Determination of Superconducting Gap of SmFeAsFxO1-x Superconductors by Andreev Reflection Spectroscopy

Abstract

The superconducting gap in FeAs-based superconductor SmFeAs(O1-xFx) (x = 0.15 and 0.30) and the temperature dependence of the sample with x = 0.15 have been measured by Andreev reflection spectroscopy. The intrinsic superconducting gap is independent of contacts while many other "gap-like" features vary appreciably for different contacts. The determined gap value of 2D = 13.34 +/-0.47 meV for SmFeAs(O0.85F0.15) gives 2D/kBTC = 3.68, close to the BCS prediction of 3.53. The superconducting gap decreases with temperature and vanishes at TC, in a manner similar to the BCS behavior but dramatically different from that of the nodal pseudogap behavior in cuprate superconductors.

13 pages, 9 figures, Special Issue of Physica C on Superconducting Pnictides

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• Evidence of a multiple boson emission in Sm${}_{1-x}$Th${}_x$OFeAs
• Gap-like feature in the normal state of $\mathbf{X}(\mathbf{F}{\mathbf{e}}_{1-\mathbf{x}}\mathbf{C}{\mathbf{o}}_{\mathbf{x}}{)}_2\mathbf{A}{\mathbf{s}}_2$, $\mathbf{X}=\mathbf{Ba},\mathbf{Sr}$ and $\mathbf{F}{\mathbf{e}}_{1+\mathbf{y}}\mathbf{Te}$ revealed by Point Contact Spectroscopy
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