Optical absorption and conductivity in quasi-two-dimensional crystals from first principles: Application to graphene

TL;DR

This paper develops a first-principles theoretical framework for analyzing the optical absorption and conductivity of quasi-two-dimensional crystals, exemplified by graphene, using the current-current response tensor within the RPA.

Contribution

It introduces a novel ab initio approach to compute electromagnetic response functions of Q2D materials, enabling accurate predictions of optical properties.

Findings

Accurately calculates optical absorption and conductivity in graphene.

Validates the theoretical approach against experimental data.

Demonstrates the method's applicability to doped and pristine graphene.

Abstract

This paper gives a theoretical formulation of the electromagnetic response of the quasi-two-dimensional (Q2D) crystals suitable for investigation of optical activity and polariton modes. The response to external electromagnetic field is described by current-current response tensor $\Pi_{\mu\nu}$ calculated by solving the Dyson equation in the random phase approximation (RPA), where current-current interaction is mediated by the photon propagator $D_{\mu\nu}$. The irreducible current-current response tensor $\Pi^0_{\mu\nu}$ is calculated from the {\em ab initio} Kohn-Sham (KS) orbitals. The accuracy of $\Pi^0_{\mu\nu}$ is tested in the long wavelength limit where it gives correct Drude dielectric function and conductivity. The theory is applied to the calculation of optical absorption and conductivity in pristine and doped single layer graphene and successfully compared with previous calculations and measurements.