• Search Research Projects
  • Search Researchers
  • How to Use
  1. Back to project page

2005 Fiscal Year Final Research Report Summary

Tunneling study of multiple order parameter and electron-phonon interaction in the high temperature layered boride superconductor

Research Project

Project/Area Number 15540346
Research Category

Grant-in-Aid for Scientific Research (C)

Allocation TypeSingle-year Grants
Section一般
Research Field Condensed matter physics II
Research InstitutionHIROSHIMA UNIVERSITY

Principal Investigator

EKINO Toshikazu  Hiroshima University, Faculty of Integrated Arts and Sciences, Associate Professor, 総合科学部, 助教授 (40185103)

Project Period (FY) 2003 – 2005
Keywordselectron tunneling / energy gap / electron-phonon interaction / boride superconductor / 2 band superconductivity / correlated 2 gap model
Research Abstract

We have investigated the high temperature layered boride superconductor MgB_2 by electron tunneling and point contact spectroscopy.
The tunneling conductance at low temperatures shows clear multiple-gap structures, which are described by the two-gap model proposed by McMillan. This indicates that the multiple gaps are due to non-trivial origin. We call this model as "the correlated two gap" model. The specific gap values are Δ=2-2.5,5-7,10-12 meV that exist up to T_c=39K. The gap ratio 2Δ/k_BT_c=5-6 for the largest gap indicates extremely strong coupling, which is the largest one among non-copper superconductors. On the other hand, the smallest gap giving the ratio 1.2-1.5 is surprisingly smaller than the BCS one 3.5, indicating an immature gap feature from induced superconductivity. From the temperature variations, we attribute that the middle gap can be due to the proximity effect. From these analyses, it is possible to consider that the largest and smallest gaps are coming from the 2 band superconductivity arising from boron σ and π bands.
The magnetic-field dependence of the gaps makes clear distinction between the gaps, namely, the larger gap vanishes at the higher critical field. This is in contrast to the temperature dependence of these gaps showing the same critical temperature. The extrapolated critical fields of 18-23 T and 7-11 T for the largest and smallest gaps correspond to in-plane and c-axis upper critical fields, respectively. These agreements indicate that the multiple gaps are intimately related to the layered structure, and the largest gap is predominant to MgB_2.
Point- contact spectra show that the peak positions are in agreement with the phonon spectra from the neutron scattering experiments. More significantly, the high-energy boron vibration modes around 60-90 meV are suggested to play an important role in the electron-phonon interaction in MgB_2.

  • Research Products

    (45 results)

All 2006 2005 2004 2003

All Journal Article (45 results)

  • [Journal Article] Spin dependent tunneling current in Junctions involving CDW metals2006

    • Author(s)
      T.Ekino
    • Journal Title

      Japanese Journal of Applied Physics 45

      Pages: 2242-2245

    • Description
      「研究成果報告書概要(和文)」より
  • [Journal Article] Tunneling measurements of CeRhAs single crystal2006

    • Author(s)
      T.Ekino
    • Journal Title

      Physica B (印刷中)

    • Description
      「研究成果報告書概要(和文)」より
  • [Journal Article] Electron tunneling experiments on La-substituted Kondo semiconductor CeRhAs2006

    • Author(s)
      T.Ekino
    • Journal Title

      Physica B (印刷中)

    • Description
      「研究成果報告書概要(和文)」より
  • [Journal Article] Tunneling spectroscopy of AlB_2 type silicide superconductor CaAlSi2006

    • Author(s)
      T.Takasaki
    • Journal Title

      Physica B (印刷中)

    • Description
      「研究成果報告書概要(和文)」より
  • [Journal Article] Tunneling spectroscopy of the electron-doped superconductors MNCl_0.7 (M=Hf,Zr)2006

    • Author(s)
      T.Takasaki
    • Journal Title

      Physica C (印刷中)

