Spontaneous breaking of four-fold rotational symmetry in two-dimensional electronic systems explained as a continuous topological transition

TL;DR

This paper explains how a topological phase transition causes spontaneous four-fold rotational symmetry breaking in strongly correlated 2D electronic systems, leading to an unconventional Fermi liquid state.

Contribution

It introduces a topological transition framework to understand symmetry breaking in 2D electronic systems, linking it to van Hove singularities and quasiparticle interactions.

Findings

Symmetry breaking occurs at a topological phase transition.

The transition is continuous and driven by van Hove saddle points.

An unconventional Fermi liquid state emerges beyond the critical point.

Abstract

The Fermi liquid approach is applied to the problem of spontaneous violation of the four-fold rotational point-group symmetry ($C_4$) in strongly correlated two-dimensional electronic systems on a square lattice. The symmetry breaking is traced to the existence of a topological phase transition. This continuous transition is triggered when the Fermi line, driven by the quasiparticle interactions, reaches the van Hove saddle points, where the group velocity vanishes and the density of states becomes singular. An unconventional Fermi liquid emerges beyond the implicated quantum critical point.