Twist-Angle-Dependent Valley Polarization of Intralayer Moiré Excitons in van der Waals Superlattices

Twistronics, which utilizes the moiré potential to induce exotic excitations in twisted material systems, has garnered significant attention in recent years. In this Letter, using the Bethe-Salpeter calculations based on a continuum model of electronic structures, we explore the optical characteristics of intralayer moiré excitons in twisted bilayer transition metal dichalcogenide heterostructures. We find the Coulomb exchange interactions strongly influence these excitons and the degree of valley polarization and that the splitting between spin-singlet and spin-triplet moiré excitons can be effectively controlled by varying the twist angle. Specifically, intralayer bright spin-singlet moiré excitons confined in a twisted WSe2/WS2 heterostructure can achieve valley polarization levels as high as 90% at small twist angles, which holds promise for future applications in valleytronics. These findings underscore the twist angle as a novel parameter for manipulating the optical properties of moiré excitons, thereby establishing moiré semiconductors as a promising platform for investigating many-body physics in solid-state systems.