Comparison of band structure and superconductivity in FeSe0.5Te0.5 and FeS
Comparison of band structure and superconductivity in FeSe0.5Te0.5 and FeS
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FeSe0.5Te0.5 和 FeS 的能带结构和超导性比较
DOI：
10.1088/1674-1056/26/12/127401
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发表时间：
2017
影响因子：
1.7
通讯作者：
Wang Wan Sheng
中科院分区：
文献类型：
--
作者：
Yang Yang;Feng Shi Quan;Xiang Yuan Yuan;Lu Hong Yan;Wang Wan Sheng
同价铁硫族化合物FeSe0.5Te0.5和FeS具有相似的晶格结构，但在超导性能方面表现非常不同。我们从理论上研究潜在的机制。通过第一性原理计算和紧密结合拟合，我们发现这些化合物的dX2−Y2轨道的谱权发生了显著的变化。FeSe0.5Te0.5和FeS中都有电子和空穴袋，但FeS中没有以dX2−Y2为主要特征的小空穴袋。我们发现dX2−Y2轨道的谱权发生了显著的变化，这对FeSe0.5Te0.5中的电子口袋和空穴口袋有贡献，而对FeS中的电子口袋只有贡献。然后，我们执行随机相位近似和无偏单模功能重正化群计算，以研究可能由这种裸带结构顶部的电子-电子相互作用触发的超导不稳定性。对于FeSe0.5Te0.5，我们发现了一个完全间隙的s±波对，可以与连接电子和空穴口袋的自旋涨落相关联。然而，对于FeS来说，节点dxy（或未展开的Broullin区中的dx2−y2）是有利的，并且可以与连接布里渊区角落周围的电子口袋的自旋涨落有关。除了硫族元素的差异外，我们认为差异的主要来源是dX2−Y2轨道，它调整了费米表面嵌套向量，从而影响了优势对对称。
The isovalent iron chalcogenides, FeSe0.5Te0.5 and FeS, share similar lattice structures but behave very differently in superconducting properties. We study the underlying mechanism theoretically. By first principle calculations and tight-binding fitting, we find the spectral weight of the dX2−Y2 orbital changes remarkably in these compounds. While there are both electron and hole pockets in FeSe0.5Te0.5 and FeS, a small hole pocket with a mainly dX2−Y2 character is absent in FeS. We find the spectral weights of dX2−Y2 orbital change remarkably, which contribute to electron and hole pockets in FeSe0.5Te0.5 but only to electron pockets in FeS. We then perform random-phase-approximation and unbiased singular-mode functional renormalization group calculations to investigate possible superconducting instabilities that may be triggered by electron-electron interactions on top of such bare band structures. For FeSe0.5Te0.5, we find a fully gapped s±-wave pairing that can be associated with spin fluctuations connecting electron and hole pockets. For FeS, however, a nodal dxy (or dx2−y2 in an unfolded Broullin zone) is favorable and can be related to spin fluctuations connecting the electron pockets around the corner of the Brillouin zone. Apart from the difference in chacogenide elements, we propose the main source of the difference is from the dX2−Y2 orbital, which tunes the Fermi surface nesting vector and then influences the dominant pairing symmetry.