Robust Transport Properties in Graphene

TL;DR

This paper investigates the transport properties of graphene's quasiparticles, revealing a disorder-independent minimal conductivity despite diffusion being strongly affected by impurity scattering.

Contribution

It demonstrates that graphene maintains a robust minimal conductivity unaffected by disorder, due to a compensation mechanism involving delocalized states.

Findings

Diffusion coefficient decreases with increasing disorder

Minimal conductivity remains constant regardless of impurity strength

Weak localization is not observed in graphene experiments

Abstract

Two-dimensional Dirac fermions are used to discuss quasiparticles in graphene in the presence of impurity scattering. Transport properties are completely dominated by diffusion. This may explain why recent experiments did not find weak localization in graphene. The diffusion coefficient of the quasiparticles decreases strongly with increasing strength of disorder. Using the Kubo formalism, however, we find a robust minimal conductivity that is independent of disorder. This is a consequence of the fact that the change of the diffusion coefficient is fully compensated by a change of the number of delocalized quasiparticle states.