Chemical Structure, Photo Physics and Emission Control of Single-Photon Emitters in Two-Dimensional Materials

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Single-photon sources are the foundation of quantum optical technologies, including quantum communications, computing and metrology. Since the first demonstration of single-photon emission from sodium atoms in a low-density atomic beam in 1977, this nonclassical phenomenon has been observed in various types of solid-state zero-dimensional (0D) and one-dimensional (1D) materials, such as single molecules, quantum dots, nitrogen-vacancy centers in diamond, silicon carbide, and carbon nanotubes.Very recently, a new class of single-photon emitter has emerged based on atomically thin two-dimensional (2D) materials, such as semiconducting transition metal dichalcogenides and hexagonal boron nitride monolayers. These novel single-photon emitters are due to the generation and recombination of excitons that are spatially localized by natural defects in 2D materials . Bright and stable light emission from these defect excitons occurs at photon energies below the delocalized exciton emission and thus exhibit ideal nonclassical single photon characteristics. Furthermore, their intrinsic presence within atomically thin 2D materials brings the advantages of the unprecedented materials compatibility and processing flexibility associated with this materials paradigm. In particular, the defects in 2D materials can be located at desired positions with atomic precision suggesting the potential to build extended quantum emitter networks. These promising properties offer a new path to the scalable integration of high-quality quantum emitters in quantum optical technologies. However, the research of 2D quantum emitters (2DQEs) is just at an early stage with many open questions about their fundamental properties, including their chemical and electronic structures and emission control. The answers to these open questions will deepen current knowledge in quantum optics and material science. Most importantly, they will guide the development of 2DQEs towards practical quantum application.