Study of point-contact spectra of FeSe in the normal and superconducting states

Since the discovery of superconductivity in FeSe, this compound has been intensively investigated. FeSe belong to the family of the iron-based superconductors and it has the simplest crystal structure among the iron pnictides and chalchogenides. FeSe shows only a structural phase transition at Ts ∼ 100K without an accompanying magnetic phase transition. The FeSe compounds consist only of a stack of electronically active layers weakly coupled by the van der Waals interaction. These layers are based on the edge-shared FeSe4 tetrahedra [1]. FeSe becomes superconducting below the critical temperature TC ∼ 9 K. Despite the fact that FeSe has a moderate TC, the latter increases up to 37 K under pressure [2]. The single layer of FeSe demonstrates a superconducting (SC) transition even superior to 100 K [3].