External gates and transport in biased bilayer graphene

TL;DR

This paper develops a theoretical framework for understanding electrical transport in biased bilayer graphene, emphasizing the roles of interlayer tunneling, coherence, and scattering effects beyond simple additive models.

Contribution

It introduces a comprehensive theory accounting for interlayer coherence and tunneling effects in bilayer graphene transport, including the impact of external gating.

Findings

Interlayer coherence significantly influences conductivity.

External gating does not alter transport properties.

Scattering within energy bands dominates low-energy transport.

Abstract

We formulate a theory of transport in graphene bilayers in the weak momentum scattering regime in such a way as to take into account contributions to the electrical conductivity to leading and next-to-leading order in the scattering potential. The response of bilayers to an electric field cannot be regarded as a sum of terms due to individual layers. Rather, interlayer tunneling and coherence between positive- and negative-energy states give the main contributions to the conductivity. At low energies, the dominant effect of scattering on transport comes from scattering within each energy band, yet a simple picture encapsulating the role of collisions in a set of scattering times is not applicable. Coherence between positive- and negative-energy states gives, as in monolayers, a term in the conductivity which depends on the order of limits. The application of an external gate, which introduces a gap between positive- and negative-energy states, does not affect transport. Nevertheless the solution to the kinetic equation in the presence of such a gate is very revealing for transport in both bilayers and monolayers.