Monolayer transition metal dichalcogenides under finite-pulse polarized radiation

TL;DR

This paper investigates how finite-pulse polarized radiation affects electron dynamics in monolayer transition metal dichalcogenides, revealing transient valley polarization and band structure modifications through advanced theoretical modeling.

Contribution

It introduces a novel theoretical approach combining Floquet engineering with the $t-t^{\u2019}$ formalism to analyze finite-pulse effects on electron states in 2D materials.

Findings

Transient valley polarization induced by finite pulses

Dynamical band structure modifications observed

Time-dependent circular dichroism revealed

Abstract

Recent advances in time-resolved angle-resolved photoemission spectroscopy have enabled access to ultrafast electron states and their spin dynamics in solids. Atomically thin transition metal dichalcogenides are paradigmatic two-dimensional materials where electron momentum and spin degrees of freedom are coupled, being suitable candidates for time-resolved spectroscopy studies. In this work, we present a thorough study of the electron dynamics when these materials are subject to an intense finite-pulse driving radiation. We extend the scope of the conventional Floquet engineering and rely of the so-called $t-t^{\prime}$ formalism to deal with driving fields described with two distinct time scales, namely the envelope amplitude timescale and the time period of the external field. The interplay between the finite-pulse timescales and the intrinsic properties of the electrons gives rise to transient valley polarization and dynamical modifications of band structures, revealed by the time-dependent circular dichroism of the sample.