    • Description
      「研究成果報告書概要(和文)」より
  • [Journal Article] Tunneling spectroscopy of single-crystal clathrate Ba_8Ga_16Sn_302006

    • Author(s)
      R.A.Ribeiro
    • Journal Title

      Physica B (印刷中)

    • Description
      「研究成果報告書概要(和文)」より
  • [Journal Article] Spin dependent tunneling current in junctions involving CDW metals2006

    • Author(s)
      T.Ekino
    • Journal Title

      Japanese Journal of Applied Physics 45

      Pages: 2242-2245

    • Description
      「研究成果報告書概要(欧文)」より
  • [Journal Article] Tunneling measurements of CeRhAs single crystal2006

    • Author(s)
      T.Ekino
    • Journal Title

      Physica B (in press)

    • Description
      「研究成果報告書概要(欧文)」より
  • [Journal Article] Electron tunneling experiments on La-substituted Kondo semiconductor CeRhAs2006

    • Author(s)
      T.Ekino
    • Journal Title

      Physica B (in press)

    • Description
      「研究成果報告書概要(欧文)」より
  • [Journal Article] Tunneling spectroscopy of AlB_2 type silicide superconductor CaAlSi2006

    • Author(s)
      T.Takasaki
    • Journal Title

      Physica B (in press)

    • Description
      「研究成果報告書概要(欧文)」より
  • [Journal Article] Tunneling spectroscopy of single-crystal clathrate Ba_8Ga_<16>Sn_<30>2006

    • Author(s)
      R.A.Ribeiro
    • Journal Title

      Physica B (in press)

    • Description
      「研究成果報告書概要(欧文)」より
  • [Journal Article] Spatially heterogeneous character of superconductivity in MgB_2 as revealed by local probe and bulk measurements,2005

    • Author(s)
      T.Ekino
    • Journal Title

      Physica C 426-431

      Pages: 230-233

    • Description
      「研究成果報告書概要(和文)」より
  • [Journal Article] Spin-polarized electron tunneling between charge-density-wave metals2005

    • Author(s)
      T.Ekino
    • Journal Title

      Low Temperature Physics 31

      Pages: 59-72

    • Description
      「研究成果報告書概要(和文)」より
  • [Journal Article] Pauli effect of the magnetic field on superconductors with charge-density waves2005

    • Author(s)
      T.Ekino
    • Journal Title

      Low Temperature Physics 31

      Pages: 41-46

    • Description
      「研究成果報告書概要(和文)」より
  • [Journal Article] Manifestations of inhomogeneity in MgB_2 : From specific heat to tunnel measurements2005

    • Author(s)
      T.Ekino
    • Journal Title

      Physica B 359-361

      Pages: 460-462

    • Description
      「研究成果報告書概要(和文)」より
  • [Journal Article] Enhancement of the paramagnetic limit for superconductors with charge-density waves2005

    • Author(s)
      T.Ekino
    • Journal Title

      Physica C 426-431

      Pages: 325-329

    • Description
      「研究成果報告書概要(和文)」より
  • [Journal Article] Point-contact spectroscopy measurements of binary superconductor MgB_22005

    • Author(s)
      T.Takasaki
    • Journal Title

      Physica C 426-431

      Pages: 300-303

    • Description
      「研究成果報告書概要(和文)」より
  • [Journal Article] Break-junction tunneling spectra of MgB_2 : influence of boron quality2005

    • Author(s)
      R.A.Ribeiro
    • Journal Title

      Physica C 426-431

      Pages: 450-453

    • Description
      「研究成果報告書概要(和文)」より
  • [Journal Article] Tunneling spectroscopy of deintercalated layered nitride superconductors ZrNCl_0.72005

    • Author(s)
      T.Takasaki
    • Journal Title

      Journal of the Physical Society of Japan 74

      Pages: 2586-2591

    • Description
      「研究成果報告書概要(和文)」より
  • [Journal Article] Current carrier localization and coulomb gap observed in SrPbO_3-6 by transport measurements and tunnel spectroscopy2005

