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

Area of Science:

• Condensed Matter Physics
• Materials Science
• Quantum Optics

Background:

• Spin-valley coupling in transition-metal dichalcogenides leads to valley polarization and coherence.
• Intervalley scattering, influenced by exciton-phonon, exciton-impurity, and electron-hole exchange interactions (EHEIs), limits these effects.
• Understanding and controlling EHEIs is crucial for exploiting spin-valley properties.

Purpose of the Study:

• To explore a novel method for tuning electron-hole exchange interactions (EHEIs).
• To investigate the influence of exciton center of mass momentum (COM) on valley dynamics.
• To establish a steady-state technique for probing valley relaxation times in 2D materials.

Main Methods:

• Utilizing higher-order optical vortex beams to control the exciton center of mass momentum (COM).
• Analyzing the photon distribution of optical vortex beams to tune EHEIs.
• Performing steady-state measurements to observe valley depolarization and decoherence.

Main Results:

• Demonstrated control over EHEIs by manipulating exciton COM.
• Observed exciton-COM-dependent valley depolarization and decoherence.
• Successfully probed valley relaxation time scales using a steady-state approach.

Conclusions:

• The developed technique offers a new method to tune EHEIs in 2D materials.
• Exciton COM is a critical parameter influencing valley dynamics.
• This steady-state approach provides a new paradigm for exploring exciton physics in two-dimensional systems.