# Valley-Polarized Exciton Dynamics in Exfoliated Monolayer WSe$_2$

## TL;DR

This study investigates the ultrafast valley polarization dynamics in monolayer WSe2, revealing rapid decay mechanisms involving radiative recombination, spin-flip transitions, and dark state formation, using time-resolved Kerr reflectometry.

## Contribution

It provides new insights into the decay processes of valley polarization in monolayer WSe2, highlighting the roles of various scattering and recombination mechanisms.

## Key findings

- Valley polarization decays rapidly due to multiple processes.
- Kerr signal originates solely from charge-neutral excitons.
- Dark states contribute to long-lived valley polarization.

## Abstract

Semiconducting transition metal dichalcogenide monolayers have emerged as promising candidates for future valleytronics-based quantum information technologies. Two distinct momentum-states of tightly-bound electron-hole pairs in these materials can be deterministically initialized via irradiation with circularly polarized light. Here, we investigate the ultrafast dynamics of such a valley polarization in monolayer tungsten diselenide by means of time-resolved Kerr reflectometry. The observed Kerr signal in our sample stems exclusively from charge-neutral excitons. Our findings support the picture of a fast decay of the valley polarization of bright excitons due to radiative recombination, intra-conduction-band spin-flip transitions, intervalley-scattering processes, and the formation of long-lived valley-polarized dark states.