Interplay of interactions and disorder at the charge-density wave transition of two-dimensional Dirac semimetals

TL;DR

This paper studies how weak disorder affects the quantum phase transition between a Dirac semimetal and a charge density wave insulator in two dimensions, revealing a stable critical point and a multi-critical point with non-Fermi liquid behavior.

Contribution

It introduces a comprehensive RG analysis of disorder effects on the GNY transition, identifying new fixed points and their impact on physical observables.

Findings

The clean GNY critical point remains stable against weak disorder.

A new dirty GNY multi-critical point emerges with finite chemical potential disorder.

Distinct non-Fermi liquid behavior arises at the multi-critical point.

Abstract

We consider the effects of weak quenched fermionic disorder on the quantum-phase transition between the Dirac semimetal and charge density wave (CDW) insulator in two spatial dimensions. The symmetry breaking transition is described by the Gross-Neveu-Yukawa (GNY) theory of Dirac fermions coupled to an Ising order parameter field. Treating the disorder using the replica method, we consider chemical potential, vector potential (gauge), and random mass disorders, which all arise from non-magnetic charge impurities. We self-consistently account for the Landau damping of long-wavelength order-parameter fluctuations by using the non-perturbative RPA re-summation of fermion loops, and compute the renormalization-group (RG) flow to leading order in the disorder strength and $1/N$ ($N$ the number of Dirac fermion flavors). We find two fixed points, the clean GNY critical point which is stable against weak disorder, and a dirty GNY multi-critical point, at which the chemical potential disorder is finite and the other forms of disorder are irrelevant. We investigate the scaling of physical observables at this finite-disorder multi-critical point which breaks Lorentz invariance and gives rise to distinct non-Fermi liquid behavior.