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John A. Schlueter - One of the best experts on this subject based on the ideXlab platform.

  • location of gap nodes in the Organic Superconductors κ et 2cu ncs 2 and κ et 2cu n cn 2 br determined by magnetocalorimetry
    Physical Review B, 2010
    Co-Authors: Liam Malone, John A. Schlueter, O J Taylor, A Carrington
    Abstract:

    We report specific-heat measurements of the Organic Superconductors {kappa}-(ET){sub 2}Cu(NCS){sub 2} and {kappa}-(ET){sub 2}Cu[N(CN){sub 2}]Br. When the magnetic field is rotated in the highly conducting planes at low temperature (T = 0.4 K), we observe clear oscillations of specific heat which have a strong fourfold component. The observed strong field and temperature dependence of this fourfold component identifies it as originating from nodes in the superconducting energy gap which point along the in-plane crystal axes (d{sub xy} symmetry).

  • interplane penetration depth and coherent transport in Organic Superconductors
    Physical Review B, 2009
    Co-Authors: T Olheiser, D D Lawrie, R W Giannetta, John A. Schlueter
    Abstract:

    Measurements of the interlayer penetration depth {lambda}{sub {perpendicular}} have been performed on single crystals of the Organic Superconductors {kappa}-(ET){sub 2}Cu[N(CN){sub 2}]Br and {kappa}-(ET){sub 2}Cu(NCS){sub 2}. We find that {lambda}{sub {perpendicular}}(0){approx}130 {micro}m for both materials. The normalized superfluid density {rho}{sub {perpendicular}} = [{lambda}{sub {perpendicular}}(0)/{lambda}{sub {perpendicular}} (T)]{sup 2} may be fit equally well to a power law 1{rho}{sub {perpendicular}} {approx} T{sup n} with n = 1.3-1.5 or to the form 1{rho}{sub {perpendicular}} = {alpha}(t{sup 2}/T{sub c})/(T+T*), consistent with a d-wave pairing state with impurity scattering. The data imply coherent transport between conducting planes, in agreement with recent magnetoresistive measurements [J. Singleton, P. A. Goddard, A. Ardavan, N. Harrison, S. J. Blundell, J. A. Schlueter, and A. M. Kini, Phys. Rev. Lett. 88, 037001 (2002)] and in contrast to the copper oxides.

  • The intrinsically broad superconducting to normal transition in Organic Superconductors
    Synthetic Metals, 2003
    Co-Authors: John Singleton, John A. Schlueter, Charles H. Mielke, Neil Harrison, Aravinda M. Kini
    Abstract:

    Abstract Although Organic Superconductors such as κ-(BEDT-TTF)2Cu(NCS)2 are in the clean limit, the superconducting transition is intrinsically broad (e.g. ∼1 K wide for Tc≈10 K). We propose that this is due to the extreme anisotropy of these materials, which greatly exacerbates the statistical effects of fluctuations.

  • thermodynamic properties of quasi two dimensional Organic Superconductors
    Synthetic Metals, 2003
    Co-Authors: J Wosnitza, S Wanka, J Hagel, M Reibelt, D Schweitzer, John A. Schlueter
    Abstract:

    Abstract High-resolution specific-heat data of the Organic superconductor κ -(ET) 2 Cu(NCS) 2 ( T c =9.3 K) can reasonably well be described by strong-coupling BCS theory. In line with our previous results for three other Organic Superconductors the electronic contribution of the specific heat vanishes exponentially towards low temperatures providing evidence for a fully-gapped order parameter. The thermal conductivity κ of κ -(ET) 2 Cu[N(CN) 2 ]Br increases strongly in the superconducting state below T c =11.5 K indicating the substantial scattering of phonons by quasiparticles in the normal state. Down to the lowest temperatures ( T ≈0.25 K) no T 3 dependence of κ is observed.

