High-order harmonic generation in gapped bilayer graphene

TL;DR

This paper develops a quantum theoretical model for high-order harmonic generation in gapped bilayer graphene, demonstrating its potential as an efficient medium for THz and infrared harmonic generation under strong electromagnetic fields.

Contribution

It introduces a numerical quantum approach to analyze harmonic generation in gapped bilayer graphene near the Dirac points, considering multiphoton and nonadiabatic regimes.

Findings

Gapped bilayer graphene can generate both even and odd high harmonics.

The process is effective in the THz and far infrared frequency domains.

The theory applies to arbitrary polarization of the driving electromagnetic wave.

Abstract

Microscopic nonlinear quantum theory of interaction of coherent electromagnetic radiation with gapped bilayer graphene is developed. The Liouville-von Neumann equation for the density matrix is solved numerically at the multiphoton excitation regime. The developed theory of interaction of charged carriers with strong driving wave field is valid near the Dirac points of the Brillouin zone. We consider the harmonic generation process in the nonadiabatic regime of interaction when the Keldysh parameter is of the order of unity. On the basis of numerical solutions, we examine the rates of odd and even high-harmonics at the particle-hole annihilation in the field of a strong pump wave of arbitrary polarization. Obtained results show that the gapped bilayer graphene can serve as an effective medium for generation of even and odd high harmonics in the THz and far infrared domains of frequencies.