ÖPG-CMD Joint Meeting 2026

Canceled: Kekulé order from diffuse nesting near higher-order Van Hove points

Sep 23, 2026, 11:30 AM

30m

HS 15.14 (University of Graz)

4) Invited talk M06 - Interaction effects in correlated systems with higher-order Van Hove singularities and flat bands Mini-Colloquium

Speaker

Ronny Thomale (Theoretische Physik I, Julius-Maximilians-Universität Würzburg)

Description

Translation symmetry-breaking order is assumed to be suppressed by the lack of Fermi surface nesting near certain higher-order Van Hove singularities (HOVHS). We show the anisotropic band-flattening inherent to such HOVHS, combined with broadening of the Fermi surface due to elevated critical temperatures, results in the Fermi surface becoming approximately nested at a wavevector unrelated to the precise shape of the Fermi surface - leading to a Kekulé density wave formation. The effect is demonstrated using unbiased renormalization group calculations for a model of the breathing kagome lattice. Our mechanism - termed diffuse nesting - represents an entirely new notion in the study of Fermi surface instabilities.