Fermi surface topology and impurity-induced resonance state in BiS$_{2}$-based superconductors

TL;DR

This study investigates how impurity scattering affects superconducting states in BiS$_{2}$-based superconductors with different Fermi surface topologies, proposing impurity-induced resonance states as a way to identify pairing symmetry.

Contribution

It introduces a detailed analysis of impurity effects on various pairing symmetries in BiS$_{2}$ superconductors using a two-orbital model and Fermi surface topology considerations.

Findings

Impurity-induced resonance states vary qualitatively with pairing symmetry.

Resonance states depend on Fermi surface topology and doping.

Proposes STM experiments to identify pairing symmetry.

Abstract

Within the two-orbital model for BiS$_{2}$-based superconductors, the effect from a single nonmagnetic impurity scattering on the superconducting-state is investigated in terms of the T-matrix approach. By considering three kinds of the typical Fermi surface topology which characterize the essential features of the doping dependence of the electronic structure in BiS$_{2}$-based superconductors, it is found that the impurity scattering on the superconducting-state with the conventional $s$-wave, the extended $s$-wave, the $\pm s$-wave, and the $d_{x^{2}-y^{2}}$-wave symmetries induces \textit{qualitatively} different resonance states due to the evolution of unique nodal structures on the Fermi surface with doping. These impurity-induced resonance states can be verified directly by the scanning tunneling microscopy experiments, and therefore they are proposed as a probe of the superconducting pairing symmetry in BiS$_{2}$-based superconductors.