ylidene)-1,3,4,6-tetrathiapentalene (BDA-TTP), is described. In contrast to the hitherto-known tetrachalcogenafulvalene pi-donors providing organic superconductors, this donor contains only the bis-fused 1,3-dithiole-2-ylidene unit as a pi-electron system, yet produces a series of ambient-pressure superconductors beta-(BDA-TTP)2X [X = SbF6 (magnetic T(c) = 6.9 K, resistive T(c) = 7.5 K), AsF6 (magnetic T(c) = 5.9 K, resistive T(c) = 5.8 K), and PF6 (magnetic T(c) = 5.9 K)], which are isostructural. The values of the intermolecular overlap integrals calculated on the donor layers of these superconductors suggest a two-dimensional (2D) electronic structure with loose donor packing. Tight-binding band calculations also indicate that these superconductors have the 2D band dispersion relations and closed Fermi surfaces.

  1. An investigation about the improvement of Tc for the n-type superconductor Nd2-xCexCuO4

    International Nuclear Information System (INIS)

    Wang Cong; Liang Jingkui; Chen Xiaolong; Min Jinrong; Cheng Xiangrong; Zhuang Weidong; Rao Guanghui

    1994-01-01

    Nd 2-x Ce x CuO 4 (x = 0.12 to 0.18) with T onset = 17 to 26 K is synthesized from the nominal composition of Nd 2-x Ce x CuO 4 + nSrCuO 2 (+nCaCuO 2 ) (n = 1, 2) under standard conditions without high pressure treatment. The sintering temperature, atmosphere, and synthetic procedure are important for the superconductivity of Nd 2-x Ce x CuO 4 . It is difficult to build up n blocks of SrCuO 2 , CaCuO 2 , or CdCuO 2 on Nd 2-x Ce x CuO 4 so as to add CuO 2 layers. In addition, the crystal structure and electrical resistance of Nd 2-x Ce x CuO 4 are studied. (orig.)

  2. Measurement of unique magnetic and superconducting phases in oxygen-doped high-temperature superconductors La2-xSrxCuO4+y

    DEFF Research Database (Denmark)

    Udby, Linda; Larsen, Jacob; Christensen, Niels Bech

    2013-01-01

    We present a combined magnetic neutron scattering and muon spin rotation study of the nature of the magnetic and superconducting phases in electronically phase separated La2-xSrxCuO4+y, x=0.04, 0.065, 0.09. For all samples, we find long-range modulated magnetic order below TN≃Tc=39 K. In sharp co...

  3. Grain boundary tunnel spectroscopy of the electron-doped cuprate superconductor La{sub 2-x}Ce{sub x}CuO{sub 4}; Korngrenzen-Tunnelspektroskopie am elektronendotierten Kupratsupraleiter La{sub 2-x}Ce{sub x}CuO{sub 4}

    Energy Technology Data Exchange (ETDEWEB)

    Wagenknecht, Michael

    2008-07-01

    The electron doped superconductor La{sub 2-x}Ce{sub x}CuO{sub 4} (LCCO) has been investigated by electric transport measurements at low temperatures T down to 5 K and high magnetic fields up to 16 T. For this purpose LCCO thin film tunnel junctions have been prepared on bicrystal substrates by molecular beam epitaxy and micro structuring. The samples were characterised by measuring the thin film resistivity and the tunnel conductance of quasi particles across the grain boundary. By these measurements an unconventional symmetry of the order parameter could be revealed for La{sub 2-x}Ce{sub x}CuO{sub 4}. Furthermore it was shown, that the tunnel conductance can be used as a probe for the upper critical field B{sub c2}(T). By using this method a value of B{sub c2}{proportional_to}24 T has been found for La{sub 2-x}Ce{sub x}CuO{sub 4}, a value roughly three times bigger than previously known. By this observation it was shown that the superconducting phase covers a larger region in the B-T-phase diagram. In addition it was concluded, that the pseudogap phase in La{sub 2-x}Ce{sub x}CuO{sub 4} is either not existent at all or covers only a small temperature region. Besides quasiparticle tunneling also the tunneling of Cooper pairs in small magnetic fields has been investigated. It was shown that the critical current across the grain boundary depends on the supplier of the bicrystal substrate. (orig.)

  4. Enhancement of electron correlation due to the molecular dimerization in organic superconductors β -(BDA-TTP )2X (X =I3, SbF6)

    Science.gov (United States)

    Aizawa, Hirohito; Kuroki, Kazuhiko; Yamada, Jun-ichi

    2015-10-01

    We perform a first-principles band calculation for quasi-two-dimensional organic superconductors β -(BDA -TTP) 2I3 and β -(BDA -TTP) 2SbF6. The first-principles band structures between the I3 and SbF6 salts are apparently different. We construct a tight-binding model for each material which accurately reproduces the first-principles band structure. The obtained transfer energies give the differences as follows: (i) larger dimerization in the I3 salt than the SbF6 salt, and (ii) different signs and directions of the interstacking transfer energies. To decompose the origin of the difference into the dimerization and the interstacking transfer energies, we adopt a simplified model by eliminating the dimerization effect and focus only on the difference caused by the interstacking transfer energies. From the analysis using the simplified model, we find that the difference of the band structure comes mainly from the strength of the dimerization. To compare the strength of the electron correlation having roots in the band structure, we calculate the physical properties originating from the effect of the electron correlation such as the spin susceptibility applying the two-particle self-consistent method. We find that the maximum value of the spin susceptibility for the I3 salt is larger than that of the SbF6 salt. Hypothetically decreasing the dimerization within the model of the I3 salt, the spin susceptibility takes almost the same value as that of the SbF6 salt for the same magnitude of the dimerization. We expect that the different ground state between the I3 and SbF6 salt mainly comes from the strength of the dimerization which is apparently masked in the band calculation along a particular k path.

  5. Magnetic excitations and phase separation in the underdoped La2-xSrxCuO4 superconductor measured by resonant inelastic X-ray scattering.

    Science.gov (United States)

    Braicovich, L; van den Brink, J; Bisogni, V; Sala, M Moretti; Ament, L J P; Brookes, N B; De Luca, G M; Salluzzo, M; Schmitt, T; Strocov, V N; Ghiringhelli, G

    2010-02-19

    We probe the collective magnetic modes of La2CuO4 and underdoped La2-xSrxCuO4 (LSCO) by momentum resolved resonant inelastic x-ray scattering (RIXS) at the Cu L3 edge. For the undoped antiferromagnetic sample, we show that the single magnon dispersion measured with RIXS coincides with the one determined by inelastic neutron scattering, thus demonstrating that x rays are an alternative to neutrons in this field. In the spin dynamics of LSCO, we find a branch dispersing up to approximately 400 meV coexisting with one at lower energy. The high-energy branch has never been seen before. It indicates that underdoped LSCO is in a dynamic inhomogeneous spin state.

  6. Development of Bulk Bi2+xSr3-yCa yCu 2O8+delta Superconductors by Partial-Melting Route for Fault Current Limiters Application

    Directory of Open Access Journals (Sweden)

    Bojan A. Marinkovic

    2002-06-01

    Full Text Available The production of bulk Bi2+xSr3-yCa yCu 2O8+delta (Bi-2212 superconductors for fault current limiter application was developed via a partial-melting route. Aiming high Ic (critical current, which is the essential superconducting characteristic for application of this material in the construction of Fault Current Limiters (FCL, the produced blocks have predominance of Bi-2212 phase (83 wt%, which characterizes with high values of zero and onset transport critical temperature of 92K and 97.5K, respectively. A relatively low transition width, deltaT, from the superconducting to the normal state of 5.5K, revealed a good intergrain connectivity. Consequently, current measurements on the blocks of Bi-2212 show promising Ic values of 230A and 850A for direct and alternate current, respectively. It is expected that further increases in the Ic values will depend on the elimination of an observed amorphous phase and further reduction of amount and grain sizes of secondary phases, still present in the blocks obtained by the proposed partial-melting route. This may be achieved by a further optimization of the partial-melting processing parameters.

  7. Critical Doping for the Onset of Fermi-Surface Reconstruction by Charge-Density-Wave Order in the Cuprate Superconductor La_{2-x}Sr_{x}CuO_{4}

    Directory of Open Access Journals (Sweden)

    S. Badoux

    2016-04-01

    Full Text Available The Seebeck coefficient S of the cuprate superconductor La_{2-x}Sr_{x}CuO_{4} (LSCO was measured in magnetic fields large enough to access the normal state at low temperatures, for a range of Sr concentrations from x=0.07 to x=0.15. For x=0.11, 0.12, 0.125, and 0.13, S/T decreases upon cooling to become negative at low temperatures. The same behavior is observed in the Hall coefficient R_{H}(T. In analogy with other hole-doped cuprates at similar hole concentrations p, the negative S and R_{H} show that the Fermi surface of LSCO undergoes a reconstruction caused by the onset of charge-density-wave modulations. Such modulations have indeed been detected in LSCO by x-ray diffraction in precisely the same doping range. Our data show that in LSCO this Fermi-surface reconstruction is confined to 0.085

  8. Growth and structural characterization of single crystals of the magnetic superconductor Ru1-xSr2-yGd1+yCu2+xO8-δ (RuGd-1212) obtained by the partial melting technique

    Science.gov (United States)

    Yamaki, K.; Bamba, Y.; Mochiku, T.; Funahashi, S.; Matsushita, Y.; Irie, A.

    2018-05-01

    In this study, cubic single crystals of the magnetic superconductor Ru1-xSr2-yGd1+yCu2+xO8-δ (RuGd-1212) with typical dimensions of 100-150 μm in length were grown by the partial melting technique. Multiple 00l reflections were first observed by XRD measurements of the bulk RuGd-1212 single crystals. The resistivity of the obtained crystals was roughly estimated to be ∼24-80 mΩ cm and no superconducting transition was observed down to 4.2 K. From the XRD measurements and refinement of the crystal structure, it was apparent that the Ru and Sr sites of the single-crystal RuGd-1212 were partially substituted by Cu and Gd, respectively. Oxygen defects were found to be minor (δ ≈ 0.1). The lattice parameters a and c of the single crystals were found to be larger and smaller, respectively, than those of a polycrystalline sample.

  9. Study of magnetic excitations in the high critical temperature La{sub 2-x}Sr{sub x}CuO{sub 4} superconductor with neutrons inelastic scattering; Etude des excitations magnetiques dans le supraconducteur a haute temperature critique La{sub 2-x}Sr{sub x}CuO{sub 4} par diffusion inelastique des neutrons

    Energy Technology Data Exchange (ETDEWEB)

    Petit, S

    1997-11-25

    In this work, we question the relevance of spin correlations in the problem of high-T{sub c} superconductivity. To characterize these correlations, we present a detailed inelastic neutron scattering study of the magnetic excitations spectrum, in the high T{sub c} La{sub 2-x}Sr{sub x}CuO{sub 4} copper oxide superconductor, as a function of temperature and strontium content x. Our study demonstrates the existence of two distinct types of fluctuations. The first type corresponds to two-dimensional isotropic fluctuations peaked at incommensurate points around the antiferromagnetic wavevector. These fluctuations show a gap below T{sub c}. The second type of fluctuations corresponds to two-dimensional very low energy, typically 1 MeV, antiferromagnetic correlations. They arise at low temperatures, for T {<=}T{sub f} {approx} 10 K {<=}T{sub c}. Different scenarios are discussed, namely particle-hole excitation arising because of nesting properties of the Fermi surface, stripes, and localized carriers in the CuO{sub 2} plane because of the La/Sr substitution disorder. Next, aiming to study the interrelation between magnetism and superconductivity, we present a theoretical perturbative treatment of the t-t`-J model. This model is believed to describe the physics of the CuO{sub 2} plane. The considered quasiparticles describe the motion of a doped hole, followed by localized spins on the copper sites. For a given doping x, two phases can exist, containing either x or 1 + x of these quasiparticles. We show at in the second phase, the exchange interaction between localized spins, combined to the intrinsic anharmonicity of these quasiparticles leads to an attractive interaction between them. We study the stability and the symmetry of a superconducting phase based on this mechanism. (author) 215 refs.

  10. Fabrication and characterization of LRE.sub.1+x./sub.Ba.sub.2-x./sub.Cu.sub.3./sub.O.sub.y./sub. (LRE:Nd, Eu, Gd,NEG) superconductors:a low oxygen partial pressure

    Czech Academy of Sciences Publication Activity Database

    Muralidhar, M.; Sakai, N.; Jirsa, Miloš; Murakami, M.

    378-381, - (2002), s. 646-650 ISSN 0921-4534. [International Symposium on Superconductors /14./. Kobe, 25.09.2001-27.09.2001] R&D Projects: GA AV ČR IAA1010919 Institutional research plan: CEZ:AV0Z1010914 Keywords : melt processing * microstructure * critical current density (J c ) * flux pinning * LRE-Ba2Cu3Oy Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.912, year: 2002

  11. The superconductor

    International Nuclear Information System (INIS)

    Lad, J.K.

    1979-01-01

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

  12. Organic superconductors

    International Nuclear Information System (INIS)

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

    1986-01-01

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

  13. Oxygen diffusion in cuprate superconductors

    International Nuclear Information System (INIS)

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

    1995-01-01

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

  14. Briefing on superconductor developments

    International Nuclear Information System (INIS)

    Larbalestier, D.

    1987-01-01

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

  15. Oxide superconductors

    International Nuclear Information System (INIS)

    Cava, R.J.

    2000-01-01

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

  16. Ceramic superconductors II

    International Nuclear Information System (INIS)

    Yan, M.F.

    1988-01-01

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

  17. Gas Phase Homo- and Co-polymerization of Ethylene over Mg(O Et){sub 2}/T HF/Si Cl{sub 4}/Ti Cl{sub 4}/ Catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Min-Chul, Chung [Korea Advanced Institute of Science and Techology., Taejeon (Korea, Republic of); Il, Kim [Univ. of Ulsan., Ulsan (Korea, Republic of); Jae-Ha, Kim [Korea Petrochemial Ind., Kyungnam (Korea, Republic of); Hong-Ki Choi [Korea Advanced Institute of Science and Technology., Taejeon (Korea, Republic of); Seung-Ihl, Woo

    1994-08-01

    Homo- and co-polymerization of ethylene were carried out in both gas and slurry phases over Mg(O Et)2/T HF/Si Cl{sub 4}/Ti Cl{sub 4}-Al Et{sub 3} catalysts in the range of temperature 20-70{sup o} C and pressure 2-10 psig. In gas phase polymerization, maximum activity was measured at the Al/Ti mole ratio of 377, and reaction rate dependence on Al Et{sub 3} concentration could be explained with the Langmuir-Hinshelwood adsorption model. Even though maximum activities were obtained at the same temperature, 60{sup o} C in both gas and slurry phases, overall activation energy was higher for the slurry phase(13 kCal/mol) than for the gas phase(4.7 kCal/mol) polymerization. The molecular weight behavior has been examined by measuring intrinsic viscosity. The molecular weight was increased as the ethylene pressure increased, and as the temperature and the concentration of Al Et{sub 3} and hydrogen decreased. Using two different co monomers(propylene and butene-1), the copolymerization of ethylene was carried out. The intrinsic viscosity and the melt index were decreased as co monomer concentration increased, and the maximum activity was observed when the concentration of comonomer is about 20 mol%. (author). 28 refs. 6 tabs. 13 figs.

  18. Making superconductors

    International Nuclear Information System (INIS)

    McDonald, W.K.

    1981-01-01

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

  19. Inhomogeneous superconductors

    International Nuclear Information System (INIS)

    Tinkham, M.

    1978-01-01

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

  20. Coulomb repulsion in (TMTSF)2X and (TMTTF)2X

    DEFF Research Database (Denmark)

    Mortensen, Kell; Engler, E. M.

    1985-01-01

    On the basis of studies of transport properties of (TMTSF)2 X, (TMTTF)2X and their binary alloys the authors discuss the role of on-site Coulomb repulsion relative to the transfer integrals. In TMTTF-salts U/ta are believed to be large, resulting in a Hubbard gap, whereas U/ta in TMTSF-salts are ......On the basis of studies of transport properties of (TMTSF)2 X, (TMTTF)2X and their binary alloys the authors discuss the role of on-site Coulomb repulsion relative to the transfer integrals. In TMTTF-salts U/ta are believed to be large, resulting in a Hubbard gap, whereas U/ta in TMTSF...

  1. Chapter 27. Superconductors

    International Nuclear Information System (INIS)

    Vavra, O.

    2007-01-01

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

  2. Ternary superconductors

    International Nuclear Information System (INIS)

    Giorgi, A.L.

    1987-01-01

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

  3. Superconductor Dynamics

    Energy Technology Data Exchange (ETDEWEB)

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

    2014-07-01

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

  4. 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.

  5. New magnetic coherence effect in superconducting La2-xSrxCuO4

    DEFF Research Database (Denmark)

    Mason, T.E.; Schröder, A.; Aeppli, G.

    1996-01-01

    We have used inelastic neutron scattering to examine the magnetic fluctuations at intermediate frequencies in the simplest high temperature superconductor, La2-xSrxCuO4. The suppression of the low energy magnetic response in the superconducting state is accompanied by an increase in the response...

  6. Localized superconductors

    International Nuclear Information System (INIS)

    Ma, M.; Lee, P.A.

    1985-01-01

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

  7. A potential method using Ge{iPrNC[N(SiMe_3)_2]NiPr}{sub 2}, (Et{sub 3}Si){sub 2}Te and anhydrous hydrazine for germanium tellurides

    Energy Technology Data Exchange (ETDEWEB)

    Du, Liyong; Du, Shulei; Ding, Yuqiang [School of Chemical and Material Engineering, Jiangnan University, Wuxi (China)

    2017-12-29

    A germanium(II)-guanidine derivative of formula Ge{iPrNC[N(SiMe_3)_2]NiPr}{sub 2} (1) was synthesized and characterized by {sup 1}H NMR, {sup 13}C NMR, elemental analysis, and X-ray diffraction method. Thermal property was also studied to identify its thermal stability and volatility. More importantly, compound 1 was synthesized to develop a new method for germanium tellurides, where anhydrous hydrazine was introduced to prompt the activity of germanium(II) guanidines (or derivatives) towards (Et{sub 3}Si){sub 2}Te. Solution reaction of compound 1, (Et{sub 3}Si){sub 2}Te, and anhydrous hydrazine was investigated to pre-identify the feasibility of this combination for ALD process. The EDS data of the black precipitate from this reaction verified the potential of this method to manufacture germanium tellurides. (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  8. 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.

  9. Superconductors with excess quasiparticles

    International Nuclear Information System (INIS)

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

    1981-01-01

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

  10. 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.

  11. P2X receptors in epithelia

    DEFF Research Database (Denmark)

    Leipziger, Jens Georg

    2015-01-01

    P2X receptors are ubiquitously expressed in all epithelial tissues but their functional roles are less well studied. Here we review the current state of knowledge by focusing on functional effects of P2X receptor in secretory and in absorptive tissues. In glandular tissue like the parotid gland...

  12. Contact spectroscopy of high-temperature superconductors. Review

    International Nuclear Information System (INIS)

    Yanson, I.K.

    1991-01-01

    We have attempted to systematize the research of high temperature superconductors by means of tunneling and point-contact spectroscopy. The theoretical grounds of the methods are briefly described. The deviations of current-voltage characteristics from ordinary superconductors are considered. The properties of point contacts with direct energy gap measurfements and the fine structure of derivatives of i(v) curves at the overlap energies are reviewed for the high-T c La 2-x Sr x CuO 4 materials

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

    DEFF Research Database (Denmark)

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

    2001-01-01

    Neutron scattering is used to characterize the magnetism of the vortices for the optimally doped high-temperature superconductor La2-xSrxCuO4 (x = 0.163) in an applied magnetic field. As temperature is reduced, Low-frequency spin fluctuations first disappear with the loss of vortex mobility......, but then reappear. We find that the vortex state can be regarded as an inhomogeneous mixture of a superconducting spin fluid and a material containing a nearly ordered antiferromagnet. These experiments show that as for many other properties of cuprate superconductors, the important underlying microscopic forces...

  14. 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.

  15. Friction in levitated superconductors

    International Nuclear Information System (INIS)

    Brandt, E.H.

    1988-01-01

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

  16. 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.

  17. Kohn anomalies in superconductors

    International Nuclear Information System (INIS)

    Flatte, M.E.

    1994-01-01

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

  18. Topological superconductors: a review.

    Science.gov (United States)

    Sato, Masatoshi; Ando, Yoichi

    2017-07-01

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

  19. Room temperature superconductors

    International Nuclear Information System (INIS)

    Sleight, A.W.

    1995-01-01

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

  20. 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.

  1. 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.

  2. Acoustic anomalies in the resonant ultrasound spectra of La2-x SrxCuO4

    International Nuclear Information System (INIS)

    Sarrao, J.L.; Lei, M.; Migliori, A.

    1992-01-01

    Resonant ultrasound spectroscopy is a novel technique for the simultaneous determination of a solid's elastic moduli. Measurements of the resonant ultrasound spectra of single crystals of La 2-x Sr x CuO 4 for several values of x are reported. Anomalies associated with the nonstoichiometric (x>0) doped superconductor have been observed. These anomalies indicate that the absence of short-wavelength translational invariance at the Brillouin-zone edge is being coupled into the zone center. Measurements of the stoichiometric (x=0) insulator will also be discussed. [This work was performed at Los Alamos National Laboratory under the auspices of the U.S. Department of Energy.

  3. Hybrid crystals of cuprates and iron-based superconductors

    Science.gov (United States)

    Xia, Dai; Cong-Cong, Le; Xian-Xin, Wu; Jiang-Ping, Hu

    2016-07-01

    We propose two possible new compounds, Ba2CuO2Fe2As2 and K2CuO2Fe2Se2, which hybridize the building blocks of two high temperature superconductors, cuprates and iron-based superconductors. These compounds consist of square CuO2 layers and antifluorite-type Fe2 X 2 (X = As, Se) layers separated by Ba/K. The calculations of binding energies and phonon spectra indicate that they are dynamically stable, which ensures that they may be experimentally synthesized. The Fermi surfaces and electronic structures of the two compounds inherit the characteristics of both cuprates and iron-based superconductors. These compounds can be superconductors with intriguing physical properties to help to determine the pairing mechanisms of high T c superconductivity. Project supported by the National Basic Research Program of China (Grant No. 2015CB921300), the National Natural Science Foundation of China (Grant Nos. 1190020 and 11334012), and the Strategic Priority Research Program of Chinese Academy of Sciences (Grant No. XDB07000000).

  4. 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

  5. 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

  6. Ivar Giaever, Tunneling, and Superconductors

    Science.gov (United States)

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

  7. 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.

  8. P2X Receptors and Synaptic Plasticity

    Czech Academy of Sciences Publication Activity Database

    Pankratov, Y.; Lalo, U.; Krishtal, A.; Verkhratsky, Alexei

    2009-01-01

    Roč. 158, č. 1 (2009), s. 137-148 ISSN 0306-4522 Institutional research plan: CEZ:AV0Z50390512 Keywords : ATP * P2X receptors * synaptic plasticity Subject RIV: FH - Neurology Impact factor: 3.292, year: 2009

  9. Photothermal measurements of superconductors

    International Nuclear Information System (INIS)

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

    1993-01-01

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

  10. An unconventional colour superconductor

    International Nuclear Information System (INIS)

    Huang Mei

    2007-01-01

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

  11. Macroscopic theory of superconductors

    International Nuclear Information System (INIS)

    Carr, W.J. Jr.

    1981-01-01

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

  12. Classical spins in superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Shiba, H [Tokyo Univ.; Maki, K

    1968-08-01

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

  13. Superconductors and medical imaging

    International Nuclear Information System (INIS)

    Aubert, Guy

    2011-01-01

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

  14. Irradiation damage in superconductors

    International Nuclear Information System (INIS)

    Quere, Y.

    1989-01-01

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

  15. HREM study of Bi-oxide based high Tc superconductors

    International Nuclear Information System (INIS)

    Hewat, E.A.

    1988-01-01

    A HREM study of the superstructure and structural defects in Bi 2-x Pb x Sr 2 CaCu 2 O 8 and Bi 2-x Pb x (SrCa) 2 CuO 6 (for x=0 and x=0.4) is presented. The superstructures are shown to involve waves of distortion along the b-axis. These waves are locked on to the lattice positions so that they have a local wave length of 4,5,6,7 or 8 times the basic unit cell. The superstructures are composed of roughly periodic combinations of these basic building blocks (waves). The lead doped superconductors show a less pronounced but more complicated superstructure along b where two distinct periodicities close to 4 and 7 times the basic unit cell predominate. In each of the compounds studied the superstructure, in the better ordered crystals, is shown to be commensurate with a unit cell between 5 and 23 times the basic unit cell. The superstructure in Bi 2-x Pb x Sr 2 CaCu 2 O 8 is orthorhombic where as the superstructure in Bi 2-x Pb x (SrCa) 2 CuO 6 is monoclinic. All these superconductors have a low ''twin'' density (ie density of 90 0 twist boundaries). They exhibit many dislocations and dislocation arrays associated with the weak bonding between BiO planes. They also form non-stoechiometric stacking faults with local changes in the c-axis spacing between layers

  16. Positron annihilation study of strontium doped YBa2Cu3Osub(7-δ) superconductors

    International Nuclear Information System (INIS)

    Huang, W.F.; Ouseph, P.J.; Fang, K.; Xu, Z.J.

    1988-01-01

    Doppler broadened lineshapes of the gamma lines from positron annihilation in Y(Basub(2-x) Srsub(x))Cu 3 )Osub(7-δ) superconductors were measured with x = 0.0 to 1.2. Results are indicative of additional oxygen vacancies introduced by doping. (author)

  17. NMR study of (Y1-xLax) Mn2X2 (X = Ge, Si) compounds

    International Nuclear Information System (INIS)

    Ichinose, K.; Nagai, H.; Tsujimura, A.; Oyasato, M.

    1988-01-01

    Nuclear magnetic resonances of 55 Mn and 139 La nuclei in (Y 1-x La x ) Mn 2 X 2 (X = Ge, Si) have been observed at 4.2 K in their ferromagnetic state for 0.3 ≤ x ≤ 1. The hyperfine fields at these nuclei are independent of La concentration. This result shows that Mn moment is almost constant when replacing Y with La

  18. Can positron 2D-ACAR resolve the electronic structure of high-Tc superconductors

    International Nuclear Information System (INIS)

    Chan, L.P.; Lynn, K.G.; Harshman, D.R.

    1992-01-01

    In this paper, the authors examine the ability of the positron Two-Dimensional Angular Correlation Annihilation Radiation (2D-ACAR) technique to resolve the electronic structures of high-T c cuprate superconductors. Following a short description of the technique, discussions of the theoretical assumptions, data analysis and experimental considerations, in relation to the high-T c superconductors, are given. The authors briefly review recent 2D-ACAR experiments on YBa 2 Cu 3 O 7-x , Bi 2 Sr 2 CaCuO 8+δ and La 2-x Sr x CuO 4 . The 2D-ACAR technique is useful in resolving the band crossings associated with the layers of the superconductors that are preferentially sampled by the positrons. Together with other Fermi surface measurements (namely angle-resolved photoemission), 2D-ACAR can resolve some of the electronic structures of high-T c cuprate superconductors

  19. Iron pnictide superconductors

    International Nuclear Information System (INIS)

    Tegel, Marcus Christian

    2011-01-01

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

  20. "Fluctuoscopy" of Superconductors

    Science.gov (United States)

    Varlamov, A. A.

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

  1. Measuring condensate fraction in superconductors

    International Nuclear Information System (INIS)

    Chakravarty, Sudip; Kee, Hae-Young

    2000-01-01

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

  2. Processing of Mixed Oxide Superconductors

    Science.gov (United States)

    1990-07-01

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

  3. Superconductor stability 90: A review

    International Nuclear Information System (INIS)

    Dresner, L.

    1990-01-01

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

  4. High Temperature Superconductor Resonator Detectors

    Data.gov (United States)

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

  5. Neutron Depolarization in Superconductors

    Science.gov (United States)

    Zhuchenko, N. K.

    1995-04-01

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

  6. Vortices and nanostructured superconductors

    CERN Document Server

    2017-01-01

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

  7. Radiation behavior of superconductors

    International Nuclear Information System (INIS)

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

    1979-01-01

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

  8. Strongly disordered superconductors

    International Nuclear Information System (INIS)

    Muttalib, K.A.

    1982-01-01

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

  9. Inter-granular current in iron-oxypnictide superconductors

    International Nuclear Information System (INIS)

    Tamegai, T.; Tsuchiya, Y.; Nakajima, Y.; Kamihara, Y.; Hosono, H.

    2010-01-01

    Inter- and intragranular currents, J c inter and J c intra , in LaFePO 0.94 F 0.06 polycrystalline sample are evaluated by measuring the remanent-state field profile using magneto-optical imaging method. Obtained images show the absence of magnetic field modulation associated with the weak-link nature of grain boundaries, indicating that J c inter and J c intra are comparable in magnitude in contrast to other iron-arsenide superconductors. J c inter is estimated to be 2 x 10 4 A/cm 2 in the limit of T = 0 K, which is larger than the values in other iron-arsenide superconductors. Implication of these J c behavior is discussed in relation with possible pairing symmetries.

  10. Testability issues in Superconductor Electronics

    NARCIS (Netherlands)

    Kerkhoff, Hans G.; Arun, Arun J.

    2004-01-01

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

  11. Method for preparation of superconductors

    Energy Technology Data Exchange (ETDEWEB)

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

    1975-07-10

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

  12. Nonmagnetic impurities in magnetic superconductors

    International Nuclear Information System (INIS)

    Mineev, V.P.

    1989-01-01

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

  13. 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....

  14. Evaluating superconductors for microwave applications

    International Nuclear Information System (INIS)

    Hammond, B.; Bybokas, J.

    1989-01-01

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

  15. Iron pnictide superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Tegel, Marcus Christian

    2011-03-22

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

  16. 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

  17. Superconductors go organic

    International Nuclear Information System (INIS)

    Singleton, John; Mielke, Charles

    2002-01-01

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

  18. Local structure and superconductivity in La2-xBaxCuO4 for x=0.125 and x=0.15

    International Nuclear Information System (INIS)

    Billinge, S.J.L.; Kwei, G.H.; Takagi, H.

    1993-01-01

    This paper reviews our recent work on characterising the structural and electronic transitions in La 2-x Ba x CuO 4 . This is a high-temperature superconductor which shows interesting an interesting interrelationship between structure and atomic properties. We have used x-ray and neutron diffraction to characterize the structure and show tat the current understanding of the structural phase transitions, and their relationship to the superconductivity, is incomplete

  19. Magnetic Scaling in Superconductors

    International Nuclear Information System (INIS)

    Lawrie, I.D.

    1997-01-01

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

  20. 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.

  1. Pinning and creep in superconductors

    International Nuclear Information System (INIS)

    Ovchinnikov, Yu.N.

    1994-01-01

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

  2. Phase diagram of (Li(1-x)Fe(x))OHFeSe: a bridge between iron selenide and arsenide superconductors.

    Science.gov (United States)

    Dong, Xiaoli; Zhou, Huaxue; Yang, Huaixin; Yuan, Jie; Jin, Kui; Zhou, Fang; Yuan, Dongna; Wei, Linlin; Li, Jianqi; Wang, Xinqiang; Zhang, Guangming; Zhao, Zhongxian

    2015-01-14

    Previous experimental results have shown important differences between iron selenide and arsenide superconductors which seem to suggest that the high-temperature superconductivity in these two subgroups of iron-based families may arise from different electronic ground states. Here we report the complete phase diagram of a newly synthesized superconducting (SC) system, (Li1-xFex)OHFeSe, with a structure similar to that of FeAs-based superconductors. In the non-SC samples, an antiferromagnetic (AFM) spin-density-wave (SDW) transition occurs at ∼127 K. This is the first example to demonstrate such an SDW phase in an FeSe-based superconductor system. Transmission electron microscopy shows that a well-known √5×√5 iron vacancy ordered state, resulting in an AFM order at ∼500 K in AyFe2-xSe2 (A = metal ions) superconductor systems, is absent in both non-SC and SC samples, but a unique superstructure with a modulation wave vector q = (1)/2(1,1,0), identical to that seen in the SC phase of KyFe2-xSe2, is dominant in the optimal SC sample (with an SC transition temperature Tc = 40 K). Hence, we conclude that the high-Tc superconductivity in (Li1-xFex)OHFeSe stems from the similarly weak AFM fluctuations as FeAs-based superconductors, suggesting a universal physical picture for both iron selenide and arsenide superconductors.

  3. Global analysis of general SU(2) x SU(2) x U(1) models with precision data

    Energy Technology Data Exchange (ETDEWEB)

    Hsieh, Ken; Yu, Jiang-Hao; Yuan, C.P. [Michigan State Univ., East Lansing, MI (United States). Dept. of Physics and Astronomy; Schmitz, Kai [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Michigan State Univ., East Lansing, MI (United States). Dept. of Physics and Astronomy

    2010-05-15

    We present the results of a global analysis of a class of models with an extended electroweak gauge group of the form SU(2) x SU(2) x U(1), often denoted as G(221) models, which include as examples the left-right, the lepto-phobic, the hadro-phobic, the fermio-phobic, the un-unified, and the non-universal models. Using an effective Lagrangian approach, we compute the shifts to the coeffcients in the electroweak Lagrangian due to the new heavy gauge bosons, and obtain the lower bounds on the masses of the Z' and W' bosons. The analysis of the electroweak parameter bounds reveals a consistent pattern of several key observables that are especially sensitive to the effects of new physics and thus dominate the overall shape of the respective parameter contours. (orig.)

  4. Global analysis of general SU(2) x SU(2) x U(1) models with precision data

    International Nuclear Information System (INIS)

    Hsieh, Ken; Yu, Jiang-Hao; Yuan, C.P.; Schmitz, Kai; Michigan State Univ., East Lansing, MI

    2010-05-01

    We present the results of a global analysis of a class of models with an extended electroweak gauge group of the form SU(2) x SU(2) x U(1), often denoted as G(221) models, which include as examples the left-right, the lepto-phobic, the hadro-phobic, the fermio-phobic, the un-unified, and the non-universal models. Using an effective Lagrangian approach, we compute the shifts to the coeffcients in the electroweak Lagrangian due to the new heavy gauge bosons, and obtain the lower bounds on the masses of the Z' and W' bosons. The analysis of the electroweak parameter bounds reveals a consistent pattern of several key observables that are especially sensitive to the effects of new physics and thus dominate the overall shape of the respective parameter contours. (orig.)

  5. Plasmons in strong superconductors

    International Nuclear Information System (INIS)

    Baldo, M.; Ducoin, C.

    2011-01-01

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

  6. Superconductor fluxoid logic

    International Nuclear Information System (INIS)

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

    1993-01-01

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

  7. Theory of disordered superconductors

    International Nuclear Information System (INIS)

    Wysokinski, K.I.

    1991-01-01

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

  8. Flux cutting in superconductors

    International Nuclear Information System (INIS)

    Campbell, A M

    2011-01-01

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

  9. Vortex cutting in superconductors

    Science.gov (United States)

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

    2015-03-01

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

  10. 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...

