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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
Project Status Completed (Fiscal Year 2005)
Budget Amount *help
¥3,500,000 (Direct Cost: ¥3,500,000)
Fiscal Year 2005: ¥900,000 (Direct Cost: ¥900,000)
Fiscal Year 2004: ¥1,600,000 (Direct Cost: ¥1,600,000)
Fiscal Year 2003: ¥1,000,000 (Direct Cost: ¥1,000,000)
Keywordselectron tunneling / energy gap / electron-phonon interaction / boride superconductor / 2 band superconductivity / correlated 2 gap model / STM / 強結合超伝導 / 超伝導ギャップ / 電子格子相互作用 / エネルギーギャップ / トンネル効果 / ホウ化物
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.

Report

(4 results)
  • 2005 Annual Research Report   Final Research Report Summary
  • 2004 Annual Research Report
  • 2003 Annual Research Report
  • Research Products

    (70 results)

All 2006 2005 2004 2003 Other

All Journal Article (64 results) Publications (6 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
    • Related Report
      2005 Final Research Report Summary
  • [Journal Article] Tunneling measurements of CeRhAs single crystal2006

    • Author(s)
      T.Ekino
    • Journal Title

      Physica B (印刷中)

    • NAID

      120000875872

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      2005 Annual Research Report 2005 Final Research Report Summary
  • [Journal Article] Electron tunneling experiments on La-substituted Kondo semiconductor CeRhAs2006

    • Author(s)
      T.Ekino
    • Journal Title

      Physica B (印刷中)

    • NAID

      120000875873

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      2005 Final Research Report Summary
  • [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
    • Related Report
      2005 Final Research Report Summary
  • [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
    • Related Report
      2005 Final Research Report Summary
  • [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
    • Related Report
      2005 Final Research Report Summary
  • [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
    • Related Report
      2005 Annual Research Report 2005 Final Research Report Summary
  • [Journal Article] Tunneling measurements of CeRhAs single crystal2006

    • Author(s)
      T.Ekino
    • Journal Title

      Physica B (in press)

    • NAID

      120000875872

    • Description
      「研究成果報告書概要(欧文)」より
    • Related Report
      2005 Final Research Report Summary
  • [Journal Article] Electron tunneling experiments on La-substituted Kondo semiconductor CeRhAs2006

    • Author(s)
      T.Ekino
    • Journal Title

      Physica B (in press)

    • NAID

      120000875873

    • Description
      「研究成果報告書概要(欧文)」より
    • Related Report
      2005 Final Research Report Summary
  • [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
    • Related Report
      2005 Final Research Report Summary
  • [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
    • Related Report
      2005 Final Research Report Summary
  • [Journal Article] Spin dependent splitting of the tunnel conductivity peaks in the magnetic field for junctions involving CDW metals2006

    • Author(s)
      T.Ekino
    • Journal Title

      Physica B (印刷中)

    • NAID

      120000875871

    • Related Report
      2005 Annual Research Report
  • [Journal Article] Electron tunneling experiments on La-substituted Kondo semiconductoy CeRhAs2006

    • Author(s)
      T.Ekino
    • Journal Title

      Physica B (印刷中)

    • Related Report
      2005 Annual Research Report
  • [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)

    • Related Report
      2005 Annual Research Report
  • [Journal Article] Tunneling spectroscopy of CaAlSi2006

    • Author(s)
      T.Takasaki
    • Journal Title

      Physica B (印刷中)

    • Related Report
      2005 Annual Research Report
  • [Journal Article] Tunneling spectroscopy of single-crystal clathrate Ba_8Ga_<16>Sn_<30>2006

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

      Physica B (印刷中)

    • Related Report
      2005 Annual Research Report
  • [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
    • Related Report
      2005 Final Research Report Summary
  • [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
    • Related Report
      2005 Final Research Report Summary 2004 Annual Research Report
  • [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
    • Related Report
      2005 Final Research Report Summary 2004 Annual Research Report
  • [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
    • Related Report
      2005 Annual Research Report 2005 Final Research Report Summary
  • [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
    • Related Report
      2005 Annual Research Report 2005 Final Research Report Summary
  • [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
    • Related Report
      2005 Final Research Report Summary
  • [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
    • Related Report
      2005 Final Research Report Summary
  • [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
    • Related Report
      2005 Final Research Report Summary
  • [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
    • Related Report
      2005 Final Research Report Summary
  • [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
    • Related Report
      2005 Annual Research Report 2005 Final Research Report Summary
  • [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
    • Related Report
      2005 Annual Research Report 2005 Final Research Report Summary 2004 Annual Research Report
  • [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
    • Related Report
      2005 Annual Research Report 2005 Final Research Report Summary
  • [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
    • Related Report
      2005 Final Research Report Summary
  • [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
    • Related Report
      2005 Final Research Report Summary
  • [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
    • Related Report
      2005 Final Research Report Summary
  • [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
    • Related Report
      2005 Final Research Report Summary
  • [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
    • Related Report
      2005 Final Research Report Summary
  • [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
    • Related Report
      2005 Final Research Report Summary
  • [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
    • Related Report
      2005 Final Research Report Summary
  • [Journal Article] Pauli effect of the magnetic field on superconductors with charge-density waves2005

    • Author(s)
      T.Ekino
    • Journal Title

      Low Temp.Phys. 31

      Pages: 41-46

    • Related Report
      2005 Annual Research Report
  • [Journal Article] Spin-polarized electron tunneling between charge-density-wave metals2005

