Universal conductance fluctuations in Dirac materials in the presence of long-range disorder

TL;DR

This study investigates how long-range disorder affects quantum conductance fluctuations in Dirac materials, revealing a universal behavior at large scales and deviations in realistic conditions, with implications for understanding experimental noise data.

Contribution

It provides the first detailed numerical analysis of conductance fluctuations in Dirac materials with non-Gaussian long-range disorder, highlighting the conditions for universality and non-universality.

Findings

Quantum transport becomes universal at large system sizes and disorder strengths.

Realistic parameters show deviations from universal conductance fluctuations.

Experimental 1/f noise data may reflect non-universal crossover regimes.

Abstract

We study quantum transport in Dirac materials with a single fermionic Dirac cone (strong topological insulators and graphene in the absence of intervalley coupling) in the presence of non-Gaussian long-range disorder. We show, by directly calculating numerically the conductance fluctuations, that in the limit of very large system size and disorder strength, quantum transport becomes universal. However, a systematic deviation away from universality is obtained for realistic system parameters. By comparing our results to existing experimental data on 1/f noise, we suggest that many of the graphene samples studied to date are in a non-universal crossover regime of conductance fluctuations.