Superfluid density (n s) in the mixed state of an iron pnictide superconductor Ba 1-xK xFe 2As 2 is determined by muon spin rotation for a sample with optimal doping (x = 0:4). The temperature dependence of n s is perfectly reproduced using the conventional BCS model for s-wave paring, where the order parameter can be either a single-gap structure with Δ = 8:35(6) meV [2Δ/k BT c = 5:09(4)] or double-gap structure with Δ 1 = 12 meV (fixed) [2Δ 1/k BT c = 7:3] and Δ 2 = 6:8(3) meV [2Δ 2/ k BT c = 4:1(2)]. The latter is consistent with the recent result obtained by the angle-resolved photoemission spectroscopy. The large gap parameters (2Δ/k BT c) indicate the extremely strong coupling of carriers to bosons that mediate the Cooper pairing.
|ジャーナル||journal of the physical society of japan|
|出版ステータス||Published - 2009 2月|
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