  11. Ac losses of transposed superconductors

    International Nuclear Information System (INIS)

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

    1975-01-01

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

  12. Quasiparticle current in superconductor-semiconductor-superconductor junctions

    International Nuclear Information System (INIS)

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

    1988-01-01

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

  13. Superconductor-ferromagnet-superconductor nanojunctions from perovskite materials

    International Nuclear Information System (INIS)

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

    2017-01-01

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

  14. Superconductor-ferromagnet-superconductor nanojunctions from perovskite materials

    Energy Technology Data Exchange (ETDEWEB)

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

    2017-02-15

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

  15. Preparation of superconductor precursor powders

    Science.gov (United States)

    Bhattacharya, Raghunath

    1998-01-01

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

  16. Kinetic equations in dirty superconductors

    International Nuclear Information System (INIS)

    Kraehenbuehl, Y.

    1981-01-01

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

  17. Electronic structure of LaFe{sub 2}X{sub 2} (X = Si,Ge)

    Energy Technology Data Exchange (ETDEWEB)

    Hase, I., E-mail: i.hase@aist.go.jp [Electronics and Photonics Research Institute, AIST, Tsukuba, Ibaraki 305-8568 (Japan); Yanagisawa, T. [Electronics and Photonics Research Institute, AIST, Tsukuba, Ibaraki 305-8568 (Japan)

    2011-11-15

    We have calculated the electronic structure of LaFe{sub 2}Si{sub 2} and LaFe{sub 2}Ge{sub 2} from first-principles. The obtained Fermi surfaces of LaFe{sub 2}Si{sub 2} and LaFe{sub 2}Ge{sub 2} resemble those of LaRu{sub 2}Ge{sub 2}, which well explains the result of the dHvA experiments of CeRu{sub 2}Ge{sub 2}. Their density of states curves show the common feature with CaFe{sub 2}As{sub 2}. D(E{sub F}) strongly depends on the distortion of the FeX{sub 4} tetrahedra and/or the height of the X atom, as also found in iron-pnictide system. Recently found iron-pnictide superconductor (Ba,K)Fe{sub 2}As{sub 2} and the heavy-fermion superconductor CeCu{sub 2}Si{sub 2} both have the same crystal structure. In this paper we have calculated the electronic structure of LaFe{sub 2}Si{sub 2} and LaFe{sub 2}Ge{sub 2} from first-principles. These compounds also have the same crystal structure and closely related to both of (Ba,K)Fe{sub 2}As{sub 2} and CeRu{sub 2}Ge{sub 2}. The obtained Fermi surfaces of LaFe{sub 2}Si{sub 2} and LaFe{sub 2}Ge{sub 2} resemble those of LaRu{sub 2}Ge{sub 2}, which are already found that they well explain the results of the dHvA experiments of CeRu{sub 2}Ge{sub 2}. Their density of states curves show the common feature with CaFe{sub 2}As{sub 2}. The density of states at the Fermi level strongly depends on the distortion of the FeX{sub 4} tetrahedra and/or the height of the X atom from the two-dimensional Fe plane, as also found in iron-pnictide system. The electronic specific heat coefficient is 11.8 mJ/mol K{sup 2} for LaFe{sub 2}Si{sub 2} and 12.5 mJ/mol K{sup 2} for LaFe{sub 2}Ge{sub 2}, which is about 1/3 and 1/2 of experimental results, respectively.

  18. Polymeric conductors and superconductors

    International Nuclear Information System (INIS)

    Goodings, E.P.

    1975-01-01

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

  19. Superconductor digital electronics

    International Nuclear Information System (INIS)

    Likharev, Konstantin K.

    2012-01-01

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

  20. Manufacturing of Superconductors

    DEFF Research Database (Denmark)

    Bech, Jakob Ilsted; Bay, Niels

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

  1. High temperature superconductor current leads

    International Nuclear Information System (INIS)

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

    1996-01-01

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

  2. Hybrid molecule/superconductor assemblies

    International Nuclear Information System (INIS)

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

    1993-01-01

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

  3. 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

    most efficient design of machine will therefore be one in which an in situ magnetizing fixture is included. The first three methods all require a solenoid which can be switched on and off. In the first method an applied magnetic field is required equal to the required magnetic field, whilst the second and third approaches require fields at least two times greater. The final method, however, offers significant advantages since it achieves the final required field by repeated applications of a small field and can utilize a permanent magnet (Coombs 2007 British Patent GB2431519 granted 2007-09-26). If we wish to pulse a field using, say, a 10 T magnet to magnetize a 30 mm x 10 mm sample then we can work out how big the solenoid needs to be. If it were possible to wind an appropriate coil using YBCO tape then, assuming an I{sub c} of 70 A and a thickness of 100 {mu}m, we would have 100 turns and 7000 A turns. This would produce a B field of approximately 7000/(20 x 10{sup -3}) x 4{pi} x 10{sup -7} = 0.4 T. To produce 10 T would require pulsing to 1400 A{exclamation_point} An alternative calculation would be to assume a J{sub c} of say 5 x 10{sup 8}A m{sup -1} and a coil 1 cm{sup 2} in cross section. The field would then be 5 x 10{sup 8} x 10{sup -2} x (2 x 4{pi} x 10{sup -7}) = 10 T. Clearly if the magnetization fixture is not to occupy more room than the puck itself then a very high activation current would be required and either constraint makes in situ magnetization a very difficult proposition. What is required for in situ magnetization is a magnetization method in which a relatively small field of the order of millitesla repeatedly applied is used to magnetize the superconductor. This paper describes a novel method for achieving this.

  4. A novel heat engine for magnetizing superconductors

    International Nuclear Information System (INIS)

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

    2008-01-01

    most efficient design of machine will therefore be one in which an in situ magnetizing fixture is included. The first three methods all require a solenoid which can be switched on and off. In the first method an applied magnetic field is required equal to the required magnetic field, whilst the second and third approaches require fields at least two times greater. The final method, however, offers significant advantages since it achieves the final required field by repeated applications of a small field and can utilize a permanent magnet (Coombs 2007 British Patent GB2431519 granted 2007-09-26). If we wish to pulse a field using, say, a 10 T magnet to magnetize a 30 mm x 10 mm sample then we can work out how big the solenoid needs to be. If it were possible to wind an appropriate coil using YBCO tape then, assuming an I c of 70 A and a thickness of 100 μm, we would have 100 turns and 7000 A turns. This would produce a B field of approximately 7000/(20 x 10 -3 ) x 4π x 10 -7 = 0.4 T. To produce 10 T would require pulsing to 1400 A! An alternative calculation would be to assume a J c of say 5 x 10 8 A m -1 and a coil 1 cm 2 in cross section. The field would then be 5 x 10 8 x 10 -2 x (2 x 4π x 10 -7 ) = 10 T. Clearly if the magnetization fixture is not to occupy more room than the puck itself then a very high activation current would be required and either constraint makes in situ magnetization a very difficult proposition. What is required for in situ magnetization is a magnetization method in which a relatively small field of the order of millitesla repeatedly applied is used to magnetize the superconductor. This paper describes a novel method for achieving this

  5. Inequalities detecting quantum entanglement for 2 x d systems

    International Nuclear Information System (INIS)

    Zhao Mingjing; Wang Zhixi; Ma Teng; Fei Shaoming

    2011-01-01

    We present a set of inequalities for detecting quantum entanglement of 2 x d quantum states. For 2 x 2 and 2 x 3 systems, the inequalities give rise to sufficient and necessary separability conditions for both pure and mixed states. For the case of d>3, these inequalities are necessary conditions for separability, which detect all entangled states that are not positive under partial transposition and even some entangled states with positive partial transposition. These inequalities are given by mean values of local observables and present an experimental way of detecting the quantum entanglement of 2 x d quantum states and even multiqubit pure states.

  6. Modelling of bulk superconductor magnetization

    International Nuclear Information System (INIS)

    Ainslie, M D; Fujishiro, H

    2015-01-01

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

  7. Systematics of c-axis phonons in the thallium- and bismuth-based cuprate superconductors

    NARCIS (Netherlands)

    Tsvetkov, A.A.; Dulic, Diana; Marel, D. van der; Damascelli, A.; Kaljushnaia, G.A.; Gorina, J.I.; Senturina, N.N.; Kolesnikov, N.N.; Ren, Z.F.; Wang, J.H.; Menovsky, A.A.; Palstra, T.T.M.

    1999-01-01

    We present grazing incidence reflectivity measurements in the far-infrared region at temperatures above and below Tc for a series of thallium- (Tl2Ba2CuO6, Tl2Ba2CaCu2O8) and bismuth- (Bi2Sr2CuO6, Bi2Sr2CaCu2O8, and Bi2-xPbxSr2CaCu2O8) based cuprate superconductors. From the spectra, which are

  8. P2X4: A fast and sensitive purinergic receptor

    Directory of Open Access Journals (Sweden)

    Jaanus Suurväli

    2017-10-01

    Full Text Available Extracellular nucleotides have been recognized as important mediators of activation, triggering multiple responses via plasma membrane receptors known as P2 receptors. P2 receptors comprise P2X ionotropic receptors and G protein-coupled P2Y receptors. P2X receptors are expressed in many tissues, where they are involved in a number of functions including synaptic transmission, muscle contraction, platelet aggregation, inflammation, macrophage activation, differentiation and proliferation, neuropathic and inflammatory pain. P2X4 is one of the most sensitive purinergic receptors (at nanomolar ATP concentrations, about one thousand times more than the archetypal P2X7. P2X4 is widely expressed in central and peripheral neurons, in microglia, and also found in various epithelial tissues and endothelial cells. It localizes on the plasma membrane, but also in intracellular compartments. P2X4 is preferentially localized in lysosomes, where it is protected from proteolysis by its glycosylation. High ATP concentration in the lysosomes does not activate P2X4 at low pH; P2X4 gets activated by intra-lysosomal ATP only in its fully dissociated tetra-anionic form, when the pH increases to 7.4. Thus, P2X4 is functioning as a Ca2+-channel after the fusion of late endosomes and lysosomes. P2X4 modulates major neurotransmitter systems and regulates alcohol-induced responses in microglia. P2X4 is one of the key receptors mediating neuropathic pain. However, injury-induced upregulation of P2X4 expression is gender dependent and plays a key role in pain difference between males and females. P2X4 is also involved in inflammation. Extracellular ATP being a pro-inflammatory molecule, P2X4 can trigger inflammation in response to high ATP release. It is therefore involved in multiple pathologies, like post-ischemic inflammation, rheumatoid arthritis, airways inflammation in asthma, neurodegenerative diseases and even metabolic syndrome. Although P2X4 remains poorly

  9. 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

  10. Topological Insulators and Superconductors for Innovative Devices

    Science.gov (United States)

    2015-03-20

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

  11. Generalized Measure of Departure from No Three-Factor Interaction Model for 2 x 2 x K Contingency Tables

    Directory of Open Access Journals (Sweden)

    Yohei Ban

    2008-12-01

    Full Text Available For 2 x 2 x K contingency tables, Tomizawa considered a Shannon entropy type measure to represent the degree of departure from a log-linear model of no three-factor interaction (the NOTFI model. This paper proposes a generalization of Tomizawa's measure for 2 x 2 x K tables. The measure proposed is expressed by using Patil-Taillie diversity index or Cressie-Read power-divergence. A special case of the proposed measure includes Tomizawa's measure. The proposed measure would be useful for comparing the degrees of departure from the NOTFI model in several tables.

  12. Superconductors: The long road ahead

    International Nuclear Information System (INIS)

    Foner, S.; Orlando, T.P.

    1988-01-01

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

  13. Studies on ceramic superconductors

    International Nuclear Information System (INIS)

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

    1987-01-01

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

  14. Structural and Molecular Modeling Features of P2X Receptors

    Directory of Open Access Journals (Sweden)

    Luiz Anastacio Alves

    2014-03-01

    Full Text Available Currently, adenosine 5'-triphosphate (ATP is recognized as the extracellular messenger that acts through P2 receptors. P2 receptors are divided into two subtypes: P2Y metabotropic receptors and P2X ionotropic receptors, both of which are found in virtually all mammalian cell types studied. Due to the difficulty in studying membrane protein structures by X-ray crystallography or NMR techniques, there is little information about these structures available in the literature. Two structures of the P2X4 receptor in truncated form have been solved by crystallography. Molecular modeling has proven to be an excellent tool for studying ionotropic receptors. Recently, modeling studies carried out on P2X receptors have advanced our knowledge of the P2X receptor structure-function relationships. This review presents a brief history of ion channel structural studies and shows how modeling approaches can be used to address relevant questions about P2X receptors.

  15. Edge instabilities of topological superconductors

    Energy Technology Data Exchange (ETDEWEB)

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

    2016-07-01

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

  16. Superconductor stability, 1983: a review

    International Nuclear Information System (INIS)

    Dresner, L.

    1983-01-01

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

  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. 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.

  19. Purinergní P2X rodina a specifické vlastnosti P2X7 podtypu

    Czech Academy of Sciences Publication Activity Database

    Jindřichová, Marie; Zemková, Hana

    2013-01-01

    Roč. 62, č. 2 (2013), s. 40-46 ISSN 1210-6313 R&D Projects: GA ČR(CZ) GPP304/12/P371 Institutional support: RVO:67985823 Keywords : extracellular ATP * purinergic P2X family * P2X7 receptor * cell proliferation and apoptosis Subject RIV: ED - Physiology

  20. Method of fabricating composite superconductors

    International Nuclear Information System (INIS)

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

    1977-01-01

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

  1. Stability of superconductor

    International Nuclear Information System (INIS)

    Wada, Hitoshi; Takeuchi, Takao; Kuroda, Tsuneo

    2000-01-01

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

  2. The role of P2X receptors in bone biology

    DEFF Research Database (Denmark)

    Jørgensen, N R; Syberg, S; Ellegaard, M

    2015-01-01

    receptors regulate bone metabolism and especially for the P2X7 receptor an impressive amount of evidence has now documented its expression in osteoblasts, osteoclasts, and osteocytes as well as important functional roles in proliferation, differentiation, and function of the cells of bone. Key evidence has...... come from studies on murine knockout models and from pharmacologic studies on cells and animals. More recently, the role of P2X receptors in human bone diseases has been documented. Loss-of-functions polymorphisms in the P2X7 receptorare associated with bone loss and increased fracture risk. Very...

  3. High field properties of superconducting BaFe{sub 2-x}Ni{sub x}As{sub 2} thin films

    Energy Technology Data Exchange (ETDEWEB)

    Richter, Stefan [Institute for Metallic Materials, IFW Dresden (Germany); Technical University Dresden (Germany); Kurth, Fritz; Grinenko, Vadim; Nielsch, Kornelius; Huehne, Ruben [Institute for Metallic Materials, IFW Dresden (Germany); Iida, Kazumasa [Nagoya University (Japan); Pervakov, Kirill [Russian Academy of Sciences (Russian Federation); Tarantini, Chiara; Jaroszynski, Jan [National High Magnetic Field Laboratory (United States); Pukenas, Aurimas; Skrotzki, Werner [Technical University Dresden (Germany)

    2016-07-01

    Fe based superconductors combine the advantages of cuprates (high upper critical field) with the small Hc{sub 2} anisotropy of classic low temperature superconductors, which makes them suitable candidates for high field applications. The study of Fe-based superconducting thin films is one crucial step to explore this potential in more detail. We present results for epitaxial BaFe{sub 2-x}Ni{sub x}As{sub 2} thin films, which have been successfully grown for the first time using pulsed laser deposition. Superconducting transition temperatures of up to 19 K have been realized in slightly overdoped films, which is in good agreement with results obtained for single crystals. The behavior of the upper critical field and critical current density has been measured in high magnetic fields up to 35 T. The results will be correlated to the observed microstructure and compared to high field data for single crystals with similar composition.

  4. 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.

  5. Superconductor with improved persistence characteristics

    International Nuclear Information System (INIS)

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

    1984-01-01

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

  6. Ceramic high-temperature superconductors

    International Nuclear Information System (INIS)

    Marquart, R.

    1989-01-01

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

  7. Testing Superconductor Logic Integrated Circuits

    NARCIS (Netherlands)

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

    2005-01-01

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

  8. 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...

  9. Vortex lattices in layered superconductors

    International Nuclear Information System (INIS)

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

    1995-01-01

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

  10. Superconductors by powder metallurgy techniques

    International Nuclear Information System (INIS)

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

    1976-05-01

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

  11. Dynamics of vortices in superconductors

    International Nuclear Information System (INIS)

    Weinan, E.

    1992-01-01

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

  12. Development of superconductor application technology

    International Nuclear Information System (INIS)

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

    1997-09-01

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

  13. 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.

  14. Strain effects in oxide superconductors

    International Nuclear Information System (INIS)

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

    1991-01-01

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

  15. J-2X Test Articles Using FDM Process

    Science.gov (United States)

    Anderson, Ted; Ruf, Joe; Steele, Phil

    2010-01-01

    This viewgraph presentation gives a brief history of the J-2X engine, along with detailed description of the material demonstrator and test articles that were created using Fused Deposition Modeling (FDM) process.

  16. Alaska Gravity Data per 2 x 4 min Cell (96)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This 2' x 4' gravity density grid for Alaska displays the distribution of about 1.1 million terrestrial and marine gravity data held in the National Geodetic Survey...

  17. Tests for homogeneity for multiple 2 x 2 contingency tables

    International Nuclear Information System (INIS)

    Carr, D.B.

    1986-01-01

    Frequently data are described by 2 x 2 contingency tables. For example, each 2 x 2 table arises from two dichotomous classifications such as control/treated and respond/did not respond. Multiple 2 x 2 tables result from stratifying the observational units on the basis of other characteristics. For example, stratifying by sex produces separate 2 x 2 tables for males and females. From each table a measure of difference between the response rates for the control and the treated groups is computed. The researcher usually wants to know if the response-rate difference is zero for each table. If the tables are homogeneous, the researcher can generalize from a statement concerning an average to a statement concerning each table. If tables are not homogeneous, homogeneous subsets of the tables should be described separately. This paper presents tests for homogeneity and illustrates their use. 11 refs., 6 tabs

  18. P2X receptors, sensory neurons and pain.

    Science.gov (United States)

    Bele, Tanja; Fabbretti, Elsa

    2015-01-01

    Pain represents a very large social and clinical problem since the current treatment provides insufficient pain relief. Plasticity of pain receptors together with sensitisation of sensory neurons, and the role of soluble mediators released from non-neuronal cells render difficult to understand the spatial and temporal scale of pain development, neuronal responses and disease progression. In pathological conditions, ATP is one of the most powerful mediators that activates P2X receptors that behave as sensitive ATP-detectors, such as neuronal P2X3 receptor subtypes and P2X4 and P2X7 receptors expressed on non-neuronal cells. Dissecting the molecular mechanisms occurring in sensory neurons and in accessory cells allows to design appropriate tissue- and cell- targeted approaches to treat chronic pain.

  19. A Result on a 2x2 Survival Experiment

    National Research Council Canada - National Science Library

    Arami, Ramin

    1997-01-01

    .... The proposed model is a combination of Cox's proportional hazards model and ANOVA model. The existence of a solution to the marginal likelihood function is examined for the case of 2x2 two-way classification...

  20. The role of P2X receptors in bone biology.

    Science.gov (United States)

    Jørgensen, N R; Syberg, S; Ellegaard, M

    2015-01-01

    Bone is a highly dynamic organ, being constantly modeled and remodeled in order to adapt to the changing need throughout life. Bone turnover involves the coordinated actions of bone formation and bone degradation. Over the past decade great effort has been put into the examination of how P2X receptors regulate bone metabolism and especially for the P2X7 receptor an impressive amount of evidence has now documented its expression in osteoblasts, osteoclasts, and osteocytes as well as important functional roles in proliferation, differentiation, and function of the cells of bone. Key evidence has come from studies on murine knockout models and from pharmacologic studies on cells and animals. More recently, the role of P2X receptors in human bone diseases has been documented. Loss-of-functions polymorphisms in the P2X7 receptorare associated with bone loss and increased fracture risk. Very recently a report from a genetic study in multiple myeloma demonstrated that decreased P2X7 receptor function was associated with increased risk of developing multiple myeloma. In contrast, the risk of developing myeloma bone disease and subsequent vertebral fractures was increased in subjects carrying P2X7 receptor gain-of-function alleles as compared to subjects only carrying loss-of-function or normal functioning alleles. It is evident that P2X receptors are important in regulating bone turnover and maintaining bone mass, and thereby holding great potential as novel drug targets for treatment of bone diseases. However, further research is needed before we fully understand the roles and effects of P2X receptors in bone.

  1. P2X1 receptors and the endothelium

    Directory of Open Access Journals (Sweden)

    LS Harrington

    2005-03-01

    Full Text Available Adenosine triphosphate (ATP is now established as a principle vaso-active mediator in the vasculature. Its actions on arteries are complex, and are mediated by the P2X and P2Y receptor families. It is generally accepted that ATP induces a bi-phasic response in arteries, inducing contraction via the P2X and P2Y receptors on the smooth muscle cells, and vasodilation via the actions of P2Y receptors located on the endothelium. However, a number of recent studies have placed P2X1 receptors on the endothelium of some arteries. The use of a specific P2X1 receptor ligand, a, b methylene ATP has demonstrated that P2X1 receptors also have a bi-functional role. The actions of ATP on P2X1 receptors is therefore dependant on its location, inducing contraction when located on the smooth muscle cells, and dilation when expressed on the endothelium, comparable to that of P2Y receptors.

  2. Fluctuoscopy of Superconductors

    Science.gov (United States)

    Varlamov, Andrey

    2012-02-01

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

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

    Science.gov (United States)

    Hosono, Hideo; Ren, Zhi-An

    2009-02-01

    -L Drechsler, N Kozlova, M Bartkowiak, J E Hamann-Borrero, G Behr, K Nenkov, H-H Klauss, H Maeter, A Amato, H Luetkens, A Kwadrin, R Khasanov, J Freudenberger, A Köhler, M Knupfer, E Arushanov, H Rosner, B Büchner and L Schultz Low-energy spin dynamics in the antiferromagnetic phase of CaFe2As2 N J Curro, A P Dioguardi, N ApRoberts-Warren, A C Shockley and P Klavins Muon spin rotation study of magnetism and superconductivity in BaFe2-xCoxAs2 and Pr1-xSrxFeAsO C Bernhard, A J Drew, L Schulz, V K Malik, M Rössle, Ch Niedermayer, Th Wolf, G D Varma, G Mu, H-H Wen, H Liu, G Wu and X H Chen Magnetic impurities in the pnictide superconductor Ba1-xKxFe2As2 Sutirtha Mukhopadhyay, Sangwon Oh, A M Mounce, Moohee Lee, W P Halperin, N Ni, S L Bud'ko, P C Canfield, A P Reyes and P L Kuhns Neutron scattering investigation of the magnetic order in single crystalline BaFe2As2 M Kofu, Y Qiu, Wei Bao, S-H Lee, S Chang, T Wu, G Wu and X H Chen An NMR study on the F-doping evolution of the iron oxypnictide LaFeAs(O1-xFx) Y Nakai, S Kitagawa, K Ishida, Y Kamihara, M Hirano and H Hosono The peculiar physical properties and phase diagram of BaFe2-xCoxAs2 single crystals X F Wang, T Wu, G Wu, R H Liu, H Chen, Y L Xie and X H Chen Synthesis of LnFeAsO1-y superconductors (Ln=La and Nd) using the high-pressure technique Kiichi Miyazawa, Kunihiro Kihou, Motoyuki Ishikado, Parasharam M Shirage, Chul-Ho Lee, Nao Takeshita, Hiroshi Eisaki, Hijiri Kito and Akira Iyo Correlation effects in the iron pnictides Qimiao Si, Elihu Abrahams, Jianhui Dai and Jian-Xin Zhu Competition/coexisitence of magnetism and superconductivity in iron pnictides probed by muon spin rotation Soshi Takeshita and Ryosuke Kadono Impurity-induced in-gap state and Tc in sign-reversing s-wave superconductors: analysis of iron oxypnictide superconductors Yuko Senga and Hiroshi Kontani Intrinsic magnetic properties of the superconductor NdFeAsO0.9F0.1 from local and global measurements R Prozorov, M E Tillman, E D Mun and P C Canfield

  4. Quantum criticality in electron-doped BaFe2-xNixAs2.

    Science.gov (United States)

    Zhou, R; Li, Z; Yang, J; Sun, D L; Lin, C T; Zheng, Guo-qing

    2013-01-01

    A quantum critical point is a point in a system's phase diagram at which an order is completely suppressed at absolute zero temperature (T). The presence of a quantum critical point manifests itself in the finite-T physical properties, and often gives rise to new states of matter. Superconductivity in the cuprates and in heavy fermion materials is believed by many to be mediated by fluctuations associated with a quantum critical point. In the recently discovered iron-pnictide superconductors, we report transport and NMR measurements on BaFe(2-x)Ni(x)As₂ (0≤x≤0.17). We find two critical points at x(c1)=0.10 and x(c2)=0.14. The electrical resistivity follows ρ=ρ₀+AT(n), with n=1 around x(c1) and another minimal n=1.1 at x(c2). By NMR measurements, we identity x(c1) to be a magnetic quantum critical point and suggest that x(c2) is a new type of quantum critical point associated with a nematic structural phase transition. Our results suggest that the superconductivity in carrier-doped pnictides is closely linked to the quantum criticality.

  5. Low-frequency Electronic Transport Noise in La2-xBaxCuO4 Nanowires

    Science.gov (United States)

    Weis, Adam; Xin, Yizhou; van Harlingen, Dale

    2013-03-01

    In the pseudogap regime, high temperature superconductors often exhibit electronic structure, such as charge stripes. Charge stripes pinned to disorder have been predicted to contribute to low-frequency resistance fluctuations when sample dimensions are comparable to the size of stripe domains (Carlson, 2006). We are extending our previous studies of resistance fluctuations in YBa2Cu3O7-δ (Bonetti, 2004; Caplan, 2010) to thin films of La-based cuprates expected to have a more stable stripe phase, particularly in the regime near 1/8-filling. We present measurements of the low-frequency electronic transport in La2-xBaxCuO4 nanowires fabricated by pulsed laser deposition and lithographic techniques. We discuss temperature dependence of the power spectral density and its relevance to correlated electron phases above Tc. This research was supported by the DOE-DMS under grant DE-FG02-07ER46453, through the Frederick Seitz Materials Research Laboratory at the University of Illinois at Urbana-Champaign.

  6. Superconductivity induced by doping Rh in CaFe2-xRhxAs2

    International Nuclear Information System (INIS)

    Qi Yanpeng; Wang Lei; Gao Zhaoshun; Wang Dongliang; Zhang Xianping; Wang Chunlei; Yao Chao; Ma Yanwei

    2011-01-01

    In this paper, we report the synthesis of iron-based superconductors CaFe 2-x Rh x As 2 using a one-step solid state reaction method that crystallizes in the ThCr 2 Si 2 -type structure with a space group I4/mmm. The systematic evolution of the lattice constants demonstrates that the Fe ions are successfully replaced by the Rh. By increasing the doping content of Rh, the spin-density-wave (SDW) transition in the parent compound is suppressed and superconductivity emerges. The maximum superconducting transition temperature is found at 18.5 K with a doping level of x=0.15. The temperature dependence of dc magnetization confirms superconducting transitions at around 15 K. The general phase diagram was obtained and found to be similar to the case of the Rh-doping Sr122 system. Our results explicitly demonstrate the feasibility of inducing superconductivity in Ca122 compounds by higher d-orbital electron doping; however, different Rh-doping effects between FeAs122 compounds and FeAs1111 systems still remains an open question.

  7. Generation of baryon excess in SUsub(L)(2) x SUsub(R)(2) x SUsub(c)(4)

    International Nuclear Information System (INIS)

    Deo, B.B.; Prasad, V.B.

    1980-08-01

    We have calculated the magnitude of the cosmological baryon asymmetry in a gauge theory based on the group SUsub(L)(2) x SUsub(R)(2) x SUsub(c)(4) and find that plausible parameters exist in the model to explain the baryon excess with a subunifying mass scale of 10 4 -10 5 GeV. The novel idea used is that the vacuum eats away antimatter through the VEV of the Higgs meson. (author)

  8. SU(2) X SU(2) X U(1) basis for symmetric SO(6) representations: matrix elements of the generators

    International Nuclear Information System (INIS)

    Piepenbring, R.; Silvestre-Brac, B.; Szymanski, Z.

    1987-01-01

    Matrix elements of the group generators for the symmetric irreducible representations of SO(6) are explicitly calculated in a closed form employing thedecomposition chain SO(6) is contained in SU(2) X SU(2) X U(1) (which is different from the well known Wigner supermultiplet scheme). The relation to the Gel'fand Tsetlin method using SO(6) contained in SO(5) up to ... SO(2) is indicated. An example of a physical application is given

  9. Surface impedance of BaFe2-xNixAs2 in the radio frequency range

    Directory of Open Access Journals (Sweden)

    A. Abbassi

    2012-08-01

    Full Text Available We report measurements of the temperature dependence of the surface impedance in superconducting BaFe1.93Ni0.07As2 crystals using the radiofrequency reflection technique in the 5superconductors BaFe2-xNixAs2 has attracted much interest. For a Ni doping level of 7% the superconducting phase transition is found around 20K. The temperature dependence of the superconducting penetration depth was determined.

  10. 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.

  11. NSSEFF Designing New Higher Temperature Superconductors

    Science.gov (United States)

    2017-04-13

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

  12. Passivation Of High-Temperature Superconductors

    Science.gov (United States)

    Vasquez, Richard P.

    1991-01-01

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

  13. Applications of superconductors to electric motors

    International Nuclear Information System (INIS)

    McConnell, B.W.

    1988-01-01

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

  14. 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

  15. Magic Doping Fractions in High-Temperature Superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Komiya, Seiki; /CRIEPI, Tokyo; Chen, Han-Dong; Zhang, Shou-Cheng; /Stanford U., Phys. Dept.; Ando, Yoichi; /CRIEPI, Tokyo

    2010-01-15

    We report hole-doping dependence of the in-plane resistivity {rho}{sub ab} in a cuprate superconductor La{sub 2-x}Sr{sub x}CuO{sub 4}, carefully examined using a series of high-quality single crystals. Our detailed measurements find a tendency towards charge ordering at particular rational hole doping fractions of 1/16, 3/32, 1/8, and 3/16. This observation appears to suggest a specific form of charge order and is most consistent with the recent theoretical prediction of the checkerboard-type ordering of the Cooper pairs at rational doping fractions x = (2m + 1)/2{sup n}, with integers m and n.

  16. Orbitals, correlation, valencies in high-Tc superconductors

    International Nuclear Information System (INIS)

    Khomskii, D.I.

    1990-09-01

    The survey is given of certain properties of high-Tc superconductors connected with the details of their electronic structure such as the kind of orbitals involved and the degree of correlation. Special attention is paid to the properties of cuprates at high doping level. The problem whether there exists a ''Mott transition'' at high electron or a hole concentration is discussed. We also discuss physical factors (d-p Coulomb interaction, orbital mixing) leading to the partial occupation of copper d x 2 -orbital. In particular we show that in localized picture (x 2 -y 2 ) and z 2 -levels in La 2-x Sr x CuO 4 may cross at x approx. 0.4 which may be responsible for a marked change of many properties at this doping. The possible role of x 2 -electrons in pairing is discussed in connection with some recent experiments. (author). 28 refs, 6 figs, 1 tab

  17. Melt processed high-temperature superconductors

    CERN Document Server

    1993-01-01

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

  18. Recent status of superconductors for accelerator magnets

    International Nuclear Information System (INIS)

    Greene, A.F.

    1992-01-01

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

  19. Electron paramagnetic resonance and AC susceptibility studies of Mn and Gd doped 1:2:3 superconductors

    International Nuclear Information System (INIS)

    La Robina, M.A.

    1997-01-01

    For many years superconductivity was considered to be a low temperature phenomenon occurring below ∼ 25K. All this changed in April 1986 when J. G. Bednorz and K. A. Muller showed that the oxide La 2-x Ba x CuO 4 becomes a superconductor at ∼ 30K. Later in December 1986 the oxides La 2-x Sr x CuO 4 and La 2-x Ba x CuO 4 synthesised under high pressure, were shown to superconduct at ∼ 40K and ∼ 50K, respectively. Finally in February 1987, Chu synthesised the classic superconductor YBa 2 Cu 3 O 6.8 , the so-called 1:2:3 material, which has a critical temperature circa 92K. In this thesis, electron paramagnetic resonance (EPR) and susceptibility measurements are reported on various superconductors. In 1987 Bowden et al., showed that pure phase 1:2:3 samples are characterised by an absence of Cu EPR signals. This contrasts sharply with the Green phase material, Y 2 Ba 1 Cu 1 O 5 , which shows a very large EPR signal with a g eff of 2.08. In an attempt to induce EPR signals, Mn doped 1:2:3 samples have been synthesised and characterised with EPR , AC susceptibility, XRD and SEM measurements. It is shown that Mn EPR signals are not evident in the Mn doped samples with a g eff of 2.09. Also, below T c the EPR signals of the lightly doped Mn samples vanish. It is argued that this is due to fluxoids motion within the superconductor, which gives rise to very large non-reproducible signals. It is suggested that the signals originate from Cu, impurity contaminants and multiple phases produced when the 1:2:3 superconductor is doped with Manganese (author)

  20. Photographing magnetic fields in superconductors

    International Nuclear Information System (INIS)

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

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

  1. Oxygen diffusion in cuprate superconductors

    Energy Technology Data Exchange (ETDEWEB)

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

    1995-01-01

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

  2. QCD as a dual superconductor

    International Nuclear Information System (INIS)

    Zachariasen, F.

    1986-01-01

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

  3. 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

  4. Interaction between light and superconductors

    Science.gov (United States)

    Gilabert, Alain

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

  5. 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.

  6. X-ray photoelectron spectroscopy of high-temperature superconductor clean surfaces and interfaces

    International Nuclear Information System (INIS)

    Hill, D.M.

