Probing the superconducting pairing symmetry from spin excitations in BiS$_2$ based superconductors

TL;DR

This paper theoretically investigates spin excitations in BiS$_2$ superconductors to identify how different pairing symmetries influence spin responses, providing a potential method to determine the pairing symmetry experimentally.

Contribution

It introduces a theoretical framework using a two-orbital model and RPA to distinguish pairing symmetries via spin excitation signatures in BiS$_2$ superconductors.

Findings

d-wave pairing shows incommensurate spin resonance at (0.7π,0.7π)

p-wave pairing enhances transverse spin excitation near (0,0)

s-wave pairing exhibits no spin resonance signature

Abstract

Starting from a two-orbital model and based on the random phase approximation, spin excitations in the superconducting state of the newly discovered BiS$_2$ superconductors with three possible pairing symmetries are studied theoretically. We show that spin response is uniquely determined by the pairing symmetry. Possible spin resonance excitations might occur for the d-wave symmetry at an incommensurate momentum about $(0.7\pi,0.7\pi)$. For the p-wave symmetry the transverse spin excitation near $(0,0)$ is enhanced. For the s-wave pairing symmetry there is no spin resonance signature. These distinct features may be used for probing or determining the pairing symmetry in this newly discovered compound.