Magnetic Penetration Depth in the FeAs-Based Superconductor KFe2As2

Transverse-field muon spin rotation measurements were performed on the iron-based superconductor, KFe 2 As 2 , in order to investigate the superconducting gap mechanism. We found that the temperature dependence of the magnetic penetration depth λ shows multiple gap-like behavior and that λ depends on the field. These results suggest the existence of quasiparticle excitations outside the vortices.

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