Strong-coupling superconductivity revealed by scanning tunneling microscope in tetragonal FeS
Strong-coupling superconductivity revealed by scanning tunneling microscope in tetragonal FeS
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扫描隧道显微镜揭示四方 FeS 的强耦合超导性
DOI：
10.1103/physrevb.94.024521
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发表时间：
2016-05
影响因子：
3.7
通讯作者：
Hai-Hu Wen
中科院分区：
文献类型：
--
作者：
Xiong Yang;Zengyi Du;Guan Du;Qiangqiang Gu;Hai Lin;Delong Fang;Huan Yang;Xiyu Zhu;Hai-Hu Wen
我们用扫描隧道显微镜/光谱研究了四相FeS超导体的电子性质。发现硫顶层的典型隧穿谱可以很好地与各向异性s波或两个超导分量的组合拟合，其中一个超导分量可能具有高度各向异性或类超导带隙。该拟合导致约Delta（max）的超导带隙类似于0.90 meV，这产生了2 Delta（max）/k（B）T（c）的比率，其近似于4.65。该值大于BCS理论在弱耦合极限下的预测值3.53，表明具有强耦合超导性。在表面上观察到两种类型的缺陷，这可以被分配到S位（四重图像）和Fe位（哑铃形）上的缺陷。杂质诱导的共振态只存在于S位上的缺陷，并停留在零偏置能量。
We investigate the electronic properties of the tetragonal FeS superconductor by using scanning tunneling microscopy/spectroscopy. It is found that the typical tunneling spectrum on the top layer of sulfur can be nicely fitted with an anisotropic s wave or a combination of two superconducting components in which one may have a highly anisotropic or nodal-like superconducting gap. The fittings lead to the superconducting gap of about Delta(max) similar to 0.90 meV, which yields a ratio of 2 Delta(max)/k(B)T(c) approximate to 4.65. This value is larger than that of the predicted value 3.53 by the BCS theory in the weak-coupling limit, indicating a strong-coupling superconductivity. Two kinds of defects are observed on the surface, which can be assigned to the defects on the S sites (fourfold image) and Fe sites (dumbbell shape). Impurity-induced resonance states are found only for the defects on the S sites and stay at zero-bias energy.