Dynamic Screening and Low Energy Collective Modes in Bilayer Graphene

TL;DR

This paper theoretically investigates the dynamic screening and plasmon modes in bilayer graphene, revealing unique non-local dispersion effects and comparing these with single and double layer graphene systems.

Contribution

It provides a detailed theoretical analysis of the dielectric function and plasmon dispersion in bilayer graphene, highlighting differences from single-layer graphene and classical 2D electron gas.

Findings

Long wavelength plasmon dispersion matches classical 2D electron gas.

Non-local corrections decrease plasmon frequency in bilayer graphene.

Distinct differences from single-layer graphene plasmon behavior.

Abstract

We theoretically study the dynamic screening properties of bilayer graphene within the random phase approximation assuming quadratic band dispersion and zero gap for the single-particle spectrum. We calculate the frequency dependent dielectric function of the system and obtain the low energy plasmon dispersion and broadening of the plasmon modes from the dielectric function. We also calculate the optical spectral weight (i.e. the dynamical structure factor) for the system. We find that the leading order long wavelength limit of the plasmon dispersion matches with the classical result for 2D electron gas. However, contrary to electron gas systems, the non-local plasmon dispersion corrections decrease the plasmon frequency. The non-local corrections are also different from the single layer graphene. Finally, we also compare our results with the double layer graphene system (i.e. a system of two independent graphene monolayers).