Current flow in biased bilayer graphene: the role of sublattices

TL;DR

This paper explores how electric fields influence current flow and charge distribution in biased bilayer graphene, revealing complex layer and sublattice effects that enable control of layer pseudospin.

Contribution

It uncovers the counterintuitive phenomenon where current flow does not align with charge density, highlighting the role of sublattice polarization and edge effects in bilayer graphene.

Findings

Current can flow over a different layer than where charge density is concentrated.

Charge becomes highly localized on one sublattice due to symmetry breaking.

Edge effects significantly influence current flow in bilayer nanoribbons.

Abstract

We investigate here how the current flows over a bilayer graphene in the presence of an external electric field perpendicularly applied (biased bilayer). Charge density polarization between layers in these systems is known to create a layer pseudospin, which can be manipulated by the electric field. Our results show that current does not necessarily flow over regions of the system with higher charge density. Charge can be predominantly concentrated over one layer, while current flows over the other layer. We find that this phenomenon occurs when the charge density becomes highly concentrated over only one of the sublattices, as the electric field breaks layer and sublattice symmetries for a Bernal-stacked bilayer. For bilayer nanoribbons, the situation is even more complex, with a competition between edge and bulk effects for the definition of the current flow. We show that, in spite of not flowing trough the layer where charge is polarized to, the current in these systems also defines a controllable layer pseudospin.