Emergent $\mathbb{Z}_2$ symmetry near a CDW multicritical point

TL;DR

This paper investigates the critical behavior of incommensurate charge-density-wave ordering under strain, revealing that emergent $$ symmetry can appear near a multicritical point, with diverse phase diagram structures depending on microscopic details.

Contribution

It demonstrates that emergent $$ symmetry can occur in the critical regime of a $U(1) imes U(1)$ multicritical point, depending on microscopic parameters, and analyzes various phase diagram structures.

Findings

Emergent $$ symmetry can appear near the multicritical point.

Phase diagrams can feature vestigial, tricritical, tetracritical, or bicritical points.

Different microscopic details lead to qualitatively different phase structures.

Abstract

We consider the critical behavior associated with incommensurate unidirectional charge-density-wave ordering in a weakly orthorhombic system subject to uniaxial strain as an experimentally significant example of $U(1)\times U(1)$ multicriticality. We show that, depending on microscopic details, the phase diagram can have qualitatively different structures which can involve a vestigial meta-nematic critical point, a pair of tricritical points, a decoupled tetracritical point, or (at least at mean-field level) a bicritical point. We analyze the emergent symmetries in the critical regime and find that these can -- at least in some cases -- involve an emergent $\mathbb{Z}_2$ order parameter symmetry.