    1989-01-01

    X-ray photoelectron spectroscopy was used to determine the characteristic spectra for the high temperature superconductors La 1.85 Sr 0.15 CuO 4 , YBa 2 Cu 3 O 7-x , and Bi 2 Sr 2-x Ca 1+x Cu 2 O 8+y and their impurity phases. The oxidation state of Cu in all of these materials was predominantly Cu 2+ . The O 1s emission for clean surfaces was a single broad peak near 529 eV derived from emission from inequivalent O sites in the superconductors. The valence bands were a -6 eV wide manifold of Cu 3d-O 2p hybrid bands in the ∼ 1-7 eV binding energy range, with very low emission at E F arising from antibonding Cu 3d-O 2p orbitals. Emission from grain boundary and other impurity phases appeared at 531 eV for the O 1s core level, and in general ∼ 1-2 eV higher energy than the superconductor peak for other core levels except for Cu 2p. Impurity phases appeared in the valence bands as a shoulder at ∼ 5 eV. The amount of impurities detected was shown to be dependent on the fracture properties of the superconductors. All of the materials were shown to be stable under vacuum. The products and spatial extent of chemical reactions with Ag, Al, Al oxide, Au, Bi, Bi oxide, CaF 2 , Cu, Fe, Si, and Si oxide overlayers on these materials also were examined. Au, CaF 2 , and metal oxides deposited by activated oxidation during evaporation were non-reactive and non-disruptive of the superconductor surfaces. Ag overlayers were unique in that they disrupted the superconductor during deposition, but exhibited no evidence of any chemical reactions. Overlayers with an affinity for oxygen withdrew O from the superconductor. The O loss occurred preferentially from Cu atoms in the superconductor and disrupted the planar bonding structure

  7. P2X receptor channels in endocrine glands

    Czech Academy of Sciences Publication Activity Database

    Stojilkovic, S. S.; Zemková, Hana

    2013-01-01

    Roč. 2, č. 4 (2013), s. 173-180 ISSN 2190-460X R&D Projects: GA ČR(CZ) GBP304/12/G069 Institutional support: RVO:67985823 Keywords : ATP * purinergic P2X receptor channels * pituitary * endocrine glands Subject RIV: ED - Physiology

  8. The contribution of valence unstable ytterbium states into kinetic properties of YbNi{sub 2-x}Ge{sub 2+x} and YbCu{sub 2-x}Si{sub 2+x}

    Energy Technology Data Exchange (ETDEWEB)

    Kuzhel, B.C. [Department of Physics, Ivan Franko National University of Lviv, 50 Dragomanow Str., 79005, Lviv (Ukraine)]. E-mail: kuzhelb@org.lviv.net; Shcherba, I.D. [Department of Physics, Ivan Franko National University of Lviv, 50 Dragomanow Str., 79005, Lviv (Ukraine); Institute of Techniques, Academy of Pedagogy, Podchorozych 2, 30-084, Krakow (Poland); Kravchenko, I.I. [Department of Physics, University of Florida, P.O. Box 118440, Gainesville, FL 32611 (United States)]. E-mail: kravch@phys.ufl.edu

    2006-11-30

    The intermetalic YbNi{sub 2-x}Ge{sub 2+x} (-0.25>=x>=0.25) and YbCu{sub 2-x}Si{sub 2+x} (-0.20>=x>=0.20) alloy systems (CeGa{sub 2}Al{sub 2} -type crystal structure) were studied by measuring X-ray absorption and diffraction at room temperatures as well as electrical resistivity and thermopower in the 4.2-300K temperature range. The temperature dependence of the contribution of valence unstable Yb ions to the total electrical resistance has been analyzed. The qualitative estimation of this contribution has been performed by utilizing the following equation:{delta}{rho}{sub Yb}(T)={rho}{sub exp}(T)-{rho}{sub YbCu{sub 2}Ge{sub 2}}(T)-{delta}{rho}{sub 4.2K},where {delta}{rho}{sub YbCu{sub 2}Ge{sub 2}}(T) is the temperature dependence of YbCu{sub 2}Ge{sub 2} electrical resistance, {delta}{rho}{sub 4.2}={rho}{sub 4.2}(exp)-{rho}{sub 4.2}(YbCu{sub 2}Ge{sub 2})

  9. The contribution of valence unstable ytterbium states into kinetic properties of YbNi2-xGe2+x and YbCu2-xSi2+x

    International Nuclear Information System (INIS)

    Kuzhel, B.C.; Shcherba, I.D.; Kravchenko, I.I.

    2006-01-01

    The intermetalic YbNi 2-x Ge 2+x (-0.25>=x>=0.25) and YbCu 2-x Si 2+x (-0.20>=x>=0.20) alloy systems (CeGa 2 Al 2 -type crystal structure) were studied by measuring X-ray absorption and diffraction at room temperatures as well as electrical resistivity and thermopower in the 4.2-300K temperature range. The temperature dependence of the contribution of valence unstable Yb ions to the total electrical resistance has been analyzed. The qualitative estimation of this contribution has been performed by utilizing the following equation:Δρ Yb (T)=ρ exp (T)-ρ YbCu 2 Ge 2 (T)-Δρ 4.2K ,where Δρ YbCu 2 Ge 2 (T) is the temperature dependence of YbCu 2 Ge 2 electrical resistance, Δρ 4.2 =ρ 4.2 (exp)-ρ 4.2 (YbCu 2 Ge 2 )

  10. P2X(3) receptor gating near normal body temperature

    Czech Academy of Sciences Publication Activity Database

    Kmyhz, V.; Maximyuk, O.; Teslenko, V.; Verkhratsky, Alexei; Krishtal, O.

    2008-01-01

    Roč. 456, č. 12 (2008), s. 339-347 ISSN 0031-6768 Institutional research plan: CEZ:AV0Z50390703 Keywords : P2X3 receptors * Temperature-sensitivity * Gating Subject RIV: FH - Neurology Impact factor: 3.526, year: 2008

  11. P2X7 receptors in satellite glial cells mediate high functional expression of P2X3 receptors in immature dorsal root ganglion neurons

    Directory of Open Access Journals (Sweden)

    Chen Yong

    2012-02-01

    Full Text Available Abstract Background The purinergic P2X3 receptor (P2X3R expressed in the dorsal root ganglion (DRG sensory neuron and the P2X7 receptor (P2X7R expressed in the surrounding satellite glial cell (SGC are two major receptors participating in neuron-SGC communication in adult DRGs. Activation of P2X7Rs was found to tonically reduce the expression of P2X3Rs in DRGs, thus inhibiting the abnormal pain behaviors in adult rats. P2X receptors are also actively involved in sensory signaling in developing rodents. However, very little is known about the developmental change of P2X7Rs in DRGs and the interaction between P2X7Rs and P2X3Rs in those animals. We therefore examined the expression of P2X3Rs and P2X7Rs in postnatal rats and determined if P2X7R-P2X3R control exists in developing rats. Findings We immunostained DRGs of immature rats and found that P2X3Rs were expressed only in neurons and P2X7Rs were expressed only in SGCs. Western blot analyses indicated that P2X3R expression decreased while P2X7R expression increased with the age of rats. Electrophysiological studies showed that the number of DRG neurons responding to the stimulation of the P2XR agonist, α,β-meATP, was higher and the amplitudes of α,β-meATP-induced depolarizations were larger in immature DRG neurons. As a result, P2X3R-mediated flinching responses were much more pronounced in immature rats than those found in adult rats. When we reduced P2X7R expression with P2X7R-siRNA in postnatal and adult rats, P2X3R-mediated flinch responses were greatly enhanced in both rat populations. Conclusions These results show that the P2X7R expression increases as rats age. In addition, P2X7Rs in SGCs exert inhibitory control on the P2X3R expression and function in sensory neurons of immature rats, just as observed in adult rats. Regulation of P2X7R expression is likely an effective way to control P2X3R activity and manage pain relief in infants.

  12. Enhancement of mechanical properties of 123 superconductors

    Science.gov (United States)

    Balachandran, U.

    1995-04-25

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

  13. Electrodynamics of spin currents in superconductors

    International Nuclear Information System (INIS)

    Hirsch, J.E.

    2008-01-01

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

  14. 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.

  15. Superconductors in the High School Classroom

    Science.gov (United States)

    Lincoln, James

    2017-01-01

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

  16. Hexatic vortex glass in disordered superconductors

    International Nuclear Information System (INIS)

    Chudnovsky, E.M.

    1989-01-01

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

  17. Method of production multifilamentary intermetallic superconductors

    International Nuclear Information System (INIS)

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

    1980-01-01

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

  18. Neutron-scattering studies of magnetic superconductors

    International Nuclear Information System (INIS)

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

    1982-01-01

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

  19. The critical current of granular superconductor

    International Nuclear Information System (INIS)

    Ignat'ev, V.K.

    1998-01-01

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

  20. Topological surface states in nodal superconductors

    International Nuclear Information System (INIS)

    Schnyder, Andreas P; Brydon, Philip M R

    2015-01-01

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

  1. Future applications of superconductors for industrial use

    International Nuclear Information System (INIS)

    Reddy, S.P.

    1988-01-01

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

  2. Deletion of P2X2 and P2X3 receptor subunits does not alter motility of the mouse colon

    Directory of Open Access Journals (Sweden)

    Matthew DeVries

    2010-03-01

    Full Text Available Purinergic P2X receptors contribute to neurotransmission in the gut. P2X receptors are ligand-gated cation channels that mediate synaptic excitation in subsets of enteric neurons. The present study evaluated colonic motility in vitro and in vivo in wild type (WT and P2X2 and P2X3 subunit knockout (KO mice. The muscarinic receptor agonist, bethanechol (0.3-3 micromolar, caused similar contractions of the longitudinal muscle in colon segments from WT, P2X2 and P2X3 subunit KO mice. Nicotine (1-300 micromolar, acting at neuronal nicotinic receptors, caused similar longitudinal muscle relaxations in colonic segments from WT and P2X2 and P2X3 subunit KO mice. Nicotine-induced relaxations were inhibited by nitro-L-arginine (NLA, 100 micromolar and apamin (0.1 micromolar which block inhibitory neuromuscular transmission. ATP (1-1000 micromolar caused contractions only in the presence of NLA and apamin. ATP-induced contractions were similar in colon segments from WT, P2X2 and P2X3 KO mice. The mouse colon generates spontaneous migrating motor complexes (MMCs in vitro. The MMC frequency was higher in P2X2 KO compared to WT tissues; other parameters of the MMC were similar in colon segments from WT, P2X2 and P2X3 KO mice. 5-Hydroxytryptophan-induced fecal output was similar in WT, P2X2 and P2X3 KO mice. These data indicate that nicotinic receptors are located predominately on inhibitory motor neurons supplying the longitudinal muscle in the mouse colon. P2X2 or P2X3 subunit containing receptors are not localized to motorneurons supplying the longitudinal muscle. Synaptic transmission mediated by P2X2 or P2X3 subunit containing receptors is not required for propulsive motility in the mouse colon.

  3. Thermal expansion of Cr2xFe2-2xMo3O12, Al2xFe2-2xMo3O12 and Al2xCr2-2xMo3O12 solid solutions

    International Nuclear Information System (INIS)

    Ari, M.; Jardim, P.M.; Marinkovic, B.A.; Rizzo, F.; Ferreira, F.F.

    2008-01-01

    The transition temperature from monoclinic to orthorhombic and the thermal expansion of the orthorhombic phase were investigated for three systems of the family A 2 M 3 O 12 : Cr 2x Fe 2-2x Mo 3 O 12 , Al 2x Fe 2-2x Mo 3 O 12 and Al 2x Cr 2-2x Mo 3 O 12 . It was possible to obtain a single-phase solid solution in all studied samples (x=0, 0.1, 0.3, 0.5, 0.7, 0.9 and 1). A linear relationship between the transition temperature and the fraction of A 3+ cations (x) was observed for each system. In all orthorhombic solid solutions studied here the observed thermal expansion was anisotropic. These anisotropic thermal expansion properties of crystallographic axes a, b and c result in a low positive or near-zero overall linear coefficient of thermal expansion (α l =α V /3). The relationship between the size of A 3+ cations in A 2 M 3 O 12 and the coefficient of thermal expansion is discussed. Near-zero thermal expansion of Cr 2 Mo 3 O 12 is explained by the behavior of Cr-O and Mo-O bond distances, Cr-Mo non-bond distances and Cr-O-Mo bond angles with increasing temperature, estimated by Rietveld analysis of synchrotron X-ray powder diffraction data. - Graphical abstract: In this figure, all published overall linear coefficients of thermal expansion for orthorhombic A 2 M 3 O 12 family obtained through diffraction methods as a function of A 3+ cation radii size, together with dilatometric results, are plotted. Our results indicate that Cr 2 Mo 3 O 12 does not exactly follow the established relationship

  4. Probe high-Tc Superconductors by neutron scattering

    International Nuclear Information System (INIS)

    Fauque, B.

    2007-10-01

    This research thesis explores two aspects of the phase diagram of high critical temperature superconductors: the evolution of AF correlations and the nature of the pseudo-gap phase. The author presents the problematic associated with these particular semiconductors, describes the neutron diffusion probe used in this study, and presents the three families of semiconductors investigated during this research: Bi 2 Sr 2 CaCu 2 O 8+x , YBa 2 Cu 3 O 6+x and La 2-x Sr x CuO 4 . He reports the results of the investigation of the spin dynamics in the Bi 2 Sr 2 CaCu 2 O 8+x . He reports a detailed investigation of the magnetic cross section associated with different types of non conventional magnetic orders proposed as candidates for the pseudo-gap phase. He reports and comments the results obtained for the pseudo-gap phase for the YBa 2 Cu 3 O 6+x and La 2-x Sr x CuO 4 families. Finally, the author discusses the consequences of the obtained results for the description of the diagram phase of high critical temperature semiconductors

  5. Positron trapping at defects in copper oxide superconductors

    International Nuclear Information System (INIS)

    McMullen, T.; Jena, P.; Khanna, S.N.; Li, Y.; Jensen, K.O.

    1991-01-01

    Positron states and lifetimes at defects in the copper oxide superconductors La 2-x Sr x CuO 4 , YBa 2 Cu 3 O 7-x , and Bi 2 Sr 2 CaCu 2 O 8+x are calculated with use of the superposed-atom model. In the Bi 2 Sr 2 CaCu 2 O 8+x compound, we find that the smaller metal-ion vacancies appear to only bind positrons weakly, while missing oxygens do not trap positrons. In contrast, metal-ion vacancies in La 2-x Sr x CuO 4 and YBa 2 Cu 3 O 7-x bind positrons by ∼1 eV, and oxygen-related defects appear to be the weak-binding sites in these materials. The sites that bind positrons only weakly, by energies ∼k BT , are of particular interest in view of the complex temperature dependences of the annihilation characteristics that are observed in these materials

  6. Common phase diagram for low-dimensional superconductors

    International Nuclear Information System (INIS)

    Michalak, Rudi

    2003-01-01

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

  7. 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.

  8. 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.

  9. Intrinsic stability of technical superconductors

    International Nuclear Information System (INIS)

    Veringa, H.J.

    1981-10-01

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

  10. 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.

  11. Renormalized modes in cuprate superconductors

    Science.gov (United States)

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

    2018-04-01

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

  12. Peak effect in twinned superconductors

    International Nuclear Information System (INIS)

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

    1995-01-01

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

  13. Thermodynamic analysis of interaction of UOsub(2+-x) with carbon

    International Nuclear Information System (INIS)

    Khromov, Yu.F.; Lyutikov, R.A.

    1980-01-01

    Measurement results of equilibrium pressure of CO (Psub(CO)) for the WO 2 +C system at carbon excess are presented. The change of oxygen potential in the range of WOsub(2+-x) homogeneity are analyzed. Equilibrium pressure of oxygen has been determined on the basis of the Knudsen method by means of direct mass-spectrometric measurements of equilibrium pressure Psub(CO) for the UOsub(1.9995)+C system. On the basis of equilibrium pressure of oxygen and equilibrium constants Ksub(p)f (T) a general analytic dependence of CO pressure is obtained and a diagram of calculated values of equilibrium pressure of Psub(CO) for the UOsub(2+-x)-UCsub(2)-C system at the temperature of 1500-2500 K and O/U values from 1.97 to 2.1 is plotted [ru

  14. Generalised Wigner surmise for (2 X 2) random matrices

    International Nuclear Information System (INIS)

    Chau Huu-Tai, P.; Van Isacker, P.; Smirnova, N.A.

    2001-01-01

    We present new analytical results concerning the spectral distributions for (2 x 2) random real symmetric matrices which generalize the Wigner surmise. The study of the statistical properties of spectra of realistic many-body Hamiltonians requires consideration of a random matrix ensemble whose elements are not independent or whose distribution is not invariant under orthogonal transformation of a chosen basis. In this letter we have concentrated on the properties of (2 x 2) real symmetric matrices whose elements are independent Gaussian variables with zero means but do not belong to the GOE. We have derived the distribution of eigenvalues for such a matrix, the nearest-neighbour spacing distribution which generalizes the Wigner surmise and we have calculated some important moments. (authors)

  15. Oxygen redistribution in (UCe)Osub(2-x)

    International Nuclear Information System (INIS)

    Guedeney, Philippe.

    1983-01-01

    Redistribution of oxygen has been investigated in (Usub(0,7)Cesub(0,3))Osub(2-x) mixed oxide subjected to a temperature gradient in laboratory experiments, in order to apply the results to the nuclear fuel (UPu)Osub(2-x). Cylindrical sintered oxide specimens were exposed to temperature up to 1300 0 C with a longitudinal thermal gradient of about 400 0 C/cm. The most interesting feature of the experimental set-up is a solid-state electrochemical gauge (ThO 2 - Y 2 O 3 ), placed in the cold part of the sample which allows a continuous measurement of the oxygen activity. The experiments showed a fast oxygen migration down the thermal gradient. The calculations performed with a model based on solid-state thermodiffusion are in good agreement with experimental results. The heat of transport Q measured for bare samples reaches (7.2+-0.5)-kcal/mole. When the sample is coated with a tight fitting metallic cladding, an extra term Qe has to be added to the heat of transport Qe. This was interpreted as an electrotransport phenomena. On the same basis, calculations applied to radial oxygen redistribution in (UPu)Osub(2-x) seem to be adequate at least during the first stage of irradiation, taking Q=(20+-5)kcal/mole [fr

  16. The J-2X Fuel Turbopump - Design, Development, and Test

    Science.gov (United States)

    Tellier, James G.; Hawkins, Lakiesha V.; Shinguchi, Brian H.; Marsh, Matthew W.

    2011-01-01

    Pratt and Whitney Rocketdyne (PWR), a NASA subcontractor, is executing the design, development, test, and evaluation (DDT&E) of a liquid oxygen, liquid hydrogen two hundred ninety four thousand pound thrust rocket engine initially intended for the Upper Stage (US) and Earth Departure Stage (EDS) of the Constellation Program Ares-I Crew Launch Vehicle (CLV). A key element of the design approach was to base the new J-2X engine on the heritage J-2S engine with the intent of uprating the engine and incorporating SSME and RS-68 lessons learned. The J-2S engine was a design upgrade of the flight proven J-2 configuration used to put American astronauts on the moon. The J-2S Fuel Turbopump (FTP) was the first Rocketdyne-designed liquid hydrogen centrifugal pump and provided many of the early lessons learned for the Space Shuttle Main Engine High Pressure Fuel Turbopumps. This paper will discuss the design trades and analyses performed for the current J-2X FTP to increase turbine life; increase structural margins, facilitate component fabrication; expedite turbopump assembly; and increase rotordynamic stability margins. Risk mitigation tests including inducer water tests, whirligig turbine blade tests, turbine air rig tests, and workhorse gas generator tests characterized operating environments, drove design modifications, or identified performance impact. Engineering design, fabrication, analysis, and assembly activities support FTP readiness for the first J-2X engine test scheduled for July 2011.

  17. Two-band superconductor magnesium diboride

    International Nuclear Information System (INIS)

    Xi, X X

    2008-01-01

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

  18. Studies of high temperature superconductors

    International Nuclear Information System (INIS)

    Narlikar, A.

    1989-01-01

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

  19. Superconductors made of niobium germanide

    International Nuclear Information System (INIS)

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

    1976-01-01

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

  20. High-Tc superconductor applications

    International Nuclear Information System (INIS)

    Anon.

    1988-01-01

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

  1. Superconductor bearings, flywheels and transportation

    International Nuclear Information System (INIS)

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

    2012-01-01

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

  2. Raman spectra of SDW superconductors

    Energy Technology Data Exchange (ETDEWEB)

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

    2005-03-15

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

  3. Raman spectra of SDW superconductors

    International Nuclear Information System (INIS)

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

    2005-01-01

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

  4. Modified entropic gravitation in superconductors

    International Nuclear Information System (INIS)

    Matos, Clovis Jacinto de

    2012-01-01

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

  5. 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...

  6. Position-sensitive superconductor detectors

    International Nuclear Information System (INIS)

    Kurakado, M.; Taniguchi, K.

    2016-01-01

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

  7. The Si(100)-Sb 2x1 and Ge(100) 2x1 surfaces: A multi-technique study

    International Nuclear Information System (INIS)

    Richter, M.

    1993-08-01

    The electronic and geometric structures of the clean and Sb terminated Si(100)2x1 and Ge(100)-2x1 surfaces have been investigated using a multi-technique approach. Low energy electron diffraction (LEED), scanning tunneling microscopy (STM), surface extended X-ray absorption fine structure (SEXAFS) spectroscopy and angle-integrated core-level photoemission electron spectroscopy (PES) were employed to measure the surface symmetry, defect structure, relevant bond lengths, atomic coordination and electronic structure. By employing a multi-technique approach, it is possible to correlate changes in the geometric structure to specific features of the core-level lineshape of the substrate. This allows for the assignment of components of the core-level lineshape to be assigned to specific surface and near-surface atoms

  8. Global analysis of general SU(2)xSU(2)xU(1) models with precision data

    International Nuclear Information System (INIS)

    Hsieh, Ken; Yu, Jiang-Hao; Yuan, C.-P.; Schmitz, Kai

    2010-01-01

    We present the results of a global analysis of a class of models with an extended electroweak gauge group of the form SU(2)xSU(2)xU(1), often denoted as G(221) models, which include as examples the left-right, the leptophobic, the hadrophobic, the fermiophobic, the un-unified, and the nonuniversal models. Using an effective Lagrangian approach, we compute the shifts to the coefficients in the electroweak Lagrangian due to the new heavy gauge bosons, and obtain the lower bounds on the masses of the Z ' and W ' bosons. The analysis of the electroweak parameter bounds reveals a consistent pattern of several key observables that are especially sensitive to the effects of new physics and thus dominate the overall shape of the respective parameter contours.

  9. 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.

  10. Superconductor in a weak static gravitational field

    Energy Technology Data Exchange (ETDEWEB)

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

    2017-08-15

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

  11. Two-dimensional Semiconductor-Superconductor Hybrids

    DEFF Research Database (Denmark)

    Suominen, Henri Juhani

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

  12. Electromagnetic properties of metals and superconductors

    International Nuclear Information System (INIS)

    Sinha, K.P.

    1977-01-01

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

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

    International Nuclear Information System (INIS)

    Hosono, Hideo

    2009-01-01

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

  14. An extraordinarily stable catalyst: Pt NPs supported on two-dimensional Ti3C2X2 (X = OH, F) nanosheets for oxygen reduction reaction.

    Science.gov (United States)

    Xie, Xiaohong; Chen, Siguo; Ding, Wei; Nie, Yao; Wei, Zidong

    2013-10-03

    High dispersion Pt nanoparticles supported on 2D Ti3C2X2 (X = OH, F) nanosheets are presented and electro-chemical measurements confirm that the Pt/Ti3C2X2 catalyst shows enhanced durability and improved ORR activity compared with the commercial Pt/C catalyst.

  15. Electrical transport properties of sputtered Nd2-xCexCuO4±δ thin films

    Science.gov (United States)

    Guarino, Anita; Leo, Antonio; Avella, Adolfo; Avitabile, Francesco; Martucciello, Nadia; Grimaldi, Gaia; Romano, Alfonso; Pace, Sandro; Romano, Paola; Nigro, Angela

    2018-05-01

    Thin films of the electron-doped high-temperature superconductor Nd2-xCexCuO4±δ have been deposited by dc sputtering technique on (100) SrTiO3 substrates. A tuning of the oxygen content in the as-grown non-superconducting samples has been achieved by changing the oxygen partial pressure during the growth in the Argon sputtering atmosphere. All samples show the superconducting transition after a suitable two-step thermal treatment in an oxygen-reducing environment. Structural and electrical transport properties on the as-grown as well as on the superconducting samples have been investigated. We find that the structural properties are consistent with a deficiency of the oxygen content with respect to optimally annealed samples, and that the transition to the superconducting phase is always accompanied by an increase of the c-axis lattice parameter. Measurements of the Hall coefficient RH as a function of temperature and in the normal state of our epitaxial films are presented and discussed. RH results negative for all the films regardless of the oxygen content and it decreases with the temperature. In particular, the Hall coefficient is only about 10% lower than the value measured in the as-grown oxygen-deficient phase, in contrast to the results reported in literature. The removal of the excess oxygen in as-grown samples seems not to be the only requirement for triggering the superconducting transition in electron-doped compounds. The microstructural change associated with the increase of the c-axis parameter in our deoxygenated samples could help in understanding the microscopic mechanism underlying the reduction process of n-type superconductors, which is still under debate.

  16. Distinct Nature of Static and Dynamic Magnetic Stripes in Cuprate Superconductors

    Science.gov (United States)

    Jacobsen, H.; Holm, S. L.; Lǎcǎtuşu, M.-E.; Rømer, A. T.; Bertelsen, M.; Boehm, M.; Toft-Petersen, R.; Grivel, J.-C.; Emery, S. B.; Udby, L.; Wells, B. O.; Lefmann, K.

    2018-01-01

    We present detailed neutron scattering studies of the static and dynamic stripes in an optimally doped high-temperature superconductor, La2 CuO4 +y . We observe that the dynamic stripes do not disperse towards the static stripes in the limit of vanishing energy transfer. Therefore, the dynamic stripes observed in neutron scattering experiments are not the Goldstone modes associated with the broken symmetry of the simultaneously observed static stripes, and the signals originate from different domains in the sample. These observations support real-space electronic phase separation in the crystal, where the static stripes in one phase are pinned versions of the dynamic stripes in the other, having slightly different periods. Our results explain earlier observations of unusual dispersions in underdoped La2 -xSrx CuO4 (x =0.07 ) and La2 -xBax CuO4 (x =0.095 ).

  17. Unconventional superconductors. Anisotropy and multiband effects

    Energy Technology Data Exchange (ETDEWEB)

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

    2012-07-01

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

  18. Performance boundaries in Nb3Sn superconductors

    NARCIS (Netherlands)

    Godeke, A.

    2005-01-01

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

  19. Unconventional superconductors anisotropy and multiband effects

    CERN Document Server

    Askerzade, Iman

    2012-01-01

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

  20. High Temperature Superconductor Bolometers for Planetary Science

    Data.gov (United States)

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

  1. 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.

  2. Neutron irradiation effects in advanced superconductors

    International Nuclear Information System (INIS)

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

    1988-01-01

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

  3. 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.

  4. Searching for superconductors with high critical temperature

    Energy Technology Data Exchange (ETDEWEB)

    Chao, C

    1977-08-18

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

  5. Force measurements for levitated bulk superconductors

    International Nuclear Information System (INIS)

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

    2000-01-01

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

  6. Force measurements for levitated bulk superconductors

    Energy Technology Data Exchange (ETDEWEB)

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

    2000-06-01

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

  7. 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

  8. Superconductors for pulsed rf accelerators

    International Nuclear Information System (INIS)

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

    1985-04-01

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

  9. Electromagnetic theory for filamentary superconductors

    International Nuclear Information System (INIS)

    Carr, W.J. Jr.

    1975-01-01

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

  10. New possibilities for superconductor electronics

    International Nuclear Information System (INIS)

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

    1989-01-01

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

  11. Plutonium helps probe protein, superconductor

    International Nuclear Information System (INIS)

    Anon.

    1990-01-01

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

  12. 10 Years of Car-2-X Communication - a Success Story?

    Science.gov (United States)

    Wischhof, Lars; Ebner, André

    2012-05-01

    For more than ten years, car-2-x communication has been a major topic of research in the scientific community and an important development focus for the automotive industry. First, this article takes a retrospective look at the evolution of car-2-x and the two different communication paradigms: decentralized car-2-car communication and centralized cellular solutions. Afterwards, a comparison of their technical advantages and limitations is presented, respectively. The result shows that in order to implement safety-relevant applications, car-2-car communication has strong advantages compared to cellular technologies but requires high market penetration. However, its introduction solely for safety applications is difficult since the required penetration will not be achieved until several years after initial deployment. Therefore, car-2-car communication must provide a benefit to the customer, even in the phase of market introduction. For this purpose, the article outlines an approach called SODAD (Segment-Oriented Data Abstraction and Dissemination). It offers a possibility to introduce decentralized vehicular applications with early customer benefit, in order to enable safety applications based on car-2-car communication on a long term.

  13. 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).

  14. Topological insulators and superconductors from string theory

    International Nuclear Information System (INIS)

    Ryu, Shinsei; Takayanagi, Tadashi

    2010-01-01

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

  15. Magnetic properties of layered superconductors

    International Nuclear Information System (INIS)

    Mansky, P.A.

    1993-01-01

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

  16. Coincident photoelectron spectroscopy on superconductors

    International Nuclear Information System (INIS)

    Voss, Stefan

    2011-01-01

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

  17. 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.

  18. 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...

  19. 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...

  20. Superconductors

    International Nuclear Information System (INIS)

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

    1977-01-01

    The structural quality of niobium germanide as a high-transition-temperature superconducting material is substantially improved by the presence of about 5 at. percent oxygen. Niobium germanide having this oxygen content may readily be prepared as a bulk coating bonded to a metallic substrate by chemical vapor deposition techniques. 2 figures, 1 table

  1. 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.

  2. Charge density wave fluctuations in La{sub 2-x}Sr{sub x}CuO{sub 4} and their competition with superconductivity

    Energy Technology Data Exchange (ETDEWEB)

    Croft, Thomas; Lester, Christopher; Hayden, Stephen [H.H. Wills Physics Laboratory, University of Bristol (United Kingdom); Bombardi, Alessandro; Senn, Mark [Diamond Light Source Ltd., Harwell Science and Innovation Campus, Didcot, Oxfordshire (United Kingdom)

    2015-07-01

    The recent observations of charge and stripe correlations in YBa{sub 2}Cu{sub 3}O{sub 6+x} and La{sub 2-x}Ba{sub x}CuO{sub 4} has reinvigorated interest in their role in influencing the superconductivity of the cuprates. However, structural complications of these systems makes it difficult to isolate the effect the lattice has in inducing the charge order. Here, we report hard X-ray diffraction measurements on three compositions (x=0.11,0.12,0.13) of the high-temperature superconductor La{sub 2-x}Sr{sub x}CuO{sub 4}, a canonical example of HTS with T{sub c} ∼ 35 K and a simple crystal structure. All samples show charge-density-wave (CDW) order with onset temperatures in the range 51-80 K and ordering wavevectors close to (0.23,0,0.5). We present a phase diagram of La{sub 2-x}Sr{sub x}CuO{sub 4} including the pseudogap phase, CDW and magnetic order.

  3. Magnetic phase diagrams of the spinels AB2xGa2-2xO4 (A = Zn, Co; B = Al, Cr) systems

    International Nuclear Information System (INIS)

    Hamedoun, M.; Masrour, R.; Bouslykhane, K.; Hourmatallah, A.; Benzakour, N.

    2008-01-01

    The magnetic properties of the spinels CoAl 2x Ga 2-2x O 4 and ZnCr 2x Ga 2-2x O 4 systems in the range 0 ≤ x ≤ 1 have been studied by mean field theory and high-temperature series expansions. By using the first theory, we have evaluated the nearest neighbour and the next-neighbour super-exchange interaction J 1 (x) and J 2 (x), respectively, for the first systems in the range 0 ≤ x ≤ 1 and J 1 (x = 1), J 2 (x = 1) for the second system. The intra-planar and the inter-planar interactions are deduced. The corresponding classical exchange energy for magnetic structure is obtained for the first system. The second theory have been applied in the spinels CoAl 2x Ga 2-2x O 4 and ZnCr 2x Ga 2-2x O 4 systems, combined with the Pade approximants method, we have obtained the magnetic phase diagrams (T N versus dilution x) in the range 0 ≤ x ≤ 1. The obtained theoretical results are in agreement with experimental ones obtained by magnetic measurements and Moessbauer spectroscopy. The threshold percolation in the second system is x p ∼ 0.4. The critical exponents associated with the magnetic susceptibility (γ) and the correlation lengths (ν) are deduced in the range 0 ≤ x ≤ 1

  4. Design study of SMES system using high temperature superconductors

    International Nuclear Information System (INIS)

    Yoshihara, T.; Masuda, M.; Shintomi, T.; Hasegawa, J.

    1988-01-01

    Various studies of high Tc superconductors are being energetically pursued all over the world, since IBM Zurich Research Laboratory reported on the superconducting oxide. A new design using a high Tc superconductor is under study for 5000 MWh, on the assumption that it is available like conventional superconductors. Problems related to the Tc SMES system, mainly thermal insulation, refrigeration system, stability of superconductors, etc., are considered. Some design examples of high Tc SMES system are proposed

  5. 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.

  6. Dynamics of superconductor bearings in a cryogenic failure

    Energy Technology Data Exchange (ETDEWEB)

    Rastogi, Amit [Department of Engineering, Cambridge University, Cambridge CB2 1PZ (United Kingdom)]. E-mail: Amit.Rastogi@avizatechnology.com; Campbell, A.M. [Department of Engineering, Cambridge University, Cambridge CB2 1PZ (United Kingdom); Coombs, T.A. [Department of Engineering, Cambridge University, Cambridge CB2 1PZ (United Kingdom)

    2006-08-01

    The dynamics of superconductor bearings in a cryogenic failure scenario have been analyzed. As the superconductor warms up, the rotor goes through multiple resonance frequencies, begins to slow down and finally touches down when the superconductor goes through its transition temperature. The bearing can be modelled as a system of springs with axial, radial and cross stiffness. These springs go through various resonant modes as the temperature of the superconductor begins to rise. We have presented possible explanations for such behaviour.

  7. Pinning and creep in high-Tc superconductors

    International Nuclear Information System (INIS)

    Ovchinnikov, Yu.N.; Ivlev, B.I.

    1992-01-01

    The angular and magnetic field dependence of a critical current parallel to the layers in the layered superconductors is studied. The critical current value is found for a superconductor with strong pinning centers. Quantum flux creep in sufficiently perfect layered high-Tc superconductors is discussed. The cross-over temperature between activated and quantum creep is found. (orig.)

  8. Studies on the adsorption behaviour of heavy rare earths with a strong cation exchanger DOWEX 50W-2X8

    International Nuclear Information System (INIS)

    Vijayalakshmi, R.; Singh, D.K.; Anitha, M.; Kotekar, M.K.; Dasgupta, K.; Singh, H.

    2014-01-01

    Rare earths have been a very fascinating area of research since long due to its wide applicability's in many field including superconductors, lasers, phosphors, medical, electronics, magnet, optics etc. Separation of rare earths is a challenging task and over the years many separation schemes based on solvent extraction, ion exchange, membrane etc have been developed and deployed. In the present work, we have investigated the adsorption behavior of heavy rare earths from a crude concentrate analyzing ∼ 80% Y 2 O 3 , ∼12% Dy 2 O 3 , ∼4% Er 2 O 3 etc., with a strong cationic exchanger namely Dowex 50W-2X8 in order to separate them in pure form. To start with, Y was selected as a representative of heavy rare earths and the conditions were optimized in batch experiments and later were applied to the feed solution containing Dy, Er, Ho etc. in a column study. Effects of experimental variables such as contact time, pH, weight of resin, concentration of the feed metal, temperature, desorption agents, on adsorption of Y was studied

  9. The color of polarization in cuprate superconductors

    International Nuclear Information System (INIS)

    Hoff, H.A.; Osofsky, M.S.; Lechter, W.L.; Pande, C.S.

    1991-01-01

    A technique for the identification of individual anisotropic grains in a heterogeneous and opaque material involves the observation of grain color in reflected light through crossed polarizers (color of polarization). Such colors are generally characteristic of particular phases. When grains of many members of the class of hole carrier cuprate superconductors are so viewed at room temperature with a 'daylight' source, a characteristic color of polarization is observed. This color was studied in many of these cuprate superconductors and a strong correlation was found between color and the existence of superconductivity. Two members were also examined of the electron cuprate superconductors and it was found that they possess the same color of polarization as the hole carrier cuprate superconductors so far examined. The commonality of the characteristic color regardless of charge carrier indicates that the presence of this color is independent of carrier type. The correlation of this color with the existence of superconductivity in the cuprate superconductors suggests that the origin of the color relates to the origin of superconductivity. Photometric techniques are also discussed

  10. Doped Tl-1212 and Tl-1223 superconductors

    International Nuclear Information System (INIS)

    Eder, M.H.

