Electromagnetic response and pseudo-zero-mode Landau levels of bilayer graphene in a magnetic field

TL;DR

This paper compares the electromagnetic response of bilayer and monolayer graphene in a magnetic field, highlighting the unique features of bilayer graphene such as pseudo-zero-mode levels and their controllability.

Contribution

It introduces a low-energy effective gauge theory for bilayer graphene and analyzes the controllable splitting of pseudo-zero-mode levels under external fields.

Findings

Bilayer graphene shows a more sizable electromagnetic response than monolayers.

Zero-mode Landau levels significantly influence the density response in bilayers.

Pseudo-zero-mode level splitting can be controlled by in-plane electric fields or current.

Abstract

The electromagnetic response of bilayer graphene in a magnetic field is studied in comparison with that of monolayer graphene. Both types of graphene turn out to be qualitatively quite similar in dielectric and screening characteristics, especially those deriving from vacuum fluctuations, but the effect is generally much more sizable for bilayers. The presence of the zero-(energy-)mode Landau levels is a feature specific to graphene. In bilayers, unlike in monolayers, the effect of the zero-mode levels becomes visible and even dominant in density response as an externally-controllable band gap develops. It is pointed out that the splitting of nearly-degenerate pseudo-zero-mode levels at each valley, specific to bilayer graphene, is controlled by an applied inplane electric field or by an injected current. In addition, a low-energy effective gauge theory of bilayer graphene is constructed.