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.
@article{arxiv.0905.2883,
title = {Dynamical response functions and collective modes of bilayer graphene},
author = {Giovanni Borghi and Marco Polini and Reza Asgari and A. H. MacDonald},
journal= {arXiv preprint arXiv:0905.2883},
year = {2009}
}