    2001-09-01

    This work describes the preparation and characterization of thallium-lead-strontium-barium-calcium-(uranium)-copperoxide (Tl-1212, Tl-1223) high-temperature superconductors. The precursors were prepared via nitrate method. After calcination the oxidic powders were mixed with stoichiometric amounts of an Tl 2 O 3 , PbO, Er 2 O 3 and Gd 2 O 3 by milling and afterwards uniaxial compressed. Sintering was carried out in silver foils. X-ray diffractometry and high-resolution microscopy in combination with scanning electron microscopy (including EDAX) were used to study the influence of varying thallium/lead-, strontium/barium-, calcium/rare earth element ratios and the effect of uranium on the phase composition and microstructure of bulk superconductors. Furthermore the influence of the composition on the electrical and magnetical properties was studied. On phase pure Tl-1212 and Tl-1223 superconductors NMR-measurements were done. Small amounts of gadolinium and erbium instead of calcium and excess-uranium have a positive impact on the electrical and magnetical properties of the Tl-1223 superconductors. Higher amounts of these doping elements favor the Tl-1212 phase. Tl-1212 superconductors with varying thallium/lead- strontium/barium- and calcium/gadolinium ratios were prepared phasepure in wide range of doping. Transition temperatures up to 96 K were achieved. It was shown that lead has an oxidation number of +4 and thallium of +3. (author)

  11. Roles of spin fluctuation and frustration in the superconductivity of β-(BDA-TTP)2X (X=SbF6,AsF6) under uniaxial compression

    Science.gov (United States)

    Ito, Hiroshi; Ishihara, Tetsuo; Tanaka, Hisaaki; Kuroda, Shin-Ichi; Suzuki, Takeo; Onari, Seiichiro; Tanaka, Yukio; Yamada, Jun-Ichi; Kikuchi, Koichi

    2008-11-01

    β -type BDA-TTP [ BDA-TTP=2,5 -bis(1,3-dithian-2-ylidene)-1,3,4,6-tetrathiapentalene] salts possess high transition temperatures TC reaching 7 K among organic superconductors. TC of β-(BDA-TTP)2X (X=SbF6,AsF6) is studied by resistive measurements under uniaxial compression. TC once increases and takes a maximum under compression parallel to the donor stack while it decreases under compression perpendicular to the donor stack. These results are in agreement with the half-filled Hubbard model on the triangular lattice in which the compression controls the spin fluctuation and frustration in the weak pressure region.

  12. Magnetotransport properties in the magnetic phase of BaFe2 -xTxAs2 (T =Co ,Ni ) : A magnetic excitations approach

    Science.gov (United States)

    Peña, J. P.; Piva, M. M.; Rosa, P. F. S.; Pagliuso, P. G.; Adriano, C.; Grant, T.; Fisk, Z.; Baggio-Saitovitch, E.; Pureur, P.

    2018-03-01

    Because of their complex Fermi surfaces, the identification of the physical phenomena contributing to electronic scattering in the Fe-based superconductors is a difficult task. Here, we report on the electrical resistivity, magnetoresistance, and Hall effect in two series of BaFe2 -xTxAs2 (T =Co ,Ni ) crystals with different values of x . The T contents were chosen so that the majority of the investigated samples present an intermediate magnetically ordered state and a superconducting ground state. We interpret the obtained results in terms of scattering of charge carriers by magnetic excitations instead of describing them as resulting uniquely from effects related to multiple-band conduction. Our samples are single crystals from the structural point of view and their overall magnetotransport properties are dominated by a single magnetic state.

  13. Experimental evidence for importance of Hund's exchange interaction for incoherence of charge carriers in iron-based superconductors

    Science.gov (United States)

    Fink, J.; Rienks, E. D. L.; Thirupathaiah, S.; Nayak, J.; van Roekeghem, A.; Biermann, S.; Wolf, T.; Adelmann, P.; Jeevan, H. S.; Gegenwart, P.; Wurmehl, S.; Felser, C.; Büchner, B.

    2017-04-01

    Angle-resolved photoemission spectroscopy is used to study the scattering rates of charge carriers from the hole pockets near Γ in the iron-based high-Tc hole-doped superconductors KxBa1 -xFe2As2 , x =0.4 , and KxEu1 -xFe2As2 , x =0.55 , and the electron-doped compound Ba (Fe1-xCox) 2As2 , x =0.075 . The scattering rate for any given band is found to depend linearly on the energy, indicating a non-Fermi-liquid regime. The scattering rates in the hole-doped compound are considerably higher than those in the electron-doped compounds. In the hole-doped systems the scattering rate of the charge carriers of the inner hole pocket is about three times higher than the binding energy, indicating that the spectral weight is heavily incoherent. The strength of the scattering rates and the difference between electron- and hole-doped compounds signals the importance of Hund's exchange coupling for correlation effects in these iron-based high-Tc superconductors. The experimental results are in qualitative agreement with theoretical calculations in the framework of combined density functional dynamical mean-field theory.

  14. 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.

  15. Coherent lattice vibrations in superconductors

    International Nuclear Information System (INIS)

    Kadin, Alan M.

    2008-01-01

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

  16. Structural behavior of cable superconductors

    International Nuclear Information System (INIS)

    Becker, H.; Marston, P.

    1983-01-01

    The structural properties of cable superconductor coils, for particle accelerators such as the Tevatron and the CBA (Colliding Beam Accelerator), depend upon direction of loading. For compression perpendicular to the ''flat faces'' of the conductor, the coils exhibit nonlinear, inelastic and time dependent behavior. The same is true for ''inplane'' compression loading perpendicular to the conductor edges. In the lengthwise direction, the coils display tension and compression stress-strain curves typical of structural metals. The loading of primary concern is compression perpendicular to the conductor faces since deformations in that direction can have a major influence on magnetic field quality. However, the coil behavior under that condition is uncertain because of the nonlinear stress strain curve complicated by creep and relaxation at the stress levels induced by preloading and Lorentz forces. Furthermore, the stiffness of the loading fixture appears to influence the data as shown by results from tests run under different conditions at Berkeley, Brookhaven and MIT. The paper displays test data on stress-strain curves for all three loading directions. Results are presented for RT, 77 K and 4 K behavior. Data of various investigators are compared. The applicability of a relatively simple power law between stress and strain is depicted

  17. Theory of Josephson effect in d-wave superconductor/diffusive ferromagnet/d-wave superconductor junctions

    NARCIS (Netherlands)

    Yokoyama, T.; Tanaka, Y.; Golubov, Alexandre Avraamovitch

    2007-01-01

    We study Josephson effect in d-wave superconductor/diffusive ferromagnet/d-wave superconductor junctions, changing the exchange field and the angles between the normal to the interfaces and the crystal axes of d-wave superconductors. We find a 0–π transition at a certain value of the exchange field.

  18. Growth of high-temperature superconductor crystals from flux

    International Nuclear Information System (INIS)

    Demianets, L.N.; Bykov, A.B.; Melnikov, O.K.; Stishov, S.M.

    1991-01-01

    Crystallization of high-temperature superconductors was studied in La-Sr-Cu-O, Y-Ba-Cu-O and Bi-Sr-Ca-Cu-O systems. Platelet crystals YBa 2 Cu 3 Osub(6.5+x) were obtained by spontaneous crystallization from homogeneous nonstoichiometric melts enriched in barium and copper oxides. Lasub(2-x)Sr x CuO 4 was prepared by slow cooling of melts enriched in copper oxide. Bi 2 (Sr, Ca)sub(n+1)Cu n O y , (n=1;2) was obtained by melting zone travelling. The crystals show transition to superconducting state at T=93K, ΔT 0.2-0.5 K (Y, Ba cuprate), T=87K, ΔT 2K (Bi, Sr, Ca-cuprate). La, Sr-cuprate single crystals obtained by Czochralski method did not show transition to superconducting state. For flux-grown crystals T c was 5-26 K depending on the composition, growth and heat treatment. The short characterization of some accessory phases (Ba 3 Y 2 Cu 3 PtO 10 , Casub(1.75)Srsub(1.5)Cusub(0.75)PtO 6 , BaCuO 2 , Ba 41 Cu 44 O 84 Cl 2 ) is reported. (author). 15 ref s., 8 figs

  19. Rf and microwave measurements at Los Alamos on oxide superconductors

    International Nuclear Information System (INIS)

    Migliori, A.; Reagor, D.W.; Peterson, D.E.; Willis, J.O.; Fisk, Z.; Smith, R.C.

    1988-01-01

    Los Alamos National Laboratory has made a substantial commitment to develop oxide superconductors for RF and microwave cavity applications. The program involves materials development, complete microstructure characterization, static thermal and electrical characterization, RF loss measurements and microwave complex-conductivity measurements. Of the high-frequency techniques, three are nearing completion and one has produced preliminary results. Those still under development include a 3 GHz Nb cavity capable of 4 K operation, a LN 2 -cooled 2.25 GHz copper cavity having a Q of 2 x 10 4 , capable of operation from 15 K to 300 K, and a picosecond-laser/photo-diode driven microstripline technique which will provide complex conductivity information from 20 GHz to 200 GHz and from 10 K to 300 K. Because all of the techniques employed sense the impedance of the samples, their sensitivity to intrinsic properties such as conductivity or surface resistance is dependent on sample geometry. However, for easily handled samples, the Nb cavity can detect losses at least four order of magnitude lower than copper, the copper cavity can detect losses two orders of magnitude lower than copper and the microstripline can detect losses comparable to copper. The technique which has produced results is a coaxial microwave bridge. In this work they report results of measurements on sintered samples using the bridge; future work will concentrate on films. 2 references, 1 figure

  20. Fracture toughness for copper oxide superconductors

    Science.gov (United States)

    Goretta, K.C.; Kullberg, M.L.

    1993-04-13

    An oxide-based strengthening and toughening agent, such as tetragonal ZrO[sub 2] particles, has been added to copper oxide superconductors, such as superconducting YBa[sub 2]Cu[sub 3]O[sub x] (123) to improve its fracture toughness (K[sub IC]). A sol-gel coating which is non-reactive with the superconductor, such as Y[sub 2]BaCuO[sub 5] (211) on the ZrO[sub 2] particles minimized the deleterious reactions between the superconductor and the toughening agent dispersed therethrough. Addition of 20 mole percent ZrO[sub 2] coated with 211 yielded a 123 composite with a K[sub IC] of 4.5 MPa(m)[sup 0.5].

  1. 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.

  2. Practical superconductor development for electrical power applications

    International Nuclear Information System (INIS)

    Goretta, K.C.

    1991-10-01

    Development of useful high-critical-temperature (high-T c ) superconductors requires synthesis of superconducting compounds; fabrication of wires, tapes, and films from these compounds; production of composite structures that incorporate stabilizers or insulators; and design and testing of efficient components. This report describes technical progress of research and development efforts aimed at producing superconducting components based on the Y-Ba-Cu, Bi-Sr-Ca-Cu, Bi-Pb-Sr-Ca-Cu, and Tl-Ba-Ca-Cu oxides systems. Topics discussed are synthesis and heat treatment of high-T c superconductors, formation of monolithic and composite wires and tapes, superconductor/metal connectors, characterization of structures and superconducting and mechanical properties, and fabrication and properties of thin films. Collaborations with industry and academia are also documented. 10 figs

  3. Stability of magnets levitated above superconductors

    International Nuclear Information System (INIS)

    Davis, L.C.; Logothetis, E.M.; Soltis, R.E.

    1988-01-01

    The stability of a permanent magnet levitated above a slab of hard superconductor is considered. The force on a dipole magnet over a perfectly diamagnetic disk is calculated. It is found that the radial component of the force is directed outward and is 10%--20% of the image (vertical) force near the edge. Estimates of the magnetic friction force due to flux motion in a hard superconductor are made using Bean's model. The magnitude of the magnetic friction is large enough to stabilize the magnet over most of the disk for typical values of the critical current in ceramic superconductors (∼10 3 A/cm 2 ), but too small for the highest values reported (>10 6 A/cm 2 ). It is conjectured that flux trapping due to inhomogeneities gives rise to transient restoring forces

  4. A nonquasiclassical description of inhomogeneous superconductors

    International Nuclear Information System (INIS)

    Zaikin, A.D.; Panyukov, S.V.

    1988-01-01

    Exact microscopic equations are derived that make it possible to describe inhomogeneous superconductors when the quasi-classical approach is not suitable. These equations are simpler than the Gorkov equations. The authors generalize the derived equations for describing the nonequilibrium states of inhomogeneous superconductors. It is demonstrated that the derived equations (including the case of a nonequilibrium quasi particle distribution function) may be written in the form of linear differential equations for the simultaneous wave function μ, ν. The quasi-classical limit of such equations is examined. Effective boundary conditions are derived for the μ, ν functions that allow description of superconductors with a sharp change in parameters within the scope of the quasi-classical approach

  5. 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.

  6. Processing Y- and Bi-based superconductors

    International Nuclear Information System (INIS)

    Balachandran, U.; Dos Santos, D.I.; von Stumberg, A.W.; Graham, S.W.; Singh, J.P.; Youngdahl, C.A.; Goretta, K.C.; Shi, D.; Poeppel, R.B.

    1989-01-01

    This paper reports on bulk specimens of YBa 2 Cu 3 O x and Bi 2 Sr 2 CaCu 2 O y formed and then processed by sintering in the solid state, in the presence of a liquid phase, or by sinter forging. Both Y- and Bi-based superconductors are difficult to densify by solid-state sintering but easy to densify in the presence of a liquid phase. Effects of sintering conditions on superconducting properties are, however, different between the two materials. These differences will be discussed. Attempts to texture microstructures and increase J c by sinter-forging techniques have been successful for Y-based superconductors, but unsuccessful for Bi-based superconductors

  7. Energy gap of ferromagnet-superconductor bilayers

    Energy Technology Data Exchange (ETDEWEB)

    Halterman, Klaus; Valls, Oriol T

    2003-10-15

    The excitation spectrum of clean ferromagnet-superconductor bilayers is calculated within the framework of the self-consistent Bogoliubov-de Gennes theory. Because of the proximity effect, the superconductor induces a gap in the ferromagnet spectrum, for thin ferromagnetic layers. The effect depends strongly on the exchange field in the ferromagnet. We find that as the thickness of the ferromagnetic layer increases, the gap disappears, and that its destruction arises from those quasiparticle excitations with wave vectors mainly along the interface. We discuss the influence that the interface quality and Fermi energy mismatch between the ferromagnet and superconductor have on the calculated energy gap. We also evaluate the density of states in the ferromagnet, and we find it in all cases consistent with the gap results.

  8. Electronic structure of ZrX2 (X = Se, Te)

    Science.gov (United States)

    Shkvarin, A. S.; Merentsov, A. I.; Shkvarina, E. G.; Yarmoshenko, Yu. M.; Píš, I.; Nappini, S.; Titov, A. N.

    2018-03-01

    The electronic structure of the ZrX2 (X = Se, Te) compounds has been studied using photoelectron, resonant photoelectron and X-ray absorption spectroscopy, theoretical calculations of the X-ray absorption spectra, and density of electronic states. It was found that the absorption spectra and valence band spectra are influenced by the chalcogen type. The results of the multiplet calculation of the Zr4+ atom show that the change in the splitting in the crystal field, which is described by the 10Dq parameter, is due to the change in the ratio of covalent and ionic contributions to the chemical bond. The resonance band near the Fermi level in the valence band spectra is observed for ZrTe2 in the Zr 3p-4d resonant excitation mode. The extent of photon energy indicates the charge localization on the Zr atom. Similar resonance band for ZrSe2 is absent; it indicates the presence of a gap at the Fermi level.

  9. Neutron diffraction studies on La2−xDyxCa2xBa2Cu4+2xOz ...

    Indian Academy of Sciences (India)

    superconductivity in these types of oxides [2–4]. The R ion in La-2125 type com- pounds provides structural stability without any effect on superconductivity similar to the role of R ion at Y-site in Y-123 superconductors. However, for R = Pr, we observed superconductivity even in the presence of higher concentrations of Pr, ...

  10. The superconductor revolutions and the (slow) applications evolution

    International Nuclear Information System (INIS)

    Foner, S.

    1990-01-01

    The discovery in the 1960's of type 2 superconductors with high critical current densities in high magnetic fields (and the development of NbTi in particular) led to the first revolution. The discovery of high temperature superconductors (HTS) started the second revolution. At this stage ceramists became involved with superconductors. I will assess the status of various superconductor applications, progress of HTS and their possible applications at 4.2K, and near-term needs for superconducting materials operating at 30T in specialized facilities. Reasons for the slow growth of superconductor applications will be reviewed

  11. 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.

  12. P2X7 receptor activation induces cell death and microparticle release in murine erythroleukemia cells.

    NARCIS (Netherlands)

    Constantinescu, P.; Wang, B.; Kovacevic, K.; Jalilian, I.; Bosman, G.J.C.G.M.; Wiley, J.S.; Sluyter, R.

    2010-01-01

    Extracellular ATP induces cation fluxes in and impairs the growth of murine erythroleukemia (MEL) cells in a manner characteristic of the purinergic P2X7 receptor, however the presence of P2X7 in these cells is unknown. This study investigated whether MEL cells express functional P2X7. RT-PCR,

  13. Iron chalcogenide superconductors at high magnetic fields

    Science.gov (United States)

    Lei, Hechang; Wang, Kefeng; Hu, Rongwei; Ryu, Hyejin; Abeykoon, Milinda; Bozin, Emil S; Petrovic, Cedomir

    2012-01-01

    Iron chalcogenide superconductors have become one of the most investigated superconducting materials in recent years due to high upper critical fields, competing interactions and complex electronic and magnetic phase diagrams. The structural complexity, defects and atomic site occupancies significantly affect the normal and superconducting states in these compounds. In this work we review the vortex behavior, critical current density and high magnetic field pair-breaking mechanism in iron chalcogenide superconductors. We also point to relevant structural features and normal-state properties. PMID:27877518

  14. Workshop on accelerator magnet superconductors. Proceedings

    International Nuclear Information System (INIS)

    2004-01-01

    The workshop on accelerator magnet superconductors has gathered 102 registered participants from research laboratories, universities and industry. 8 European companies, active in superconducting materials and cables were present. This workshop has been organized to deal with the status of the world research and development on superconducting materials and cables for high field magnets (B > 10 T). The workshop has also reviewed the status of high temperature superconductors and transmission line cables for potential use in low field superconducting magnets for injectors and beam transfer lines, as well as cables for pulsed magnets that might be used in future hadron colliders or injectors

  15. Aluminium stabilized Nb$-3$/Sn superconductors

    International Nuclear Information System (INIS)

    Thoener, M.; Krauth, H.; Rudolph, J.; Szulczyk, A.

    1988-01-01

    Composite superconductors made of reacted Nb 3 Sn stabilized with high purity Al were produced. Two methods were tested. The first involved soft soldering a Cu clad aluminum tape to the Nb 3 Sn conductor. In the second method the conductor, cable or monolith, was coextruded with the aluminum. Results obtained from using both methods indicated that mechanically reinforcing materials can be easily introduced into superconductors. Tests were conducted to determine magnetoresistance, electric contact resistance, yield strength, Young modulus, critical current, and other properties of the composites. Strengthening with Duratherm during coextrusion was also evaluated

  16. London limit for lattice model of superconductor

    International Nuclear Information System (INIS)

    Ktitorov, S.A.

    2004-01-01

    The phenomenological approach to the strong-bond superconductor, which is based on the Ginzburg-Landau equation in the London limit, is considered. The effect of the crystalline lattice discreteness on the superconductors electromagnetic properties is studied. The classic problems on the critical current and magnetic field penetration are studied within the frames of the lattice model for thin superconducting films. The dependence of the superconducting current on the thin film order parameter is obtained. The critical current dependence on the degree of deviation from the continual approximation is calculated [ru

  17. 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.

  18. Higher twist contributions to the structure functions F{sub 2}(x, Q{sup 2}) and g{sub 2}(x, Q{sup 2})

    Energy Technology Data Exchange (ETDEWEB)

    Bluemlein, Johannes; Boettcher, Helmut

    2012-07-15

    We report on recent results on higher twist contributions to the unpolarized structure functions F{sup p,d}{sub 2}(x,Q{sup 2}) at N{sup 3}LO in the large x region and constraints on the twist-3 contribution to polarized structure function g{sub 2}(x,Q{sup 2}).

  19. X1X1X2X2/X1X2Y sex chromosome systems in the Neotropical Gymnotiformes electric fish of the genus Brachyhypopomus

    Directory of Open Access Journals (Sweden)

    Adauto Lima Cardoso

    2015-06-01

    Full Text Available Several types of sex chromosome systems have been recorded among Gymnotiformes, including male and female heterogamety, simple and multiple sex chromosomes, and different mechanisms of origin and evolution. The X1X1X2X2/X1X2Y systems identified in three species of this order are considered homoplasic for the group. In the genus Brachyhypopomus, only B. gauderio presented this type of system. Herein we describe the karyotypes of Brachyhypopomus pinnicaudatus and B. n. sp. FLAV, which have an X1X1X2X2/X1X2Y sex chromosome system that evolved via fusion between an autosome and the Y chromosome. The morphology of the chromosomes and the meiotic pairing suggest that the sex chromosomes of B. gauderio and B. pinnicaudatus have a common origin, whereas in B . n. sp. FLAV the sex chromosome system evolved independently. However, we cannot discard the possibility of common origin followed by distinct processes of differentiation. The identification of two new karyotypes with an X1X1X2X2/X1X2Y sex chromosome system in Gymnotiformes makes it the most common among the karyotyped species of the group. Comparisons of these karyotypes and the evolutionary history of the taxa indicate independent origins for their sex chromosomes systems. The recurrent emergence of the X1X1X2X2/X1X2Y system may represent sex chromosomes turnover events in Gymnotiformes.

  20. Direct imaging by atomic force microscopy of surface-localized self-assembled monolayers on a cuprate superconductor and surface X-ray scattering analysis of analogous monolayers on the surface of water

    DEFF Research Database (Denmark)

    Schougaard, Steen B.; Reitzel, Niels; Bjørnholm, Thomas

    2007-01-01

    A self-assembled monolayer of CF3(CF2)(3)(CH2)(11)NH2 atop the (001) surface of the high-temperature superconductor YBa2Cu3O7-x was imaged by atomic force microscopy (AFM). The AFM images provide direct 2D-structural evidence for the epitaxial 5.5 angstrom square root 2 x root 2R45 degrees unit...... was studied by grazing-incidence X-ray diffraction and specular X-ray reflectivity. Structural differences and similarities between the water-supported and superconductor-localized monolayers are discussed....

  1. Chronic administration of the selective P2X3, P2X2/3 receptor antagonist, A-317491, transiently attenuates cancer-induced bone pain in mice

    DEFF Research Database (Denmark)

    Hansen, Rikke Rie; Nasser, Arafat; Falk, Sarah

    2012-01-01

    The purinergic P2X3 and P2X2/3 receptors are in the peripheral nervous system almost exclusively confined to afferent sensory neurons, where they are found both at peripheral and central synapses. The P2X3 receptor is implicated in both neuropathic and inflammatory pain. However, the role of the ......X3 receptor in chronic cancer-induced bone pain is less known. Here we investigated the effect of systemic acute and chronic administration of the selective P2X3, P2X2/3 receptor antagonist (5-[[[(3-Phenoxyphenyl)methyl][(1S)-1,2,3,4-tetrahydro-1-naphthalenyl]amino]carbonyl]-1...

  2. Microgravity Processing of Oxide Superconductors

    Science.gov (United States)

    Olive, James R.; Hofmeister, William H.; Bayuzick, Robert J.; Vlasse, Marcus

    1999-01-01

    Considerable effort has been concentrated on the synthesis and characterization of high T(sub c) oxide superconducting materials. The YBaCuO system has received the most intense study, as this material has shown promise for the application of both thin film and bulk materials. There are many problems with the application of bulk materials- weak links, poor connectivity, small coherence length, oxygen content and control, environmental reactivity, phase stability, incongruent melting behavior, grain boundary contamination, brittle mechanical behavior, and flux creep. The extent to which these problems are intrinsic or associated with processing is the subject of controversy. This study seeks to understand solidification processing of these materials, and to use this knowledge for alternative processing strategies, which, at the very least, will improve the understanding of bulk material properties and deficiencies. In general, the phase diagram studies of the YBaCuO system have concentrated on solid state reactions and on the Y2BaCuO(x) + liquid yields YBa2Cu3O(7-delta) peritectic reaction. Little information is available on the complete melting relations, undercooling, and solidification behavior of these materials. In addition, rare earth substitutions such as Nd and Gd affect the liquidus and phase relations. These materials have promising applications, but lack of information on the high temperature phase relations has hampered research. In general, the understanding of undercooling and solidification of high temperature oxide systems lags behind the science of these phenomena in metallic systems. Therefore, this research investigates the fundamental melting relations, undercooling, and solidification behavior of oxide superconductors with an emphasis on improving ground based synthesis of these materials.

  3. Polymorphism in 2-X-adamantane derivatives (X = Cl, Br).

    Science.gov (United States)

    Negrier, Philippe; Barrio, María; Tamarit, Josep Ll; Mondieig, Denise

    2014-08-14

    The polymorphism of two 2-X-adamantane derivatives, X = Cl, X = Br, has been studied by X-ray powder diffraction and normal- and high-pressure (up to 300 MPa) differential scanning calorimetry. 2-Br-adamantane displays a low-temperature orthorhombic phase (space group P212121, Z = 4) and a high-temperature plastic phase (Fm3̅m, Z = 4) from 277.9 ± 1.0 K to the melting point at 413.4 ± 1.0 K. 2-Cl-adamantane presents a richer polymorphic behavior through the temperature range studied. At low temperature it displays a triclinic phase (P1̅, Z = 2), which transforms to a monoclinic phase (C2/c, Z = 8) at 224.4 ± 1.0 K, both phases being ordered. Two high-temperature orientationally disordered are found for this compound, one hexagonal (P63/mcm, Z = 6) at ca. 241 K and the highest one, cubic (Fm3̅m, Z = 4), being stable from 244 ± 1.0 K up to the melting point at 467.5 ± 1.0 K. No additional phase appears due to the increase in pressure within the studied range. The intermolecular interactions are found to be weak, especially for the 2-Br-adamantane compound for which the Br···Br as well as C-Br···H distances are larger than the addition of the van der Waals radii, thus confirming the availability of this compound for building up diamondoid blocks.

  4. Neuropharmacology of Purinergic Receptors in Human Submucous Plexus: Involvement of P2X1, P2X2, P2X3 Channels, P2Y and A3 Metabotropic Receptors in Neurotransmission

    Science.gov (United States)

    Liñán-Rico, A.; Wunderlich, JE.; Enneking, JT.; Tso, DR.; Grants, I.; Williams, KC.; Otey, A.; Michel, K.; Schemann, M.; Needleman, B.; Harzman, A.; Christofi, FL.

    2015-01-01

    Rationale The role of purinergic signaling in the human ENS is not well understood. We sought to further characterize the neuropharmacology of purinergic receptors in human ENS and test the hypothesis that endogenous purines are critical regulators of neurotransmission. Experimental Approach LSCM-Fluo-4-(Ca2+)-imaging of postsynaptic Ca2+ transients (PSCaTs) was used as a reporter of neural activity. Synaptic transmission was evoked by fiber tract electrical stimulation in human SMP surgical preparations. Pharmacological analysis of purinergic signaling was done in 1,556 neurons from 234 separate ganglia 107 patients; immunochemical labeling for P2XRs of neurons in ganglia from 19 patients. Real-time MSORT (Di-8-ANEPPS) imaging was used to test effects of adenosine on fast excitatory synaptic potentials (fEPSPs). Results Synaptic transmission is sensitive to pharmacological manipulations that alter accumulation of extracellular purines. Apyrase blocks PSCaTs in a majority of neurons. An ecto-NTPDase-inhibitor 6-N,N-diethyl-D-β,γ-dibromomethyleneATP or adenosine deaminase augments PSCaTs. Blockade of reuptake/deamination of eADO inhibits PSCaTs. Adenosine inhibits fEPSPs and PSCaTs (IC50=25μM), sensitive to MRS1220-antagonism (A3AR). A P2Y agonist ADPβS inhibits PSCaTs (IC50=111nM) in neurons without stimulatory ADPβS responses (EC50=960nM). ATP or a P2X1,2,2/3 (α,β-MeATP) agonist evokes fast, slow, biphasic Ca2+ transients or Ca2+ oscillations (EC50=400μM). PSCaTs are sensitive to P2X1 antagonist NF279. Low (20nM) or high (5μM) concentrations of P2X antagonist TNP-ATP block PSCaTs in different neurons; proportions of neurons with P2XR-ir follow the order P2X2>P2X1≫P2X3; P2X1+ P2X2 and P2X3+P2X2 are co-localized. RT-PCR identified mRNA-transcripts for P2X1-7,P2Y1,2,12-14R. Responsive neurons were also identified by HuC/D-ir. Conclusions Purines are critical regulators of neurotransmission in the human enteric nervous system. Purinergic signaling involves

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

    International Nuclear Information System (INIS)

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

    1989-01-01

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

  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. Electronic structure of Fe-based superconductors

    Indian Academy of Sciences (India)

    Abstract. Fe-based superconductors have drawn much attention during the last decade due to the presence of superconductivity in materials containing the magnetic element, Fe, and the coexistence of superconductivity and magnetism. Extensive study of the electronic structure of these systems suggested the dominant ...

  8. Development of superconductors for fusion technology

    International Nuclear Information System (INIS)

    Wilson, M.N.; Walters, C.R.

    1976-04-01

    A report is presented on the development of a 10 4 Amp NbTi cryogenically stabilized superconductor. The long term objective was the construction of a superconducting toroidal field magnet for a post JET Tokamak experiment. The report is in sections entitled: magnet reference parameters; specific conductor designs; theoretical studies; experimental measurements; fabrication techniques; discussion, summary, conclusions and recommendations. (U.K.)

  9. Anomalous infrared absorption in granular superconductors

    International Nuclear Information System (INIS)

    Carr, G.L.; Garland, J.C.; Tanner, D.B.

    1983-01-01

    Granular superconductors are shown to have a far-infrared absorption that is larger when the samples are superconducting than when they are normal. By constrast, theoretical models for these materials predict that when the samples become superconducting, the absorption should decrease

  10. Electronic structure of Fe-based superconductors

    Indian Academy of Sciences (India)

    2015-05-29

    May 29, 2015 ... Fe-based superconductors have drawn much attention during the last decade due to the presence of superconductivity in materials containing the magnetic element, Fe, and the coexistence of superconductivity and magnetism. Extensive study of the electronic structure of these systems suggested the ...

  11. 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...

  12. 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...

  13. New superconductor LaRhSb

    International Nuclear Information System (INIS)

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

    1994-01-01

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

  14. The Effective Coherence Length in Anisotropic Superconductors

    International Nuclear Information System (INIS)

    Polturak, E.; Koren, G.; Nesher, O

    1999-01-01

    If electrons are transmitted from a normal conductor(N) into a superconductor(S), common wisdom has it that the electrons are converted into Cooper pairs within a coherence length from the interface. This is true in conventional superconductors with an isotropic order parameter. We have established experimentally that the situation is rather different in high Tc superconductors having an anisotropic order parameter. We used epitaxial thin film S/N bilayers having different interface orientations in order to inject carriers from S into N along different directions. The distance to which these carriers penetrate were determined through their effect on the Tc of the bilayers. We found that the effective coherence length is 20A only along the a or b directions, while in other directions we find a length of 250dr20A out of plane, and an even larger value for in-plane, off high symmetry directions. These observations can be explained using the Blonder-Tinkham-Klapwijk model adapted to anisotropic superconductivity. Several implications of our results on outstanding problems with high Tc junctions will be discussed

  15. Deformation of high-temperature superconductors

    International Nuclear Information System (INIS)

    Goretta, K.C.; Routbort, J.L.; Miller, D.J.; Chen, N.; Dominguez-Rodriguez, A.; Jimenez-Melendo, M.; De Arellano-Lopez, A.R.

    1994-08-01

    Of the many families of high-temperature superconductors, only the properties of those discovered prior to 1989 - Y-Ba-Cu-O, Tl-Ba(Sr)-Ca-Cu-O, and Bi(Pb)-Sr-Ca-Cu-O - have been studied extensively. Deformation tests have been performed on YBa 2 Cu 3 O x (Y-123), YBa 2 Cu 4 O x (Y-124), TlBa 2 Ca 2 Cu 3 O x (Bi-2223). The tests have revealed that plasticity is generally limited in these compounds and that the rate-controlling diffusional kinetics for creep are very slow. Nevertheless, hot forming has proved to be quite successful for fabrication of bulk high-temperature superconductors, so long as deformation rates are low or large hydrostatic stresses are applied. Steady-state creep data have proved to be useful in designing optimal heat treatments for superconductors and in support of more-fundamental diffusion experiments. The high-temperature superconductors are highly complex oxides, and it is a challenge to understand their deformation responses. In this paper, results of interest and operant creep mechanisms will be reviewed

  16. Nonmonotonic critical temperature in superconductor ferromagnet bilayers

    NARCIS (Netherlands)

    Fominov, Ya. V.; Fominov, I.V.; Chtchelkatchev, N.M.; Golubov, Alexandre Avraamovitch

    2002-01-01

    The critical temperature Tc of a superconductor/ferromagnet (SF) bilayer can exhibit nonmonotonic dependence on the thickness df of the F layer. SF systems have been studied for a long time; according to the experimental situation, a ¿dirty¿ limit is often considered which implies that the mean free

  17. Scalar Condensation of Holographic Superconductors using ...

    Indian Academy of Sciences (India)

    Abstract. We study holographic superconductors analytically by using the Ginzburg–Landau action with the γ-quartic term | |4. Our results show that γ-term plays a role in the scalar condensation. It is found that the system displays two kinds of critical temperatures. One is independent of γ. But the other increases with ...

