Spin valley dynamics of phonons entangled with circularly polarized light in WSe2

Abstract

Monolayer transition metal dichalcogenides (TMDs) have generated considerable interest in optoelectronics and valence-band electronics due to their unique electronic structures. In this paper, we incorporate the spin–orbit coupling effects and use the left-handed circularly polarized excitation of K-valley electrons as an example to investigate the excited-state dynamics of the coupling between the optical field and phonons in WSe₂. We reveal that left-handed light selectively excites K-valley electrons, while right-handed light selectively excites K′-valley electrons, inducing periodic Rabi oscillations. As the temperature increases from 100 K to 300 K, enhanced phonon interactions alter the primary electron relaxation pathways. At 100 K, post-depolarisation equilibrium sees over 70% of electrons distributed across and CB@K′↑, with approximately 20% residing in the CB@K↑ state. At 300 K, enhanced spin–orbit coupling induces frequent spin flips between the CB@K↓ and CB@K′↑ states following depolarisation equilibrium. Finally, we define the initial electron at the K-valley VB@K↑ and excite it with left-handed light. This achieves a comprehensive simulation of the electron transitioning from the ground state to the excited state and subsequently relaxing to the equilibrium state under the combined effects of the optical field and phonons. And this combined action of light field and phonons activates the inter-valley scattering pathway (VB@K↑ → CB@K′↑).