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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, Z. Hiroi

DOI 10.1103/PhysRevLett.98.257004 · Physical Review Letters

T1

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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 Tp∼8 K, 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.

Source-reported materials — not catalogue approval

FormulaReported Tc (K)Pressure (GPa)Type
KOs2O6

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9.5Pressure not reportedunknown

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