Manifestation of nonlocal electron-electron interaction in graphene

TL;DR

This paper investigates how nonlocal electron-electron interactions influence the electronic structure of graphene, revealing deviations from local density approximation predictions through doping-dependent ARPES measurements.

Contribution

It demonstrates the importance of nonlocal exchange interactions in accurately describing graphene's band structure under doping conditions.

Findings

Band shift with doping is non-rigid, with the band bottom moving less than the Dirac point.

Local density approximation fails to explain the observed band shifts.

Nonlocal exchange interactions are essential for understanding electron behavior in graphene.

Abstract

Graphene is an ideal platform to study many-body effects due to its semimetallic character and the possibility to dope it over a wide range. Here we study the width of graphene's occupied $\pi$-band as a function of doping using angle-resolved photoemission. Upon increasing electron doping, we observe the expected shift of the band to higher binding energies. However, this shift is not rigid and the bottom of the band moves less than the Dirac point. We show that the observed shift cannot be accounted for by band structure calculations in the local density approximation but that non-local exchange interactions must be taken into account.