Sublattice Interference promotes Pair Density Wave order in Kagome Metals

TL;DR

This paper investigates how sublattice interference in kagome metals influences electron interactions, leading to the emergence of pair density wave order, especially near van Hove singularities, through RG analysis and Hartree-Fock calculations.

Contribution

It reveals that sublattice interference uniquely affects interactions in kagome lattices, promoting PDW order over other competing phases.

Findings

Sublattice interference alters interaction flow, favoring PDW formation.

RG analysis shows charge-density-wave as a leading instability in weak coupling.

Hartree-Fock confirms PDW order at intermediate coupling.

Abstract

Motivated by the observation of a pair density wave (PDW) in the kagome metal CsV${}_3$Sb${}_5$, we consider the fate of electrons near a p-type van Hove singularity (vHS) in the presence of local repulsive interactions. We study the effect of such interactions on Fermi surface "patches" at the vHS. We show how a feature unique to the Kagome lattice known as sublattice interference crucially affects the form of the interactions among the patches. The renormalization group (RG) flow of such interactions results in a regime where the nearest neighbor interaction $V$ exceed the onsite repulsion $U$. We identify this condition as being favorable for the formation of charge-density-wave (CDW) and PDW orders. In the weak coupling limit, we find a complex CDW order as the leading instability, which breaks time reversal symmetry. Beyond RG, we perform a Hartree-Fock study to a $V$-only model and find the pair-density-wave order indeed sets in at some intermediate coupling.