Interlayer and intralayer excitons in MoSe₂/WS₂ twisted moiré heterostructures

Twisted, vertically stacked heterostructures of monolayer transition metal dichalcogenides (TMDs) have emerged as a unique platform for the generation of tunable optoelectronic properties. The individual layers host strongly bound excitons, and stacked heterostructures of TMDs typically present type II band alignment leading to the formation of long-lived, spatially separated interlayer excitons. The MoSe₂/WS₂ twisted heterobilayer presents a unique case in which the two conduction bands align nearly degenerately, leading to more complex interpretation of the intralayer and interlayer exciton landscape. In this work, we employ time- and angle-resolved photoemission spectroscopy to probe excitons in a variety of twisted MoSe₂/WS₂ heterobilayers to directly visualize the exciton occupation of the layers in momentum space. By characterizing the observed exciton signals for structures of different twist angles and layer stacking, we observe that MoSe₂/WS₂ heterobilayers show evidence for type I band alignment providing important insights for the observed ultrafast exciton dynamics in these systems.