Phenomenology of bond and flux orders in kagome metals

TL;DR

This paper provides a comprehensive symmetry classification and theoretical analysis of charge, flux, and bond orders in kagome metals, offering insights into their complex behaviors under external perturbations like strain and magnetic fields.

Contribution

It introduces a detailed symmetry-based framework for understanding charge orders in kagome metals, including flux and bond orders, and analyzes their responses to external perturbations.

Findings

Symmetry classification of possible charge orders in kagome metals.

Landau free energy formulation for flux and bond orders.

Predictions for experimental tests under strain and magnetic fields.

Abstract

Despite much experimental and theoretical work, the nature of the charge order in the kagome metals belonging to the family of materials AV$_3$Sb$_5$ (A=Cs,Rb,K) remains controversial. A crucial ingredient for the identification of the ordering in these materials is their response to external perturbations, such as strain or magnetic fields. To this end, we provide a comprehensive symmetry classification of the possible charge orders in kagome materials with a $2\times2$ increase of the unit cell. Motivated by the experimental reports of time-reversal-symmetry breaking and rotational anisotropy, we consider the interdependence of flux and bond orders. Deriving the relevant Landau free energy for possible orders, we study the effect of symmetry-breaking perturbations such as strain and magnetic fields. Our results, thus, provide a roadmap for future tests of these intricate orders.