Effects of Rattling Phonons on the Dynamics of Quasiparticle Excitation in the β-Pyrochlore KOs2O6 Superconductor

Y. Shimono, T. Shibauchi, Y. Kasahara, T. Kato, K. Hashimoto, Y. Matsuda, J. Yamaura, Y. Nagao, and Z. Hiroi
Phys. Rev. Lett. 98, 257004 – Published 22 June 2007

Abstract

Microwave penetration depth λ and surface resistance at 27 GHz are measured in high quality crystals of KOs2O6. Firm evidence for fully gapped superconductivity is provided from λ(T). Below the second transition at Tp8K, the superfluid density shows a steplike change with a suppression of effective critical temperature Tc. Concurrently, the extracted quasiparticle scattering time shows a steep enhancement, indicating a strong coupling between the anomalous rattling motion of K ions and quasiparticles. The results imply that the rattling phonons help to enhance superconductivity, and that K sites freeze to an ordered state with long quasiparticle mean free path below Tp.

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  • Received 26 February 2007

DOI:https://doi.org/10.1103/PhysRevLett.98.257004

©2007 American Physical Society

Authors & Affiliations

Y. Shimono1, T. Shibauchi1, Y. Kasahara1, T. Kato1, K. Hashimoto1, Y. Matsuda1,2, J. Yamaura2, Y. Nagao2, and Z. Hiroi2

  • 1Department of Physics, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan
  • 2Institute for Solid State Physics, University of Tokyo, Kashiwa, Chiba 277-8581, Japan

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Issue

Vol. 98, Iss. 25 — 22 June 2007

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