Interlayer Exciton Traps in Van der Waals Heterostructures

Two-dimensional (2D) van der Waals materials such as single layer transition metal dichalcogenides (TMDs) and hexagonal boron nitride (BN) have sparked interest in the study of atomically thin semiconducting heterostructures. The 2D nature and large excitonic binding energy of TMDs allow for the exploration of novel quantum optical effects. Using type-II heterostructures formed by stacking MoSe₂ and WSe₂ monolayers, we study interlayer excitons, bound electrons and holes residing in spatially separated layers. We fabricate dual-gated, BN encapsulated devices with electrical contacts in each layer, giving us pristine samples with full electrical control. Interlayer excitons in our heterostructures have near-infrared energies and lifetimes on the order of 100ns, both of which can be tunable using out-of-plane electric field. We observe localization of interlayer excitons in naturally formed traps that have longer lifetimes and higher intensities than in the non-localized regions. In addition, we can form artificial traps through confinement potentials using out-of-plane electric fields. Because of the large binding energies, interlayer excitons can serve as a platform for exploring the physics of light-matter interactions and Bose-Einstein condensates at high temperatures.