Universal dynamical conductance in graphite

TL;DR

This paper experimentally demonstrates that graphite's optical conductance per layer closely matches the theoretical value for monolayer graphene, with calculations explaining the minimal impact of interlayer hopping on conductance across a specific energy range.

Contribution

It provides experimental evidence and theoretical explanation for the universal dynamical conductance in graphite, linking it to monolayer graphene behavior despite interlayer interactions.

Findings

Optical sheet conductance per layer is close to (/2)e^2/h.

Interlayer hopping minimally affects conductance between 0.1 and 0.6 eV.

Temperature increases Drude spectral weight at the expense of low-energy spectral weight.

Abstract

We find experimentally that the optical sheet conductance of graphite per graphene layer is very close to $(\pi/2)e^2/h$, which is the theoretically expected value of dynamical conductance of isolated monolayer graphene. Our calculations within the Slonczewski-McClure-Weiss model explain well why the interplane hopping leaves the conductance of graphene sheets in graphite almost unchanged for photon energies between 0.1 and 0.6 eV, even though it significantly affects the band structure on the same energy scale. The f-sum rule analysis shows that the large increase of the Drude spectral weight as a function of temperature is at the expense of the removed low-energy optical spectral weight of transitions between hole and electron bands.