Dynamic Screening and Spectral Functions in Bilayer Graphene

We study the dynamic screening of Coulomb interactions in a bilayer graphene system within Random phase approximation. We derive an analytic expression for the dielectric function of the system and study the dispersion and damping of low energy plasmon modes. The quadratic dispersion and chirality of bilayer graphene systems lead to a plasmon dispersion which is distinct both from 2D electron gas and monolayer graphene plasmons. We also look at the effects of dynamic screening on the single particle spectral function of the system. We determine the quasiparticle weight, the effective mass and the damping of quasiparticles, which give a complete description of the low energy spectral function of the system.The compressibility of the system is also obtained from the self-energy renormalization of the chemical potential. We find that the presence of the second band leads to a well screened effective interaction, leading to much smaller renormalization of the Fermi liquid parameters in comparison to a 2D electron gas. However, the dynamic nature of the screening is very important in obtaining the single particle properties of this system.