Intervalley scattering, long-range disorder, and effective time reversal symmetry breaking in graphene

TL;DR

This paper explores how static disorder in graphene, such as curvature or topological defects, can induce effective time reversal symmetry breaking, affecting quantum corrections to conductivity and explaining experimental observations.

Contribution

It reveals that certain types of disorder can break time reversal symmetry in graphene, altering weak localization effects and requiring new theoretical regimes.

Findings

Disorder-induced effective time reversal symmetry breaking suppresses quantum correction.

Long or comparable intervalley scattering times are critical for this effect.

Results align with recent experimental observations of magnetoresistance in graphene.

Abstract

We discuss the effect of certain types of static disorder, like that induced by curvature or topological defects, on the quantum correction to the conductivity in graphene. We find that when the intervalley scattering time is long or comparable to $\tau_{\phi}$, these defects can induce an effective time reversal symmetry breaking of the hamiltonian associated to each one of the two valleys in graphene. The phenomenon suppresses the magnitude of the quantum correction to the conductivity and may result in the complete absence of a low field magnetoresistance, as recently found experimentally. Our work shows that a quantitative description of weak localization in graphene must include the analysis of new regimes, not present in conventional two dimensional electron gases.