Nematic superconductivity in LiFeAs
Nematic superconductivity in LiFeAs
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DOI：
10.1103/physrevb.102.184502
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发表时间：
2020-11-03
影响因子：
3.7
通讯作者：
Borisenko, S., V
中科院分区：
文献类型：
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作者：
Kushnirenko, Y. S.;Evtushinsky, D., V;Borisenko, S., V
在高温超导机制中，超有序的作用一直备受争议。在大多数铁基超导体（IBS）中，四方对称性在正常状态下已经被打破，导致正交晶格畸变，静态条纹磁序，或两者兼而有之。然后，至少在弱掺杂下，超导性已经从C-4旋转对称性破缺的状态出现。砷化铁锂是为数不多的化学计量IBSs之一，在18 K以下超导，在正常状态下不显示结构或磁性转变。在这里，我们证明，使用角分辨光电子能谱，即使在LiFeAs的超导状态也是一个超导体。我们观察到自发破缺的旋转对称性的差距幅度上的所有费米表面，以及单向的费米口袋的扭曲。值得注意的是，这些变形在超导T-c以上几乎不可见。我们的结果证实了超导诱导向列性现象在离子注入系统中的实现，强调了它们之间的密切关系。我们提出了一个理论解释的基础上出现的二次不稳定性的超导状态，这导致了在差距函数的S级和s-d混合。
The role of nematic order for the mechanism of high-temperature superconductivity is highly debated. In most iron-based superconductors (IBSs) the tetragonal symmetry is broken already in the normal state, resulting in orthorhombic lattice distortions, static stripe magnetic order, or both. Superconductivity then emerges, at least at weak doping, already from the state with broken C-4 rotational symmetry. One of the few stoichiometric IBSs, lithium iron arsenide superconducts below 18 K and does not display either structural or magnetic transition in the normal state. Here we demonstrate, using angle-resolved photoemission spectroscopy, that even the superconducting state in LiFeAs is also a nematic one. We observe spontaneous breaking of the rotational symmetry in the gap amplitude on all Fermi surfaces, as well as unidirectional distortion of the Fermi pockets. Remarkably, these deformations are hardly visible above superconducting T-c. Our results demonstrate the realization of the phenomenon of superconductivity-induced nematicity in IBSs, emphasizing the intimate relation between them. We suggest a theoretical explanation based on the emergence of a secondary instability inside the superconducting state, which leads to the nematic order and s-d mixing in the gap function.