Transport Between Twisted Graphene Layers

TL;DR

This paper develops a theory of interlayer transport in twisted few-layer graphene, showing that conductance varies with twist angle and other parameters, revealing complex behavior near commensurate angles.

Contribution

It introduces a comprehensive theoretical framework for understanding how interlayer conductance in twisted graphene depends on twist angle, state lifetime, magnetic field, and bias.

Findings

Conductance is large and negative near commensurate angles.

Conductance is small and positive at incommensurate angles.

Transport properties are highly sensitive to twist angle and external conditions.

Abstract

Commensurate-incommensurate transitions are ubiquitous in physics and are often accompanied by intriguing phenomena. In few-layer graphene (FLG) systems, commensurability between honeycomb lattices on adjacent layers is regulated by their relative orientation angle theta, which is in turn dependent on sample preparation procedures. Because incommensurability suppresses inter-layer hybridization, it is often claimed that graphene layers can be electrically isolated by a relative twist, even though they are vertically separated by a fraction of a nanometer. We present a theory of interlayer transport in FLG systems which reveals a richer picture in which the specific conductance depends sensitively on theta, single-layer Bloch state lifetime, in-plane magnetic field, and bias voltage. We find that linear and differential conductances are generally large and negative near commensurate values of theta, and small and positive otherwise.