High- and low-energy many-body effects of graphene in a unified approach

We show that the many-body features of graphene band structure and electronic response can be accurately evaluated by applying many-body perturbation theory to a tight-binding (TB) model. In particular, we compare TB results for the optical conductivity with previous ab initio calculations, showing nearly perfect agreement both in the low-energy region near the Dirac cone (∼100 meV) and at the higher energies of the π plasmon (∼5 eV). A reasonable agreement is reached also for the density-density response at the Brillouin zone corner. With the help of the reduced computational cost of the TB model, we study the effect of self-consistency on the screened interaction (W) and on the quasiparticle corrections, a task that is not yet achievable in ab initio frameworks. We find that self-consistency is important to reproduce the experimental results on the divergence of the Fermi velocity, as confirmed by previous studies, while it marginally affects the optical conductivity. Finally, we study the robustness of our results against doping or the introduction of a uniform dielectric environment.