Twist-Angle-Dependent Valley Polarization of Intralayer Moire<acute accent> Excitons in van der Waals Superlattices

Twistronics, which utilizes the moire<acute accent> 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 moire<acute accent> 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 moire<acute accent> excitons can be effectively controlled by varying the twist angle. Specifically, intralayer bright spin-singlet moire<acute accent> 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 moire<acute accent> excitons, thereby establishing moire<acute accent> semiconductors as a promising platform for investigating many-body physics in solid-state systems.