Scalable Quantum Light Sources Achieved Via Deterministic Exciton Confinement in 2D Semiconductors

Single-photon emitters represent a crucial component for advancements in secure communication and photonic technologies, yet creating practical, scalable devices remains a considerable hurdle. Raziel Itzhak, Alex Hayat, and Ilya Goykhman, from Technion and The Hebrew University of Jerusalem, now present a theoretically demonstrated method for reliably confining excitons within two-dimensional semiconductors. Their approach utilises local dielectric engineering, specifically by positioning a high-dielectric-constant nanopillar near the 2D material, to create a spatially varying environment that supports localised exciton states. This innovative technique enables deterministic single-photon emission compatible with standard lithography, crucially avoiding the need for material strain, defects, or etching, and offers a promising pathway towards integrating these emitters into advanced optoelectronic devices.

Deterministic Quantum Emitters in Two Dimensions

Scientists are developing methods to create and control quantum emitters, specifically excitons, within two-dimensional materials like molybdenum disulfide and tungsten diselenide. This research focuses on achieving precise placement, high brightness, and desirable optical properties for use in future quantum technologies. A central approach involves carefully controlling the surrounding dielectric environment to tailor the properties of these emitters. A key challenge lies in overcoming intrinsic imperfections and variations within 2D materials, which lead to randomly distributed and poorly defined quantum emitters.

Other limitations include low emission brightness, sensitivity to environmental factors, and the need to control exciton localization and maintain quantum coherence. To address these challenges, researchers are employing dielectric engineering, strain engineering, heterostructure design, and other innovative techniques. Dielectric engineering, in particular, allows for tuning the bandgap, enhancing screening of Coulomb interactions, confining excitons, and modifying the dielectric constant. This approach, combined with techniques like substrate selection and nanobubble formation, aims to create deterministic quantum emitters for applications in single-photon sources, quantum computing, quantum sensors, and advanced optoelectronics. This research represents a significant step towards realizing the full potential of 2D materials for quantum technologies by gaining unprecedented control over exciton properties.

Dielectric Confinement of Excitons in 2D Materials

Scientists have engineered a novel approach to confine excitons within two-dimensional semiconductors by precisely manipulating the surrounding dielectric environment. This involves positioning high-permittivity nanopillars above or beneath the 2D material, creating a spatially varying dielectric landscape that supports localized exciton states. Detailed numerical calculations reveal discrepancies between established analytical models and the actual electrostatic potential experienced by excitons, necessitating a numerical solution of the Poisson equation within the multilayer dielectric geometry. Results demonstrate that increasing the dielectric constant or pillar radius significantly reduces the potential beneath the pillar, effectively creating deeper and broader attractive traps for excitons. Numerical solutions of the two-dimensional Schrödinger equation confirm the formation of bound exciton states, with higher dielectric constants and larger pillar radii leading to reduced exciton binding energies and broader wavefunctions. This detailed analysis confirms that carefully optimizing both the dielectric constant and radius of the pillar allows for precise engineering of the confinement potential, facilitating strong spatial localization of 2D excitons and paving the way for deterministic single-photon emission.

Dielectric Nanopillars Confine Excitons in 2D Materials

Scientists have demonstrated a novel approach to confine excitons within two-dimensional materials using local dielectric engineering. This involves positioning a high-dielectric-constant nanopillar above or beneath the 2D material, creating a spatially varying dielectric environment that supports localized exciton states. This method enables deterministic single-photon emission without relying on strain, defects, or etching of the 2D layer, offering a pathway toward scalable on-chip quantum emitters compatible with CMOS fabrication. Calculations reveal that confinement depths exceeding 100 meV are achievable, demonstrating a strong potential for trapping excitons within the engineered dielectric landscape. Researchers found that increased dielectric screening reduces both exciton binding energy and quasiparticle band gap, with the band gap reduction exceeding the exciton binding energy reduction. This differential energy shift reinforces the exciton confinement potential, maximizing the ability to trap and localize excitons, and paving the way for reliable single-photon emission and scalable quantum photonic devices.

Dielectric Nanopillars Confine and Control Excitons

Scientists have demonstrated a scalable approach to confining excitons within two-dimensional semiconductors using dielectric nanopillars. By carefully engineering the dielectric environment surrounding the material, the team achieves strong spatial confinement of excitons without resorting to techniques like etching or applying strain. Numerical simulations confirm that the lowest-energy exciton state becomes strongly localized beneath a high-dielectric pillar, while higher-energy states remain more broadly distributed, offering a means of selective quantum state control. The key finding is that manipulating the band-gap energy through dielectric engineering dominates over changes in exciton binding energy, creating an effective potential well for the exciton. This well, exceeding 140 meV in depth, provides sufficient confinement for single-level control, potentially even at room temperature. This method offers a pathway to create quantum-dot-like behavior in two-dimensional materials, fully compatible with standard CMOS fabrication processes, and thus enabling the development of integrated quantum photonic devices.