High harmonic generation in monolayer and bilayer of transition metal dichalcogenide

TL;DR

This paper presents a theoretical study on how high harmonic generation (HHG) can be used to probe the electronic and structural properties of monolayer and bilayer MoS2, revealing insights into valleytronics and spin-orbit effects.

Contribution

It introduces a theoretical approach using HHG to investigate the effects of pseudospin, valley indexes, and structural differences in TMDCs like MoS2.

Findings

HHG encodes pseudospin and valley information in emitted photons

Circularly polarized laser can probe Berry curvature effects

The study suggests potential for ultrafast valleytronics manipulation

Abstract

In transition metal dichalcogenides (TMDCs), charge carriers have spin, pseudospin, and valley degrees of freedom associated with magnetic moments. The monolayers and bilayers of the TMDCs, in particular, MoS$_2$, lead strong couplings between the spin and pseudospin effects. This feature have drawn attention to TMDCs for their potential use in advanced tech devices. Meanwhile, high-order harmonic generation (HHG) has recently been applied to the characterization of the electronic structure of solids, such as energy dispersion, Berry-curvature, and topological properties. Here, we show theoretical results obtained with the `philosophy' of using HHG to investigate the structural effects of the monolayer and bilayers of MoS$_2$ on nonlinear optical emission. We use a simple model for MoS$_2$ in the 3R AB staking. We find that the pseudospin and valley indexes (the Berry curvature and the dipole transition matrix element) in TMDC driven by circularly polarized laser (CPL) can encode in the high energy photon emissions. This theoretical investigation is expected to pave the way for the ultrafast manipulation of valleytronics and lead to new questions concerning the spin-obit-coupling (SOC) effects on TMDC materials, Weyl Semimetals, and topological phases and transitions in topological insulators.