Plasmon anomaly in the dynamical optical conductivity of graphene

TL;DR

This paper theoretically investigates how plasmon collective modes influence the frequency-dependent optical conductivity of graphene, revealing a disorder and interaction-dependent broad peak linked to plasmon effects.

Contribution

It introduces an analytical approach for relativistic Dirac electrons in graphene, showing how plasmon modes cause a frequency-dependent impurity scattering rate affecting optical conductivity.

Findings

Presence of a broad peak in optical conductivity due to plasmon effects

Peak position and amplitude depend on disorder and interaction parameters

Spectral weight redistribution aligns with experimental observations

Abstract

We theoretically consider the effect of plasmon collective modes on the frequency-dependent conductivity of graphene in the presence of the random static potential of charged impurities. We develop an equation of motion approach suitable for the relativistic Dirac electrons in graphene that allows analytical high-frequency asymptotic solution in the presence of both disorder and interaction. We show that the presence of the acoustic plasmon pole (i.e. the plasmon frequency vanishing at long wavelengths as the square-root of wavevector) in the inverse dynamical dielectric function of graphene gives rise to a strong variation with frequency of the screening effect of the relativistic electron gas in graphene on the potential of charged impurities. The resulting frequency-dependent impurity scattering rate gives rise to a broad peak in the frequency-dependent graphene optical conductivity with the amplitude and the position of the peak being sensitive to the detailed characteristics of disorder and interaction in the system. This sample (i.e. disorder, elecron density and interaction strength) dependent redistribution of the spectral weight in the frequency-dependent graphene conductivity may have already been experimentally observed in optical measurements.