Pairing Symmetry in Layered BiS$_2$ Compounds Driven by Electron-Electron Correlation

TL;DR

This study explores the pairing symmetry in layered BiS$_2$ compounds, finding that extended s-wave pairing driven by electron-electron interactions is dominant and robust, with specific doping-dependent characteristics.

Contribution

It demonstrates that extended s-wave pairing symmetry prevails over d-wave in BiS$_2$ compounds considering short-range electron correlations, and shows its robustness against spin-orbital coupling.

Findings

Extended s-wave pairing dominates over d-wave.

Pairing strength peaks at doping level x=0.5.

Extended s-wave is robust against spin-orbital coupling.

Abstract

We investigate the pairing symmetry of layered BiS$_2$ 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 s-wave pairing by measuring and comparing superconducting gaps of different Fermi surfaces.