Coulomb screening and collective excitations in biased bilayer graphene

TL;DR

This paper studies how an electric bias in bilayer graphene affects Coulomb screening and plasmon modes, revealing the potential for long-lived plasmons useful in devices.

Contribution

It provides a detailed analysis of how an electric bias modifies collective excitations and plasmon damping in bilayer graphene, highlighting the emergence of undamped, long-lived modes.

Findings

Bias opens an energy gap in bilayer graphene.

The gap causes plasmon modes to soften and become undamped.

Long-lived plasmon modes could be observed experimentally.

Abstract

We have investigated the Coulomb screening properties and plasmon spectrum in a bilayer graphene under a perpendicular electric bias. The bias voltage applied between the two graphene layers opens a gap in the single particle energy spectrum and modifies the many-body correlations and collective excitations. The energy gap can soften the plasmon modes and lead to a crossover of the plasmons from a Landau damped mode to being undamped. Plasmon modes of long lifetime may be observable in experiments and may have potentials for device applications.