  • Raman studies of Organic Superconductors
    Synthetic Metals, 2001
    Co-Authors: John E. Eldridge, Aravinda M. Kini, Hsien-hau Wang, John A. Schlueter
    Abstract:

    The temperature-dependence of the frequency of one of the components of the v9 (A g ) doublet in the Raman spectra of several Organic Superconductors has been measured. The frequency of this mode was observed to soften below 100K, in those compounds in which NMR data indicates antiferromagnetic oscillations in the same temperature range. This is evidence for spin-phonon interactions.

G. Saito - One of the best experts on this subject based on the ideXlab platform.

  • Organic Superconductors
    Chemical Record, 2011
    Co-Authors: G. Saito, Yukihiro Yoshida
    Abstract:

    The present status of Organic Superconductors of charge-transfer (CT) type based on donor molecules is reviewed. Along with the superconducting phases of such materials and also of oxide Superconductors, reside spin-ordered phases such as spin-density wave (SDW) and antiferromagnetic (AF) phases. We briefly describe the recent development of Superconductors having a superconducting phase next to a spin-disorder state (quantum spin liquid state). In addition to the CT type Superconductors, there are a few single-component Superconductors under high pressure.

  • Mixed state properties of Organic Superconductors
    Physica B-condensed Matter, 1994
    Co-Authors: Takehiko Ishiguro, Yu.v. Sushko, A. Otsuka, G. Saito
    Abstract:

    Abstract The physical properties of Organic Superconductors under a magnetic field are reviewed. With the aid of recent advances in theories for phenomenology, the superconductivity transitions of BEDT-TTF salts and A3C60 are analyzed by taking account of fluctuation, and thereby the physical parameters are reevaluated, while (TMTSF)2X can be treated by an anisotropic effective mass tensor model. Other properties relevant to vortex dynamics and paramagnetic pair breaking effect are also mentioned.

  • Organic Superconductors based on sulfur and selenium compounds
    Phosphorus Sulfur and Silicon and The Related Elements, 1992
    Co-Authors: G. Saito
    Abstract:

    Abstract This paper describes brief background and outline of the Organic Superconductors based on TMTSF and BEDT-TTF. Especially we discuss the structural and physical properties of the specific Organic Superconductors (TMTSF)2C104 and K-(BEDT-TTF)2Cu(NCS)2, emphasizing their dimensionality characteristics.

  • new ambient pressure Organic Superconductors based on bedt ttf cu n cn 2 and cn with tc 10 7k and 3 8k
    Solid State Communications, 1991
    Co-Authors: Tokutaro Komatsu, Nozomu Matsukawa, Masami Kusunoki, Hideki Yamochi, G. Saito, Toshikazu Nakamura, T. Ishiguro, Ken Ichi Sakaguchi
    Abstract:

    Abstract Syntheses and superconductivities of two new ambient-pressure Organic Superconductors of BEDT-TTF with Cu, N(CN)2 and CN are described. The resistivity measurements showed Tc (midpoint of resistive transition) of 10.7K (high Tc salt) and 3.8K (low Tc salt) while the SQUID measurements showed the onset of superconductivity at 10.5–11.0K and >3.5K, respectively. They have almost the same lattice parameters but slightly different diffraction patterns and crystal densities.

  • recent progress in Organic Superconductors
    Physica B-condensed Matter, 1991
    Co-Authors: G. Saito, Tokutaro Komatsu, Hideki Yamochi, Toshikazu Nakamura, Kokichi Oshima, Hatsumi Mori, Masako Nakashima
    Abstract:

    Abstract This paper describes part of the present status of the research in Japan on the crystal structures and physical properties of Organic Superconductors κ-(BEDT-TTF) 2 [Cu(NCS) 2 ], κ-(BETD-TTF) 2 Cu[N(CN) 2 ]Br, α-(BEDT-TTF) 2 [NH 4 Hg(SCN) 4 ] and other related materials. The Cu(NCS) 2 salt shows an inverse isotope effect. The Cu[N(CN) 2 ]Br salt shows T c of 11.7 K. H c2 value and lattice parameters of these κ-type salts are compared.

