Observation of giant dipole moments of interlayer excitons via layer engineering

Interlayer excitons in van der Waals (vdW) heterostructures (HSs) have garnered significant attention due to their unique properties, including prolonged lifetimes and long-range transport. While extensive studies have been conducted on interlayer excitons in HSs composed of different monolayers, research on HSs formed by multilayer constituents remains limited, particularly regarding dipole moments, which play a crucial role in light-matter interactions. In this study, we investigate the dipole moments of interlayer excitons in multilayer WS₂ and InSe HSs using the quantum-confined Stark effect. Our findings reveal that the dipole moment increases monotonically with the number of layers in InSe or WS₂, reaching a maximum of 3.18 e nm, which is the largest value reported to date. Consequently, the dipole-dipole interaction is enhanced with the increasing layer number, as demonstrated by excitation power-dependent measurements. Ab initio calculations further support our experimental results, indicating the delocalization of the excitonic wave function with increasing layer thickness. Our findings introduce a novel layer-engineered mechanism for tuning the dipole moments of interlayer excitons in vdW heterostructures, paving the way for manipulating many-body interactions in low-dimensional quantum systems.