Orientation dependence of high-harmonic generation in monolayer transition metal dichalcogenides

TL;DR

This theoretical study reveals unique orientation-dependent high-harmonic generation behaviors in monolayer TMDCs, showing distinct harmonic orders in parallel and perpendicular emissions, linked to their atomic and lattice symmetries.

Contribution

It uncovers the orientation-dependent harmonic emission properties in TMDCs, highlighting their potential for high-harmonic spectroscopy and advancing understanding of their symmetry effects.

Findings

Parallel emissions contain only odd harmonics.

Perpendicular emissions contain only even harmonics.

Harmonic emissions exhibit opposite phases but same periodicity.

Abstract

We theoretically investigate the orientation dependence of high-harmonic generation (HHG) in monolayer transition metal dichalcogenides (TMDCs). We find that, unlike conventional solid-state and atomic layered materials such as graphene, both parallel and perpendicular emissions with respect to the incident electric field exist in TMDCs. Interestingly, the parallel (perpendicular) emissions principally contain only odd-(even-) order harmonics. Both harmonics show the same periodicity in the crystallographic orientations but opposite phases. These peculiar behaviors can be understood on the basis of the dipole moments in TMDCs, which reflect the symmetries of both atomic orbitals and lattice structures. Our findings are qualitatively consistent with recent experi- mental results and provide a possibility for high-harmonic spectroscopy of solid-state materials.