Applying experimental constraints to a one-dimensional model for BiS2 superconductivity

TL;DR

This paper develops a one-dimensional three-orbital model for BiS2-based superconductors, incorporating experimental constraints to explain the pressure-induced increase in Tc and the multi-gap nature of superconductivity.

Contribution

It introduces a new one-dimensional model with ab initio derived kinetic terms and pair-scattering, systematically matching experimental superconducting features.

Findings

Superconducting dome with maximum Tc at specific chemical potential

Tc increases with hopping amplitude, consistent with pressure effects

Multi-gap superconductivity is essential for experimental agreement

Abstract

Recent ARPES measurements [Phys. Rev. B 92, 041113 (2015)] have confirmed the one-dimensional character of the electronic structure of CeO0.5F0.5BiS2, a representative of BiS2-based superconductors. In addition, several members of this family present sizable increase in the superconducting transition temperature Tc under application of hydrostatic pressure. Motivated by these two results, we propose a one-dimensional three-orbital model, whose kinetic energy part, obtained through ab initio calculations, is supplemented by pair-scattering terms, which are treated at the mean-field level. We solve the gap equations self-consistently and then systematically probe which combination of pair-scattering terms gives results consistent with experiment, namely, a superconducting dome with a maximum Tc at the right chemical potential and a sizable increase in Tc when the magnitude of the hoppings is increased. For these constraints to be satisfied multi-gap superconductivity is required, in agreement with experiments, and one of the hoppings has a dominant influence over the increase of Tc with pressure.