High energy shift in the optical conductivity spectrum of the bilayer graphene

TL;DR

This paper theoretically investigates the optical conductivity of bilayer graphene, revealing a high-energy shift caused by excitonic effects that suppress traditional intraband transitions and introduce a new optical gap.

Contribution

It introduces a comprehensive theoretical analysis of optical conductivity in bilayer graphene considering excitonic effects and interlayer coupling beyond tight-binding models.

Findings

Excitonic effects cause a high-energy shift in optical conductivity.

Suppression of Drude intraband transitions at high frequencies.

Emergence of a new optical gap due to interactions.

Abstract

We calculate theoretically the optical conductivity in the bilayer graphene by considering Kubo-Green-Matsubara formalism. Different regimes of the interlayer coupling parameter have been considered in the paper. We show that the excitonic effects substantially affect the optical conductivity spectrum at the high-frequency regime when considering the full interaction bandwidth, leading to a total suppression of the usual Drude intraband optical transition channels and by creating a new type of optical gap. We discuss the role of the interlayer coupling parameter and the Fermi level on the conductivity spectrum, going far beyond the usual tight-binding approximation scheme for the extrinsic bilayer graphene.