A correlated Anderson insulator on the honeycomb lattice

TL;DR

This paper investigates how disorder influences the phase transition in a honeycomb lattice Hubbard model, revealing a transition from a semimetal to an insulator with a disordered phase featuring a crossover from Anderson to Mott insulators.

Contribution

It provides the first detailed quantum Monte Carlo study of disorder effects on the semimetal-Mott insulator transition in the honeycomb lattice.

Findings

Disorder induces a non-magnetic insulating phase.

A crossover from Anderson to Mott insulator occurs within the disordered phase.

The clean system exhibits a single quantum critical point.

Abstract

We study the effect of disorder on the semimetal -- Mott insulator transition in the half-filled repulsive Hubbard model on a honeycomb lattice, a system that features vanishing density of states at the Fermi level. Using the determinant quantum Monte Carlo method, we characterize various phases in terms of the bulk-limit antiferromagnetic (AF) order parameter, compressibility, and temperature-dependent DC conductivity. In the clean limit, our data are consistent with previous results showing a single quantum critical point separating the semi-metallic and AF Mott insulating phases. With the presence of randomness, a non-magnetic disordered insulating phase emerges. Inside this disordered insulator phase, there is a crossover from a gapless Anderson-like insulator to a gapped Mott-like insulator.