Pairing symmetry in layered BiS2 compounds driven by electron-electron correlation

We investigate the pairing symmetry of layered BiS₂ compounds by assuming that electron-electron correlation is still important so that the pairing is rather short range. We find that the extended s-wave pairing symmetry always wins over d-wave when the pairing is confined between two short range sites up to next nearest neighbors. The pairing strength is peaked around the doping level x = 0.5, which is consistent with experimental observation. The extended s-wave pairing symmetry is very robust against spin-orbital coupling because it is mainly determined by the structure of Fermi surfaces. Moreover, the extended s-wave pairing can be distinguished from conventional swave pairing by measuring and comparing superconducting gaps of different Fermi surfaces.