Ab initio GW many-body effects in graphene

TL;DR

This paper presents a comprehensive ab initio GW calculation for graphene, revealing significant quasiparticle effects, a velocity renormalization, and a kink in the dispersion, aligning well with experimental observations.

Contribution

The study introduces a fully first-principles GW approach accounting for real graphene's structure and dynamical self-energy effects, improving agreement with experiments.

Findings

Fermi velocity increased by 17% compared to DFT-LDA

Identified a kink in the dispersion near the Dirac point due to plasmons

GW self-energy does not induce a band gap in graphene

Abstract

We present an {\it ab initio} many-body GW calculation of the self-energy, the quasiparticle band plot and the spectral functions in free-standing undoped graphene. With respect to other approaches, we numerically take into account the full ionic and electronic structure of real graphene and we introduce electron-electron interaction and correlation effects from first principles. Both non-hermitian and also dynamical components of the self-energy are fully taken into account. With respect to DFT-LDA, the Fermi velocity is substantially renormalized and raised by a 17%, in better agreement with magnetotransport experiments. Furthermore, close to the Dirac point the linear dispersion is modified by the presence of a kink, as observed in ARPES experiments. Our calculations show that the kink is due to low-energy $\pi \to \pi^*$ single-particle excitations and to the $\pi$ plasmon. Finally, the GW self-energy does not open the band gap.