点接触Andreev反射谱研究SmFeAsO $_{0.8}$ F $_{0.2}$中双能隙无结超导电性
Evidence for two-gap nodeless superconductivity in SmFeAsO$_{0.8}$F$_{0.2}$ from point-contact Andreev-reflection spectroscopy
摘要：
在T_c为\simeq 53 K的SmFeAsO_{0.8} F_{0.2}多晶中进行了点接触Andreev反射测量。实验电导曲线可重复地显示出\pm 6 mV附近的峰和V \sim 16-20 mV处的肩，表明存在两个无结超导间隙。虽然单带Blonder-Tinkham-Klapwijk拟合只能再现电导曲线的一小部分，但双带隙拟合可以很好地解释整个实验dI/dV的形状。归一化曲线的拟合给出Δ_1（0）= 6.15 \pm 0.45 meV和Δ_2（0）= 18 \pm 3 meV。两个间隙在相同的温度下闭合，并遵循BCS样行为。
英文摘要：
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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