Light absorption in deformed graphene

TL;DR

This paper models the optical absorption in deformed graphene using a relativistic quantum electrodynamics framework, revealing an intrinsic Faraday Rotation effect caused by induced mass terms without external magnetic fields.

Contribution

It introduces a theoretical model for light absorption in deformed graphene considering parity and time-reversal symmetry breaking, predicting an intrinsic Faraday Rotation effect.

Findings

Light absorption is linked to the transverse conductivity of graphene.

An intrinsic Faraday Rotation effect occurs due to induced mass, not external magnetic fields.

Potential applications include optically tunable filters based on mechanical deformation.

Abstract

We model the low energy dynamics of graphene in the continuum in terms of a version of Reduced Quantum Electrodynamics restricting fermions to a (2+1)-dimensional brane, whilst photons remain within the (3+1)-dimensional bulk. For charge carriers, besides the Dirac mass gap, we consider a Haldane mass term which is induced by parametrizing an effective parity $\mathcal{P}$ and time-reversal $\mathcal{T}$ symmetry breaking that occurs on the brane when deformations of the honeycomb array are such that the equivalence between sublattices is lost. We make use of the relativistic Kubo formula and carry out an explicit calculation of the transverse conductivity. As expected, the filling factor is a half (in natural units) for each fermion species. Furthermore, assuming that a sample of this material is radiated perpendicularly with polarized monochromatic light of frequency $\omega$, from the modified Maxwell's equations we study the problem of light absorption in graphene in terms of the said conductivity. We observe an analog effect to the Faraday Rotation due the Induced Mass (FRIM)--and not to an external magnetic field-- in which light penetrating the sample changes its angle of polarization solely by effect of the induced mass. This effect might be relevant for the development of optic filters based on mechanical stretching of graphene flakes.