Microscopic quantum theory of nonlinear absorption of strong electromagnetic radiation in doped graphene

TL;DR

This paper develops a microscopic quantum model for nonlinear absorption of strong terahertz electromagnetic radiation in doped graphene, focusing on Dirac fermions interacting with impurity Coulomb fields.

Contribution

It introduces an analytical solution to the density matrix for 2D Dirac particles under strong electromagnetic fields, enabling calculation of nonlinear absorption rates in doped graphene.

Findings

Efficient nonlinear absorption coefficient achievable in doped graphene.

Analytical solution for the density matrix in the presence of strong fields.

Nonlinear inverse-bremsstrahlung absorption rate derived for Dirac fermions.

Abstract

Microscopic quantum theory of nonlinear stimulated scattering of 2D Dirac particles in doped graphene on Coulomb field of impurity ions at the presence of an external strong coherent electromagnetic radiation is developed. We consider high Fermi energies and low frequencies (actually terahertz radiation) to exclude the valence electrons excitations. The Liouville-von Neumann equation for the density matrix is solved analytically, taking into account the interaction of electrons with the scattering potential in the Born approximation. With the help of this solution, the nonlinear inverse-bremsstrahlung absorption rate for a grand canonical ensemble of 2D Dirac fermions is calculated. It is shown that one can achieve the efficient absorption coefficient by this mechanism.