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.

Twist-Driven Deep-Ultraviolet-Wavelength Exciton Funnel Effect in Bilayer Boron Nitride

“…Experimental realizations of quantum emitter arrays in strain textured monolayers MoS 2 and WSe 2 were reported previously by utilizing indented nanopillars, confirming the theoretical predictions of exciton funnel effect in a strain-engineered continuously varying band gap landscape. Besides, we note that recently, there are experimental efforts in realizing the quantum-dot light emitters in MoS 2 /WSe 2 heterostructures, and in hexagonal and orthorhombic boron nitride crystals, via the formation of defect states. Our work provides another general and intrinsic approach for achieving excitonic quantum dot arrays in moiré superlattices, which can be verified by photoluminescent measurements on twist-stacked exfoliated monolayer BN.…”

“…Quantum dots (QDs), also known as “artificial atoms”, have been widely utilized as fundamental building blocks in various applications, including light emitters/detectors, , photovoltaics, biomedical sensors, and photo/electrocatalysis. , Recent advancements in twisted two-dimensional (2D) van der Waals (vdW) bilayers have opened up new possibilities for creating arrays of QDs with uniform sizes. , The formation of moiré superlattices in these systems, with periodic potential landscapes spanning hundreds or thousands of unit cells, naturally creates quantum wells for carrier confinement. Twisted transition metal dichalcogenide (TMD) heterostructures have particularly been demonstrated to hold promise in realizing a variety of quantum emitters with high purity. − However, most intrinsic few-layer TMDs are indirect band gap semiconductors, limiting their optical quantum yield and efficiency . To overcome this limitation, heterostructures with a type II band alignment have been employed to create few-layer systems with direct band gaps. , Electronically doped TMD moiré heterostructures have been shown to exhibit Mott insulating states and generalized Wigner crystals with atomic-like orbitals. − Excitonic quantum emitter arrays are proposed in twisted TMD bilayers under an electric field .…”

“…Twisted transition metal dichalcogenide (TMD) heterostructures have particularly been demonstrated to hold promise in realizing a variety of quantum emitters with high purity. − However, most intrinsic few-layer TMDs are indirect band gap semiconductors, limiting their optical quantum yield and efficiency . To overcome this limitation, heterostructures with a type II band alignment have been employed to create few-layer systems with direct band gaps. , Electronically doped TMD moiré heterostructures have been shown to exhibit Mott insulating states and generalized Wigner crystals with atomic-like orbitals. − Excitonic quantum emitter arrays are proposed in twisted TMD bilayers under an electric field . Nonetheless, the moiré confinement potential induced in these TMD systems is typically less than 100 meV, − ,, making their optical performance and correlated properties temperature-sensitive, and the increased material complexity and required external fields further limit their broader applications.…”

Enhancing Single Photon Emission Purity via Design of van der Waals Heterostructures

“…An alternative approach has recently been described which utilizes a gold substrate film to quench background emission from TMD layers which come into contact with the gold between dielectric nanopillars formed on the gold, providing clean spectral isolation and high purity of the SPEs localized on the nanopillars. 48 Although the graphite cap layer and fast interlayer charge transfer also reduce the desired SPE intensity, this can be compensated for by photonic cavity, plasmonic or dielectric antenna effects to enhance the single photon emission rate. In contrast, no corresponding avenue exists to enhance the emission purity.…”

Cavity-Enhanced 2D Material Quantum Emitters Deterministically Integrated with Silicon Nitride Microresonators

“…31,32 Both indistinguishability and onchip brightness are important, and thus it is critical to maximize the coupling efficiency−indistinguishability product (η × V) while maintaining a high purity of the emitters. While including hBN emitters at UV 15,57 and visible 25 wavelengths, TMD monolayers, 23,26,52 and TMD heterostructures, 24,58 exhibiting a rich spectrum of quantum emitters spanning the ultraviolet-to-telecommunications wavelength transparency window of silicon nitride photonics. The height of each bar indicates the reported intensity of the photoluminescence from the class of emitters (the gray data points are brightness-corrected for the objective extraction efficiency, whereas the blue data points are reported at the detector).…”