Kazuhiko Kuroki - One of the best experts on this subject based on the ideXlab platform.

  • recent topics of Organic Superconductors
    Journal of the Physical Society of Japan, 2012
    Co-Authors: Arzhang Ardavan, Hatsumi Mori, Kazuhiko Kuroki, Seiichi Kagoshima, S E Brown, Kazushi Kanoda, Masao Ogata, J Wosnitza
    Abstract:

    Recent developments in research into superconductivity in Organic materials are reviewed. In the epoch-defining quasi-one-dimensional TMTSF Superconductors with T c ∼1 K, T c decreases monotonicall...

  • pairing symmetry competition in Organic Superconductors
    Journal of the Physical Society of Japan, 2006
    Co-Authors: Kazuhiko Kuroki
    Abstract:

    A review is given on theoretical studies concerning the pairing symmetry in Organic Superconductors. In particular, we focus on (TMTSF) 2 X and κ-(BEDT-TTF) 2 X, in which the pairing symmetry has been extensively studied both experimentally and theoretically. Possibilities of various pairing symmetry candidates and their possible microscopic origin are discussed. Also some tests for determining the actual pairing symmtery are surveyed.

  • effect of interchain interaction on pairing symmetry competition in Organic Superconductors tmtsf 2x
    Journal of the Physical Society of Japan, 2005
    Co-Authors: Kazuhiko Kuroki, Yukio Tanaka
    Abstract:

    We investigate the effect of interchain repulsive interaction on the pairing symmetry competition in quasi-one-dimensional Organic Superconductors (TMTSF) 2 X by applying random phase approximation and quantum Monte Carlo calculation to an extended Hubbard model. We find that interchain repulsive interaction enhances the 2 k F charge fluctuations, thereby making the possibility of spin-triplet f -wave pairing dominating over spin-singlet d -wave pairing realistic.

  • microscopic theory of spin triplet f wave pairing in quasi one dimensional Organic Superconductors
    Physical Review B, 2004
    Co-Authors: Yukio Tanaka, Kazuhiko Kuroki
    Abstract:

    We present a microscopic theory of fluctuation-mediated pairing mechanism in Organic Superconductors ${(\mathrm{TMTSF})}_{2}X$, where the experimentally observed coexistence of $2{k}_{F}$ charge fluctuation and $2{k}_{F}$ spin fluctuation is naturally taken into account. We have studied, within the random phase approximation, the extended Hubbard model at quarter filling on a quasi-one-dimensional lattice, where we consider the off-site repulsive interaction up to third next-nearest neighbors along with the on-site repulsion. The results show that spin-triplet $f$-wave-like pairing can be realized in this system, dominating over singlet $d$-wave-like pairing, if $2{k}_{F}$ spin and $2{k}_{F}$ charge fluctuations coexist.

  • zero bias conductance peak splitting due to multiband effect in tunneling spectroscopy of Organic Superconductors
    Physical Review B, 2003
    Co-Authors: Y Tanuma, Kazuhiko Kuroki, Yukio Tanaka, Satoshi Kashiwaya
    Abstract:

    We study how the multiplicity of the Fermi surface affects the zero-bias peak in conductance spectra of tunneling spectroscopy. As case studies, we consider models for Organic Superconductors $\ensuremath{\kappa}\ensuremath{-}(\mathrm{BEDT}\ensuremath{-}\mathrm{TTF}{)}_{2}\mathrm{Cu}(\mathrm{NCS}{)}_{2}$ and $(\mathrm{TMTSF}{)}_{2}{\mathrm{ClO}}_{4}.$ We find that the multiplicity of the Fermi surfaces can lead to a splitting of the zero-bias conductance peak (ZBCP). We propose that the presence/absence of the ZBCP splitting is used as a probe to distinguish the pairing symmetry in $\ensuremath{\kappa}\ensuremath{-}(\mathrm{BEDT}\ensuremath{-}\mathrm{TTF}{)}_{2}\mathrm{Cu}(\mathrm{NCS}{)}_{2}.$

Hideki Yamochi - One of the best experts on this subject based on the ideXlab platform.