    • Author(s)
      V.A.Drozd
    • Journal Title

      Journal of Physics; Condensed Matter 17

      Pages: 7407-7416

    • Description
      「研究成果報告書概要(和文)」より
  • [Journal Article] Electrical resistivity and tunneling anomalies in CeCuAs_22005

    • Author(s)
      E.V.Sampathkumaran
    • Journal Title

      Physica B 359-361

      Pages: 108-110

    • Description
      「研究成果報告書概要(和文)」より
  • [Journal Article] Possible application of carbon nanotubes to the field emission electron source for portable betatrons2005

    • Author(s)
      T.Ohnishi
    • Journal Title

      Nuclear Instruments and Methods in Physics Research A 539

      Pages: 16-24

    • Description
      「研究成果報告書概要(和文)」より
  • [Journal Article] Spatially heterogeneous character of superconductivity in MgB_2 as revealed by local probe and bulk measurements2005

    • Author(s)
      T.Ekino
    • Journal Title

      Physica C 426-431

      Pages: 230-233

    • Description
      「研究成果報告書概要(欧文)」より
  • [Journal Article] Pauli effect of the magnetic field on superconductors with charge-density waves2005

    • Author(s)
      T.Ekino
    • Journal Title

      Low temperature Physics 31

      Pages: 41-46

    • Description
      「研究成果報告書概要(欧文)」より
  • [Journal Article] Manifestation of inhomogeneity in MgB2 : From specific heat to tunnel measurements2005

    • Author(s)
      T.Ekino
    • Journal Title

      Physica B 359-361

      Pages: 460-462

    • Description
      「研究成果報告書概要(欧文)」より
  • [Journal Article] Point-contact spectroscopy measurements of bunary superconductor MgB_22005

    • Author(s)
      T.Takasaki
    • Journal Title

      Physica C 426-431

      Pages: 300-303

    • Description
      「研究成果報告書概要(欧文)」より
  • [Journal Article] Break-junction tunneling spectra of MgB_2 : Influence of boron quality2005

    • Author(s)
      R.A.Ribeiro
    • Journal Title

      Physica C 436-431

      Pages: 450-453

    • Description
      「研究成果報告書概要(欧文)」より
  • [Journal Article] Tunneling spectroscopy of deintercalated layered nitride superconductor ZrNCl_<0.7>2005

    • Author(s)
      T.Takasaki
    • Journal Title

      Journal of the Physical Society of Japan 74

      Pages: 2586-2591

    • Description
      「研究成果報告書概要(欧文)」より
  • [Journal Article] Current carrier localization and Coulomb gap observed in SrPbO_<3-δ> by transport measurements and tunnel spectroscopy2005

    • Author(s)
      V.A.Drozd
    • Journal Title

      Journal of Physics : Condensed Matter 17

      Pages: 7407-7416

    • Description
      「研究成果報告書概要(欧文)」より
  • [Journal Article] Possible application of carbon nanotubes to the field emission electron source for portable betatrons2005

    • Author(s)
      T.Ohnishi
    • Journal Title

      Nuclear Instruments and Models in Physics Research A 539

      Pages: 16-24

    • Description
      「研究成果報告書概要(欧文)」より
  • [Journal Article] Tunneling measurements of superconducting NbB_22004

    • Author(s)
      T.Ekino
    • Journal Title

      Physica C 408-410

      Pages: 828-829

    • Description
      「研究成果報告書概要(和文)」より
  • [Journal Article] Multiple-gap features from break junction tunneling in the superconducting MgB_22004

    • Author(s)
      T.Takasaki
    • Journal Title

      Journal of the Physical Society of Japan 73

      Pages: 1902-1913

    • Description
      「研究成果報告書概要(和文)」より
  • [Journal Article] Formation of midgap states and ferromagnetism in semiconducting CaB_62004

    • Author(s)
      B.K.Cho
    • Journal Title

      Physical Review B 69

      Pages: 113202(1-4)

