Velocity renormalization and anomalous quasiparticle dispersion in extrinsic graphene

TL;DR

This paper uses many-body perturbation theory to analyze how electron-electron interactions in doped graphene lead to velocity renormalization and anomalous dispersion, with predictions for experimental signatures and spectrum instability at low wave vectors.

Contribution

It provides a detailed quantitative analysis of many-body effects on graphene's quasiparticle dispersion and velocity, including substrate and density dependence, within the ring diagram approximation.

Findings

Interaction causes velocity renormalization in graphene.

Spectrum instability occurs at low wave vectors.

Significant difference between on-shell and off-shell self-energy predictions.

Abstract

Using many-body diagrammatic perturbation theory we consider carrier density- and substrate-dependent many-body renormalization of doped or gated graphene induced by Coulombic electron-electron interaction effects. We quantitatively calculate the many-body spectral function, the renormalized quasiparticle energy dispersion, and the renormalized graphene velocity using the leading-order self-energy in the dynamically screened Coulomb interaction within the ring diagram approximation. We predict experimentally detectable many-body signatures, which are enhanced as the carrier density and the substrate dielectric constant are reduced, finding an intriguing instability in the graphene excitation spectrum at low wave vectors where interaction completely destroys all particle-like features of the noninteracting linear dispersion. We also make experimentally relevant quantitative predictions about the carrier density and wave-vector dependence of graphene velocity renormalization induced by electron-electron interaction. We compare on-shell and off-shell self-energy approximations within the ring diagram approximation, finding a substantial quantitative difference between their predicted velocity renormalization corrections in spite of the generally weak-coupling nature of interaction in graphene.