Novel criticality of Dirac fermions from lattice symmetry breaking

TL;DR

This paper investigates how spontaneous lattice symmetry breaking influences the critical behavior of strongly interacting 2D Dirac fermions, revealing violations of emergent Lorentz invariance and describing topological phase transitions.

Contribution

It introduces a new effective field theory for Dirac fermions coupled to order parameters, highlighting the impact of lattice symmetry breaking on criticality and Lorentz invariance.

Findings

Emergent Lorentz invariance is violated in the studied system.

Topological phase transitions are effectively described by the proposed theory.

Lattice symmetry breaking significantly alters the critical behavior of Dirac fermions.

Abstract

We consider the role of spontaneous lattice symmetry breaking in strongly interacting two dimensional Dirac systems. The fermion induced quantum (multi-)criticality is described by Dirac fermions coupled to a dynamical order parameter that is composed of mass and emergent gauge fields. This is illustrated for the example of translational symmetry breaking due to charge-density wave order on the honeycomb lattice. Using a renormalization-group analysis we find that the putative emergent Lorentz invariance is violated. Finally, we identify that topological phase transitions are well described by this effective field theory.