Effective minimal model and unconventional spin-singlet pairing in Kagome superconductor CsV3Sb5

TL;DR

This paper develops an effective minimal model for CsV$_3$Sb$_5$ Kagome superconductor, revealing unconventional spin-singlet pairing driven by spin fluctuations and how Coulomb interactions influence pairing strength and symmetry.

Contribution

It introduces a 6-band effective model and uses RPA to analyze spin-fluctuation pairing, highlighting the unconventional superconductivity in Kagome AV$_3$Sb$_5$ compounds.

Findings

Superconducting pairing strength increases with Coulomb correlation.

The pairing symmetry is spin-singlet with antisymmetric gap functions.

Unconventional superconductivity is indicated by the gap symmetry.

Abstract

Recently synthesized Kagome compounds AV$_3$Sb$_5$ attract great attention due to the unusual coexistence of the topology, charge density wave and superconductivity. In this {\it Letter}, based on the band structures for CsV$_3$Sb$_5$ in pristine phase, we fit an effective 6-band model for the low-energy processes; utilizing the random phase approximation (RPA) on the effective minimal model, we obtain the momentum-resolved static spin susceptibility attributing the spin-fluctuation pairing mechanism, we find that the superconducting pairing strengths increase with the lift of the Coulomb correlation, and the superconductive pairing symmetry is singlet, the gap functions are antisymmetric with respect to the x-axis and the y-axis in the intermediate to strong Coulomb correlated regime,indicating the unconventional superconductivity in Kagome compounds AV$_3$Sb$_5$.