Anomalous Dirac point transport due to extended defects in bilayer graphene

TL;DR

This paper explains the coexistence of insulating and metallic charge transport states at the Dirac point in bilayer graphene, attributing it to the interplay of evanescent modes and extended defects like partial dislocations.

Contribution

It reveals how extended defects influence charge transport states at the Dirac point, providing a unified explanation for observed insulating and metallic behaviors.

Findings

Conductivity distribution peaks at both insulating and metallic limits.

The distribution is strongly peaked at the Dirac point.

Extended defects cause the coexistence of different transport states.

Abstract

Charge transport at the Dirac point in bilayer graphene exhibits two dramatically different transport states, insulating and metallic, that occur in apparently otherwise indistinguishable experimental samples. We demonstrate that the existence of these two transport states has its origin in an interplay between evanescent modes, that dominate charge transport near the Dirac point, and disordered configurations of extended defects in the form of partial dislocations. In a large ensemble of bilayer systems with randomly positioned partial dislocations, the conductivity distribution $P(\sigma)$ is found to be strongly peaked at both the insulating and metallic limits. We argue that this distribution form, that occurs only at the Dirac point, lies at the heart of the observation of both metallic and insulating states in bilayer graphene.