Microwave surface-impedance measurements of the magnetic penetration depth in single crystal Ba1-xKxFe2As2 superconductors: Evidence for a disorder-dependent superfluid density

K. Hashimoto, T. Shibauchi, S. Kasahara, K. Ikada, S. Tonegawa, T. Kato, R. Okazaki, C. J. Van Der Beek, M. Konczykowski, H. Takeya, K. Hirata, T. Terashima, Y. Matsuda

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Abstract

We report high-sensitivity microwave measurements of the in-plane penetration depth λab and quasiparticle scattering rate 1/τ in several single crystals of the hole-doped Fe-based superconductor Ba1-xKxFe2As2 (x≈0.55). While a power-law temperature dependence of λab with a power ∼2 is found in crystals with large 1/τ, we observe an exponential temperature dependence of the superfluid density consistent with the existence of fully opened two gaps in the cleanest crystal we studied. The difference may be a consequence of different levels of disorder inherent in the crystals. We also find a linear relation between the low-temperature scattering rate and the density of quasiparticles, which shows a clear contrast to the case of d-wave cuprate superconductors with nodes in the gap. These results demonstrate intrinsically nodeless order parameters in the Fe arsenides.

Original languageEnglish
Article number207001
JournalPhysical Review Letters
Volume102
Issue number20
DOIs
Publication statusPublished - May 18 2009
Externally publishedYes

ASJC Scopus subject areas

  • Physics and Astronomy(all)

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