# On the universal AC optical background in graphene - Condensed Matter > Strongly Correlated Electrons

Abstract: The latest experiments have confirmed the theoretically expected universalvalue $\pi e^2-2h$ of the ac conductivity of graphene and have revealeddepartures of the quasiparticle dynamics from predictions for the Diracfermions in idealized graphene. We present analytical expressions for the acconductivity in graphene which allow one to study how it is affected byinteractions, temperature, external magnetic field and the opening of a gap inthe quasiparticle spectrum. We show that the ac conductivity of graphene doesnot necessarily give a metrologically accurate value of the von Klitzingconstant $h-e^2$, because it is depleted by the electron-phonon interaction. Ina weak magnetic field the ac conductivity oscillates around the universal valueand the Drude peak evolves into a peak at the cyclotron frequency.

Author: V.P. Gusynin, S.G. Sharapov, J.P. Carbotte

Source: https://arxiv.org/