Dynamical response functions and collective modes of bilayer graphene

TL;DR

This paper provides analytical expressions for the density response functions of bilayer graphene, revealing how its electronic fluctuations can switch between different character types based on energy and doping levels.

Contribution

It introduces new analytical and semi-analytical formulas for the density response functions of bilayer graphene using the four-band continuum model.

Findings

Density fluctuations can be single-component massive-chiral or two-layer in character.

Response functions depend on energy and doping levels.

Results enhance understanding of electronic behavior in bilayer graphene.

Abstract

Bilayer graphene (BLG) has recently attracted a great deal of attention because of its electrically tunable energy gaps and its unusual electronic structure. In this Letter we present analytical and semi-analytical expressions, based on the four-band continuum model, for the layer-sum and layer-difference density response functions of neutral and doped BLG. These results demonstrate that BLG density-fluctuations can exhibit either single-component massive-chiral character or standard two-layer character, depending on energy and doping.