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, MoS2, lead to strong couplings between the spin and pseudospin effects. This feature has 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 MoS2 on nonlinear optical emission. We use a simple model for MoS2 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 a 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.
Highlights
Since high-order harmonics were first experimentally observed in ZnO [1,2,3], their potential in the nonlinear optical spectroscopy of solids has attracted the attention of ultrafast sciences and condensed matter physics [3,4,5,6]
The results show an interesting interconnection between the selection rules as well as a particular enhancement in the High-order Harmonic Generation (HHG) spectrum for a few harmonic orders (HOs)
Our theory shows that the high-harmonic generation (HHG) spectrum is:
Summary
Since high-order harmonics were first experimentally observed in ZnO [1,2,3], their potential in the nonlinear optical spectroscopy of solids has attracted the attention of ultrafast sciences and condensed matter physics [3,4,5,6]. These quantities contain pseudospin and valley indexes information of Mo2 for the monolayer or bilayer This suggests that the angular rotation of the harmonics can be linked to DTMEs. Surprisingly, in our HHG produced by RCP light, we notice that the HOs in the plateau region exhibit a layer difference with respect to the Berry Curvature and DTMEs. We take advantage of these quantities to analyze our numerical results, the selection rules that these quantities impose and the accumulating phase of the electron and hole wavepackets at each band (Appendix B). We will describe the time-dependent density matrix formalism to compute the density at the time and k-space
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