Crossover between electron-electron and electron-phonon mediated pairing on the Kagome lattice

TL;DR

This paper investigates how electron-electron and electron-phonon interactions on the Kagome lattice near van Hove fillings influence unconventional pairing states, revealing a crossover region with enhanced exotic superconducting pairings.

Contribution

It demonstrates the combined effects of electron-electron and electron-phonon interactions on pairing symmetries, highlighting the promotion of non-s-wave pairings near van Hove singularities on the Kagome lattice.

Findings

Electron-phonon interaction becomes momentum-dependent due to Fermi surface texture.

Exotic pairings like p-wave and f-wave are favored near specific van Hove fillings.

The study discusses implications for vanadium-based kagome superconductors AV$_3$Sb$_5$.

Abstract

We study electron-electron and electron-phonon mediated pairing in the Holstein extended Hubbard model on the Kagome lattice near the van Hove fillings, and investigate their combined effects on electron pairing states. We find that their combination can promote exotic pairings in a crossover region, where the filling is close to a van Hove singularity. In particular, at the $p$-type van Hove filling the $E_{1u}$ ($p$-wave) and $B_{2u}$ ($f_{y^3-3yx^2}$-wave) pairings become leading, and at the $m$-type van Hove filling the $E_{1u}$ and $A_{2g}$ ($i$-wave) pairings get promoted. Moreover, we show that the electron-phonon interaction acquires a significant momentum dependence, due to the sublattice texture of the Fermi surfaces, which can promote non $s$-wave pairing. We present a detailed analysis of these pairing propensities and discuss implications for the vanadium-based kagome superconductors AV$_3$Sb$_5$.