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A Steady-State Approach for Studying Valley Relaxation Using an Optical Vortex Beam

Aswini Kumar Pattanayak¹, Pritam Das¹, Avijit Dhara¹

¹Department of Physics, Indian Institute of Technology, Kharagpur 721302, India.

|June 7, 2022

Abstract:

Spin-valley coupling in monolayer transition-metal dichalcogenides gives rise to valley polarization and coherence effect, limited by intervalley scattering caused by exciton-phonon, exciton-impurity, and electron-hole exchange interactions (EHEIs). We explore an approach to tune the EHEI by controlling the exciton center of mass momentum (COM) utilizing the photon distribution of higher-order optical vortex beams. By virtue of this, we have observed exciton-COM-dependent valley depolarization and decoherence, which gives us the ability to probe the valley relaxation time scale in a steady-state measurement. Our steady-state technique to probe the valley dynamics can open up a new paradigm to explore the physics of excitons in two-dimensional systems.

Keywords:

angular momentum of light e−h exchange interaction light−matter interaction optical vortex transition-metal dichalcogenides valleytronics

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