Laterally Confined Monolayer WS ₂ Nanodots for Enhanced Excitonic Interaction

Monolayer transition-metal dichalcogenides (TMDCs) host tightly bound excitons with unique valley pseudospin properties, establishing them as an emerging material platform for nanophotonics and quantum technologies. Exciton-exciton interactions modify light-matter coupling and significantly affect the formation of exciton complexes. Here, we employ a top-down nanofabrication technique to manipulate interexcitonic interactions in WS₂ monolayers through lateral confinement. By restricting the motion of excitons in confined two-dimensional (2D) spaces, interexcitonic interactions are significantly modified, resulting in strong biexcitonic emission in nanodots smaller than 100 nm that is obscured in pristine monolayers. Moreover, we demonstrate selective optical excitation of valley pseudospins for excitonic quasiparticles in confined monolayers. Our work highlights the role of spatial confinement in excitonic behavior in 2D systems and provides new insights into the development of future photonic and valleytronic devices with low-dimensional platforms.