  18. P2X receptors in the cardiovascular system and their potential as therapeutic targets in disease.

    Science.gov (United States)

    Ralevic, Vera

    2015-01-01

    This review considers the expression and roles of P2X receptors in the cardiovascular system in health and disease and their potential as therapeutic targets. P2X receptors are ligand gated ion channels which are activated by the endogenous ligand ATP. They are formed from the assembly of three P2X subunit proteins from the complement of seven (P2X1-7), which can associate to form homomeric or heteromeric P2X receptors. The P2X1 receptor is widely expressed in the cardiovascular system, being located in the heart, in the smooth muscle of the majority of blood vessels and in platelets. P2X1 receptors expressed in blood vessels can be activated by ATP coreleased with noradrenaline as a sympathetic neurotransmitter, leading to smooth muscle depolarisation and contraction. There is evidence that the purinergic component of sympathetic neurotransmission is increased in hypertension, identifying P2X1 receptors as a possible therapeutic target in this disorder. P2X3 and P2X2/3 receptors are expressed on cardiac sympathetic neurones and may, through positive feedback of neuronal ATP at this prejunctional site, amplify sympathetic neurotransmission. Activation of P2X receptors expressed in the heart increases cardiac myocyte contractility, and an important role of the P2X4 receptor in this has been identified. Deletion of P2X4 receptors in the heart depresses contractile performance in models of heart failure, while overexpression of P2X4 receptors has been shown to be cardioprotective, thus P2X4 receptors may be therapeutic targets in the treatment of heart disease. P2X receptors have been identified on endothelial cells. Although immunoreactivity for all P2X1-7 receptor proteins has been shown on the endothelium, relatively little is known about their function, with the exception of the endothelial P2X4 receptor, which has been shown to mediate endothelium-dependent vasodilatation to ATP released during shear stress. The potential of P2X receptors as therapeutic targets

  19. Isotope and multiband effects in layered superconductors.

    Science.gov (United States)

    Bussmann-Holder, Annette; Keller, Hugo

    2012-06-13

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

  20. The new Fe-based superconductors

    International Nuclear Information System (INIS)

    Mao, Zhiqiang

    2011-01-01

    The discovery of unconventional superconductivity in doped iron pnictides has ushered in a new era of high temperature superconductivity. The superconductivity of these materials occurs in close proximity to magnetic instability; superconductivity is achieved by suppressing a long-range antiferromagnetic (AFM) order through charge carrier doping or pressure. In this talk, I will first give a brief overview of the phase diagrams of iron-based superconductors, and then talk about our recent research on iron chalcogenide Fe 1+y (Te 1-x Se x ) superconductors, which is structurally the simplest of the Fe-based superconductors. Although the Fermi surface of iron chalcogenides is similar to iron pnictides, the parent compound Fe 1+y Te exhibits AFM order with in-plane magnetic wave-vector (π, 0). This contrasts the pnictide parent compounds where the magnetic order has an in-plane magnetic wave-vector (π, π) that connects hole and electron parts of the Fermi surface. Despite these differences, both the pnictide and chalcogenide Fe-superconductors exhibit superconducting spin resonances around (π, π), suggesting a common symmetry for their superconducting order parameter. A central question in this burgeoning field is therefore how (π, π) superconductivity can emerge from a (π, 0) magnetic instability. I will address this issue in my talk. I will show the phase diagram of electronic and magnetic properties we recently established for this system and discuss the relationship between magnetic coupling and electronic properties. Our results reveal that the magnetic soft mode evolving from the (π, 0)-type magnetic long-range order is associated with weak charge carrier localization. Bulk superconductivity occurs only as magnetic correlations near (π, 0) are strongly suppressed and the magnetic mode at (π, π) becomes dominant; this suggests a common magnetic origin for superconductivity in iron chalcogenide and pnictide superconductors. (author)

  1. Weak links in high critical temperature superconductors

    Science.gov (United States)

    Tafuri, Francesco; Kirtley, John R.

    2005-11-01

    The traditional distinction between tunnel and highly transmissive barriers does not currently hold for high critical temperature superconducting Josephson junctions, both because of complicated materials issues and the intrinsic properties of high temperature superconductors (HTS). An intermediate regime, typical of both artificial superconductor-barrier-superconductor structures and of grain boundaries, spans several orders of magnitude in the critical current density and specific resistivity. The physics taking place at HTS surfaces and interfaces is rich, primarily because of phenomena associated with d-wave order parameter (OP) symmetry. These phenomena include Andreev bound states, the presence of the second harmonic in the critical current versus phase relation, a doubly degenerate state, time reversal symmetry breaking and the possible presence of an imaginary component of the OP. All these effects are regulated by a series of transport mechanisms, whose rules of interplay and relative activation are unknown. Some transport mechanisms probably have common roots, which are not completely clear and possibly related to the intrinsic nature of high-TC superconductivity. The d-wave OP symmetry gives unique properties to HTS weak links, which do not have any analogy with systems based on other superconductors. Even if the HTS structures are not optimal, compared with low critical temperature superconductor Josephson junctions, the state of the art allows the realization of weak links with unexpectedly high quality quantum properties, which open interesting perspectives for the future. The observation of macroscopic quantum tunnelling and the qubit proposals represent significant achievements in this direction. In this review we attempt to encompass all the above aspects, attached to a solid experimental basis of junction concepts and basic properties, along with a flexible phenomenological background, which collects ideas on the Josephson effect in the presence

  2. Weak links in high critical temperature superconductors

    International Nuclear Information System (INIS)

    Tafuri, Francesco; Kirtley, John R

    2005-01-01

    The traditional distinction between tunnel and highly transmissive barriers does not currently hold for high critical temperature superconducting Josephson junctions, both because of complicated materials issues and the intrinsic properties of high temperature superconductors (HTS). An intermediate regime, typical of both artificial superconductor-barrier-superconductor structures and of grain boundaries, spans several orders of magnitude in the critical current density and specific resistivity. The physics taking place at HTS surfaces and interfaces is rich, primarily because of phenomena associated with d-wave order parameter (OP) symmetry. These phenomena include Andreev bound states, the presence of the second harmonic in the critical current versus phase relation, a doubly degenerate state, time reversal symmetry breaking and the possible presence of an imaginary component of the OP. All these effects are regulated by a series of transport mechanisms, whose rules of interplay and relative activation are unknown. Some transport mechanisms probably have common roots, which are not completely clear and possibly related to the intrinsic nature of high-T C superconductivity. The d-wave OP symmetry gives unique properties to HTS weak links, which do not have any analogy with systems based on other superconductors. Even if the HTS structures are not optimal, compared with low critical temperature superconductor Josephson junctions, the state of the art allows the realization of weak links with unexpectedly high quality quantum properties, which open interesting perspectives for the future. The observation of macroscopic quantum tunnelling and the qubit proposals represent significant achievements in this direction. In this review we attempt to encompass all the above aspects, attached to a solid experimental basis of junction concepts and basic properties, along with a flexible phenomenological background, which collects ideas on the Josephson effect in the presence

  3. Normal zone soliton in large composite superconductors

    International Nuclear Information System (INIS)

    Kupferman, R.; Mints, R.G.; Ben-Jacob, E.

    1992-01-01

    The study of normal zone of finite size (normal domains) in superconductors, has been continuously a subject of interest in the field of applied superconductivity. It was shown that in homogeneous superconductors normal domains are always unstable, so that if a normal domain nucleates, it will either expand or shrink. While testing the stability of large cryostable composite superconductors, a new phenomena was found, the existence of stable propagating normal solitons. The formation of these propagating domains was shown to be a result of the high Joule power generated in the superconductor during the relatively long process of current redistribution between the superconductor and the stabilizer. Theoretical studies were performed in investigate the propagation of normal domains in large composite super conductors in the cryostable regime. Huang and Eyssa performed numerical calculations simulating the diffusion of heat and current redistribution in the conductor, and showed the existence of stable propagating normal domains. They compared the velocity of normal domain propagation with the experimental data, obtaining a reasonable agreement. Dresner presented an analytical method to solve this problem if the time dependence of the Joule power is given. He performed explicit calculations of normal domain velocity assuming that the Joule power decays exponentially during the process of current redistribution. In this paper, the authors propose a system of two one-dimensional diffusion equations describing the dynamics of the temperature and the current density distributions along the conductor. Numerical simulations of the equations reconfirm the existence of propagating domains in the cryostable regime, while an analytical investigation supplies an explicit formula for the velocity of the normal domain

  4. Recrystallization of high temperature superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Kouzoudis, Dimitris [Iowa State Univ., Ames, IA (United States)

    1996-05-09

    Currently one of the most widely used high Tc superconductors is the Bi-based compounds Bi2Sr2CaCu2Oz and Bi2Sr2Ca2Cu3Oz (known as BSCCO 2212 and 2223 compounds) with Tc values of about 85 K and 110 K respectively. Lengths of high performance conductors ranging from 100 to 1000 m long are routinely fabricated and some test magnets have been wound. An additional difficulty here is that although Bi-2212 and Bi-2223 phases exist over a wide range of stoichiometries, neither has been prepared in phase-pure form. So far the most successful method of constructing reliable and robust wires or tapes is the so called powder-in-tube (PIT) technique [1, 2, 3, 4, 5, 6, 7] in which oxide powder of the appropriate stoichiometry and phase content is placed inside a metal tube, deformed into the desired geometry (round wire or flat tape), and annealed to produce the desired superconducting properties. Intermediate anneals are often incorporated between successive deformation steps. Silver is the metal used in this process because it is the most compatible with the reacting phase. In all of the commercial processes for BSCCO, Ag seems to play a special catalytic role promoting the growth of high performance aligned grains that grow in the first few micrometers near the Ag/BSCCO interface. Adjacent to the Ag, the grain alignment is more perfect and the current density is higher than in the center of the tape. It is known that Ag lowers the melting point of several of the phases but the detailed mechanism for growth of these high performance grains is not clearly understood. The purpose of this work is to study the nucleation and growth of the high performance material at this interface.

  5. Post-translational regulation of P2X receptor channels: modulation by phospholipids

    Directory of Open Access Journals (Sweden)

    Louis-Philippe eBernier

    2013-11-01

    Full Text Available P2X receptor channels mediate fast excitatory signaling by ATP and play major roles in sensory transduction, neuro-immune communication and inflammatory response. P2X receptors constitute a gene family of calcium-permeable ATP-gated cation channels therefore the regulation of P2X signaling is critical for both membrane potential and intracellular calcium homeostasis. Phosphoinositides (PIPn are anionic signaling phospholipids that act as functional regulators of many types of ion channels. Direct PIPn binding was demonstrated for several ligand- or voltage-gated ion channels, however no generic motif emerged to accurately predict lipid-protein binding sites. This review presents what is currently known about the modulation of the different P2X subtypes by phospholipids and about critical determinants underlying their sensitivity to PIPn levels in the plasma membrane.All functional mammalian P2X subtypes tested, with the notable exception of P2X5, have been shown to be positively modulated by PIPn, i.e. homomeric P2X1, P2X2, P2X3, P2X4, and P2X7, as well as heteromeric P2X1/5 and P2X2/3 receptors. Based on various results reported on the aforementioned subtypes including mutagenesis of the prototypical PIPn-sensitive P2X4 and PIPn-insensitive P2X5 receptor subtypes, an increasing amount of functional, biochemical and structural evidence converges on the modulatory role of a short polybasic domain located in the proximal C-terminus of P2X subunits. This linear motif, semi-conserved in the P2X family, seems necessary and sufficient for encoding direct modulation of ATP-gated channels by PIPn. Furthermore, the physiological impact of the regulation of ionotropic purinergic responses by phospholipids on pain pathways was recently revealed in the context of native crosstalks between phospholipase C-linked metabotropic receptors and P2X receptor channels in DRG sensory neurons and microglia.

  6. Properties of half metallic (Ba0.8Sr0.2)2-x La2x/3x/3FeMoO6 double perovskites

    International Nuclear Information System (INIS)

    Serrate, D.; De Teresa, J.M.; Blasco, J.; Morellon, L.; Ibarra, M.R.

    2005-01-01

    Previous work in (Ba 0.8 Sr 0.2 ) 2- x La x FeMoO 6 and Ba 1+ x Sr 1-3 x La 2 x FeMoO 6 have stated electron doping as the most important parameter in terms of T c enhancement. Here we report complementary structural, magnetic and transport properties, say a series where there is no doping and only structural parameters are changed: (Ba 0.8 Sr 0.2 ) 2- x La 2 x /3 x /3 FeMoO 6 . We propose a complete phase diagram where structural and bandfilling impact on the Curie temperature is clearly evidenced

  7. Fabrication and study of hybrid molecule/superconductor assemblies

    International Nuclear Information System (INIS)

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

    1994-01-01

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

  8. Targeting of the P2X7 receptor in pancreatic cancer and stellate cells

    DEFF Research Database (Denmark)

    Giannuzzo, Andrea; Saccomano, Mara; Napp, Joanna

    2016-01-01

    of PDAC. In the in vitro studies we show that human PDAC cells with luciferase gene (PancTu-1 Luc cells) express high levels of P2X7R protein. Allosteric P2X7R antagonist AZ10606120 inhibited cell proliferation in basal conditions, indicating that P2X7R was tonically active. Extracellular ATP and Bz......ATP, to which the P2X7R is more sensitive, further affected cell survival and confirmed complex functionality of P2X7R. PancTu-1 Luc migration and invasion was reduced by AZ10606120, and it was stimulated by PSCs, but not by PSCs from P2X7(-/-) animals. PancTu-1 Luc cells were orthotopically transplanted...

  9. Superconducting properties of Zr1+xNi2-xGa and Zr1-xNi2+xGa Heusler compounds

    Directory of Open Access Journals (Sweden)

    Saad Alzahrani

    2017-05-01

    Full Text Available The superconducting properties of a series of Zr1+xNi2-xGa and Zr1-xNi2+xGa compounds have been investigated by x-ray diffraction, electrical resistivity, dc magnetization, and ac susceptibility measurements. While the parent compound, ZrNi2Ga, exhibited the cubic L21 Heusler structure, multiple non-cubic structures formed in the Zr and Ni rich doped materials. For x ≤ 0.3, all Zr1-xNi2+xGa compounds demonstrated superconducting behavior, but no superconductivity was observed in the Zr1+xNi2-xGa alloys for x > 0.2. The magnetization data revealed that all materials in both Zr1+xNi2-xGa and Zr1-xNi2+xGa series exhibited type-II superconductivity. With increasing doping concentration x, the paramagnetic ordering were enhanced in both systems while the superconducting properties were found to weaken. The observations are discussed considering the structural disorders in the systems.

  10. Novel protective role of endogenous cardiac myocyte P2X4 receptors in heart failure.

    Science.gov (United States)

    Yang, Tiehong; Shen, Jian-bing; Yang, Ronghua; Redden, John; Dodge-Kafka, Kimberly; Grady, James; Jacobson, Kenneth A; Liang, Bruce T

    2014-05-01

    Heart failure (HF), despite continuing progress, remains a leading cause of mortality and morbidity. P2X4 receptors (P2X4R) have emerged as potentially important molecules in regulating cardiac function and as potential targets for HF therapy. Transgenic P2X4R overexpression can protect against HF, but this does not explain the role of native cardiac P2X4R. Our goal is to define the physiological role of endogenous cardiac myocyte P2X4R under basal conditions and during HF induced by myocardial infarction or pressure overload. Mice established with conditional cardiac-specific P2X4R knockout were subjected to left anterior descending coronary artery ligation-induced postinfarct or transverse aorta constriction-induced pressure overload HF. Knockout cardiac myocytes did not show P2X4R by immunoblotting or by any response to the P2X4R-specific allosteric enhancer ivermectin. Knockout hearts showed normal basal cardiac function but depressed contractile performance in postinfarct and pressure overload models of HF by in vivo echocardiography and ex vivo isolated working heart parameters. P2X4R coimmunoprecipitated and colocalized with nitric oxide synthase 3 (eNOS) in wild-type cardiac myocytes. Mice with cardiac-specific P2X4R overexpression had increased S-nitrosylation, cyclic GMP, NO formation, and were protected from postinfarct and pressure overload HF. Inhibitor of eNOS, L-N(5)-(1-iminoethyl)ornithine hydrochloride, blocked the salutary effect of cardiac P2X4R overexpression in postinfarct and pressure overload HF as did eNOS knockout. This study establishes a new protective role for endogenous cardiac myocyte P2X4R in HF and is the first to demonstrate a physical interaction between the myocyte receptor and eNOS, a mediator of HF protection. © 2014 American Heart Association, Inc.

  11. 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.

  12. Functional development in density functional theory for superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Sanna, Antonio; Gross, E.K.U.; Essenberger, Frank [Max Planck Institute of Microstructure Physics, Halle (Saale) (Germany)

    2015-07-01

    Density functional theory for superconductors (SCDFT) is a fully parameter-free approach to superconductivity that allows for accurate predictions of critical temperature and properties of superconductors. We report on the most recent extensions of the method, in particular the development of new functionals to: (1) incorporate in a correct fashion Migdal's theorem; (2) compute the excitation spectrum; (3) include spin-fluctuation mediated pairing Applications and predictions are shown for a set of materials, including conventional and unconventional superconductors.

  13. 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.

  14. On the electronegativity of the high-Tc oxide superconductor

    International Nuclear Information System (INIS)

    Zhang Liyuan.

    1991-08-01

    We employ a very useful quantity, the electronegativity, to classify the superconductor. The value of the group average electronegativity to separate superconductor into two categories is 2. Each category has unique chemical bond features. The high-T c oxide superconductor belongs to the second category with group average electronegativity being larger than 2. Their unusual bond nature also gives new insight into some essential factors beneficial to enhance superconductivity. (author). 9 refs, 2 tabs

  15. The iron pnictide superconductors an introduction and overview

    CERN Document Server

    Citro, Roberta

    2017-01-01

    This book covers different aspects of the physics of iron-based superconductors ranging from the theoretical, the numerical and computational, to the experimental ones. It starts from the basic theory modeling many-body physics in Fe-superconductors and other multi-orbital materials and drreaches up to the magnetic and Cooper pair fluctuations and nematic order. Finally, it offers a comprehensive overview of the most recent advancements in the experimental investigations of iron based superconductors. .

  16. Filters for mobile radio from high Tc ceramic superconductors

    International Nuclear Information System (INIS)

    Peterson, G.E.; Wong, E.; Alford, N.McN.

    1990-01-01

    Mobile radio frequencies lie between 30 MHz and 1,000 MHz. This frequency range is ideal for ceramic high T c superconductors. We have designed Chebyshev, Butterworth and interdigital filters that can employ high T c superconductors in the form of rods, tubes and helices. In general, the performance of these filters at milliwatt power levels is excellent. We will describe fabrication of the superconductors and filter design

  17. Optimization of superconductor--normal-metal--superconductor Josephson junctions for high critical-current density

    International Nuclear Information System (INIS)

    Golub, A.; Horovitz, B.

    1994-01-01

    The application of superconducting Bi 2 Sr 2 CaCu 2 O 8 and YBa 2 Cu 3 O 7 wires or tapes to electronic devices requires the optimization of the transport properties in Ohmic contacts between the superconductor and the normal metal in the circuit. This paper presents results of tunneling theory in superconductor--normal-metal--superconductor (SNS) junctions, in both pure and dirty limits. We derive expressions for the critical-current density as a function of the normal-metal resistivity in the dirty limit or of the ratio of Fermi velocities and effective masses in the clean limit. In the latter case the critical current increases when the ratio γ of the Fermi velocity in the superconductor to that of the weak link becomes much less than 1 and it also has a local maximum if γ is close to 1. This local maximum is more pronounced if the ratio of effective masses is large. For temperatures well below the critical temperature of the superconductors the model with abrupt pair potential on the SN interfaces is considered and its applicability near the critical temperature is examined

  18. Electronic properites of electron-doped cuprate superconductors probed by high-field magnetotransport

    International Nuclear Information System (INIS)

    Helm, Toni

    2013-01-01

    In the present work the normal-state properties of the electron-doped cuprate superconductor Nd 2-x Ce x CuO 4 (NCCO) are investigated for a broad doping range, covering almost the whole phase diagram of this material. Magnetotransport measurements in the world's highest non-destructive magnetic fields were used as a spectroscopic tool for probing the electronic structure of single-crystalline NCCO as a function of the carrier concentration x. Quantum and semiclassical oscillations in the magnetoresistance provided new insights into various properties of the Fermi surface and the nature of the ground state in the system. The detailed investigations of the field- and temperature-dependent transport and its dependence on the field orientation have revealed a close correlation between symmetry-breaking ordering instabilities and the superconducting state.

  19. Characteristics of YBa2Cu3O7 high-Tc superconductor with KCl

    Science.gov (United States)

    Yoon, Ki Hyun; Chang, Sung Sik

    1990-03-01

    The lattice parameters, microstructural change, transition temperature, and electrical properties of the YBa2-xKxCu3O7 high-Tc superconductor in the range from x=0 to x=0.25 have been investigated. The high-Tc orthorhombic phase increases with increasing KCl up to x=0.20, above which it decreases. The lattice parameters decrease with increasing KCl up to x=0.10, and then become nearly uniform. The grain size increases with increasing KCl up to x=0.20 due to its role as sintering agent. The specimens with x=0.2 have transition temperatures of 96 K and high magnetic susceptibility due to the contraction of lattice parameters a and b and the increase of orthorhombic distortion.

  20. A high temperature superconductor tape RF receiver coil for a low field magnetic resonance imaging system

    International Nuclear Information System (INIS)

    Cheng, M C; Yan, B P; Lee, K H; Ma, Q Y; Yang, E S

    2005-01-01

    High temperature superconductor (HTS) thin films have been applied in making a low loss RF receiver coil for improving magnetic resonance imaging image quality. However, the application of these coils is severely limited by their limited field of view (FOV). Stringent fabrication environment requirements and high cost are further limitations. In this paper, we propose a simpler method for designing and fabricating HTS coils. Using industrial silver alloy sheathed Bi (2-x) Pb x Sr 2 Ca 2 Cu 3 O 10 (Bi-2223) HTS tapes, a five-inch single-turn HTS solenoid coil has been developed, and human wrist images have been acquired with this coil. The HTS tape coil has demonstrated an enhanced FOV over a six-inch YBCO thin film surface coil at 77 K with comparable signal-to-noise ratio

  1. Electronic properites of electron-doped cuprate superconductors probed by high-field magnetotransport

    Energy Technology Data Exchange (ETDEWEB)

    Helm, Toni

    2013-09-18

    In the present work the normal-state properties of the electron-doped cuprate superconductor Nd{sub 2-x}Ce{sub x}CuO{sub 4} (NCCO) are investigated for a broad doping range, covering almost the whole phase diagram of this material. Magnetotransport measurements in the world's highest non-destructive magnetic fields were used as a spectroscopic tool for probing the electronic structure of single-crystalline NCCO as a function of the carrier concentration x. Quantum and semiclassical oscillations in the magnetoresistance provided new insights into various properties of the Fermi surface and the nature of the ground state in the system. The detailed investigations of the field- and temperature-dependent transport and its dependence on the field orientation have revealed a close correlation between symmetry-breaking ordering instabilities and the superconducting state.

  2. Effect of Pb and Cr Substitutions on Phase Formation and Excess Conductivity of Bi-2212 Superconductor

    International Nuclear Information System (INIS)

    Khir, F. L. M.; Mohamed, Z.; Yusuf, A. A.; Yusof, M. I. M.; Yahya, A. K.

    2010-01-01

    The influence of Pb and Cr substitutions on the superconducting properties of Bi 2 Sr 2 CaCu 2 O 8 (Bi-2212) superconductors is reported. The samples were prepared from Bi 2-x Pb x Sr 2 Ca 2-y Cr y Cu 3 O 10-δ (x = 0-0.3, y = 0-0.3) starting composition by the solid-state-reaction method. XRD analysis showed formation of pure Bi-2212 for (x = 0, y = 0), (x = 0.3, y = 0.2,) and (x = 0.3, y = 0.2,) starting compositions. Excess conductivity analysis based on Asmalazov-Larkin theory on single-phased Bi2212 samples showed 2D to 3D transition in superconducting fluctuation behavior (SFB) for all the samples. Highest 2D-3D transition temperature, T 2D-3D was observed at Pb and Cr substitutions of x = 0.3, and x = 0.2, respectively.

  3. Electronic properites of electron-doped cuprate superconductors probed by high-field magnetotransport

    Energy Technology Data Exchange (ETDEWEB)

    Helm, Toni

    2013-09-18

    In the present work the normal-state properties of the electron-doped cuprate superconductor Nd{sub 2-x}Ce{sub x}CuO{sub 4} (NCCO) are investigated for a broad doping range, covering almost the whole phase diagram of this material. Magnetotransport measurements in the world's highest non-destructive magnetic fields were used as a spectroscopic tool for probing the electronic structure of single-crystalline NCCO as a function of the carrier concentration x. Quantum and semiclassical oscillations in the magnetoresistance provided new insights into various properties of the Fermi surface and the nature of the ground state in the system. The detailed investigations of the field- and temperature-dependent transport and its dependence on the field orientation have revealed a close correlation between symmetry-breaking ordering instabilities and the superconducting state.

  4. Blockade of human P2X7 receptor function with a monoclonal antibody.

    Science.gov (United States)

    Buell, G; Chessell, I P; Michel, A D; Collo, G; Salazzo, M; Herren, S; Gretener, D; Grahames, C; Kaur, R; Kosco-Vilbois, M H; Humphrey, P P

    1998-11-15

    A monoclonal antibody (MoAb) specific for the human P2X7 receptor was generated in mice. As assessed by flow cytometry, the MoAb labeled human blood-derived macrophage cells natively expressing P2X7 receptors and cells transfected with human P2X7 but not other P2X receptor types. The MoAb was used to immunoprecipitate the human P2X7 receptor protein, and in immunohistochemical studies on human lymphoid tissue, P2X7 receptor labeling was observed within discrete areas of the marginal zone of human tonsil sections. The antibody also acted as a selective antagonist of human P2X7 receptors in several functional studies. Thus, whole cell currents, elicited by the brief application of 2',3'-(4-benzoyl)-benzoyl-ATP in cells expressing human P2X7, were reduced in amplitude by the presence of the MoAb. Furthermore, preincubation of human monocytic THP-1 cells with the MoAb antagonized the ability of P2X7 agonists to induce the release of interleukin-1beta.

  5. Towards ferromagnet/superconductor junctions on graphene

    International Nuclear Information System (INIS)

    Pakkayil, Shijin Babu

    2015-01-01

    Ever since A. Aspect et al. performed the famous 1982 experiment to prove the violation of Bell's inequality, there have been suggestions to conduct the same experiment in a solid state system. Some of those proposals involve superconductors as the source of entangled electron pair and spin depended interfaces as the optical analogue of polariser/filter. Semiconductors can serve as the best medium for such an experiment due to their long relaxation lengths. So far there are no reports on a ferromagnet/superconductor junctions on a semiconductor even though such junctions has been successfully realised in metallic systems. This thesis reports the successful fabrication of ferromagnet/superconductor junction along with characterising measurements in a perfectly two dimensional zero-gap semiconductor known as graphene. Since it's discovery in 2004, graphene has attracted prodigious interest from both academia and industry due to it's inimitable physical properties: very high mobility, high thermal and electrical conductivity, a high Young's modulus and impermeability. Graphene is also expected to have very long spin relaxation length and high spin life time because of it's low spin orbit coupling. For this reason and since researchers are always looking for novel materials and devices to comply with the high demands for better and faster data storage devices, graphene has emanated as a brand new material system for spin based devices. The very first spin injection and detection in graphene was realised in 2007 and ever since, the focal point of the research has been to improve the spin transport properties. A part of this thesis discusses a new fabrication recipe which has a high yield for successfully contacting graphene with a ferromagnet. A high starting yield for ferromagnetic contacts is a irremissible condition for combining superconducting contacts to the device to fabricate ferromagnet/superconductor junctions. Any fabrication recipe

  6. Towards ferromagnet/superconductor junctions on graphene

    Energy Technology Data Exchange (ETDEWEB)

    Pakkayil, Shijin Babu

    2015-07-01

    Ever since A. Aspect et al. performed the famous 1982 experiment to prove the violation of Bell's inequality, there have been suggestions to conduct the same experiment in a solid state system. Some of those proposals involve superconductors as the source of entangled electron pair and spin depended interfaces as the optical analogue of polariser/filter. Semiconductors can serve as the best medium for such an experiment due to their long relaxation lengths. So far there are no reports on a ferromagnet/superconductor junctions on a semiconductor even though such junctions has been successfully realised in metallic systems. This thesis reports the successful fabrication of ferromagnet/superconductor junction along with characterising measurements in a perfectly two dimensional zero-gap semiconductor known as graphene. Since it's discovery in 2004, graphene has attracted prodigious interest from both academia and industry due to it's inimitable physical properties: very high mobility, high thermal and electrical conductivity, a high Young's modulus and impermeability. Graphene is also expected to have very long spin relaxation length and high spin life time because of it's low spin orbit coupling. For this reason and since researchers are always looking for novel materials and devices to comply with the high demands for better and faster data storage devices, graphene has emanated as a brand new material system for spin based devices. The very first spin injection and detection in graphene was realised in 2007 and ever since, the focal point of the research has been to improve the spin transport properties. A part of this thesis discusses a new fabrication recipe which has a high yield for successfully contacting graphene with a ferromagnet. A high starting yield for ferromagnetic contacts is a irremissible condition for combining superconducting contacts to the device to fabricate ferromagnet/superconductor junctions. Any fabrication recipe

  7. Phonon characteristics of high Tc superconductors from neutron Doppler broadening measurements

    International Nuclear Information System (INIS)

    Trela, W.J.; Kwei, G.H.; Lynn, J.E.; Meggers, K.

    1994-01-01

    Statistical information on the phonon frequency spectrum of materials can be measured by neutron transmission techniques if they contain nuclei with low energy resonances, narrow enough to be Doppler-broadened, in their neutron cross sections. The authors have carried out some measurements using this technique for materials of the lanthanum barium cuprate class, La 2-x Ba x CuO 4 . Two samples with slightly different concentrations of oxygen, one being superconductive, the other not, were examined. Pure lanthanum cuprate was also measured. Lanthanum, barium and copper all have relatively low energy narrow resonances. Thus it should be possible to detect differences in the phonons carried by different kinds of atom in the lattice. Neutron cross section measurements have been made with high energy resolution and statistical precision on the 59m flight path of LANSCE, the pulsed spallation neutron source at Los Alamos National Laboratory. Measurements on all three materials were made over a range of temperatures from 15K to 300K, with small steps through the critical temperature region near 27K. No significant changes in the mean phonon energy of the lanthanum atoms were observed near the critical temperature of the super-conducting material. It appears however that the mean phonon energy of lanthanum in the superconductor is considerably higher than that in the non-superconductors. The samples used in this series of experiments were too thin in barium and copper to determine anything significant about their phonon spectra

  8. Quantum critical scaling at the edge of Fermi liquid stability in a cuprate superconductor.

    Science.gov (United States)

    Butch, Nicholas P; Jin, Kui; Kirshenbaum, Kevin; Greene, Richard L; Paglione, Johnpierre

    2012-05-29

    In the high-temperature cuprate superconductors, the pervasiveness of anomalous electronic transport properties suggests that violation of conventional Fermi liquid behavior is closely tied to superconductivity. In other classes of unconventional superconductors, atypical transport is well correlated with proximity to a quantum critical point, but the relative importance of quantum criticality in the cuprates remains uncertain. Here, we identify quantum critical scaling in the electron-doped cuprate material La(2-x)Ce(x)CuO(4) with a line of quantum critical points that surrounds the superconducting phase as a function of magnetic field and charge doping. This zero-temperature phase boundary, which delineates a metallic Fermi liquid regime from an extended non-Fermi liquid ground state, closely follows the upper critical field of the overdoped superconducting phase and gives rise to an expanse of distinct non-Fermi liquid behavior at finite temperatures. Together with signatures of two distinct flavors of quantum fluctuations, these facts suggest that quantum criticality plays a significant role in shaping the anomalous properties of the cuprate phase diagram.

  9. Impurities and conductivity in a D-wave superconductor

    International Nuclear Information System (INIS)

    Balatsky, A.V.

    1994-01-01

    Impurity scattering in the unitary limit produces low energy quasiparticles with anisotropic spectrum in a two-dimensional d-wave superconductor. The authors describe a new quasi-one-dimensional limit of the quasiparticle scattering, which might occur in a superconductor with short coherence length and with finite impurity potential range. The dc conductivity in a d-wave superconductor is predicted to be proportional to the normal state scattering rate and is impurity-dependent. They show that quasi-one-dimensional regime might occur in high-T c superconductors with Zn impurities at low temperatures T approx-lt 10 K

  10. Method and apparatus to trigger superconductors in current limiting devices

    Science.gov (United States)

    Yuan, Xing; Hazelton, Drew Willard; Walker, Michael Stephen

    2004-10-26

    A method and apparatus for magnetically triggering a superconductor in a superconducting fault current limiter to transition from a superconducting state to a resistive state. The triggering is achieved by employing current-carrying trigger coil or foil on either or both the inner diameter and outer diameter of a superconductor. The current-carrying coil or foil generates a magnetic field with sufficient strength and the superconductor is disposed within essentially uniform magnetic field region. For superconductor in a tubular-configured form, an additional magnetic field can be generated by placing current-carrying wire or foil inside the tube and along the center axial line.

  11. Surface electrostatic waves in bounded high temperature superconductors

    International Nuclear Information System (INIS)

    Averkov, Yu.O.; Yakovenko, V.M.

    2008-01-01

    The dispersion relations of surface electrostatic waves propagating along the surface of semi bounded layered superconductor and in the slab of layered superconductor are theoretically investigated. An arbitrary inclination of superconductor layers to the interface of a vacuum - crystal and an arbitrary direction of propagation of surface waves in the plane of the interface are taking into account. The possibility of initiation of an absolute instability during the propagation of a non-relativistic plasma stream above the surface of the layered superconductor is shown

  12. Non-centrosymmetric superconductors introduction and overview

    CERN Document Server

    Sigrist, Manfred

    2012-01-01

    Superconductivity in materials without inversion symmetry in the respective crystal structures occurs in the presence of antisymmetric spin-orbit coupling as a consequence of an emerging electric field gradient. The superconducting condensate is then a superposition of spin-singlet and spin-triplet Cooper pairs. This scenario accounts for various experimental findings such as nodes in the superconducting gap or extremely large upper critical magnetic fields. Spin-triplet pairing can occur in non-centrosymmetric superconductors in spite of Anderson’s theorem that spin-triplet pairing requires a crystal structure that exhibits inversion symmetry. This book, authored and edited by leading researchers in the field, is both an introduction to and overview on this exciting branch of novel superconductors. Its self-contained and tutorial style makes it particularly suitable for self-study and as source of teaching material for special seminars and courses. At the same time it constitutes an up-to-date and authorit...

  13. Method for fabrication of high temperature superconductors

    Science.gov (United States)

    Balachandran, Uthamalingam [Hinsdale, IL; Ma, Beihai [Naperville, IL; Miller, Dean [Darien, IL

    2009-07-14

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

  14. 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.

  15. Local electromagnetic waves in layered superconductors

    International Nuclear Information System (INIS)

    Gvozdikov, V.M.; Vega-Monroy, R.

    1999-01-01

    A dispersion equation for electromagnetic waves localized on a defect layer of a layered superconductor is obtained in the frame of a model which neglects electron hopping between layers but assumes an arbitrary current-current response function within the layers. The defect layer differs from the rest of the layers by density and mass of charge carriers. It is shown that near the critical temperature in the London limit the local mode lies within the superconducting gap and has a wave vector threshold depending on the layered crystal and defect layer parameters. In the case of highly anisotropic layered superconductors, like Bi- or Tl-based high-T c cuprates, the local mode exists within a narrow range of positive variations of the mass and charge carriers. (author)

  16. Propagation of normal zones in composite superconductors

    International Nuclear Information System (INIS)

    Dresner, L.

    1976-08-01

    This paper describes calculations of propagation velocities of normal zones in composite superconductors. Full accounting is made for (1) current sharing, (2) the variation with temperature of the thermal conductivity of the copper matrix, and the specific heats of the matrix and the superconductor, and (3) the variation with temperature of the steady-state heat transfer at a copper-helium interface in the nucleate-boiling, transition, and film-boiling ranges. The theory, which contains no adjustable parameters, is compared with experiments on bare (uninsulated) conductors. Agreement is not good. It is concluded that the effects of transient heat transfer may need to be included in the theory to improve agreement with experiment

  17. Critical current enhancement in high Tc superconductors

    International Nuclear Information System (INIS)

    Jin, S.; Graebner, J.E.; Tiefel, T.H.

