Chiral excitonic order from twofold van Hove singularities in kagome metals.

ABSTRACT: Recent experiments on kagome metals AV₃Sb₅ (A=K,Rb,Cs) identify twofold van Hove singularities (TvHS) with opposite concavity near the Fermi energy, generating two approximately hexagonal Fermi surfaces - one electron-like and the other hole-like. Here we propose that a TvHS generates a novel time-reversal symmetry breaking excitonic order - arising due to bound pairs of electrons and holes located at opposite concavity van Hove singularities. We introduce a minimal model for the TvHS and investigate interaction induced many-body instabilities via the perturbative renormalisation group technique and a free energy analysis. Specialising to parameters appropriate for the kagome metals AV₃Sb₅, we construct a phase diagram comprising chiral excitons,

SUBMITTER: Scammell HD 

PROVIDER: S-EPMC9899280 | biostudies-literature | 2023 Feb

REPOSITORIES: biostudies-literature