Manipulating Interlayer Excitons for Ultra-pure Quantum Light Generation

Abstract Interlayer excitons (IXs) formed at the interface of two different atomically-thin semiconductors have been emerging as an exciting ground not only for exploring fascinating many-body phenomena such as exciton condensation,1-4 but also for realizing exciton-based information processing technologies.5, 6 In a parallel development, nanoscale strain engineering has emerged as an effective means for the localization of 2D intra-layer excitons and activation of defect states for quantum light generation.7-11 Exploring the intersection of these two exciting areas, where strain and defects are exploited for the manipulation of IX toward the emergence of new functionalities, is currently at a nascent stage.6 Here, using MoS2/WSe2 heterostructure as a model system, we demonstrate how strain, defects, and layering can be utilized as control knobs toward novel defect-bound IXs capable of bright, robust, and tunable quantum light emission in the technologically important near-infrared spectral range. More significantly, because the deep-level sulfur vacancy states isolate our quantum emitters (QEs) from any of the intra- and inter-layer excitons, we were able to achieve ultra-high single-photon purity with g(2)(0) = 0.01 meeting the critical milestone for quantum key distribution (QKD), logic gate and memory technologies.12 Our strategy of creating site-controlled QEs from the defect-bound IXs represents a paradigm shift in 2D quantum photonics research, from engineering intralayer exciton in monolayer structures towards IXs at the interface of 2D heterostructures.