Impact of Charge-Transfer Excitons on Unidirectional Exciton Transport in Lateral TMD Heterostructures

Lateral heterostructures built of monolayers of transition-metal dichalcogenides host a thin one-dimensional interface exhibiting a large energy offset. Recently, the formation of spatially separated charge-transfer (CT) excitons at the interface has been demonstrated, but their impact on technologically important exciton propagation across the interface has remained in the dark. In this theoretical work, we microscopically investigate the spatiotemporal exciton dynamics in the exemplary hBN-encapsulated WSe₂-MoSe₂ lateral heterostructure. We reveal a highly interesting interplay of energy-offset-driven unidirectional exciton drift across the interface and efficient capture into energetically lower CT excitons at the interface. This interplay triggers a counterintuitive thermal control of exciton transport with less efficient propagation at lower temperatures, opposite to conventional semiconductors. We predict clear signatures of this intriguing exciton propagation in both far- and near-field photoluminescence experiments. Our results present an advance in the microscopic understanding of technologically relevant unidirectional exciton transport in lateral heterostructures.