Probing spin dynamics of 2D excitons with twisted light

TL;DR

This paper introduces a novel method using twisted light beams to control and probe spin-flip scattering of excitons in 2D materials, revealing temperature-dependent dynamics and offering new experimental avenues.

Contribution

The study demonstrates how optical vortex beams can modulate intra-valley spin-flip scattering rates in 2D TMDs, providing a new technique for exciton manipulation and investigation.

Findings

Intra-valley scattering rate can be tuned by vortex beam topological charge.

Photoluminescence intensity varies with topological charge, showing a crossover temperature.

Technique enables exploration of exciton physics in 2D systems.

Abstract

We propose a mechanism of intravalley spin-flip scattering in spin-valley coupled two dimensional systems by transferring momentum of light into exciton center of mass using optical vortex (OV) beams. By varying the dispersion of light using the topological charge of OV beam, we demonstrate a unique approach to control the intra-valley spin-flip scattering rate of excitons. From our photoluminescence measurements, we demonstrate that the intra-valley scattering rate in W-based TMDs can be tuned externally by OV beams. Variation of photoluminescence intensity with topological charges shows a crossover temperature (> 150 K), indicating competitions among time scales involving radiative recombination, spin-flip scattering, and thermal relaxations. Our proposed technique utilizing a structured light beam can open up a new approach to explore the physics of excitons in 2D systems.