    1990-01-01

    Progress toward major technological applications of the bulk, high T c superconductors has been hindered by two major barriers, i.e., the Josephson weak-links at grain boundaries and the lack of sufficient intragrain flux pinning. It has been demonstrated that the weak link problem can be overcome by extreme alignment of grains such as in melt-textured-growth (MTG) materials. Modified or improved processing by various laboratories has produced further increased critical currents. However, the insufficient flux pinning seems to limit the critical current density in high fields to about 10 4 --10 5 A/cm 2 at 77K, which is not satisfactory for many applications. In this paper, processing, microstructure, and critical current behavior of the MTG type superconductors are described, and various processing possibilities for flux pinning enhancement are discussed

  18. 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...

  19. Flux Tube Dynamics in the Dual Superconductor

    International Nuclear Information System (INIS)

    Lampert, M.; Svetitsky, B.

    1999-01-01

    We have studied plasma oscillations in a flux tube created in a dual superconductor. The theory contains an Abelian gauge field coupled magnetically to a Higgs field that confines electric charge via the dual Meissner effect. Starting from a static flux tube configuration, with electric charges at either end, we release a fluid of electric charges in the system that accelerate and screen the electric field. The weakening of the electric field allows the flux tube to collapse, and the inertia of the charges forces it open again. We investigate both Type I and Type II superconductors, with plasma frequencies both above and below the threshold for radiation into the Higgs vacuum. (The parameters appropriate to QCD are in the Type II regime; the plasma frequency depends on the mass taken for the fluid constituents.) The coupling of the plasma oscillations to the Higgs field making up the flux tube is the main new feature in our work

  20. Positron annihilation studies on high temperature superconductors

    International Nuclear Information System (INIS)

    Sundar, C.S.; Bharathi, A.

    1996-01-01

    A survey of the positron annihilation studies on high temperature superconductors (HTSC), with results drawn mainly from our work, is presented. These include results of the studies on the temperature dependence of positron lifetime across T c , which have been carried out in the whole gamut of oxide superconductors. These experimental results are discussed in conjunction with the results of theoretically calculated positron density distribution, and it is shown that the observed temperature dependence of lifetime is intimately linked to the probing of the Cu-O network by the positrons. Results on the investigation of oxygen defects, which play a crucial role in HTSC, are presented. The most significant contribution of positrons to HTSC relates to the investigation of Fermi surface and the results of these studies, drawn from literature, are indicated. Some of our recent results in other novel superconducting materials, viz., the fullerenes and borocarbides are also presented. (author). 69 refs., 15 figs

  1. Superconductors for W VII-X coils

    International Nuclear Information System (INIS)

    Maurer, W.

    1987-01-01

    Superconductor concepts are discussed with respect to operational current, cooling and bending behavior, and ac losses. The encouraging results for NbTi superconducting technology are recalled. It is argued that the WVII-X stellarator modular superconducting coils can be built just as the modular Cu coils for WVII-AS. Special attention must be paid to the dB/dt allowed for the conductor. Shape and price depend on the means used to avoid ac losses. Formula to elucidate the main physical parameters influencing ac loss behavior of superconductors are given. Configurations investigated with respect to plasma behavior are compared. Masses to be cooled were estimated for two configurations. The estimated cooling power is of the order of 3kW

  2. High-Tc ferroelectrics and superconductors

    International Nuclear Information System (INIS)

    Muller, K.A.

    1990-01-01

    The meaning of the title refers to transition temperatures T c in ferroelectrics (FE) and superconductors (S). The highest T c 's in either field are observed in oxides: 1770 K in the ferroelectric La 2 TiO 7 and 125 K in the superconductor Tl 2 Ca 2 Cu 3 O 10 . Therefore, the question can be asked whether the observed high T c 's in oxide FE and S are a pure coincidence or whether there may be an underlying reason for it. This question is addressed first by recalling recent advances concerning anharmonic FE-properties and then by reviewing S-findings in the new compounds related to these properties

  3. 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.

  4. Voltage current characteristics of type III superconductors

    International Nuclear Information System (INIS)

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

    1980-01-01

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

  5. Voltage current characteristics of type III superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Dorofeiev, G L; Imenitov, A B; Klimenko, E Y [Gosudarstvennyi Komitet po Ispol' zovaniyu Atomnoi Ehnergii SSSR, Moscow. Inst. Atomnoi Ehnergii

    1980-06-01

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

  6. Vortex-antivortex patterns in mesoscopic superconductors

    International Nuclear Information System (INIS)

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

    2003-01-01

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

  7. Preparation of silver doped high temperature superconductors

    International Nuclear Information System (INIS)

    Stavek, Jiri; Zapletal, Vladimir

    1989-01-01

    High temperature superconductors were prepared by the controlled double-jet precipitation to manipulate the chemical composition, composition gradients, average grain size, grain size distribution, and other factors which contribute to the actual properties and performance of HTSC. The cations (Y-Ba-Cu or Bi-Pb-Ca-Sr-Cu) and oxalic anions solutions were simultaneously separately introduced to the crystallizer with a stirred solution of gelatin under conditions where the temperature, excess of oxalic anions in solution, pH, reactant addition rate, and other reaction conditions were tightly controlled to prepare the high sinterability powder. To increase the sinterability of submicron particles of produced precursor, the silver ions were introduced at the end of the controlled double-jet precipitation. This approach improves the electrical and mechanical properties of produced HTSC specimens. The controlled double jet precipitation provides a viable technique for preparation of oxide superconductors and the process is amenable for scaling up

  8. Conductive polymer/superconductor bilayer structures

    International Nuclear Information System (INIS)

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

    1994-01-01

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

  9. Optical and electron microanalysis of cuprate superconductors

    International Nuclear Information System (INIS)

    Hoff, H.A.; Osofsky, M.S.; Toth, L.E.; Richards, L.E.; Pande, C.S.; Lechter, W.L.

    1990-01-01

    Individual anisotropic grains in heterogeneous and opaque cuprate materials, when viewed in a reflected-light optical microscope through crossed polarizers, often have characteristic colors, when a daylight source is used. Of the cuprate superconductors, regardless of charge carrier type, examined so far, only one characteristic color has been observed We have studied the presence of color and found a strong correlation with the existence of superconductivity. The change in color from insulator to metal to superconductor and the compositions corresponding to these changes found by quantitative energy dispersive x-ray spectroscopy on superconducting Tl-Sr-Ca-Cu-O and metallic but not superconducting La-Sr-Cu-O materials is discussed

  10. Alloy model for high temperature superconductors

    International Nuclear Information System (INIS)

    Weissmann, M.; Saul, A.

    1991-07-01

    An alloy model is proposed for the electronic structure of high temperature superconductors. It is based on the assumption that holes and extra electrons are localized in small copper oxygen clusters, that would be the components of such alloy. This model, when used together with quantum chemical calculations on small clusters, can explain the structure observed in the experimental densities of states of both hole and electron superconductors close to the Fermi energy. The main point is the strong dependence of the energy level distribution and composition on the number of electrons in a cluster. The alloy model also suggests a way to correlate Tc with the number of holes, or extra electrons, and the number of adequate clusters to locate them. (author). 21 refs, 4 figs, 1 tab

  11. Processing of R-Ba-Cu-O superconductors

    International Nuclear Information System (INIS)

    Wu, H.

    1998-01-01

    Precipitation processes were developed to introduce second phases as flux pinning centers in Gd-Ba-Cu-O and Nd-Ba-Cu-O superconductors. In Gd-Ba-Cu-O, precipitation is caused by the decrease of the upper solubility limit of Gd 1+x Ba 2-x Cu 3 O 7 solid solution (Gd123ss) in low oxygen partial pressure. Processing of supersaturated Gd 1.2 Ba 1.8 Cu 3 O 7 in low oxygen partial pressure can produce dispersed second phases. Gd211 is formed as a separate phase while extensive Gd124 type stacking fault is formed instead of a separate CuO phase. As a result of the precipitation reaction, the transition temperature and critical current density are increased. In Nd-Ba-Cu-O, precipitation is caused by the decrease of the lower solubility limit of Nd 1+x Ba 2-x Cu 3 O 7 solid solution (Nd123ss) in oxygen. DTA results reveal the relative stability of Nd123ss in different oxygen partial pressures. In 1 bar oxygen partial pressure, Nd123ss with x = 0.1 is the most stable phase. In lower oxygen partial pressures, the most stable composition shifts towards the stoichiometric composition. The relative stability changes faster with decreasing oxygen partial pressure. Therefore, processing in oxygen and air tends to produce broad superconducting transitions but sharp transitions can be achieved in 0.01 bar and 0.001 bar oxygen partial pressures. While the lower solubility limits in 0.01 bar and 0.001 bar oxygen partial pressures remain at x = 0.00, the solubility limits in oxygen and air show a narrowing with decreasing temperature. Because of the narrowing of the solubility range in oxygen, oxygen annealing of Nd123 initially processed in low oxygen partial pressures will result in precipitation of second phases. The equilibrium second phase is BaCuO 2 for temperature above 608 C, and at lower temperatures the equilibrium second phases are Ba 2 CuO 3.3 and Ba 2 Cu 3 O 5+y . However, annealing at low temperature may produce a fine metastable transition phase. A coherent intermediate

  12. Transmission formalism for supercurrent flow in multiprobe superconductor-semiconductor-superconductor devices

    International Nuclear Information System (INIS)

    van Wees, B.J.; Lenssen, K.H.; Harmans, C.J.P.M.

    1991-01-01

    A theoretical study is given of supercurrent flow in a one-dimensional semiconductor channel coupled to superconductors at both ends. In addition, the channel is coupled to a semiconductor reservoir by means of a junction with variable coupling strength var-epsilon. The supercurrent I(cphi) is calculated from the phase-coherent propagation of electronlike and holelike excitations emitted by the superconductor reservoirs, together with electron and hole excitations from the semiconductor reservoir. The effect of temperature and var-epsilon on I(cphi) is studied. It is shown that a voltage applied between the semiconductor reservoir and the superconductors modifies the I(cphi) relation, even in the limit var-epsilon →0

  13. Theory of tunneling in metal--superconductor devices: Supercurrents in the superconductor gap at zero temperature

    International Nuclear Information System (INIS)

    Garcia, N.; Flores, F.; Guinea, F.

    1988-01-01

    Tunneling experiments in metal-oxide superconductor have shown the existence of ''leakage'' currents for applied voltages V smaller than one-half of the superconductor gap Δ. These currents are independent of temperature T. Recently experiments with scanning tunneling microscopy (STM) and squeezable tunnel junctions have shown that the observation of the superconductor gap depends strongly on the resistance in the junction. In fact only for resistances larger than ∼10 6 Ω the gap is clearly observable. These experiments have been explained in terms of the perturbative Hamiltonian formalism of Bardeen. However, it may happen that this theory while applicable for very large resistances may not be so for small tunnel resistances. We present here a nonperturbative theory in all orders of the transmitivity chemical bondTochemical bond 2 and show the existence of supercurrents for values of V 2 . We believe that experiments in STM and other junctions should be interpreted in the frame of this theory

  14. The new superconductors. Les nouveaux supraconducteurs

    Energy Technology Data Exchange (ETDEWEB)

    Gervais, F

    1991-01-01

    The first half of the book is a scanning of superconductivity from 1911 to our days, with Bardeen-Cooper-Schrieffer theory in 1957, with the concept of phonons and the importance of the Brillouin zone, with the discovery of high-tc superconductors oxides by Bednortz and Mueller in 1986. The second part is dealing with physical investigation means for trying to explain this high-tc superconductivity.

  15. Far infrared reflectivity study of ceramic superconductors

    International Nuclear Information System (INIS)

    Memon, A.; Khan, M.N.; Al-Dallal, S.; Tanner, D.B.; Porter, C.D.

    1992-01-01

    In this paper, the authors report on a study of the far-infrared reflectivity of mixed rare earths and lanthnides ceramic superconductors RBa 2 Cu 3 O 7 in the normal state. The authors' results show that the strength of the phonon modes is reduced when yttrium is partially replaced by gadolinium and europium. Also the critical temperature of these mixed materials is reduced as indicated by the four probe technique

  16. Critical de Broglie wavelength in superconductors

    Science.gov (United States)

    Talantsev, E. F.

    2018-03-01

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

  17. High temperature superconductors applications in telecommunications

    International Nuclear Information System (INIS)

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

    1994-01-01

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

  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. Magnetic properties of heavy-fermion superconductors

    International Nuclear Information System (INIS)

    Rauchschwalbe, U.

    1986-01-01

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

  20. Immunocytochemical analysis of P2X2 in rat circumvallate taste buds.

    Science.gov (United States)

    Yang, Ruibiao; Montoya, Alana; Bond, Amanda; Walton, Jenna; Kinnamon, John C

    2012-05-23

    Our laboratory has shown that classical synapses and synaptic proteins are associated with Type III cells. Yet it is generally accepted that Type II cells transduce bitter, sweet and umami stimuli. No classical synapses, however, have been found associated with Type II cells. Recent studies indicate that the ionotropic purinergic receptors P2X2/P2X3 are present in rodent taste buds. Taste nerve processes express the ionotropic purinergic receptors (P2X2/P2X3). P2X2/P2X3(Dbl-/-) mice are not responsive to sweet, umami and bitter stimuli, and it has been proposed that ATP acts as a neurotransmitter in taste buds. The goal of the present study is to learn more about the nature of purinergic contacts in rat circumvallate taste buds by examining immunoreactivity to antisera directed against the purinergic receptor P2X2. P2X2-like immunoreactivity is present in intragemmal nerve processes in rat circumvallate taste buds. Intense immunoreactivity can also be seen in the subgemmal nerve plexuses located below the basal lamina. The P2X2 immunoreactive nerve processes also display syntaxin-1-LIR. The immunoreactive nerves are in close contact with the IP(3)R3-LIR Type II cells and syntaxin-1-LIR and/or 5-HT-LIR Type III cells. Taste cell synapses are observed only from Type III taste cells onto P2X2-LIR nerve processes. Unusually large, "atypical" mitochondria in the Type II taste cells are found only at close appositions with P2X2-LIR nerve processes. P2X2 immunogold particles are concentrated at the membranes of nerve processes at close appositions with taste cells. Based on our immunofluorescence and immunoelectron microscopical studies we believe that both perigemmal and most all intragemmal nerve processes display P2X2-LIR. Moreover, colloidal gold immunoelectron microscopy indicates that P2X2-LIR in nerve processes is concentrated at sites of close apposition with Type II cells. This supports the hypothesis that ATP may be a key neurotransmitter in taste transduction

  1. Immunocytochemical analysis of P2X2 in rat circumvallate taste buds

    Directory of Open Access Journals (Sweden)

    Yang Ruibiao

    2012-05-01

    Full Text Available Abstract Background Our laboratory has shown that classical synapses and synaptic proteins are associated with Type III cells. Yet it is generally accepted that Type II cells transduce bitter, sweet and umami stimuli. No classical synapses, however, have been found associated with Type II cells. Recent studies indicate that the ionotropic purinergic receptors P2X2/P2X3 are present in rodent taste buds. Taste nerve processes express the ionotropic purinergic receptors (P2X2/P2X3. P2X2/P2X3Dbl−/− mice are not responsive to sweet, umami and bitter stimuli, and it has been proposed that ATP acts as a neurotransmitter in taste buds. The goal of the present study is to learn more about the nature of purinergic contacts in rat circumvallate taste buds by examining immunoreactivity to antisera directed against the purinergic receptor P2X2. Results P2X2-like immunoreactivity is present in intragemmal nerve processes in rat circumvallate taste buds. Intense immunoreactivity can also be seen in the subgemmal nerve plexuses located below the basal lamina. The P2X2 immunoreactive nerve processes also display syntaxin-1-LIR. The immunoreactive nerves are in close contact with the IP3R3-LIR Type II cells and syntaxin-1-LIR and/or 5-HT-LIR Type III cells. Taste cell synapses are observed only from Type III taste cells onto P2X2-LIR nerve processes. Unusually large, “atypical” mitochondria in the Type II taste cells are found only at close appositions with P2X2-LIR nerve processes. P2X2 immunogold particles are concentrated at the membranes of nerve processes at close appositions with taste cells. Conclusions Based on our immunofluorescence and immunoelectron microscopical studies we believe that both perigemmal and most all intragemmal nerve processes display P2X2-LIR. Moreover, colloidal gold immunoelectron microscopy indicates that P2X2-LIR in nerve processes is concentrated at sites of close apposition with Type II cells. This supports the hypothesis

  2. Non-nucleotide Agonists Triggering P2X7 Receptor Activation and Pore Formation

    Directory of Open Access Journals (Sweden)

    Francesco Di Virgilio

    2018-02-01

    Full Text Available The P2X7 receptor (P2X7R is a ligand-gated plasma membrane ion channel belonging to the P2X receptor subfamily activated by extracellular nucleotides. General consensus holds that the physiological (and maybe the only agonist is ATP. However, scattered evidence generated over the last several years suggests that ATP might not be the only agonist, especially at inflammatory sites. Solid data show that NAD+ covalently modifies the P2X7R of mouse T lymphocytes, thus lowering the ATP threshold for activation. Other structurally unrelated agents have been reported to activate the P2X7R via a poorly understood mechanism of action: (a the antibiotic polymyxin B, possibly a positive allosteric P2X7R modulator, (b the bactericidal peptide LL-37, (c the amyloidogenic β peptide, and (d serum amyloid A. Some agents, such as Alu-RNA, have been suggested to activate the P2X7R acting on the intracellular N- or C-terminal domains. Mode of P2X7R activation by these non-nucleotide ligands is as yet unknown; however, these observations raise the intriguing question of how these different non-nucleotide ligands may co-operate with ATP at inflammatory or tumor sites. New information obtained from the cloning and characterization of the P2X7R from exotic mammalian species (e.g., giant panda and data from recent patch-clamp studies are strongly accelerating our understanding of P2X7R mode of operation, and may provide hints to the mechanism of activation of P2X7R by non-nucleotide ligands.

  3. Knocking out P2X receptors reduces transmitter secretion in taste buds

    Science.gov (United States)

    Huang, Yijen A.; Stone, Leslie M.; Pereira, Elizabeth; Yang, Ruibiao; Kinnamon, John C.; Dvoryanchikov, Gennady; Chaudhari, Nirupa; Finger, Thomas E.; Kinnamon, Sue C.; Roper, Stephen D.

    2011-01-01

    In response to gustatory stimulation, taste bud cells release a transmitter, ATP, that activates P2X2 and P2X3 receptors on gustatory afferent fibers. Taste behavior and gustatory neural responses are largely abolished in mice lacking P2X2 and P2X3 receptors (P2X2 and P2X3 double knockout, or “DKO” mice). The assumption has been that eliminating P2X2 and P2X3 receptors only removes postsynaptic targets but that transmitter secretion in mice is normal. Using functional imaging, ATP biosensor cells, and a cell-free assay for ATP, we tested this assumption. Surprisingly, although gustatory stimulation mobilizes Ca2+ in taste Receptor (Type II) cells from DKO mice, as from wild type (WT) mice, taste cells from DKO mice fail to release ATP when stimulated with tastants. ATP release could be elicited by depolarizing DKO Receptor cells with KCl, suggesting that ATP-release machinery remains functional in DKO taste buds. To explore the difference in ATP release across genotypes, we employed reverse transcriptase (RT)-PCR, immunostaining, and histochemistry for key proteins underlying ATP secretion and degradation: Pannexin1, TRPM5, and NTPDase2 (ecto-ATPase) are indistinguishable between WT and DKO mice. The ultrastructure of contacts between taste cells and nerve fibers is also normal in the DKO mice. Finally, quantitative RT-PCR show that P2X4 and P2X7, potential modulators of ATP secretion, are similarly expressed in taste buds in WT and DKO taste buds. Importantly, we find that P2X2 is expressed in WT taste buds and appears to function as an autocrine, positive feedback signal to amplify taste-evoked ATP secretion. PMID:21940456

  4. Knocking out P2X receptors reduces transmitter secretion in taste buds.

    Science.gov (United States)

    Huang, Yijen A; Stone, Leslie M; Pereira, Elizabeth; Yang, Ruibiao; Kinnamon, John C; Dvoryanchikov, Gennady; Chaudhari, Nirupa; Finger, Thomas E; Kinnamon, Sue C; Roper, Stephen D

    2011-09-21

    In response to gustatory stimulation, taste bud cells release a transmitter, ATP, that activates P2X2 and P2X3 receptors on gustatory afferent fibers. Taste behavior and gustatory neural responses are largely abolished in mice lacking P2X2 and P2X3 receptors [P2X2 and P2X3 double knock-out (DKO) mice]. The assumption has been that eliminating P2X2 and P2X3 receptors only removes postsynaptic targets but that transmitter secretion in mice is normal. Using functional imaging, ATP biosensor cells, and a cell-free assay for ATP, we tested this assumption. Surprisingly, although gustatory stimulation mobilizes Ca(2+) in taste Receptor (Type II) cells from DKO mice, as from wild-type (WT) mice, taste cells from DKO mice fail to release ATP when stimulated with tastants. ATP release could be elicited by depolarizing DKO Receptor cells with KCl, suggesting that ATP-release machinery remains functional in DKO taste buds. To explore the difference in ATP release across genotypes, we used reverse transcriptase (RT)-PCR, immunostaining, and histochemistry for key proteins underlying ATP secretion and degradation: Pannexin1, TRPM5, and NTPDase2 (ecto-ATPase) are indistinguishable between WT and DKO mice. The ultrastructure of contacts between taste cells and nerve fibers is also normal in the DKO mice. Finally, quantitative RT-PCR show that P2X4 and P2X7, potential modulators of ATP secretion, are similarly expressed in taste buds in WT and DKO taste buds. Importantly, we find that P2X2 is expressed in WT taste buds and appears to function as an autocrine, positive feedback signal to amplify taste-evoked ATP secretion.

  5. High-Tc superconductor quantum interference devices

    International Nuclear Information System (INIS)

    1991-01-01

    This patent describes a superconductive quantum interferometric device for sensing a characteristic of a magnetic field. It comprises a substrate having a surface, the substrate being selected from the group which consists of strontium titanate, aluminum oxide, sapphire, ZrO 2 and mixtures thereof; a coating of MgO on the surface of the substrate; two identical thin-strip films of a high-critical temperature superconductor on the coating, each of the films having a pair of mutually parallel arms in the form of superconductor strips extending toward and aligned with super conductor strips forming corresponding arms of the other thin-strip film, and a crossbar strip connecting the arms of each thin-strip film at right angles to the arms, the high-critical-temperature superconductor being selected from the group which consists of yttrium-barium-calcium-copper-oxides, bismuth-strontium-calcium-copper-oxides, thallium-barium-copper-oxides, thallium-barium-calcium-copper-oxides, barium oxide: potassium oxide: bismuth oxides, and calcium oxide: zinc oxide: iron oxides; and insulating films on the coating between corresponding free ends of the arms thin-strip films, the insulating films being composed of a material selected from the group which consists of silicon dioxide, silicon nitride, magnesium oxide and mixture thereof

  6. 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.

  7. Pair breaking and charge relaxation in superconductors

    International Nuclear Information System (INIS)

    Nielson, J.B.; Pethick, C.J.; Rammer, J.; Smith, H.

    1982-01-01

    We present a general formalism based on the quasiclassical Green's function for calculating charge imbalance in nonequilibrium superconductors. Our discussion is sufficiently general that it applies at arbitrary temperatures, and under conditions when the width of quasiparticle states are appreciable due to pair breaking processes, and when strong coupling effects are significant. As a first application we demonstrate in detail how in the limit of smallpair breaking and for a weak coupling superconductor the collision term in the formalism reduces to the one in the quasiparticle Boltzmann equation. We next treat the case of charge imbalance generated by tunnel injection, with pair breaking by phonons and magnetic impurities. Over the range of temperatures investigated exerimentally to date, the calculated charge imbalance is rather close to that evaluated using the Boltzmann equation, even if pair braeking is so strong as almost to destroy superconductivity. Finally we consider charge imbalance generated by the combined influence of a supercurrent and a temperature gradient. We give calculations for a dirty superconductor with scattering by phonons as the pair breaking mechanism, and the results give a reasonable account of the experimental data of Clarke, Fjordboge, and Lindelof. We carry out calculations for the case of impurity scattering along which are valid not only in the clean and dirty limits, but also for intermediate situations. These enable us to see how the large contribution to the charge imbalance found for energies close to the gap edge in the clean case is reduced with increasing impurity scattering

  8. Superconductor Digital-RF Receiver Systems

    Science.gov (United States)

    Mukhanov, Oleg A.; Kirichenko, Dmitri; Vernik, Igor V.; Filippov, Timur V.; Kirichenko, Alexander; Webber, Robert; Dotsenko, Vladimir; Talalaevskii, Andrei; Tang, Jia Cao; Sahu, Anubhav; Shevchenko, Pavel; Miller, Robert; Kaplan, Steven B.; Sarwana, Saad; Gupta, Deepnarayan

    Digital superconductor electronics has been experiencing rapid maturation with the emergence of smaller-scale, lower-cost communications applications which became the major technology drivers. These applications are primarily in the area of wireless communications, radar, and surveillance as well as in imaging and sensor systems. In these areas, the fundamental advantages of superconductivity translate into system benefits through novel Digital-RF architectures with direct digitization of wide band, high frequency radio frequency (RF) signals. At the same time the availability of relatively small 4K cryocoolers has lowered the foremost market barrier for cryogenically-cooled digital electronic systems. Recently, we have achieved a major breakthrough in the development, demonstration, and successful delivery of the cryocooled superconductor digital-RF receivers directly digitizing signals in a broad range from kilohertz to gigahertz. These essentially hybrid-technology systems combine a variety of superconductor and semiconductor technologies packaged with two-stage commercial cryocoolers: cryogenic Nb mixed-signal and digital circuits based on Rapid Single Flux Quantum (RSFQ) technology, room-temperature amplifiers, FPGA processing and control circuitry. The demonstrated cryocooled digital-RF systems are the world's first and fastest directly digitizing receivers operating with live satellite signals in X-band and performing signal acquisition in HF to L-band at ˜30GHz clock frequencies.

  9. Pressure effect on iron based superconductors

    International Nuclear Information System (INIS)

    Arumugam, S.; Kanagaraj, M.

    2011-01-01

    A tuning of macroscopic thermo dynamical parameters such as temperature, pressure and volume play a crucial role in strongly correlated electron systems especially high T c superconductors, which leads to increasing conductivity as well as effective way of reducing intrinsic magnetic moments. Application of chemical and external pressure exhibits significant increases of critical temperature of recently discovered iron pnictides and chalcogenides superconductors. In this present report, we have investigated hydrostatic pressure effects on resistivity and magnetization of some 1111 type based oxypnictide superconductors such as Co doped CeFeAsO, La 0.8 Th 0.2 FeAsO, Ce 0.6 Y 0.4 FeAsO 0.8 F 0.2 and Yb doped CeFeAsO systems respectively. The initially applied pressure increases the T c and its down to lower value when beyond increasing pressure also has been observed and pressure effects on crystal structure were also discussed. From that all the obtained results reveal that controlling of magnetic instability and structure distortion at higher pressure is a dominant way to further developing of T c of these new ferropnictides compounds. (author)

  10. Charge Distribution and Local Structure and Speciation in the UO2+x and PuO2+x Binary Oxides for x

    International Nuclear Information System (INIS)

    Conradson, Steven D.; Begg, Bruce D.; Clark, David L.; Den Auwer, Christophe J.; Ding, Mei; Dorhout, Peter K.; Espinosa-Faller, Francisco J.; Gordon, Pamela L.; Haire, Richard G.; Hess, Nancy J.; Hess, Ryan F.; Keogh, D. Webster; Lander, Gerard H.; Manara, Dario; Morales, Luis A.; Neu, Mary P.; Paviet-Hartmann, Patricia; Rebizant, Jean; Rondinella, Vincenzo V.; Runde, Wolfgang; Tait, C. Drew; Veirs, D. Kirk; Villella, Phillip M.; Wastin, Franck

    2005-01-01

    The local structure and chemical speciation of the mixed valence, fluorite-based oxides UO2+x (0.00pxp0.20) and PuO2+x/PuO2+x*y(OH)2y * zH2O have been determined by U/Pu LIII XAFS spectroscopy. The U spectra indicate (1) that the O atoms are incorporated as oxo groups at short (1.75A ? ) U?O distances consistent with U(VI) concomitant with a large range of U displacements that reduce the apparent number of U neighbors and (2) that the UO2 fraction remains intact implying that these O defects interact to form clusters and give the heterogeneous structure consistent with the diffraction patterns. The PuO2+x system, which does not show a separate phase at its x ? 0:25 endpoint, also displays (1) oxo groups at longer 1.9A ? distances consistent with Pu(V+d), (2) a multisite Pu?O distribution even when x is close to zero indicative of the formation of stable species with H2O and its hydrolysis products with O2*, and (3) a highly disordered, spectroscopically invisible Pu?Pu component. The structure and bonding in AnO2+x are therefore more complicated than have previously been assumed and show both similarities but also distinct differences among the different elements

  11. Charge Distribution and Local Structure and Speciation in the UO2+x and PuO2+x Binary Oxides for x <= 0.25

    Energy Technology Data Exchange (ETDEWEB)

    Conradson, Steven D.; Begg, Bruce D.; Clark, David L.; Den Auwer, Christophe J.; Ding, Mei; Dorhout, Peter K.; Espinosa-Faller, Francisco J.; Gordon, Pamela L.; Haire, Richard G.; Hess, Nancy J.; Hess, Ryan F.; Keogh, D. Webster; Lander, Gerard H.; Manara, Dario; Morales, Luis A.; Neu, Mary P.; Paviet-Hartmann, Patricia; Rebizant, Jean; Rondinella, Vincenzo V.; Runde, Wolfgang; Tait, C DREW.; Veirs, D. Kirk; Villella, Phillip M.; Wastin, Franck

    2005-02-01

    The local structure and chemical speciation of the mixed valence, fluorite-based oxides UO2+x (0.00pxp0.20) and PuO2+x/PuO2+x*y(OH)2y * zH2O have been determined by U/Pu LIII XAFS spectroscopy. The U spectra indicate (1) that the O atoms are incorporated as oxo groups at short (1.75A ? ) U?O distances consistent with U(VI) concomitant with a large range of U displacements that reduce the apparent number of U neighbors and (2) that the UO2 fraction remains intact implying that these O defects interact to form clusters and give the heterogeneous structure consistent with the diffraction patterns. The PuO2+x system, which does not show a separate phase at its x ? 0:25 endpoint, also displays (1) oxo groups at longer 1.9A ? distances consistent with Pu(V+d), (2) a multisite Pu?O distribution even when x is close to zero indicative of the formation of stable species with H2O and its hydrolysis products with O2*, and (3) a highly disordered, spectroscopically invisible Pu?Pu component. The structure and bonding in AnO2+x are therefore more complicated than have previously been assumed and show both similarities but also distinct differences among the different elements.

  12. P2X7 on mouse T cells: one channel, many functions

    Directory of Open Access Journals (Sweden)

    Björn eRissiek

    2015-05-01

    Full Text Available The P2X7 receptor is an adenosine triphosphate (ATP-gated cation channel that is expressed by several cells of the immune system. P2X7 is best known for its proinflammatory role in promoting inflammasome formation and release of mature IL-1β by innate immune cells. Mounting evidence indicates that P2X7 is also an important regulatory receptor of murine and human T cell functions. Murine T cells express a sensitive splice variant of P2X7 that can be activated either by non-covalent binding of ATP or, in the presence of nicotinamide adenine dinucleotide (NAD+, by its covalent ADP-ribosylation catalyzed by the ecto-ADP-ribosyltransferase ARTC2.2. Prolonged activation of P2X7 by either one of these pathways triggers the induction of T cell death. Conversely, lower concentrations of ATP can activate P2X7 to enhance T cell proliferation and production of IL-2. In this review we will highlight the molecular and cellular consequences of P2X7 activation on mouse T cells and its versatile role in T cell homeostasis and activation. Further, we will discuss important differences in the function of P2X7 on human and murine T cells.

  13. Nociceptive transmission and modulation via P2X receptors in central pain syndrome.

    Science.gov (United States)

    Kuan, Yung-Hui; Shyu, Bai-Chuang

    2016-05-26

    Painful sensations are some of the most frequent complaints of patients who are admitted to local medical clinics. Persistent pain varies according to its causes, often resulting from local tissue damage or inflammation. Central somatosensory pathway lesions that are not adequately relieved can consequently cause central pain syndrome or central neuropathic pain. Research on the molecular mechanisms that underlie this pathogenesis is important for treating such pain. To date, evidence suggests the involvement of ion channels, including adenosine triphosphate (ATP)-gated cation channel P2X receptors, in central nervous system pain transmission and persistent modulation upon and following the occurrence of neuropathic pain. Several P2X receptor subtypes, including P2X2, P2X3, P2X4, and P2X7, have been shown to play diverse roles in the pathogenesis of central pain including the mediation of fast transmission in the peripheral nervous system and modulation of neuronal activity in the central nervous system. This review article highlights the role of the P2X family of ATP receptors in the pathogenesis of central neuropathic pain and pain transmission. We discuss basic research that may be translated to clinical application, suggesting that P2X receptors may be treatment targets for central pain syndrome.

  14. Mobility Patterns Informing V2X Research Projects: Eco-Routing and Electrified Roadway Project Examples

    Energy Technology Data Exchange (ETDEWEB)

    Gonder, Jeff; Brooker, Aaron; Burton, Evan; Wang, Lijuan; Wood, Eric

    2016-05-19

    Presentation given at an 'Expert Workshop on V2X Enabled Electric Vehicles' hosted at NREL on behalf of the International Energy Agency (IEA) Hybrid and Electric Vehicle Implementing Agreement for Task 28: Home Grids and V2X Technologies.

  15. Colossal magnetoresistance in layered manganite Nd2−2xSr1+ ...

    Indian Academy of Sciences (India)

    starting compounds, have been obtained. Except for x=0.4, which is found to be an antiferromagnetic insulator, all other x values yielded metal–insulator transition and ferromagnetic ordering. Keywords. Colossal magnetoresistance; layered manganites; Nd2−2x Sr1+2x Mn2O7. PACS Nos 75.30.Vn; 71.30.+h. 1. Introduction.

  16. Thermodynamics of vortices in disordered superconductors

    International Nuclear Information System (INIS)

    Van der Beek, Cornelis Jacominus

    2009-01-01

    The emergence of the High Temperature Superconductors (HTSC) has not only profoundly affected solid state physics, it has also provoked a revolution in the understanding of the behaviour of quantified vortex lines that traverse the superconducting material when this is placed in a magnetic field. Owing to the conspiracy of extreme parameter values characterizing High Temperature Superconductors, all physical properties of flux vortices, their dynamics, and their phase diagram in the (B,T) plane could now be studied in hitherto inaccessible detail. Thus, it was established that the true phase transition to the superconducting state occurs nt at the upper critical field Bc2, but at the melting transition of the vortex ensemble. In disordered superconductors, an entirely new phenomenology, linked to flux line pinning by material defects, appeared. New thermodynamic vortex phases have been postulated, and sometimes found. The aim of this document is to take a critical look at the mechanism leading to the melting transition of the vortex ensemble in HTSC, as well as at the role played by material disorder on vortex physics. First and foremost, the materials under study are characterized. that is, not only are their fundamental parameters such as the critical temperature, critical fields, and penetration depth established, but also their purity and the nature of the disorder they contain. In this, the present work finds all its meaning in having been performed at the Laboratoire des Solides Irradies, whose primary goal is to investigate the role of material disorder introduced by irradiation on materials and physics. We then study the vortex melting transition in Bi 2 Sr 2 CaCu 2 O 8 by a method that is peculiar to layered superconductors: the Josephson Plasma Resonance. This technique will allow us to evaluate the average thermal displacements of the vortex lines in the vicinity of the transition, in as-grown as well as in irradiated crystals. The role of crystalline

  17. 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, FeSe 1- x Te x and alkali-metal-doped A x Fe 2- y Se 2 ( 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 T c of FeSe increases with Te substitution in FeSe 1- 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 T c shows that it does not support superconductivity. The presence of same wave vector as that of other Fe-based superconductors in FeSe 1- x Te x and the observation of the resonance mode demonstrate that FeSe 1- 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 A x Fe 2- y Se 2 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 A x Fe 2- y Se 2 has an exceptional superconducting symmetry among Fe-based superconductors.

