Excitonic effects in the optical conductivity of gated graphene

TL;DR

This paper investigates how electron-electron interactions and excitonic effects influence the optical conductivity of gated graphene, explaining experimental features and extending theoretical models.

Contribution

It generalizes Elliot's formula for optical intensity in graphene, incorporating excitonic resonances and aligning with ab initio calculations.

Findings

Excitonic resonances explain mid-infrared optical features.

Enhanced conductivity beyond the universal value due to excitons.

Agreement with ab initio calculations in the neutral regime.

Abstract

We study the effect of electron-electron interactions in the optical conductivity of graphene under applied bias and derive a generalization of Elliot's formula, commonly used for semiconductors, for the optical intensity. We show that {\it excitonic resonances} are responsible for several features of the experimentally measured mid-infrared response of graphene such as the increase of the conductivity beyond the "universal" value above the Fermi blocked regime, the broadening of the absorption at the threshold, and the decrease of the optical conductivity at higher frequencies. Our results are also in agreement with {\it ab initio} calculations in the neutral regime.