Superconducting pairing symmetry in the kagome-lattice Hubbard model

TL;DR

This study uses quantum Monte Carlo simulations to identify the dominant superconducting pairing symmetries in the kagome-lattice Hubbard model, revealing doping-dependent unconventional d-wave and s*-wave pairings with topological features.

Contribution

It provides the first detailed analysis of pairing symmetry in the kagome Hubbard model using determinant quantum Monte Carlo, highlighting doping-dependent pairing channels and topological superconductivity.

Findings

D-wave pairing dominates in hole-doped cases.

s*-wave pairing is favored in electron-doped cases.

Superconductivity persists up to the Van Hove singularity.

Abstract

The dominating superconducting pairing symmetry of the kagome-lattice Hubbard model is investigated using the determinant quantum Monte Carlo method. The superconducting instability occurs when doping the correlated insulators formed by the Hubbard interaction near the Dirac filling, and the superconducting state exhibits an electron-hole asymmetry. Among the pairing symmetries allowed, we demonstrate that the dominating channel is d-wave in the hole-doped case. This opens the possibility of condensation into an unconventional $d_{x^2-y^2}+id_{xy}$ phase, which is characterized by an integer topological invariant and gapless edge states. In contrast, the $s^*$-wave channel, which has no change of sign in the pairing function, is favored by electron doping. We further find the dominating $s^*$-wave pairing persists up to the Van Hove singularity. The results are closely related to the recent experimental observations in kagome compounds AV3Sb5(A: K, Rb, Cs), and provide insight into the pairing mechanism of their superconducting states.