    • Description
      「研究成果報告書概要(和文)」より
  • [Journal Article] Tunneling currents in charge-density-wave metal-insulator-charge-density-wave metal structures : Magnetic field-induced spin-splitting of the conductance peaks2004

    • Author(s)
      A.M.Gabovich
    • Journal Title

      Journal of the Physical Society of Japan 73

      Pages: 1931-1937

    • Description
      「研究成果報告書概要(和文)」より
  • [Journal Article] Enhanced paramagnetic limit of the upper critical magnetic field for superconductors with charge-density waves2004

    • Author(s)
      A.M.Gabovich
    • Journal Title

      Journal of Physics; Condensed Matter 16

      Pages: 3681-3690

    • Description
      「研究成果報告書概要(和文)」より
  • [Journal Article] Multiple gap feature from break junction tunneling in the superconducting MgB_22004

    • Author(s)
      T.Takasaki
    • Journal Title

      Journal of the Physical Society of Japan 73

      Pages: 1902-1913

    • Description
      「研究成果報告書概要(欧文)」より
  • [Journal Article] Enhanced paramagnetic limit of the upper critical magnetic field for superconductors with charge-density waves2004

    • Author(s)
      A.M.Gabovich
    • Journal Title

      Journal of Physics ; Condensed Matter 16

      Pages: 3681-3690

    • Description
      「研究成果報告書概要(欧文)」より
  • [Journal Article] Tunneling spectroscopy of the superconducting gap in MgB_22003

    • Author(s)
      T.Ekino
    • Journal Title

      Physical Review B 67

      Pages: 094504(1-6)

    • Description
      「研究成果報告書概要(和文)」より
  • [Journal Article] Tunneling spectroscopy of the energy gap in MgB_2 under magnetic fields2003

    • Author(s)
      T.Ekino
    • Journal Title

      Acta Physica Polonica 24

      Pages: 523-527

    • Description
      「研究成果報告書概要(和文)」より
  • [Journal Article] Tunneling spectroscopy of MgB_2 and Li_0.5(THF)_jHfNCl2003

    • Author(s)
      T.Ekino
    • Journal Title

      Physica B 328 (2003) 23-35 328

      Pages: 23-25

    • Description
      「研究成果報告書概要(和文)」より
  • [Journal Article] Tunneling spectroscopy of the electron doped layered superconductor Li_0.48(THF)_0.3HfNCl2003

    • Author(s)
      T.Ekino
    • Journal Title

      Physica C 388-389

      Pages: 573-574

    • Description
      「研究成果報告書概要(和文)」より
  • [Journal Article] Multiple-gap structure of the binary superconductor MgB_22003

    • Author(s)
      T.Takasaki
    • Journal Title

      Physica C 388-389

      Pages: 147-148

    • Description
      「研究成果報告書概要(和文)」より
  • [Journal Article] Tunneling spectroscopy of the energy gap in MgB_2 under magnetic fields2003

    • Author(s)
      T.Ekino
    • Journal Title

      Acta Physica Polonia 34

      Pages: 523-527

    • Description
      「研究成果報告書概要(欧文)」より
  • [Journal Article] Tunneling spectroscopy of MgB_2 and Li_<0.5>(THF)_γHfNCl2003

    • Author(s)
      T.Ekino
    • Journal Title

      Physica B 328

      Pages: 23-25

    • Description
      「研究成果報告書概要(欧文)」より
  • [Journal Article] Tunneling spectroscopy of the electron doped layered superconductor Li_<0.48>(THF)_<0.3>HfNCl2003

    • Author(s)
      T.Ekino
    • Journal Title

      Physica C 388-389

      Pages: 573-574

    • Description
      「研究成果報告書概要(欧文)」より

URL: 

Published: 2007-12-13  

Information User Guide FAQ News Terms of Use Attribution of KAKENHI

Powered by NII kakenhi