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

• We use a tight-binding 1d Hamiltonian whose parameters are obtained from ab initio DFT
• Self-consistent gap equations are solved at the mean-field level.
• Pair-scattering terms are judged on their ability to reproduce experimental facts.
• Antisymmetric hybridization between Bismuth and Sulfur enhances the superconductivity.

Recent ARPES measurements [Sugimoto et al., Phys. Rev. B 92 (2015) 041113] have confirmed the one-dimensional character of the electronic structure of CeO0.5 F0.5 BiS2, 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 an effective 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.