  • muon spin relaxation measurements of magnetic penetration depth in Organic Superconductors bedt ttf 2 x x cu ncs 2 and cu
    Physical Review Letters, 1992
    Co-Authors: L P Le, G M Luke, B J Sternlieb, W D Wu, Y J Uemura, J H Brewer, T M Riseman, C E Stronach, G Saito, Hideki Yamochi
    Abstract:

    The magnetic-field penetration depth λ in the Organic Superconductors κ-(BEDT-TTF) 2 Cu(NCS) 2 and κ-(BEDT-TTF) 2 Cu[N(CN) 2 ]Br has been measured over a wide temperature region 20 mK≤T≤15 K via the muon-spin-relaxation technique. Linear variation of λ with T at low temperatures, found in both systems, is consistent with anisotropic superconducting pairings with line nodes in the energy gap. In the latter compound, we oberve flux depinning at T∼5 K, well below T c =12 K

  • EXAFS study in Organic Superconductors
    Physica C-superconductivity and Its Applications, 1991
    Co-Authors: Kokichi Oshima, Hironobu Maeda, Hitoshi Yamazaki, Hiroshi Maruyama, Hidekazu Kimura, Manabu Fujita, Hatsumi Mori, Shoji Tanaka, Hideki Yamochi
    Abstract:

    Abstract Cu K-edge extended X-ray absorption fine structure (EXAFS) measurements have been made in the Organic Superconductors, ϰ-(BEDT-TTF)2Cu(NCS)2 and ϰ-(BEDT-TTF)2Cu[N(CN)2]Br from 300 K down to 20 K. Some anomalies of the local structure were found from the temperature dependence of EXAFS signal, in particular nearest neighbors distance (R). The anomalies can be ascribed to the hydrogen bonds between cations and anions.

  • new ambient pressure Organic Superconductors based on bedt ttf cu n cn 2 and cn with tc 10 7k and 3 8k
    Solid State Communications, 1991
    Co-Authors: Tokutaro Komatsu, Nozomu Matsukawa, Masami Kusunoki, Hideki Yamochi, G. Saito, Toshikazu Nakamura, T. Ishiguro, Ken Ichi Sakaguchi
    Abstract:

    Abstract Syntheses and superconductivities of two new ambient-pressure Organic Superconductors of BEDT-TTF with Cu, N(CN)2 and CN are described. The resistivity measurements showed Tc (midpoint of resistive transition) of 10.7K (high Tc salt) and 3.8K (low Tc salt) while the SQUID measurements showed the onset of superconductivity at 10.5–11.0K and >3.5K, respectively. They have almost the same lattice parameters but slightly different diffraction patterns and crystal densities.

  • recent progress in Organic Superconductors
    Physica B-condensed Matter, 1991
    Co-Authors: G. Saito, Tokutaro Komatsu, Hideki Yamochi, Toshikazu Nakamura, Kokichi Oshima, Hatsumi Mori, Masako Nakashima
    Abstract:

    Abstract This paper describes part of the present status of the research in Japan on the crystal structures and physical properties of Organic Superconductors κ-(BEDT-TTF) 2 [Cu(NCS) 2 ], κ-(BETD-TTF) 2 Cu[N(CN) 2 ]Br, α-(BEDT-TTF) 2 [NH 4 Hg(SCN) 4 ] and other related materials. The Cu(NCS) 2 salt shows an inverse isotope effect. The Cu[N(CN) 2 ]Br salt shows T c of 11.7 K. H c2 value and lattice parameters of these κ-type salts are compared.

