Single Photon Emitters in 2D Materials

Single photon emitters (SPEs), or quantum emitters, are key components in a wide range of nascent quantum-based technologies. A solid state host offers many advantages for realization of a functional system, but creation and placement of SPEs are difficult to control. We describe here a novel paradigm for encoding strain into 2D materials to create and deterministically place SPEs in arbitrary locations with nanometer-scale precision [1]. We demonstrate the direct writing of SPEs in monolayer WSe2 using an atomic force microscope nano-indentation process. This quantum calligraphy allows deterministic placement and real time design of arbitrary patterns of SPEs for facile coupling with photonic waveguides, cavities and plasmonic structures. Because monolayer WSe2 is a direct gap semiconductor, SPE emission at a given wavelength is often intermixed with classical light resulting from conventional excitonic recombination, reducing the purity of the quantum emission as quantified by the second order autocorrelation function g(2)(t=0). We show that this undesirable classical emission, arising primarily from defect bound excitonic processes, can be significantly suppressed by electrostatic gating [2] or incorporating the WSe2 layer in a simple van der Waals heterostructure [3]. Suppression of this classical emission allows a more accurate assessment of the quantum emission character, and results in values of g(2) as low as 0.07 at low temperature. In addition, the SPE intensity at a given wavelength can be strongly modulated by changing the polarity of the gate bias, a feature of technological importance for practical applications. Initial results for SPEs in hBN will also be summarized, time permitting.<br/>[1] M.R. Rosenberger et al, ACS Nano 13, 904 (2019). https://doi.org/10.1021/acsnano.8b08730<br/>[2] C.E Stevens et al, ACS Nano 16, 20956 (2022). https://doi.org/10.1021/acsnano.2c08553<br/>[3] H.-J. Chuang et al, under review (2023).<br/>*Work done in collaboration with Matthew R. Rosenberger (Notre Dame), Hsun-Jen Chuang, Sungjoon Lee and Kathleen M. McCreary (Naval Research Laboratory), and Christopher Stevens and Joshua R. Hendrickson (Air Force Research Laboratory, Wright-Patterson AFB).<br/>† This work was supported by core programs at NRL.