Chiral excitonic order from twofold van Hove singularities in kagome metals

Abstract

Recent experiments have found a two-fold van Hove singularity (TvHS) in the kagome metal CsV3Sb5. Here, the authors use perturbative renormalization group calculations to find that the leading instability in a model of TvHS is a chiral condensate of electron-hole pairs, breaking time-reversal symmetry.