  • New ambient-pressure Organic Superconductors based on BEDT-TTF, Cu, N(CN)2and CN with Tc= 10.7K and 3.8K
    Solid State Communications, 1991
    Co-Authors: Tokutaro Komatsu, Nozomu Matsukawa, Masami Kusunoki, Hiroshi Ito, Takehiko Ishiguro, Hideki Yamochi, G. Saito, Toshikazu Nakamura, Ken Ichi Sakaguchi
    Abstract:

    Syntheses and superconductivities of two new ambient-pressure Organic Superconductors of BEDT-TTF with Cu, N(CN)2and CN are described. The resistivity measurements showed Tc (midpoint of resistive transition) of 10.7K (high Tc salt) and 3.8K (low Tc salt) while the SQUID measurements showed the onset of superconductivity at 10.5-11.0K and >3.5K, respectively. They have almost the same lattice parameters but slightly different diffraction patterns and crystal densities. © 1991.

John Singleton - One of the best experts on this subject based on the ideXlab platform.

  • The intrinsically broad superconducting to normal transition in Organic Superconductors
    Synthetic Metals, 2003
    Co-Authors: John Singleton, John A. Schlueter, Charles H. Mielke, Neil Harrison, Aravinda M. Kini
    Abstract:

    Abstract Although Organic Superconductors such as κ-(BEDT-TTF)2Cu(NCS)2 are in the clean limit, the superconducting transition is intrinsically broad (e.g. ∼1 K wide for Tc≈10 K). We propose that this is due to the extreme anisotropy of these materials, which greatly exacerbates the statistical effects of fluctuations.

  • quasi two dimensional Organic Superconductors a review
    Contemporary Physics, 2002
    Co-Authors: John Singleton, C H Mielke
    Abstract:

    Quasi-two-dimensional Organic Superconductors are reviewed. These systems exhibit many interesting phenomena, including reduced dimensionality, strong electron - electron and electron - phonon interactions and the proximity of antiferromagnetism, insulator states and superconductivity. Moreover, it has been possible to measure the electronic bands of many of the Organics in great detail, in contrast to the situation in other well-known systems in which similar phenomena occur. The crystal structure and normal-state properties of the Organics are described before the experimental evidence is presented for and against exotic superconductivity mediated by antiferromagnetic fluctuations. Finally, three instances of field-induced unconventional superconductivity are described.

  • millimetre wave measurements of the bulk magnetoconductivity of anisotropic metals application to the Organic Superconductors κ bedt ttf 2cu ncs 2 and β bedt ttf 2sf5ch2cf2so3 bedt ttf bis ethylene dithio tetrathiafulvalene
    Journal of Physics: Condensed Matter, 2001
    Co-Authors: Marije J Schrama, John A. Schlueter, John Singleton, R S Edwards, Arzhang Ardavan, E Rzepniewski, Robert Harris, M Gross, Mohamedally Kurmoo
    Abstract:

    We describe a novel resonant cavity system which allows the bulk magneto-conductivity of single crystals of anisotropic metals to be measured at GHz frequencies. The cavity can be made to rotate in a static magnetic field, permitting detailed studies of the dependence on the magnetic field orientation of the high-frequency magnetoconductivity. In this paper, the apparatus is used to measure the Fermi-surface topology of two Organic Superconductors; the details revealed are inaccessible to conventional fermiological techniques such as the de Haas-van Alphen effect. In κ-(BEDT-TTF)2Cu(NCS)2, Fermi-surface traversal resonances (FTRs) are observed. The angle dependence of the FTRs shows that the quasi-one-dimensional (Q1D) Fermi sheets of this material possess two distinct corrugations, with corrugation axes making angles of 17.3° and -19.4° with the ka-axis. Such data form important input parameters for current models of superconductivity in the Organics, which invoke spin-density-wave-like fluctuations caused by partial nesting of the Q1D Fermi sheets. In β''-(BEDT-TTF)2SF5CH2CF2SO3, cyclotron resonance is observed, along with its second and third harmonics. The detailed angle dependence of the intensities of the various cyclotron harmonics allows the elongation and orientation of the closed section of the Fermi surface to be deduced, and strongly suggests that the interplane transport is coherent in this material. The effective mass deduced from the cyclotron resonance measurements is greater than that determined from magnetic quantum oscillations, in agreement with recent theoretical predictions.