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Thermal conductivity measurements of the energy-gap anisotropy of superconducting LaFePO at low temperatures

M. Yamashita, N. Nakata, Y. Senshu, S. Tonegawa, K. Ikada, K. Hashimoto, H. Sugawara, T. Shibauchi, and Y. Matsuda
Phys. Rev. B 80, 220509(R) – Published 28 December 2009

Abstract

The superconducting gap structure of LaFePO (Tc=7.4K) is studied by thermal conductivity (κ) at low temperatures in fields H parallel and perpendicular to the c axis. A clear two-step field dependence of κ(H) with a characteristic field Hs(350Oe) much lower than the upper critical field Hc2 is observed. In spite of the large anisotropy of Hc2, κ(H) in both H directions is nearly identical below Hs. Above Hs, κ(H) grows gradually with H with a convex curvature, followed by a steep increase with strong upward curvature near Hc2. These results indicate multigap superconductivity with active two-dimensional (2D) and passive three-dimensional bands having contrasting gap values. Together with the recent penetration depth results, we suggest that the 2D bands consist of nodal and nodeless ones, consistent with extended s-wave symmetry.

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  • Received 14 July 2009

DOI:https://doi.org/10.1103/PhysRevB.80.220509

©2009 American Physical Society

Authors & Affiliations

M. Yamashita1, N. Nakata1, Y. Senshu1, S. Tonegawa1, K. Ikada1, K. Hashimoto1, H. Sugawara2,*, T. Shibauchi1, and Y. Matsuda1

  • 1Department of Physics, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan
  • 2Faculty of Integrated Arts and Sciences, The University of Tokushima, Tokushima 770-8502, Japan

  • *Present address: Department of Physics, Kobe University, Kobe 657–8501, Japan.

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Issue

Vol. 80, Iss. 22 — 1 December 2009

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