    • Author(s)
      T.Ekino
    • Journal Title

      Low Temp.Phys. 31

      Pages: 59-72

    • Related Report
      2005 Annual Research Report
  • [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 ; Condens.Matter 17

      Pages: 7407-7416

    • Related Report
      2005 Annual Research Report
  • [Journal Article] Tunneling spectroscopy of deintercalated layered nitride superconductors ZrNCl_<0.7>2005

    • Author(s)
      T.Takasaki
    • Journal Title

      J.Phys.Soc.Japan 74

      Pages: 2586-2591

    • Related Report
      2005 Annual Research Report
  • [Journal Article] Point-contact spectroscopy measurements of binary superconductor MgB_22005

    • Author(s)
      T.Takasaki
    • Journal Title

      Physica C. 426-431

      Pages: 300-303

    • Related Report
      2005 Annual Research Report
  • [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

    • Related Report
      2005 Annual Research Report
  • [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 印刷中

      Pages: 4-4

    • Related Report
      2004 Annual Research Report
  • [Journal Article] Manifestations of inhomogeneity in MgB_2 : From specific heat to tunnel measurements2005

    • Author(s)
      T.Ekino
    • Journal Title

      Physica B 印刷中

      Pages: 3-3

    • Related Report
      2004 Annual Research Report
  • [Journal Article] Point-contact spectroscopy measurements of binary superconductor MgB_22005

    • Author(s)
      T.Takasaki
    • Journal Title

      Physica C 印刷中

      Pages: 4-4

    • Related Report
      2004 Annual Research Report
  • [Journal Article] Enhancement of the paramagnetic limit for superconductors with charge-density waves2005

    • Author(s)
      T.Ekino
    • Journal Title

      Physica C 印刷中

      Pages: 4-4

    • Related Report
      2004 Annual Research Report
  • [Journal Article] Break-junction tunneling spectra of MgB_2 : influence of boron quality2005

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

      Physica C 印刷中

      Pages: 4-4

    • Related Report
      2004 Annual Research Report
  • [Journal Article] Electrical resistivity and tunneling anomalies in CeCuAs_22005

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

      Physica B 印刷中

      Pages: 4-4

    • Related Report
      2004 Annual Research Report
  • [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
    • Related Report
      2005 Final Research Report Summary 2004 Annual Research Report
  • [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
    • Related Report
      2005 Final Research Report Summary 2004 Annual Research Report
  • [Journal Article] Formation of midgap states and ferromagnetism in semiconducting CaB_62004

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

      Physical Review B 69

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      2005 Final Research Report Summary 2004 Annual Research Report
  • [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
    • Related Report
      2005 Final Research Report Summary 2004 Annual Research Report
  • [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
    • Related Report
      2005 Final Research Report Summary
  • [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
    • Related Report
      2005 Final Research Report Summary
  • [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
    • Related Report
      2005 Final Research Report Summary
  • [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

    • Related Report
      2004 Annual Research Report
  • [Journal Article] Energy gap structure in the binary superconductor MB_2 (M=Nb and Mg)2004

    • Author(s)
      T.Takasaki
    • Journal Title

      Physica C 412-414

      Pages: 266-269

    • Related Report
      2004 Annual Research Report
  • [Journal Article] Tunneling spectroscopy of the superconducting gap in MgB_22003

    • Author(s)
      T.Ekino
    • Journal Title

      Physical Review B 67

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      2005 Final Research Report Summary
  • [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
    • Related Report
      2005 Final Research Report Summary
  • [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
    • Related Report
      2005 Final Research Report Summary
  • [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
    • Related Report
      2005 Final Research Report Summary
  • [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
    • Related Report
      2005 Final Research Report Summary
  • [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
    • Related Report
      2005 Final Research Report Summary
  • [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
    • Related Report
      2005 Final Research Report Summary
  • [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
    • Related Report
      2005 Final Research Report Summary
  • [Publications] T.Ekino et al.浴野稔一他: "Tunneling spectroscopy of the super conducting gap in MgB_2"Physical Review B. 67. 094504-1-094504-6 (2003)

    • Related Report
      2003 Annual Research Report
  • [Publications] T.Ekino et al.: "Tunneling Spectroscopy of MgB_2 and Li_<0.5>(THF)_yHfNCl"Physica B. 328. 23-25 (2003)

    • Related Report
      2003 Annual Research Report
  • [Publications] T.Takasaki, T.Ekino et al.: "Multiple gap structure of the binary superconductor MgB_2"Physica C. 388-389. 147-148 (2003)

    • Related Report
      2003 Annual Research Report
  • [Publications] T.Ekino et al.: "Tunneling measurements of superconducting NbB_2"Physica C. 印刷中. (2) (2004)

    • Related Report
      2003 Annual Research Report
  • [Publications] T.Takasaki, T.Ekino et al.: "Energy gap structure in the binary superconductor MB_2(M : Nb, Mg)"Physica C. 印刷中. (3) (2004)

    • Related Report
      2003 Annual Research Report
  • [Publications] T.Ekino et al.: "Tunneling Spectroscopy of the electron-doped layered Superconductor Lio48(THF)_<0-3>HiMe"Physica C. 388-389. 573-574 (2003)

    • Related Report
      2003 Annual Research Report

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Published: 2003-04-01   Modified: 2020-05-15  

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