# Microscopic nonlinear quantum theory of absorption of coherent electromagnetic radiation in doped bilayer graphene

## TL;DR

This paper develops a microscopic quantum model for nonlinear electromagnetic absorption in doped bilayer graphene, revealing significant multiphoton absorption in terahertz and near-infrared frequencies.

## Contribution

It presents an analytical solution to the quantum dynamics of chiral particles in bilayer graphene under strong electromagnetic fields, including Coulomb interactions.

## Key findings

- Significant nonlinear absorption in terahertz and near-infrared ranges.
- Multiphoton stimulated bremsstrahlung as the dominant mechanism.
- Analytical solution of the density matrix dynamics.

## Abstract

The microscopic quantum theory of nonlinear stimulated scattering of chiral particles in doped $AB$ stacked bilayer graphene on Coulomb field of charged impurities in the presence of strong coherent electromagnetic radiation is presented. The Liouville-von Neumann equation for the density matrix is solved analytically. Here the interaction of electrons with the scattering potential is taken into account as a perturbation. The absorption rate of nonlinear inverse-bremsstrahlung for a grand canonical ensemble of fermionic chiral particles is calculated using the obtained solution. The analysis of the obtained rate shows that in the terahertz and near-infrared range of frequencies there is significant absorption of incident radiation via multiphoton stimulated bremsstrahlung mechanism.