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arXiv · 0812.1141

Evidence for two-gap nodeless superconductivity in SmFeAsO$_{0.8}$F$_{0.2}$ from point-contact Andreev-reflection spectroscopy

D. Daghero·M. Tortello·R. S. Gonnelli·V. A. Stepanov·N. D. Zhigadlo·J. Karpinski
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Abstract

Point-contact Andreev-reflection measurements were performed in SmFeAsO_{0.8}F_{0.2} polycrystals with T_c \simeq 53 K. The experimental conductance curves reproducibly exhibit peaks around \pm 6 mV and shoulders at V \sim 16-20 mV, indicating the presence of two nodeless superconducting gaps. While the single-band Blonder-Tinkham-Klapwijk fit can only reproduce a small central portion of the conductance curve, the two-gap one accounts remarkably well for the shape of the whole experimental dI/dV. The fits of the normalized curves give Delta_1(0) = 6.15 \pm 0.45 meV and Delta_2(0) = 18 \pm 3 meV. Both gaps close at the same temperature and follow a BCS-like behavior.

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D. Daghero, M. Tortello, R. S. Gonnelli, V. A. Stepanov, N. D. Zhigadlo, J. Karpinski. 2008-12-05. Evidence for two-gap nodeless superconductivity in SmFeAsO$_{0.8}$F$_{0.2}$ from point-contact Andreev-reflection spectroscopy. https://doi.org/10.1103/physrevb.80.060502

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