AC conductivity of graphene: from tight-binding model to 2+1-dimensional quantum electrodynamics

TL;DR

This paper explores the connection between the tight-binding model of graphene and 2+1D quantum electrodynamics, analyzing how symmetry breaking and finite Dirac mass influence optical conductivity and related experimental signatures.

Contribution

It establishes a detailed mapping between graphene's tight-binding Hamiltonian and continuum QED, highlighting symmetry considerations and their impact on optical properties.

Findings

Finite Dirac mass affects optical conductivity signatures.

Symmetry breaking influences optical sum rules.

Mapping provides insights into experimental observables.

Abstract

We consider the relationship between the tight-binding Hamiltonian of the two-dimensional honeycomb lattice of carbon atoms with nearest neighbor hopping only and the 2+1 dimensional Hamiltonian of quantum electrodynamics which follows in the continuum limit. We pay particular attention to the symmetries of the free Dirac fermions including spatial inversion, time reversal, charge conjugation and chirality. We illustrate the power of such a mapping by considering the effect of the possible symmetry breaking which corresponds to the creation of a finite Dirac mass, on various optical properties. In particular, we consider the diagonal AC conductivity with emphasis on how the finite Dirac mass might manifest itself in experiment. The optical sum rules for the diagonal and Hall conductivities are discussed.