The optical conductivity of graphene in the visible region of the spectrum

TL;DR

This paper calculates the optical conductivity of graphene in the visible spectrum beyond the Dirac cone approximation, showing small corrections and aiding the interpretation of experimental data.

Contribution

It provides a full expression for graphene's optical conductivity in the visible range, including effects of next nearest neighbor hopping, extending beyond the Dirac cone approximation.

Findings

Corrections to Dirac cone approximation are only a few percent in the visible range.

The full expression for optical conductivity enables better interpretation of experimental results.

Transmission and reflection coefficients are derived from the conductivity calculations.

Abstract

We compute the optical conductivity of graphene beyond the usual Dirac cone approximation, giving results that are valid in the visible region of the conductivity spectrum. The effect of next nearest neighbor hoping is also discussed. Using the full expression for the optical conductivity, the transmission and reflection coefficients are given. We find that even in the optical regime the corrections to the Dirac cone approximation are surprisingly small (a few percent). Our results help in the interpretation of the experimental results reported by Nair {\it et al.} [Science {\bf 320}, 1308 (2008)].