Nonlinear dynamics of electromagnetic field and valley polarization in WSe$_{2}$ monolayer

TL;DR

This study explores the nonlinear optical behavior and valley polarization effects in WSe₂ monolayers under various laser intensities, revealing complex responses, high harmonic generation, and circular dichroism driven by chiral resonant pulses.

Contribution

It provides a detailed analysis of the nonlinear optical response and valley polarization in WSe₂ monolayers using advanced simulation methods, highlighting new effects of laser intensity and polarization.

Findings

Linear response at low intensity (10^{10} W/cm^2)

Nonlinear behavior and saturable absorption at high intensity (10^{12} W/cm^2)

High harmonic generation up to the 11th order and circular dichroism effects

Abstract

Linear and nonlinear optical response of WSe$_{2}$ monolayer is investigated by two-dimensional Maxwell plus time-dependent density functional theory with spin-orbit interaction. By applying the chiral resonant pulses, the electron dynamics along with high harmonic generation are examined at weak and strong laser fields. WSe$_{2}$ monolayer shows the linear optical response at the intensity I = 10$^{10}$~W/cm$^{2}$ while a complex nonlinear behavior is observed at I = 10$^{12}$~W/cm$^{2}$. The nonlinear response of WSe$_{2}$ monolayer in terms of saturable absorption is observed at strong laser field. By changing the chirality of the resonant light, a strong circular dichroic effect is observed in the excited state population. A relatively weak laser field shows effective valley polarization while strong field induces spin-polarized carrier peak between $K$($K'$) and $\mathit{\Gamma}$-point via nonlinear process. On the other hand, the strong laser field shows high harmonics up to the 11th order. Our results demonstrate that circularly polarized resonant pulse generate high harmonics in WSe$_{2}$ monolayer of order 3n$\pm1$.