Anisotropy of graphite optical conductivity

TL;DR

This paper investigates the anisotropic optical conductivity of graphite across a range of frequencies, revealing near-universal in-plane conductivity and significantly lower out-of-plane conductivity due to electron hopping.

Contribution

It provides a detailed evaluation of graphite's optical conductivity anisotropy, highlighting the frequency-dependent behavior and the underlying electronic dispersion effects.

Findings

In-plane conductivity approaches the universal graphene value.

Out-of-plane conductivity is about 1% of in-plane conductivity.

Conductivity exhibits a singularity related to electron dispersion peculiarities.

Abstract

The graphite conductivity is evaluated for frequencies between 0.1 eV, the energy of the order of the electron-hole overlap, and 1.5 eV, the electron nearest hopping energy. The in-plane conductivity per single atomic sheet is close to the universal graphene conductivity $e^2/4\hbar$ and, however, contains a singularity conditioned by peculiarities of the electron dispersion. The conductivity is less in the $c-$direction by the factor of the order of 0.01 governed by electron hopping in this direction.