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2000 Fiscal Year Final Research Report Summary

NMR STUDY OF THE ELECTRONIC STRUCTURE OF VORTICES IN D-WAVE SUPERCONDUCTORS

Research Project

Project/Area Number 11640350
Research Category

Grant-in-Aid for Scientific Research (C)

Allocation TypeSingle-year Grants
Section一般
Research Field 固体物性Ⅱ(磁性・金属・低温)
Research InstitutionOSAKA UNIVERSITY

Principal Investigator

ZHENG Guo-qing  Graduate School of Engineering Science, Research Associate, 大学院・基礎工学研究科, 助手 (50231444)

Project Period (FY) 1999 – 2000
Keywordshigh temperature superconductor / vortex / NMR / spin susceptibility
Research Abstract

Magnetic field penetrates into a second-kind superconductor in a form of quantized vortex flux. In an s-wave superconductor with isotropic energy gap, the quasiparticle is localized within the vortex core whose radius is the superconducting coherence length. By contrary, the energy gap of d-wave superconductors, such as the high temperature superconductors, is anisotropic with line-nodes in the gap structure. Because of this gap anisotropy, the electronic state is expected to be quite different from that in an s-wave superconductor. In fact, recent theories predict that the quasiparticle state may be extended along the nodal directions to the outside of the core. However, this prediction is yet to be confirmed by experiments. In this project, we have studied the electronic structure around a vortex using the ^<63>Cu NMR method.
In an overdoped high-T_c cuprate TlSr_2CaCu_2O_<6.8>(T_c=68 K), we have measured the Knight shift in the superconducting state as a function of magnetic field up to 28 Tesla. We find that the spin shift increases as increasing field. This gives an experimental evidence that there exist quasiparticle states outside the vortex core. Analysis shows that the spin shift increases as a square root of the applied field, which is in agreement with what is predicted by recent theories for a d-wave superconductor. Furthermore, we find that among the field-induced density of states, 85% of it are extended outside of the vortex core, and 15% is localized in the core.
This study provides a quantitative account for the quasiparticle density of states associated with a vortex for the first time.

  • Research Products

    (12 results)

All Other

All Publications (12 results)

  • [Publications] G.-q.Zheng: "Effects of High Magnetic Fields on the Pseudogap and d-wave Superconductivity in the underdoped and overdoped High-T_C Superconductors"Physica. C341-348. 819-822 (2000)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] G.-q.Zheng: "d-wave Vortex and Pseudogap in Underdoped High-T_C Cuprate YBa_2Cu_4O_8.-High-Magnetic-Field NMR-"Physica. B281-282. 901-903 (2000)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] G.-q.Zheng: "Superconducting Fluctuations and the Pseudogap in the slightly-overdoped high-T_c superconductor TlSr_2CaCu_2O_<6.8> : high magnetic field NMR study"Phys.Rev.Lett.. 85. 405-408 (2000)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] G.-q.Zheng: "Characterizing the pseudogap in the high-T_<2C> superconductors using very high magnetic fields : implications on the phase diagram."Physica. C(印刷中). (2001)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] G.-q.Zheng: "Pseudogap and Superconductivity under High Magnetic Fields in Underdoped High-T_C Cuprates."Int.J.Mod.Phys.. B13. 3764-3766 (1999)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] G.-q.Zheng: "d-wave Vortex and Pseudogap in Underdoped High-T_C Cuprate YBa_2Cu_4O_8.-High-Magnetic-Field NMR-"Physica. B281-282. 901-903 (2000)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] G.-q.Zheng, Y.Kitaoka, K.Asayama, Y.Kodama, W.G.Clark, P.Kuhns and W.Moulton: "Pseudogap and Superconductivity under High Magnetic Fields in Underdoped High-Tc Cuprates."Int.J.Mod.Phys.. B13. 3764-3766 (1999)

    • Description
      「研究成果報告書概要(欧文)」より
  • [Publications] G.-q.Zheng, W.G.Clark, Y.Kitaoka, K.Asayama, Y.Kodama, P.Kuhns and W.Moulton: "d-wave Vortex and Pseudogap in Underdoped High-Tc Cuprate YBa_2Cu_4O_<>8.-High-Magnetic-Field NMR-"Physica. B281-282. 901-903 (2000)

    • Description
      「研究成果報告書概要(欧文)」より
  • [Publications] G.-q.Zheng, H.Ozaki, W.G.Clark, Y.Kitaoka, P.Kuhns, A.P.Reyes, W.Moulton, T.Kondo, Y.Shimakawa and Y.Kubo: "Superconducting Fluctuations and the Pseudogap in the slightly-overdoped high-Tc superconductor TlSr_2CaCu_2O_<6.8> : high magnetic field NMR study."Phys.Rev.Lett.. 85. 405 (2000)

    • Description
      「研究成果報告書概要(欧文)」より
  • [Publications] G.-q.Zheng, H.0zaki, W.G.Clark, M.Sakai, Y.Kitaoka, P.Kuhns, A.P.Reyes, W.Moulton, T.Kondo, Y.Shimakawa and Y.Kubo: "Effects of High Magnetic Fields on the Pseudogap and d-wave Superconductivity in the underdoped and overdoped High-Tc Superconductors."Physica. C341-348. 819-822 (2000)

    • Description
      「研究成果報告書概要(欧文)」より
  • [Publications] G.-q.Zheng, H.Ozaki, W.G.Clark, M.Sakai, Y.Kitaoka, P.Kuhns, A.P.Reyes, W.Moulton, T.Kondo, Y.Shimakawa and Y.Kubo: "Spin Gap and the superconducting fluctuations in High-Tc Cuprates probed by ^<63>Cu NMR."J.Phys.Chem.Solids. 62. 25-27 (2001)

    • Description
      「研究成果報告書概要(欧文)」より
  • [Publications] G.-q.Zheng, H.Ozaki, W.G.Clark, M.Sakai, Y.Kitaoka, P.Kuhns, A.P.Reyes, W.Moulton, T.Kondo, Y.Shimakawa and Y.Kubo: "Characterizing the pseudogap in the high-Tc superconductors using very high magnetic fields : implications on the phase diagram."Physica C. (in press). (2001)

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

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Published: 2002-03-26  

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