  18. Localization of P2X receptor subtypes 2, 3 and 7 in human urinary bladder.

    Science.gov (United States)

    Svennersten, Karl; Hallén-Grufman, Katarina; de Verdier, Petra J; Wiklund, N Peter; Poljakovic, Mirjana

    2015-08-08

    Voiding dysfunctions are a common problem that has a severe negative impact on the quality of life. Today there is a need for new drug targets for these conditions. The role of ATP receptors in bladder physiology has been studied for some time, primarily in animal models. The aim of this work is to investigate the localization of the ATP receptors P2X2, P2X3 and P2X7 and their colocalization with vimentin and actin in the human urinary bladder. Immunohistochemical analysis was conducted on full-thickness bladder tissues from fundus and trigonum collected from 15 patients undergoing open radical cystectomy due to chronic cystitis, bladder cancer or locally advanced prostate cancer. Colocalization analyses were performed between the three different P2X subtypes and the structural proteins vimentin and actin. Specimens were examined using epifluorescence microscopy and correlation coefficients were calculated for each costaining as well as the mean distance from the laminin positive basal side of the urothelium to the vimentin positive cells located in the suburothelium. P2X2 was expressed in vimentin positive cells located in the suburothelium. Less distinct labelling of P2X2 was also observed in actin positive smooth muscle cells and in the urothelium. P2X3 was expressed in vimentin positive cells surrounding the smooth muscle, and in vimentin positive cells located in the suburothelium. Weaker P2X3 labelling was seen in the urothelium. P2X7 was expressed in the smooth muscle cells and the urothelium. In the suburothelium, cells double positive for P2X2 and vimentin where located closer to the urothelium while cells double positive for P2X3 and vimentin where located further from the urothelium. The results from this study demonstrate that there is a significant difference in the expression of the purinergic P2X2, P2X3 and P2X7 receptors in the different histological layers of the human urinary bladder.

  19. Vaporization study on nonstoichiometric NbOsub(2+-x) by mass-spectrometric method

    International Nuclear Information System (INIS)

    Matsui, T.; Naito, K.

    1981-01-01

    The vapor pressures over nonstoichiometric NbOsub(2+-x)(s) (1.972 2 (g) and NbO(g) over nonstoichiometric NbOsub(2+-x), from which the partial molar enthalpies and entropies of oxygen were calculated as a function of O/Nb composition. The composition dependence of the partial molar enthalpy and entropy obtained suggested the existence of some kind of short-range ordering in the nonstoichiometric Nbsub(2+-x) (s) phase. The enthalpies of formation of nonstoichiometric NbOsub(2+-x) (s) were also determined as a function of composition by combining the partial molar enthalpies of oxygen with the enthalpy of formation of stoichiometric NbOsub(2.000) (s). The phase diagram around NbOsub(2+-x) at high temperatures was determined from the vaporization study. (orig.)

  20. Functional polymorphisms in the P2X7 receptor gene are associated with osteoporosis

    DEFF Research Database (Denmark)

    Husted, L B; Harsløf, T; Stenkjær, L

    2013-01-01

    variant allele, which has been associated with increased receptor function in monocytes, was associated with increased total hip BMD in women. With the exception of His155Tyr for which we found conflicting results in men and women, our results are consistent with the phenotype of the knockout mouse......UNLABELLED: The P2X(7) receptor is an ATP-gated cation channel. We investigated the effect of both loss-of-function and gain-of-function polymorphisms in the P2X(7) receptor gene on BMD and risk of vertebral fractures and found that five polymorphisms and haplotypes containing three...... of these polymorphisms were associated with BMD and fracture risk. INTRODUCTION: The P2X(7) receptor is an ATP-gated cation channel. P2X(7) receptor knockout mice have reduced total bone mineral content, and because several functional polymorphisms have been identified in the human P2X(7) receptor gene, we wanted...

  1. Relationship between the new superconductors and two-or three-dimensional antiferromagnetism. Relations entre les nouveaux supraconducteurs et l'antiferromagnetisme bi et tridimensionnel

    Energy Technology Data Exchange (ETDEWEB)

    Burger, J P [Ecole Superieure de Physique et Chimie Industrielles, 75 - Paris (France); Zanoun, Y

    1992-04-01

    With the classical superconductors there is nearly always an opposition with the local or itinerant magnetism. For the new superconductors there is a coexistence regime with the two-dimensional Cu antiferromagnetism of short coherence length, a fact which can be related to a new attractive interaction due to magnetic fluctuations. However, the opposition between this new superconducting state and the three-dimensional antiferromagnetism is analyzed as a function of x proportional to the density of conduction electrons or holes, through the Ginzburg-Landau opposition term {gamma}M{sup 2}{psi}{sup 2} between the two order parameters: if {gamma} is beyond a critical value then there can be no overlap of the two transition temperatures T{sub CM}(x) and T{sub CS}(x), with nevertheless a common border observed for Nd{sub 2-x}Ce{sub x}CuO{sub 4}.

  2. P2X purinoceptors as a link between hyperexcitability and neuroinflammation in status epilepticus.

    Science.gov (United States)

    Henshall, David C; Engel, Tobias

    2015-08-01

    There remains a need for more efficacious treatments for status epilepticus. Prolonged seizures result in the release of ATP from cells which activates the P2 class of ionotropic and metabotropic purinoceptors. The P2X receptors gate depolarizing sodium and calcium entry and are expressed by both neurons and glia throughout the brain, and a number of subtypes are upregulated after status epilepticus. Recent studies have explored the in vivo effects of targeting ATP-gated P2X receptors in preclinical models of status epilepticus, with particular focus on the P2X7 receptor (P2X7R). The P2X7R mediates microglial activation and the release of the proepileptogenic inflammatory cytokine interleukin 1β. The receptor may also directly modulate neurotransmission and gliotransmission and promote the recruitment of immune cells into brain parenchyma. Data from our group and collaborators show that status epilepticus produced by intraamygdala microinjection of kainic acid increases P2X7R expression in the hippocampus and neocortex of mice. Antagonism of the P2X7R in the model reduced seizure severity, microglial activation and interleukin 1β release, and neuronal injury. Coadministration of a P2X7R antagonist with a benzodiazepine also provided seizure suppression in a model of drug-refractory status epilepticus when either treatment alone was minimally effective. More recently, we showed that status epilepticus in immature rats is also reduced by P2X7R antagonism. Together, these findings suggest that P2X receptors may be novel targets for seizure control and interruption of neuroinflammation after status epilepticus. This article is part of a Special Issue entitled "Status Epilepticus". Copyright © 2015 Elsevier Inc. All rights reserved.

  3. P2X receptors as targets for the treatment of status epilepticus

    Science.gov (United States)

    Henshall, David C.; Diaz-Hernandez, Miguel; Miras-Portugal, M. Teresa; Engel, Tobias

    2013-01-01

    Prolonged seizures are amongst the most common neurological emergencies. Status epilepticus is a state of continuous seizures that is life-threatening and prompt termination of status epilepticus is critical to protect the brain from permanent damage. Frontline treatment comprises parenteral administration of anticonvulsants such as lorazepam that facilitate γ-amino butyric acid (GABA) transmission. Because status epilepticus can become refractory to anticonvulsants in a significant proportion of patients, drugs which act on different neurotransmitter systems may represent potential adjunctive treatments. P2X receptors are a class of ligand-gated ion channel activated by ATP that contributes to neuro- and glio-transmission. P2X receptors are expressed by both neurons and glia in various brain regions, including the hippocampus. Electrophysiology, pharmacology and genetic studies suggest certain P2X receptors are activated during pathologic brain activity. Expression of several members of the family including P2X2, P2X4, and P2X7 receptors has been reported to be altered in the hippocampus following status epilepticus. Recent studies have shown that ligands of the P2X7 receptor can have potent effects on seizure severity during status epilepticus and mice lacking this receptor display altered seizures in response to chemoconvulsants. Antagonists of the P2X7 receptor also modulate neuronal death, microglial responses and neuroinflammatory signaling. Recent work also found altered neuronal injury and inflammation after status epilepticus in mice lacking the P2X4 receptor. In summary, members of the P2X receptor family may serve important roles in the pathophysiology of status epilepticus and represent novel targets for seizure control and neuroprotection. PMID:24324404

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

    International Nuclear Information System (INIS)

    Anon.

    1990-01-01

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

  5. Creation of point defects in superconductors. A short review

    International Nuclear Information System (INIS)

    Quere, Yves; Rullier-Albenque, Florence.

    1981-11-01

    Many experiments have been published concerning the radiation damage in superconductors, but relatively few about the mechanisms of defect creation. A short review is presented of what is known on point defect creation in superconductors either by cold-work or by irradiation

  6. A phenomenological approach to high Tc oxide superconductors

    International Nuclear Information System (INIS)

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

    1987-06-01

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

  7. Five-fold way to new high Tc superconductors

    Indian Academy of Sciences (India)

    Discovery of high c superconductivity in La2−BaCuO4 by Bednorz and Muller in 1986 was a breakthrough in the 75-year long search for new superconductors. Since then new high c superconductors, not involving copper, have also been discovered. Superconductivity in cuprates also inspired resonating valence ...

  8. Unconventional superconductivity in heavy fermionic and high-Tc superconductors

    International Nuclear Information System (INIS)

    Volovik, G.E.

    1989-01-01

    Splitting of the superconducting transition and glass spectrum in heavy fermion companies and oxide superconductors are discussed. The multicomponent order parameter leads to splitting of transition due to magnetic field, impurities, orthorhombic distortion, etc... Linear specific heat in oxide superconductors may be explained in terms of the Fermi-surface arising in superconducting state if interband is pairing strong enough

  9. Chemical doping in pnictides superconductors: The case of Ca(Fe1-xXx) 2As2 , X = Co, Ni, Pt

    Science.gov (United States)

    Continenza, Alessandra; Profeta, Gianni

    2018-04-01

    We present a comparative and detailed study of transition metal doping in CaFe2As2. Comparing with several experimental results and carefully analyzing how the states at the Fermi level are affected by doping we show that: i) simulation of real doping and considering induces structural relaxations are crucial to correctly address the physical mechanisms induced by transition metal substitutions; ii) different dopant concentration induces changes on the band structure that can not be described within a simple rigid-band picture; iii) careful comparison with the available ARPES results shows that the main effects on band filling and symmetry can be caught within DFT.

  10. Out-of-equilibrium spin transport in mesoscopic superconductors.

    Science.gov (United States)

    Quay, C H L; Aprili, M

    2018-08-06

    The excitations in conventional superconductors, Bogoliubov quasi-particles, are spin-[Formula: see text] fermions but their charge is energy-dependent and, in fact, zero at the gap edge. Therefore, in superconductors (unlike normal metals) spin and charge degrees of freedom may be separated. In this article, we review spin injection into conventional superconductors and focus on recent experiments on mesoscopic superconductors. We show how quasi-particle spin transport and out-of-equilibrium spin-dependent superconductivity can be triggered using the Zeeman splitting of the quasi-particle density of states in thin-film superconductors with small spin-mixing scattering. Finally, we address the spin dynamics and the feedback of quasi-particle spin imbalances on the amplitude of the superconducting energy gap.This article is part of the theme issue 'Andreev bound states'. © 2018 The Author(s).

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

    International Nuclear Information System (INIS)

    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 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 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

  12. Axial force in a superconductor magnet journal bearing

    Science.gov (United States)

    Postrekhin, E.; Chong, Wang; Ki Bui, Ma; Chen, Quark; Chu, Wei-Kan

    Using superconductors and magnets, a journal bearing could be made from a permanent magnet cylinder in a superconductor ring. We have assembled a prototype superconductor magnet journal bearing of this configuration, and investigated the behavior of the axial force that it can provide. We have put together a numerical model of the interaction between the permanent magnet and the superconductor that is capable of describing these experimental results semi-quantitatively. Combining direct experimental measurements and using the numerical models proposed, we have achieved a qualitative understanding of the behavior of the axial force and its relationship of to the dimensions of the magnet and material quality such as the homogeneity of the superconductor that constitute the bearing.

  13. 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.

  14. 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.

  15. 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…

  16. Electrochemical treatment of an oxide material, application to superconductors, and obtained superconductors

    International Nuclear Information System (INIS)

    Grenier, J.C.; Pouchard, M.; Wattiaux, A.

    1991-01-01

    The present invention describes the electrochemical treatment of a superconductor oxide so as to modify its stoichiometry. These materials comprise in their anionic lattice oxygenated and hydrogenated species. These treated materials are prepared by an electrochemical process in which the oxide is an electrode in a liquid electrolysis. 3 refs., 3 figs

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

    International Nuclear Information System (INIS)

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

    2013-01-01

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

  18. Yu-Shiba-Rusinov states in phase-biased superconductor-quantum dot-superconductor junctions

    DEFF Research Database (Denmark)

    Kirsanskas, Gediminas; Goldstein, Moshe; Flensberg, Karsten

    2015-01-01

    supercurrent, and the differential conductance as measured by a normal-metal tunnel probe. In absence of a phase difference only one linear combination of the superconductor lead electrons couples to the spin, which gives a single YSR state. With finite phase difference, however, it is effectively a two...

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

    International Nuclear Information System (INIS)

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

    1983-01-01

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

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

    International Nuclear Information System (INIS)

    Navani, R.

    1974-01-01

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

  1. The P2X7 ATP receptor modulates renal cyst development in vitro

    International Nuclear Information System (INIS)

    Hillman, Kate A.; Woolf, Adrian S.; Johnson, Tanya M.; Wade, Angela; Unwin, Robert J.; Winyard, Paul J.D.

    2004-01-01

    P2X 7 , a piercing receptor, is expressed in renal collecting ducts as they undergo fulminant cysto genesis in the cpk/cpk mouse model of autosomal recessive polycystic kidney disease (ARPKD). Dissociated cpk/cpk kidneys generate cysts from cell aggregates within 24 h of suspension culture and we demonstrate that BzATP, a P2X 7 agonist, reduces cystogenesis. This effect is P2X 7 -specific, because: (i) equimolar concentrations of other purinergic agonists, ATP and UTP, had lesser effects and (ii) the P2X 7 inhibitor, oxidized ATP, abrogated the BzATP-mediated reduction in cystogenesis. BzATP did not significantly affect total cell number, proliferation, LDH release or caspase 3 activity, and zVAD-fmk, a caspase blocker, failed to modulate BzATP effects. In addition, this P2X 7 agonist did not significantly alter cyst size, probably excluding altered vectorial transport. In vivo, ATP was detected in cyst fluid from cpk/cpk kidneys; moreover, P2X 7 protein was also upregulated in human fetal ARPKD epithelia versus normal fetal collecting ducts. Thus, ATP may inhibit pathological renal cyst growth through P2X 7 signaling

  2. Lack of the purinergic receptor P2X7 results in resistance to contact hypersensitivity

    Science.gov (United States)

    Weber, Felix C.; Esser, Philipp R.; Müller, Tobias; Ganesan, Jayanthi; Pellegatti, Patrizia; Simon, Markus M.; Zeiser, Robert; Idzko, Marco; Jakob, Thilo

    2010-01-01

    Sensitization to contact allergens requires activation of the innate immune system by endogenous danger signals. However, the mechanisms through which contact allergens activate innate signaling pathways are incompletely understood. In this study, we demonstrate that mice lacking the adenosine triphosphate (ATP) receptor P2X7 are resistant to contact hypersensitivity (CHS). P2X7-deficient dendritic cells fail to induce sensitization to contact allergens and do not release IL-1β in response to lipopolysaccharide (LPS) and ATP. These defects are restored by pretreatment with LPS and alum in an NLRP3- and ASC-dependent manner. Whereas pretreatment of wild-type mice with P2X7 antagonists, the ATP-degrading enzyme apyrase or IL-1 receptor antagonist, prevents CHS, IL-1β injection restores CHS in P2X7-deficient mice. Thus, P2X7 is a crucial receptor for extracellular ATP released in skin in response to contact allergens. The lack of P2X7 triggering prevents IL-1β release, which is an essential step in the sensitization process. Interference with P2X7 signaling may be a promising strategy for the prevention of allergic contact dermatitis. PMID:21059855

  3. Rab5 regulates internalisation of P2X4 receptors and potentiation by ivermectin.

    Science.gov (United States)

    Stokes, Leanne

    2013-03-01

    The P2X4 receptor is an ATP-gated ion channel expressed in neurons, endothelia and immune cells. Plasma membrane expression of P2X4 is regulated by dynamin-dependent endocytosis, and this study identifies a Rab5-dependent pathway of receptor internalisation. Expression of Rab5 constructs altered the distribution of P2X4 in HEK-293 cells, and both constitutive internalisation and agonist-induced desensitisation of P2X4 were increased by co-expression of wild-type Rab5 or constitutively active Rab5 (Q79L). Expression of inactive dynamin K44A and Rab5 S34N constructs abolished agonist-induced desensitisation, suggesting internalisation as the underlying mechanism. Blocking P2X4 internalisation in this way also abolished potentiation of ATP-induced currents by the allosteric modulator ivermectin. This suggests that the dynamin-Rab5 internalisation pathway is essential for the ivermectin potentiation effect. In agreement with this hypothesis, the co-expression of wild-type dynamin, wild-type Rab5 or active Rab5 (Q79L) could increase the potentiation of the ATP-induced P2X4 response by ivermectin. These findings highlight Rab5 GTPase as a key regulator of P2X4 receptor cell surface expression and internalisation.

  4. Hyperglycemia-induced Renal P2X7 Receptor Activation Enhances Diabetes-related Injury

    Directory of Open Access Journals (Sweden)

    Robert I. Menzies

    2017-05-01

    Full Text Available Diabetes is a leading cause of renal disease. Glomerular mesangial expansion and fibrosis are hallmarks of diabetic nephropathy and this is thought to be promoted by infiltration of circulating macrophages. Monocyte chemoattractant protein-1 (MCP-1 has been shown to attract macrophages in kidney diseases. P2X7 receptors (P2X7R are highly expressed on macrophages and are essential components of pro-inflammatory signaling in multiple tissues. Here we show that in diabetic patients, renal P2X7R expression is associated with severe mesangial expansion, impaired glomerular filtration (≤40 ml/min/1.73 sq. m., and increased interstitial fibrosis. P2X7R activation enhanced the release of MCP-1 in human mesangial cells cultured under high glucose conditions. In mice, P2X7R-deficiency prevented glomerular macrophage attraction and collagen IV deposition; however, the more severe interstitial inflammation and fibrosis often seen in human diabetic kidney diseases was not modelled. Finally, we demonstrate that a P2X7R inhibitor (AZ11657312 can reduce renal macrophage accrual following the establishment of hyperglycemia in a model of diabetic nephropathy. Collectively these data suggest that P2X7R activation may contribute to the high prevalence of kidney disease found in diabetics.

  5. Blockade of P2X7 receptors or pannexin-1 channels similarly attenuates postischemic damage.

    Science.gov (United States)

    Cisneros-Mejorado, Abraham; Gottlieb, Miroslav; Cavaliere, Fabio; Magnus, Tim; Koch-Nolte, Friederich; Scemes, Eliana; Pérez-Samartín, Alberto; Matute, Carlos

    2015-05-01

    The role of P2X7 receptors and pannexin-1 channels in ischemic damage remains controversial. Here, we analyzed their contribution to postanoxic depolarization after ischemia in cultured neurons and in brain slices. We observed that pharmacological blockade of P2X7 receptors or pannexin-1 channels delayed the onset of postanoxic currents and reduced their slope, and that simultaneous inhibition did not further enhance the effects of blocking either one. These results were confirmed in acute cortical slices from P2X7 and pannexin-1 knockout mice. Oxygen-glucose deprivation in cortical organotypic cultures caused neuronal death that was reduced with P2X7 and pannexin-1 blockers as well as in organotypic cultures derived from mice lacking P2X7 and pannexin 1. Subsequently, we used transient middle cerebral artery occlusion to monitor the neuroprotective effect of those drugs in vivo. We found that P2X7 and pannexin-1 antagonists, and their ablation in knockout mice, substantially attenuated the motor symptoms and reduced the infarct volume to ~50% of that in vehicle-treated or wild-type animals. These results show that P2X7 receptors and pannexin-1 channels are major mediators of postanoxic depolarization in neurons and of brain damage after ischemia, and that they operate in the same deleterious signaling cascade leading to neuronal and tissue demise.

  6. 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...

  7. Charge transport in junctions between d-wave superconductors

    International Nuclear Information System (INIS)

    Barash, Y.S.; Galaktionov, A.V.; Zaikin, A.D.

    1995-01-01

    We develop a microscopic analysis of superconducting and dissipative currents in junctions between superconductors with d-wave symmetry of the order parameter. We study the proximity effect in such superconductors and show that for certain crystal orientations the superconducting order parameter can be essentially suppressed in the vicinity of a nontransparent specularly reflecting boundary. This effect strongly influences the value and the angular dependence of the dc Josephson current j S . At T∼T c it leads to a crossover between j S ∝T c -T and j S ∝(T c -T) 2 respectively for homogeneous and nonhomogeneous distribution of the order parameter in the vicinity of a tunnel junction. We show that at low temperatures the current-phase relation j S (cphi) for superconductor--normal-metal--superconductor junctions and short weak links between d-wave superconductors is essentially nonharmonic and contains a discontinuity at cphi=0. This leads to further interesting features of such systems which can be used for pairing symmetry tests in high-temperature superconductors (HTSC). We also investigated the low-temperature I-V curves of normal-metal--superconductor and superconductor-superconductor tunnel junctions and demonstrated that depending on the junction type and crystal orientation these curves show zero-bias anomalies I∝V 2 , I∝V 2 ln(1/V), and I∝V 3 caused by the gapless behavior of the order parameter in d-wave superconductors. Many of our results agree well with recent experimental findings for HTSC compounds

  8. Elliptic Curve Integral Points on y2 = x3 + 3x ‑ 14

    Science.gov (United States)

    Zhao, Jianhong

    2018-03-01

    The positive integer points and integral points of elliptic curves are very important in the theory of number and arithmetic algebra, it has a wide range of applications in cryptography and other fields. There are some results of positive integer points of elliptic curve y 2 = x 3 + ax + b, a, b ∈ Z In 1987, D. Zagier submit the question of the integer points on y 2 = x 3 ‑ 27x + 62, it count a great deal to the study of the arithmetic properties of elliptic curves. In 2009, Zhu H L and Chen J H solved the problem of the integer points on y 2 = x 3 ‑ 27x + 62 by using algebraic number theory and P-adic analysis method. In 2010, By using the elementary method, Wu H M obtain all the integral points of elliptic curves y 2 = x 3 ‑ 27x ‑ 62. In 2015, Li Y Z and Cui B J solved the problem of the integer points on y 2 = x 3 ‑ 21x ‑ 90 By using the elementary method. In 2016, Guo J solved the problem of the integer points on y 2 = x 3 + 27x + 62 by using the elementary method. In 2017, Guo J proved that y 2 = x 3 ‑ 21x + 90 has no integer points by using the elementary method. Up to now, there is no relevant conclusions on the integral points of elliptic curves y 2 = x 3 + 3x ‑ 14, which is the subject of this paper. By using congruence and Legendre Symbol, it can be proved that elliptic curve y 2 = x 3 + 3x ‑ 14 has only one integer point: (x, y) = (2, 0).

  9. High pressure study of high temperatures superconductors: Material base, universal Tc-behavior, and charge transfer

    International Nuclear Information System (INIS)

    Chu, C.W.; Hor, P.H.; Lin, J.G.; Xiong, Q.; Huang, Z.J.; Meng, R.L.; Xue, Y.Y.; Jean, Y.C.

    1991-01-01

    The superconducting transition temperature (T c ) has been measured in YBa 2 Cu 3 O 6.7 , YBa 2 Cu 3 O 7 , Y 2 Ba 4 Cu 7 O 15 , YBa 2 Cu 4 O 8 , Tl 2 Ba 2 Ca n-1 Cu n O n+4-δ , La 2-x Sr x CuO 4 , and La 2-x Ba x CuO 4 under high pressures. The pressure effect on the positron lifetime (τ) has also been determined in the first four compounds. Based on these and other high pressure data, the authors suggest that (1) all known cuprate high temperature superconductors (HTS's) may be no more than mere modifications of either 214-T, 214-T', 123, or a combination of 214-T' and 123, (2) a nonmonotonic T c -behavior may govern the T c -variation of all hole cuprate HTS's and (3) pressure can induce charge transfer leading to a T c -change. The implications of these suggestions will also be discussed

  10. Atmospheric chemistry of perfluorinated aldehyde hydrates (n-C(x)F(2x+1)CH(OH)2, x = 1, 3, 4)

    DEFF Research Database (Denmark)

    Andersen, Mads Peter Sulbæk; Toft, A.; Nielsen, O.J.

    2006-01-01

    . Bubbling CF(3)CHO/air mixtures through liquid water led to >80% conversion of CF(3)CHO into the hydrate within the approximately 2 s taken for passage through the bubbler. These results suggest that OH radical initiated oxidation of C(x)F(2x+1)CH(OH)(2) hydrates could be a significant source...

  11. Color-Space-Based Visual-MIMO for V2X Communication

    OpenAIRE

    Jai-Eun Kim; Ji-Won Kim; Youngil Park; Ki-Doo Kim

    2016-01-01

    In this paper, we analyze the applicability of color-space-based, color-independent visual-MIMO for V2X. We aim to achieve a visual-MIMO scheme that can maintain the original color and brightness while performing seamless communication. We consider two scenarios of GCM based visual-MIMO for V2X. One is a multipath transmission using visual-MIMO networking and the other is multi-node V2X communication. In the scenario of multipath transmission, we analyze the channel capacity numerically and w...

  12. Modulation of Central Synapses by Astrocyte-Released ATP and Postsynaptic P2X Receptors

    Science.gov (United States)

    Pankratov, Yuriy

    2017-01-01

    Communication between neuronal and glial cells is important for neural plasticity. P2X receptors are ATP-gated cation channels widely expressed in the brain where they mediate action of extracellular ATP released by neurons and/or glia. Recent data show that postsynaptic P2X receptors underlie slow neuromodulatory actions rather than fast synaptic transmission at brain synapses. Here, we review these findings with a particular focus on the release of ATP by astrocytes and the diversity of postsynaptic P2X-mediated modulation of synaptic strength and plasticity in the CNS. PMID:28845311

  13. System Engineering and Technical Challenges Overcome in the J-2X Rocket Engine Development Project

    Science.gov (United States)

    Ballard, Richard O.

    2012-01-01

    Beginning in 2006, NASA initiated the J-2X engine development effort to develop an upper stage propulsion system to enable the achievement of the primary objectives of the Constellation program (CxP): provide continued access to the International Space Station following the retirement of the Space Station and return humans to the moon. The J-2X system requirements identified to accomplish this were very challenging and the time expended over the five years following the beginning of the J- 2X effort have been noteworthy in the development of innovations in both the fields for liquid rocket propulsion and system engineering.

  14. Modulation of Central Synapses by Astrocyte-Released ATP and Postsynaptic P2X Receptors

    Directory of Open Access Journals (Sweden)

    Eric Boué-Grabot

    2017-01-01

    Full Text Available Communication between neuronal and glial cells is important for neural plasticity. P2X receptors are ATP-gated cation channels widely expressed in the brain where they mediate action of extracellular ATP released by neurons and/or glia. Recent data show that postsynaptic P2X receptors underlie slow neuromodulatory actions rather than fast synaptic transmission at brain synapses. Here, we review these findings with a particular focus on the release of ATP by astrocytes and the diversity of postsynaptic P2X-mediated modulation of synaptic strength and plasticity in the CNS.

  15. Atmospheric chemistry of n-CxF2x+1CHO (x = 1, 2, 3, 4)

    DEFF Research Database (Denmark)

    Hurley, M. D.; Ball, J. C.; Wallington, T. J.

    2006-01-01

    Smog chamber/FTIR techniques were used to study the atmospheric fate of n-C(x)F(2)(x)(+1)C(O) (x = 1, 2, 3, 4) radicals in 700 Torr O(2)/N(2) diluent at 298 +/- 3 K. A competition is observed between reaction with O(2) to form n-C(x)()F(2)(x)()(+1)C(O)O(2) radicals and decomposition to form n-C(x...... to the atmospheric chemistry of n-C(x)F(2)(x)(+1)C(O) radicals and their possible role in contributing to the formation of perfluorocarboxylic acids in the environment....

  16. Measurement of oxygen chemical diffusion in PuO{sub 2-x} and analysis of oxygen diffusion in PuO{sub 2-x} and (Pu,U)O{sub 2-x}

    Energy Technology Data Exchange (ETDEWEB)

    Kato, Masato; Uchida, Teppei [Advanced Nuclear System Research and Development Directorate, Japan Atomic Energy Agency, 4-33 Muramatsu, Tokai-mura, Ibaraki 319-1194 (Japan); Sunaoshi, Takeo [Inspection Development Company Ltd., 4-33 Muramatsu, Tokai-mura, Ibaraki 319-1194 (Japan)

    2013-02-15

    Oxygen chemical diffusion in PuO{sub 2-x} was investigated in the temperature range of 1473-1873 K by thermogravimetry as functions of oxygen-to-metal (O/M) ratios and temperatures. The oxygen chemical diffusion coefficients, D were determined assuming that the reduction curves were dominated by a diffusion process. The O/M ratio and Pu content dependence on the chemical diffusion coefficients were evaluated. The chemical diffusion coefficient had its minimum value at around O/M=1.98 and decreased with increasing Pu content in (U,Pu)O{sub 2-x}. The self-diffusion coefficients were evaluated. A model for describing the relationship among O/M ratio, oxygen chemical diffusion, and self-diffusion was proposed based on defect chemistry. (copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  17. Measurement of oxygen chemical diffusion in PuO2-x and analysis of oxygen diffusion in PuO2-x and (Pu,U)O2-x

    International Nuclear Information System (INIS)

    Kato, Masato; Uchida, Teppei; Sunaoshi, Takeo

    2013-01-01

    Oxygen chemical diffusion in PuO 2-x was investigated in the temperature range of 1473-1873 K by thermogravimetry as functions of oxygen-to-metal (O/M) ratios and temperatures. The oxygen chemical diffusion coefficients, D were determined assuming that the reduction curves were dominated by a diffusion process. The O/M ratio and Pu content dependence on the chemical diffusion coefficients were evaluated. The chemical diffusion coefficient had its minimum value at around O/M=1.98 and decreased with increasing Pu content in (U,Pu)O 2-x . The self-diffusion coefficients were evaluated. A model for describing the relationship among O/M ratio, oxygen chemical diffusion, and self-diffusion was proposed based on defect chemistry. (copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  18. Condensation energy density in Bi-2212 superconductors

    International Nuclear Information System (INIS)

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

    2006-01-01

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

  19. 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)

  20. Iron-based superconductors via soft chemistry

    International Nuclear Information System (INIS)

    Friederichs, Gina Maya

    2015-01-01

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

  1. Zeeman effects in heavy electron superconductors

    International Nuclear Information System (INIS)

    Michal, Vincent

    2012-01-01

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

  2. Chemical pressure induced change in multiferroicity of Bi{sub 1+2x}Gd{sub 2x/2}Fe{sub 1−2x}O{sub 3} bulk ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Pradhan, S.K. [Institute of Materials Science, Bhubaneswar 751013 Odisha (India); Center for Materials Research, Norfolk State University, Norfolk (United States); Sahu, D.R., E-mail: diptirs@yahoo.com [Institute of Materials Science, Bhubaneswar 751013 Odisha (India); Department of Natural and Applied Science, Namibia University of Science and Technology, Windhoek (Namibia); Rout, P.P.; Das, S.K. [Institute of Materials Science, Bhubaneswar 751013 Odisha (India); Pradhan, A.K. [Center for Materials Research, Norfolk State University, Norfolk (United States); Srinivasu, V.V. [Department of Physics, University of South Africa (South Africa); Roul, B.K., E-mail: ims@iopb.res.in [Institute of Materials Science, Bhubaneswar 751013 Odisha (India)

    2017-04-01

    We have optimized Gd ion substitution in BiFeO{sub 3} (BFO) and observed prominently change in structural, electrical and magnetic behavior of Bi{sub 1+2x}Gd{sub 2x/2}Fe{sub 1−2x}O{sub 3} ceramics synthesized through slow step sintering schedule. It is observed that with the increase in concentration of Gd (x=0.1), original structure of BFO is transformed from rhombohedral R3c space group to orthorhombic Pn21a space group. Surprisingly, unit cell volume is drastically contracted (35% for x=0.2) and the sintered specimen showed enhanced room temperature ferromagnetic behavior although the original BFO is normally G-type antiferromagnetic in nature at 643 K. It is expected that intrinsic chemical pressure within the bulk body built by the substitution of Gd in presence of excess bismuth greatly supported through unidirectional movement of electrical dipole moment with in each individual domain as a result of which suppression of leakage current with enhanced dielectric and ferroelectric hysteresis is observed.

  3. 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-

  4. 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

  5. An infrared view of high Tc superconductors

    International Nuclear Information System (INIS)

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

    1989-01-01

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

  6. Magnetic pinning in superconductor-ferromagnet multilayers

    International Nuclear Information System (INIS)

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

    2000-01-01

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

  7. Magnetic pinning in superconductor-ferromagnet multilayers

    Energy Technology Data Exchange (ETDEWEB)

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

    2000-05-01

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

  8. Critical state of anisotropic hard superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Romero-Salazar, C; Perez-RodrIguez, F [Instituto de FIsica, Universidad Autonoma de Puebla, Apdo Post J-48, Puebla, Pue 72570 (Mexico)

    2003-11-01

    The magnetic response of anisotropic irreversible type-II superconductors is investigated theoretically. Using an elliptic vertical law for the electric field E as a function of the current density J, we have reproduced available experimental magnetization curves of YBCO samples with the c axis lying in the sample plane. Specifically, we could reproduce quantitatively and interpret correctly the appearance of additional extrema and segments with relatively small slopes of the virgin magnetization curves when the direction of the applied magnetic field differs from the principal axes. The notable deformation of magnetization curves in a tilted magnetic field is connected to the strong coupling between the components of the magnetic induction.

  9. High Tc superconductors using solution techniques

    International Nuclear Information System (INIS)

    Barboux, P.; Valente, I.; Henry, M.; Morineau, R.; Tarascon, J.M.; Khan, S.; Shokoohi, F.; Bagley, B.G.

