High-order harmonic generation in graphene: nonlinear coupling of intra and interband transitions

TL;DR

This paper explores high-order harmonic generation in graphene, revealing that nonlinear coupling between intra- and interband transitions under elliptically polarized light enhances HHG, with interference effects influencing the process.

Contribution

It provides a microscopic analysis of HHG in graphene, identifying the nonlinear coupling mechanisms and interference effects that influence harmonic enhancement.

Findings

Enhancement of HHG is due to nonlinear coupling between intra- and interband transitions.

Destructive interference between excitation channels affects HHG efficiency.

Manipulating band-gap or chemical potential could optimize HHG output.

Abstract

We investigate high-order harmonic generation (HHG) in graphene with a quantum master equation approach. The simulations reproduce the observed enhancement in HHG in graphene under elliptically polarized light [N. Yoshikawa et al, Science 356, 736 (2017)]. On the basis of a microscopic decomposition of the emitted high-order harmonics, we find that the enhancement in HHG originates from an intricate nonlinear coupling between the intraband and interband transitions that are respectively induced by perpendicular electric field components of the elliptically polarized light. Furthermore, we reveal that contributions from different excitation channels destructively interfere with each other. This finding suggests a path to potentially enhance the HHG by blocking a part of the channels and canceling the destructive interference through band-gap or chemical potential manipulation.