paper

Evidence for Two Gaps and Breakdown of the Uemura Plot in Ba $_{0.6}$ K $_{0.4}$ Fe $_{2}$ As $_{2}$ Single Crystals

arXiv:0808.0805 · doi:10.1103/PhysRevLett.101.257006

Abstract

We report a detailed investigation on the lower critical field $H_{c 1}$ of the superconducting Ba $_{0.6}$ K $_{0.4}$ Fe $_{2}$ As $_{2}$ (FeAs-122) single crystals. A pronounced kink is observed on the $H_{c 1} (T)$ curve, which is attributed to the existence of two superconducting gaps. By fitting the data $H_{c 1} (T)$ to the two-gap BCS model in full temperature region, a small gap of $I^_{a} (0) = 2.0 \pm 0.3$ meV and a large gap of $I^_{b} (0) = 8.9 \pm 0.4$ meV are obtained. The in-plane penetration depth $I^»_{ab} (0)$ is estimated to be 105 nm corresponding to a rather large superfluid density, which points to the breakdown of the Uemura plot in FeAs-122 superconductors.

5 pages, 4 figures

Evidence for Two Gaps and Breakdown of the Uemura Plot in Ba0.6​K0.4​Fe2​As2​ Single Crystals

Abstract

Evidence for Two Gaps and Breakdown of the Uemura Plot in Ba $_{0.6}$ K $_{0.4}$ Fe $_{2}$ As $_{2}$ Single Crystals