    1989-01-01

    The authors have investigated different solution techniques to synthesize the Cu-based superconductors in the thick film form. Thick films of YBa 2 Cu 3 O 7 have been produced using controlled precipitation techniques. Bi-based and Tl-based materials have been deposited by spraying of ionic solutions. The numerous difficulties encountered during each process are analyzed in order to propose new synthesis procedures such as a new method, based on the precipitation of hydroxides only, which is described as a prospective for lowering the synthesis temperature and shortening the reaction time

  10. Charge-imbalance fluctuations in superconductors

    International Nuclear Information System (INIS)

    Lemberger, T.R.

    1981-01-01

    We calculate that the mean-square amplitude of the fluctuations of the condensate chemical potential μ/sub s/ due to charge-imbalance fluctuations in the limit Δ/k/sub B/T 2 > = 2(k/sub B/T) 2 /πdeltaΩN(0) in a volume Ω of superconductor. We relate these fluctuations via Nyquist's theorem to measured values of the contribution of self-injected charge imbalance to the dc resistance of SIN tunnel junctions. In this relation the dynamic charge-imbalance relaxation rate is 1/tau/sub E/, the electron-phonon scattering rate

  11. Proximity effects in ferromagnet/superconductor structures

    International Nuclear Information System (INIS)

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

    2004-01-01

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

  12. Modeling forces in high-temperature superconductors

    International Nuclear Information System (INIS)

    Turner, L. R.; Foster, M. W.

    1997-01-01

    We have developed a simple model that uses computed shielding currents to determine the forces acting on a high-temperature superconductor (HTS). The model has been applied to measurements of the force between HTS and permanent magnets (PM). Results show the expected hysteretic variation of force as the HTS moves first toward and then away from a permanent magnet, including the reversal of the sign of the force. Optimization of the shielding currents is carried out through a simulated annealing algorithm in a C++ program that repeatedly calls a commercial electromagnetic software code. Agreement with measured forces is encouraging

  13. Infrared properties of high Tc superconductors

    International Nuclear Information System (INIS)

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

    1991-01-01

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

  14. Oxygen diffusion in high-Tc superconductors

    International Nuclear Information System (INIS)

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

    1992-07-01

    The cuprate superconductors are fascinating not only because of their technical promise, but also because of their structures, especially the anisotropy of the crystal lattice. There are some structural similarities among these compounds, but also significant differences. Measurements of the oxygen tracer diffusion coefficients have been carried out as a function of temperature, oxygen partial pressure, crystal orientation, and doping in the La-Sr-Cu-0, Y-Ba-Cu-0, and Bi-Sr-Ca-Cu-0 systems. These measurements have revealed a variety of defect mechanisms operating in these compounds; the exact nature of the mechanism depends on the details of the structure

  15. Application of high temperature superconductors for fusion

    International Nuclear Information System (INIS)

    Fietz, W.H.; Heller, R.; Schlachter, S.I.; Goldacker, W.

    2011-01-01

    The use of High Temperature Superconductor (HTS) materials in future fusion machines can increase the efficiency drastically. For ITER, W7-X and JT-60SA the economic benefit of HTS current leads was recognized after a 70 kA HTS current lead demonstrator was designed, fabricated and successfully tested by Karlsruhe Institute of Technology (KIT, which is a merge of former Forschungszentrum Karlsruhe and University of Karlsruhe). For ITER, the Chinese Domestic Agency will provide the current leads as a part of the superconducting feeder system. KIT is in charge of design, construction and test of HTS current leads for W7-X and JT-60SA. For W7-X 14 current leads with a maximum current of 18.2 kA are required that are oriented with the room temperature end at the bottom. JT60-SA will need 26 current leads (20 leads - 20 kA and 6 leads - 25.7 kA) which are mounted in vertical, normal position. These current leads are based on BiSCCO HTS superconductors, demonstrating that HTS material is now state of the art for highly efficient current leads. With respect to future fusion reactors, it would be very promising to use HTS material not only in current leads but also in coils. This would allow a large increase of efficiency if the coils could be operated at temperatures ≥65 K. With such a high temperature it would be possible to omit the radiation shield of the coils, resulting in a less complex cryostat and a size reduction of the machine. In addition less refrigeration power is needed saving investment and operating costs. However, to come to an HTS fusion coil it is necessary to develop low ac loss HTS cables for currents well above 20 kA at high fields well above 10 T. The high field rules BiSCCO superconductors out at temperatures above 50 K, but RE-123 superconductors are promising. The development of a high current, high field RE-123 HTS fusion cable will not be targeted outside fusion community and has to be in the frame of a long term development programme for

  16. Using Decision Trees to Detect and Isolate Leaks in the J-2X

    Data.gov (United States)

    National Aeronautics and Space Administration — Full title: Using Decision Trees to Detect and Isolate Simulated Leaks in the J-2X Rocket Engine Mark Schwabacher, NASA Ames Research Center Robert Aguilar, Pratt...

  17. Role of P2X7 on steroid synthesis in murine luteal cells

    Directory of Open Access Journals (Sweden)

    Chunping Zhang

    2016-03-01

    Full Text Available The extracellular adenosine triphosphate (ATP regulates different cellular functions through activating purinergic receptors as a signalling molecule or neurotransmitter. P2X7 is highly expressed in murine small luteal cells. In this study, murine luteal cells were cultured in vitro and treated with P2X7 agonists – ATP and 2′(3′-O-(4-benzoyl-benzoyl-adenosine 50-triphosphate (BzATP and with P2X7 antagonist – brilliant blue G (BBG. We found that ATP and BzATP increased the production of progesterone and had no influence on the production of estradiol. BBG reversed the effect of BzATP and ATP. Further studies demonstrated that ATP and BzATP promoted the expression of CYP11A. These results revealed that P2X7 receptor activation is involved in the steroid synthesis in corpus luteum.

  18. Substitutions in cation Nd/Ba subsystem in thin films of high-temperature superconductor NdBa2Cu3Oy

    International Nuclear Information System (INIS)

    Mozhaev, P.B.; Komissinskij, F.V.; Ivanov, Z.G.; Ovsyannikov, G.A.

    2000-01-01

    Thin films of the Nd 1+x Ba 2-x Cu 3 O y (NBCO) high-temperature superconductor with various neodymium and barium ratio are obtained through the method of combined laser spraying of targets with different elements composition. The films with neodymium excess (x >0) had low density of particles on the surface and roughness, however the critical temperature decreased with growth of x. The films with barium excess (x z particles. The NbCO structure and superconducting properties demonstrate strong dependence on the conditions of the films saturation with oxygen [ru

  19. Corneal epithelium expresses a variant of P2X(7 receptor in health and disease.

    Directory of Open Access Journals (Sweden)

    Courtney Mankus

    Full Text Available Improper wound repair of the corneal epithelium can alter refraction of light resulting in impaired vision. We have shown that ATP is released after injury, activates purinergic receptor signaling pathways and plays a major role in wound closure. In many cells or tissues, ATP activates P2X(7 receptors leading to cation fluxes and cytotoxicity. The corneal epithelium is an excellent model to study the expression of both the full-length P2X(7 form (defined as the canonical receptor and its truncated forms. When Ca(2+ mobilization is induced by BzATP, a P2X(7 agonist, it is attenuated in the presence of extracellular Mg(2+ or Zn(2+, negligible in the absence of extracellular Ca(2+, and inhibited by the competitive P2X7 receptor inhibitor, A438079. BzATP enhanced phosphorylation of ERK. Together these responses indicate the presence of a canonical or full-length P2X(7 receptor. In addition BzATP enhanced epithelial cell migration, and transfection with siRNA to the P2X(7 receptor reduced cell migration. Furthermore, sustained activation did not induce dye uptake indicating the presence of truncated or variant forms that lack the ability to form large pores. Reverse transcription-polymerase chain reaction and Northern blot analysis revealed a P2X(7 splice variant. Western blots identified a full-length and truncated form, and the expression pattern changed as cultures progressed from monolayer to stratified. Cross-linking gels demonstrated the presence of homo- and heterotrimers. We examined epithelium from age matched diabetic and non-diabetic corneas patients and detected a 4-fold increase in P2X(7 mRNA from diabetic corneal epithelium compared to non-diabetic controls and an increased trend in expression of P2X(7variant mRNA. Taken together, these data indicate that corneal epithelial cells express full-length and truncated forms of P2X(7, which ultimately allows P2X(7 to function as a multifaceted receptor that can mediate cell proliferation and

  20. Fully reconfigurable 2x2 optical cross-connect using tunable wavelength switching modules

    DEFF Research Database (Denmark)

    Liu, Fenghai; Zheng, Xueyan; Pedersen, Rune Johan Skullerud

    2001-01-01

    A modular tunable wavelength switching module is proposed and used to construct 2x2 fully reconfigurable optical cross-connects. Large size optical switch is avoided in the OXC and it is easy to upgrade to more wavelength channels.......A modular tunable wavelength switching module is proposed and used to construct 2x2 fully reconfigurable optical cross-connects. Large size optical switch is avoided in the OXC and it is easy to upgrade to more wavelength channels....

  1. UV Written 2x8 Optical Power Splitter for FTTH Applications

    DEFF Research Database (Denmark)

    Olivero, Massimo; Svalgaard, Mikael

    2006-01-01

    Silica based integrated optical 2x8 power splitters are reported for the first time using UV-writing waveguide fabrication technology. High performance, compactness and low production costs make these components well suited for deployment in FTTH networks.......Silica based integrated optical 2x8 power splitters are reported for the first time using UV-writing waveguide fabrication technology. High performance, compactness and low production costs make these components well suited for deployment in FTTH networks....

  2. DESENSITIZATION PROPERTIES OF P2X3 RECEPTORS SHAPING PAIN SIGNALLING

    Directory of Open Access Journals (Sweden)

    Rashid eGiniatullin

    2013-12-01

    Full Text Available ATP-gated P2X3 receptors are mostly expressed by nociceptive sensory neurons and participate in transduction of pain signals. P2X3 receptors show a combination of fast desensitization onset and slow recovery. Moreover, even low nanomolar agonist concentrations unable to evoke a response, can induce desensitization via a phenomenon called ‘high affinity desensitization’. We have also observed that recovery from desensitization is agonist-specific and can range from seconds to minutes. The recovery process displays unusually high temperature dependence. Likewise, recycling of P2X3 receptors in peri-membrane regions shows unexpectedly large temperature sensitivity. By applying kinetic modeling, we have previously shown that desensitization characteristics of P2X3 receptor are best explained with a cyclic model of receptor operation involving three agonist molecules binding a single receptor and that desensitization is primarily developing from the open receptor state. Mutagenesis experiments suggested that desensitization depends on a certain conformation of the ATP binding pocket and on the structure of the transmembrane domains forming the ion pore. Further molecular determinants of desensitization have been identified by mutating the intracellular N- and C-termini of P2X3 receptor. Unlike other P2X receptors, the P2X3 subtype is facilitated by extracellular calcium that acts via specific sites in the ectodomain neighboring the ATP binding pocket. Thus, substitution of serine275 in this region (called ‘left flipper’ converts the natural facilitation induced by extracellular calcium to receptor inhibition. Given such their strategic location in nociceptive neurons and unique desensitization properties, P2X3 receptors represent an attractive target for development of new analgesic drugs via promotion of desensitization aimed at suppressing chronic pain.

  3. Powder processing of high Tc oxide superconductors and their properties

    International Nuclear Information System (INIS)

    Vajpei, A.C.; Upadhyaya, G.S.

    1992-01-01

    Powder processing of ceramics is an established technology and in the area of high T c superconductors, its importance is felt even more significantly. The present monograph is an attempt in this direction to explore the perspectives and practice of powder processing routes towards control and optimization of the microstructure and pertinent properties of high T c oxide superconductors. The monograph consists of 6 chapters. After a very brief introduction (Chapter 1), Chapter 2 describes various classes of high T c oxide superconductors and their phase equilibria. Chapter 3 highlights the preparation of oxide superconductor powders through various routes and details their subtle distinctions. Chapter 4 briefly covers characterisation of the oxide superconductors, laying emphasis on the process-analysis and microstructure. Chapter 5 describes in detail various fabrication techniques for bulk superconductors through the powder routes. The last Chapter (Chapter 6) describing properties of bulk oxide superconductors, discusses the role of subtituents, compositional variations and processing methods on such properties. References are given at the end of each chapter. (orig.)

  4. Superconductors at the nanoscale. From basic research to applications

    Energy Technology Data Exchange (ETDEWEB)

    Woerdenweber, Roger [Forschungszentrum Juelich GmbH (Germany). Peter Gruenberg Inst.; Moshchalkov, Victor [KU Leuven (Belgium). Inst. for Nanoscale Physics and Chemistry; Bending, Simon [Bath Univ. (United Kingdom). School of Physics; Tafuri, Francesco (ed.) [Seconda Univ. di Napoli, Aversa (Italy)

    2017-07-01

    By covering theory, design, and fabrication of nanostructured superconducting materials, this monograph is an invaluable resource for research and development. This book contains the following chapters: Tutorial on nanostructured superconductors; Imaging vortices in superconductors: from the atomic scale to macroscopic distances; Probing vortex dynamics on a single vortex level by scanning ac-susceptibility microscopy; STM studies of vortex cores in strongly confined nanoscale superconductors; Type-1.5 superconductivity; Direct visualization of vortex patterns in superconductors with competing vortex-vortex interactions; Vortex dynamics in nanofabricated chemical solution deposition high-temperature superconducting films; Artificial pinning sites and their applications; Vortices at microwave frequencies; Physics and operation of superconducting single-photon devices; Josephson and charging effect in mesoscopic superconducting devices; NanoSQUIDs: Basics and recent advances; Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8} intrinsic Josephson junction stacks as emitters of terahertz radiation; Interference phenomena in superconductor-ferromagnet hybrids; Spin-orbit interactions, spin currents, and magnetization dynamics in superconductor/ferromagnet hybrids; Superconductor/ferromagnet hybrids.

  5. GaN/NbN epitaxial semiconductor/superconductor heterostructures

    Science.gov (United States)

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

    2018-03-01

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

  6. P2X7 receptor-deficient mice are susceptible to bone cancer pain

    DEFF Research Database (Denmark)

    Hansen, Rikke Rie; Nielsen, Christian K.; Nasser, Arafat

    2011-01-01

    The purinergic P2X7 receptor is implicated in both neuropathic and inflammatory pain, and has been suggested as a possible target in pain treatment. However, the specific role of the P2X7 receptor in bone cancer pain is unknown. We demonstrated that BALB/cJ P2X7 receptor knockout (P2X7R KO) mice...... were susceptible to bone cancer pain and moreover had an earlier onset of pain-related behaviours compared with cancer-bearing, wild-type mice. Furthermore, acute treatment with the selective P2X7 receptor antagonist, A-438079, failed to alleviate pain-related behaviours in models of bone cancer pain...... with and without astrocyte activation (BALB/cJ or C3H mice inoculated with 4T1 mammary cancer cells or NCTC 2472 osteosarcoma cells, respectively), suggesting that astrocytic P2X7 receptors play a negligible role in bone cancer pain. The results support the hypothesis that bone cancer pain is a separate pain state...

  7. 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.

  8. Topological insulators and superconductors: tenfold way and dimensional hierarchy

    International Nuclear Information System (INIS)

    Ryu, Shinsei; Schnyder, Andreas P; Furusaki, Akira; Ludwig, Andreas W W

    2010-01-01

    It has recently been shown that in every spatial dimension there exist precisely five distinct classes of topological insulators or superconductors. Within a given class, the different topological sectors can be distinguished, depending on the case, by a Z or a Z 2 topological invariant. This is an exhaustive classification. Here we construct representatives of topological insulators and superconductors for all five classes and in arbitrary spatial dimension d, in terms of Dirac Hamiltonians. Using these representatives we demonstrate how topological insulators (superconductors) in different dimensions and different classes can be related via 'dimensional reduction' by compactifying one or more spatial dimensions (in 'Kaluza-Klein'-like fashion). For Z-topological insulators (superconductors) this proceeds by descending by one dimension at a time into a different class. The Z 2 -topological insulators (superconductors), on the other hand, are shown to be lower-dimensional descendants of parent Z-topological insulators in the same class, from which they inherit their topological properties. The eightfold periodicity in dimension d that exists for topological insulators (superconductors) with Hamiltonians satisfying at least one reality condition (arising from time-reversal or charge-conjugation/particle-hole symmetries) is a reflection of the eightfold periodicity of the spinor representations of the orthogonal groups SO(N) (a form of Bott periodicity). Furthermore, we derive for general spatial dimensions a relation between the topological invariant that characterizes topological insulators and superconductors with chiral symmetry (i.e., the winding number) and the Chern-Simons invariant. For lower-dimensional cases, this formula relates the winding number to the electric polarization (d=1 spatial dimensions) or to the magnetoelectric polarizability (d=3 spatial dimensions). Finally, we also discuss topological field theories describing the spacetime theory of

  9. Magnetic relaxation, flux pinning and critical currents in superconductors

    International Nuclear Information System (INIS)

    Lichtenberger, K.S.

    1991-01-01

    A systematic study of the magnetic flux pinning properties in superconductors has been undertaken in an attempt to understand the differences between the flux creep behavior of classical superconductors and high-temperature superconductors (HTSC's). In HTSC's, the ratio of the effective flux pinning energy to the thermal energy, U 0 /kT, is much smaller than that of conventional superconductors, often approaching unity. This results in much larger creep rates in HTSC's than in conventional superconductors. It is necessary to find suitable models that describe flux creep in both classical superconductors and HTSC's. Results show that while these two classes of materials are quantitatively very different, a single pinning barrier mode adequately describes both, within the proper region of the H-T plane. The model is applied to a variety of superconductors and the results are contrasted. Although the H-T plane appears to be very different HTSC's than for conventional superconductors, qualitatively the same physics describes both. In HTSC's, near the upper critical field there exists a relatively wide region of superconducting fluctuations, followed successively by regions of thermodynamic reversibility, thermally assisted flux, flux creep, and finally rigid flux lattice where little, if any, motion of the flux lattice occurs. All of these regions are also present in conventional superconductors, but often much more difficult, especially the irreversibility transition and the fluctuation region. The central finding of the flux creep analysis is that the region of flux creep is defined as a band in the H-T plane in which 2 ≤ U 0 /kT ≤ 100, and that the flux creep model applies best within this band

  10. 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).

  11. Optical conductivity of iron-based superconductors

    International Nuclear Information System (INIS)

    Charnukha, A

    2014-01-01

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

  12. Electronic phase separation and high temperature superconductors

    International Nuclear Information System (INIS)

    Kivelson, S.A.

    1994-01-01

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

  13. Positron annihilation studies on high temperature superconductors

    International Nuclear Information System (INIS)

    Sundar, C.S.; Bharathi, A.

    1991-01-01

    The results of positron annihilation measurements as a function of temperature, across Tc, in a variety of high temperature superconductors such as Y-Ba-Cu-O (Y1237), Y-Ba-Cu-O (Y1248), Bi-Sr-Ca-Cu-O, Tl-Ba-Ca-Cu-O, Ba-K-Bi-O and Nd-Ce-Cu-O are presented. It is shown that the variation of annihilation parameters in the superconducting state is correlated with the diposition of the positron density distribution with respect to the superconducting CuO planes. An increase in positron lifetime is observed below Tc when the positrons probe the CuO planes whereas a decrease in lifetime is observed when the positron density overlaps predominantly with the apical oxygen atom. With this correlation, the different temperature variation of annihilation parameters, seen in the various high temperature superconductors, is understood in terms of a local charge transfer from the planar oxygen atom to the apical oxygen atom. The significance of these results in the context of various theoretical models of high temperature superconductivity is discussed. In addition, the application of positron annihilation spectroscopy to the study of oxygen defects in the Y-Ba-Cu-O, Bi-Sr-Ca-Cu-O and Nd-Ce-Cu-O is presented. (author). 53 refs., 17 figs., 2 tabs

  14. Advantageous grain boundaries in iron pnictide superconductors

    Science.gov (United States)

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

    2011-01-01

    High critical temperature superconductors have zero power consumption and could be used to produce ideal electric power lines. The principal obstacle in fabricating superconducting wires and tapes is grain boundaries—the misalignment of crystalline orientations at grain boundaries, which is unavoidable for polycrystals, largely deteriorates critical current density. Here we report that high critical temperature iron pnictide superconductors have advantages over cuprates with respect to these grain boundary issues. The transport properties through well-defined bicrystal grain boundary junctions with various misorientation angles (θGB) were systematically investigated for cobalt-doped BaFe2As2 (BaFe2As2:Co) epitaxial films fabricated on bicrystal substrates. The critical current density through bicrystal grain boundary (JcBGB) remained high (>1 MA cm−2) and nearly constant up to a critical angle θc of ∼9°, which is substantially larger than the θc of ∼5° for YBa2Cu3O7–δ. Even at θGB>θc, the decay of JcBGB was much slower than that of YBa2Cu3O7–δ. PMID:21811238

  15. High-temperature superconductors make major progress

    CERN Multimedia

    CERN Bulletin

    2014-01-01

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

  16. Voltage current characteristics of type III superconductors

    Science.gov (United States)

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

    1980-06-01

    An adequate description of voltage-current characteristics is important in order to understand the nature of high critical current for the electrodynamic construction of type-III superconductors and for commercial superconductor specification. Homogenious monofilament and multifilament Nb-Ti, Nb-Zr, Nb 3Sn wires were investigated in different ranges of magnetic field, temperature and current. The longitudinal electric field for homogenious wires may be described by E=J ρnexp- T c/T 0+ T/T 0+ B/B 0+ J/J 0, where To, Bo, Jo are the increasing parameters, which depend weakly on B and T, of the electric field. The shape of the voltage-current characteristics of multifilament wires, and the parameter's dependence on temperature and magnetic field may be explained qualitatively by the longitudinal heterogeneous nature of the filaments. A method of attaining the complete specification of the wire's electro-physical properties is proposed. It includes the traditional description of a critical surface (ie the surface corresponding to a certain conventional effective resistivity in T, B, J - space) and a description of any increasing parameter that depends on B and T.

  17. Charged vortices in high-Tc superconductors

    International Nuclear Information System (INIS)

    Matsuda, Y.; Kumagai, K.

    2002-01-01

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

  18. 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.

  19. Emergent Gauge Fields in Holographic Superconductors

    CERN Document Server

    Domènech, Oriol; Pomarol, Alex; Salvio, Alberto; Silva, Pedro J

    2010-01-01

    Holographic superconductors have been studied so far in the absence of dynamical electromagnetic fields, namely in the limit in which they coincide with holographic superfluids. It is possible, however, to introduce dynamical gauge fields if a Neumann-type boundary condition is imposed on the AdS-boundary. In 3+1 dimensions, the dual theory is a 2+1 dimensional CFT whose spectrum contains a massless gauge field, signaling the emergence of a gauge symmetry. We study the impact of a dynamical gauge field in vortex configurations where it is known to significantly affect the energetics and phase transitions. We calculate the critical magnetic fields H_c1 and H_c2, obtaining that holographic superconductors are of Type II (H_c1 < H_c2). We extend the study to 4+1 dimensions where the gauge field does not appear as an emergent phenomena, but can be introduced, by a proper renormalization, as an external dynamical field. We also compare our predictions with those arising from a Ginzburg-Landau theory and identif...

  20. Percolation effect in thick film superconductors

    International Nuclear Information System (INIS)

    Sali, R.; Harsanyi, G.

    1994-01-01

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

  1. Critical fields in high temperature superconductors

    International Nuclear Information System (INIS)

    Finnemore, D.K.

    1991-01-01

    An analysis of various methods to obtain the critical fields of the high temperature superconductors from experimental data is undertaken in order to find definitions of these variables that are consistent with the models used to define them. Characteristic critical fields of H c1 , H c2 and H c that occur in the Ginsburg-Landau theory are difficult to determine experimentally in the high temperature superconductors because there are additional physical phenomena that obscure the results. The lower critical field is difficult to measure because there are flux pinning and surface barrier effects to flux entry; the upper critical field is difficult because fluctuation effects are large at this phase boundary; the thermodynamic critical field is difficult because fluctuations make it difficult to know the field where the magnetization integral should be terminated. In addition to these critical fields there are at least two other cross-over fields. There is the so called irreversibility line where the vortices transform from a rigid flux line lattice to a fluid lattice and there is a second cross-over field associated with the transition from the fluctuation to the Abrikosov vortex regime. The presence of these new physical effects may require new vocabulary

  2. 2D electromagnetic modelling of superconductors

    International Nuclear Information System (INIS)

    Morandi, Antonio

    2012-01-01

    Some issues concerning the numerical analysis of superconductors are discussed and a novel approach to 2D modelling is proposed. Both axial and translational symmetric as well as current driven and voltage driven systems are examined in detail. The E–J power law is chosen instead of the critical state model as a constitutive relation of the material and the need to modify this relation in order to account for the normal state transition at high currents is discussed. A linear space reconstruction of the current density by means of nodal shape functions is used in order to build the finite dimensional model. A method to relax the tangential continuity of the current density, which is inherent to the discretization method used, is discussed. The performance of the proposed approach, both in terms of current distribution and AC loss, is evaluated with reference to some cases of practical interest involving composite materials. The role of the electric field as a natural state variable for superconducting problems is also pointed out. The use of the method as an alternative to the circuit approach or edge elements for modelling the superconductors is finally discussed. (paper)

  3. Dual superconductor models of color confinement

    CERN Document Server

    Ripka, Georges

    2004-01-01

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

  4. Kohn anomaly in phonon driven superconductors

    International Nuclear Information System (INIS)

    Das, M P; Chaudhury, R

    2014-01-01

    Anomalies often occur in the physical world. Sometimes quite unexpectedly anomalies may give rise to new insight to an unrecognized phenomenon. In this paper we shall discuss about Kohn anomaly in a conventional phonon-driven superconductor by using a microscopic approach. Recently Aynajian et al.'s experiment showed a striking feature; the energy of phonon at a particular wave-vector is almost exactly equal to twice the energy of the superconducting gap. Although the phonon mechanism of superconductivity is well known for many conventional superconductors, as has been noted by Scalapino, the new experimental results reveal a genuine puzzle. In our recent work we have presented a detailed theoretical analysis with the help of microscopic calculations to unravel this mystery. We probe this aspect of phonon behaviour from the properties of electronic polarizability function in the superconducting phase of a Fermi liquid metal, leading to the appearance of a Kohn singularity. We show the crossover to the standard Kohn anomaly of the normal phase for temperatures above the transition temperature. Our analysis provides a nearly complete explanation of this new experimentally discovered phenomenon. This report is a shorter version of our recent work in JPCM.

  5. Thermal voltage noise in layered superconductors

    International Nuclear Information System (INIS)

    Ashkenazy, V.D.; Jung, G.; Shapiro, B.Y.

    1995-01-01

    Thermal voltage noise in the mixed state of type-II superconductors has been calculated taking into account fluctuation modes of nonrigid vortices. It has been shown that bending of vortices leads to new effects in thermal-voltage-noise spectra at high frequencies. The power spectrum reflecting fluctuations of rigid vortices is suppressed at very low frequencies and saturates into a white spectrum at a characteristic frequency depending on the strip width. At high frequencies tilt modes of flexible vortices start to contribute to the fluctuating voltages and the power spectrum undergoes three subsequent magnitude increases, following ω 1/2 -, ω 2 -, and again ω 1/2 -like behavior before becoming white again. It has been shown that for layered superconductors of a moderate anisotropy the second ω 1/2 -like increase disappears at magnetic fields exceeding a certain threshold field corresponding to the crossover field between two-dimensional and three-dimensional vortex-lattice melting. Field dependencies of characteristic frequencies separating different regimes of spectral behavior have been evaluated and shown to be qualitatively different for low and high magnetic fields

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

    International Nuclear Information System (INIS)

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

    2006-01-01

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

  7. Magnetization studies in high temperature and conventional superconductors

    International Nuclear Information System (INIS)

    Grover, A.K.; Chaddah, P.

    1991-01-01

    In this paper, the authors state the contemporary view of the physical basis of a celebrated phenomenological model for hard superconductors. The authors highlight the qualitative and general predictions of this model relevant to various magnetic measurements. The authors give prescriptions to correlate data of different experiments with the predictions of the model with the intention of extracting information on material parameters, like J c (H), pinning potential, etc. These prescriptions will be illustrated with the data on both conventional and HTSC superconductors. The correlation of these data with the predictions of the model underscores the similarity in behaviour between the two classes of hard superconductors

  8. Experimental constraints on theories of high Tc superconductors

    International Nuclear Information System (INIS)

    Little, W.A.

    1989-01-01

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

  9. 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.

  10. Focusing and guiding intense electron beams by a superconductor tube

    International Nuclear Information System (INIS)

    Roth, P.

    1996-01-01

    An intense electron beam travelling axially through the opening of a superconductor tube was studied. Model calculations showed that the beam is focused by the superconductor tube when the space-charge effect of the beam electrons is compensated. The tube functions as a lens for electrons injected parallel to the tube axis and also for electrons having a small initial radial velocity component. The electron trajectories were computed, and the focal length of the superconductor tube was estimated. (author). 2 figs., 6 refs

  11. Application of superconductors to motors, generators, and transmission lines

    International Nuclear Information System (INIS)

    Kirtley, J.L.

    1989-01-01

    Superconductors are of interest to the designers of electric power equipment because they can carry current without loss, currents that are large enough to make very intense magnetic fields. This means that superconductors, used in suitable applications, can make electric power equipment smaller, lighter, more efficient, and perhaps with better dynamic response. Two specific applications are considered here: electric machinery (motors and generators) and transmission lines. The so-called high-T c superconductors will have beneficial impact on motors, generators, and transmission lines only if conductors with sufficient mechanical properties and current-carrying capabilities can be developed

  12. Holographic superconductor in the analytic hairy black hole

    International Nuclear Information System (INIS)

    Myung, Yun Soo; Park, Chanyong

    2011-01-01

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

  13. Fluxons in thin-film superconductor-insulator superlattices

    DEFF Research Database (Denmark)

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

    1993-01-01

    In a system of thin alternating layers of superconductors and insulators the equations describing static and dynamic fluxon solutions are derived. The approach, represented by a useful compact matrix form, is intended to describe systems fabricated for example of niobium or niobium-nitride thin...... 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...

  14. Voltage fluctuations in granular superconductors in the perpendicular configuration

    International Nuclear Information System (INIS)

    Gerashchenko, O V

    2003-01-01

    The spectral density of voltage fluctuations in granular YBa 2 Cu 3 O 7-δ superconductors in the perpendicular configuration has been studied in the flux flow mode. It has been found that, in this case, the 1/f-voltage noise observed depends weakly on temperature and is associated with motion of a magnetic flux in the superconductor. A comparison of the data obtained with the results of previous measurements in parallel configuration has shown that voltage noise is produced by a single common source, which is presumably associated with self-organization of the critical state in granular superconductors

  15. Behaviour of magnetic superconductors in a magnetic field

    International Nuclear Information System (INIS)

    Buzdin, A.I.

    1984-01-01

    The behaviour of magnetic superconductors with close ferromagnetic and superconducting transition temperatures in a magnetic field is considered. It is shown that on lowering of the temperature the superconducting transition changes from a second to first order transition. The respective critical fields and dependence of the magnetization on the magnetic field and temperature are found. The magnetization discontinuity in the vortex core in magnetic superconductors is noted. Due to this property and the relatively large scattering cross section, magnetic superconductors are convenient for studying the superconducting vortex lattice by neutron diffraction techniques

  16. Forces and energy dissipation in inhomogeneous non-equilibrium superconductors

    International Nuclear Information System (INIS)

    Poluehktov, Yu.M.; Slezov, V.V.

    1987-01-01

    The phenomenological theory of volume forces and dissipation processes in inhomogeneous non-equilibrium superconductors near temperature transition from the normal to superconducting state is constructed. The approach is based on application of dynamic equations of superconductivity formulated on the basis of the Lagrangian formalism. These equations are generalized the Ginzburg-Landau theory in the nonstationary non-equilibrium case for ''foul'' superconductors. The value estimations of volume forces arising in inhomogeneities during relaxation of an order parameter and when the electrical field is penetrated into the superconductor, are given

  17. Focusing and guiding intense electron beams by a superconductor tube

    Energy Technology Data Exchange (ETDEWEB)

    Roth, P

    1997-12-31

    An intense electron beam travelling axially through the opening of a superconductor tube was studied. Model calculations showed that the beam is focused by the superconductor tube when the space-charge effect of the beam electrons is compensated. The tube functions as a lens for electrons injected parallel to the tube axis and also for electrons having a small initial radial velocity component. The electron trajectories were computed, and the focal length of the superconductor tube was estimated. (author). 2 figs., 6 refs.

  18. Levitation of a magnet over a flat type II superconductor

    International Nuclear Information System (INIS)

    Hellman, F.; Gyorgy, E.M.; Johnson, D.W. Jr.; O'Bryan, H.M.; Sherwood, R.C.

    1988-01-01

    Levitation of a magnet over a type II superconductor where the field at the superconductor exceeds H/sub c/ 1 is described and shown. The penetration and pinning of the flux lines in the superconductor cause the position of the magnet to be stable over a flat disk; a complete Meissner effect would make this position unstable. Furthermore, the observed dependence of the height of levitation on such variables as the thickness of the superconducting disk and the size of the magnet are consistent with a model described in this paper based on the energy cost of flux penetration through vortices and inconsistent with a Meissner effect model

  19. Density of states and tunneling characteristics of layered superconductors

    International Nuclear Information System (INIS)

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

    1993-04-01

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

  20. Bi:Ge substitution - its effect on the structural and electrical properties of the Bi2212 superconductor

    International Nuclear Information System (INIS)

    Saligan, P.P.

    1997-03-01

    The critical temperature determined from dc resistance and ac magnetic susceptibility measurements, and the coherence length obtained from the of fluctuation conductivity of polycrystalline Bi 2-x Ge x Sr 2 CaCu 2 O 8 +δ were studied. The effect of sample quality was also studied by making two kinds of pellet samples: (1) by conventional sintering process and (2) by conventional sintering process followed annealing at high temperature. The rough phase diagram of Bi 2-x Ge x Sr 2 CaCu 2 O 8 +δ was constructed and it was found that from x=0 to x=0.3 a predominantly Bi2212 phase can be obtained. The critical temperature of the unsubstituted Bi 2 Sr 2 CaCu 2 O 8 +δ is sensitive to the cold press and anneal method. The resistive transition T c based on the maximum dR(T)dT of the as-sintered Bi 2 Sr 2 CaCu 2 O 8 +δ is about 74 K. The resistive T c of the cold-pressed-annealed samples either (1) remain near 74 K or (2) increase to approximately 85 K or (3) show two values at about 74 K and 85 K. A structural relaxation is observed in the Bi 2-x Ge x Sr 2 CaCu 2 O 8 +δ the c-axis decreases with increasing x and the a-axis increases at x=0.1 then settles back to its unsubstituted value at higher x. The as-sintered samples show an increasing resistive T c with x, 74 K for x=0 and 79 K for x>0. The resistive T c 's of the cold-pressed-annealed samples are almost independent of x, 85 K for x=0 and 87 K for x>0. The increase in the magnetic critical temperature induced by the cold press and anneal method is considerably larger compared to the increase in the resistive critical temperature, independent of the Bi:Ge substitution. An analysis of fluctuation conductivity just above T c using the Aslamasov-Larkin model for two-dimensional superconductors and the Lawrence-Doniach model for layered superconductors was done. The Aslamasov-Larkin model gives the thickness of the two dimensional superconductor to be ∼34 A also independent of the Bi:Ge substitution. The Lawrence