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Bilayer graphene spectral function in the random phase approximation and self-consistent GW approximation

Journal article
Authors Andro Sabashvili
Stellan Östlund
Mats Granath
Published in Physical Review B. Condensed Matter and Materials Physics
Volume 88
Pages artikel nr 085439
ISSN 1098-0121
Publication year 2013
Published at Department of Physics (GU)
Pages artikel nr 085439
Language en
Links dx.doi.org/10.1103/PhysRevB.88.0854...
Keywords graphene, plasmon, plasmaron
Subject categories Condensed Matter Physics

Abstract

We calculate the single-particle spectral function for doped bilayer graphene in the low energy limit, described by two parabolic bands with zero band gap and long range Coulomb interaction. Calculations are done using thermal Green's functions in both the random phase approximation (RPA) and the fully self-consistent GW approximation. Consistent with previous studies RPA yields a spectral function which, apart from the Landau quasiparticle peaks, shows additional coherent features interpreted as plasmarons, i.e., composite electron-plasmon excitations. In the GW approximation the plasmaron becomes incoherent and peaks are replaced by much broader features. The deviation of the quasiparticle weight and mass renormalization from their noninteracting values is small which indicates that bilayer graphene is a weakly interacting system. The electron energy loss function, Im[−εq−1(ω)] shows a sharp plasmon mode in RPA which in the GW approximation becomes less coherent and thus consistent with the weaker plasmaron features in the corresponding single-particle spectral function.

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