Browsing by Author "Voronine, Dmitri V."

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    Quantum plasmonic control of trions in a picocavity with monolayer WS2
    (AAAS, 2019) He, Zhe; Han, Zehua; Yuan, Jiangtan; Sinyukov, Alexander M.; Eleuch, Hichem; Niu, Chao; Zhang, Zhenrong; Lou, Jun; Hu, Jonathan; Voronine, Dmitri V.; Scully, Marlan O.
    Monitoring and controlling the neutral and charged excitons (trions) in two-dimensional (2D) materials are essential for the development of high-performance devices. However, nanoscale control is challenging because of diffraction-limited spatial resolution of conventional far-field techniques. Here, we extend the classical tip-enhanced photoluminescence based on tip-substrate nanocavity to quantum regime and demonstrate controlled nano-optical imaging, namely, tip-enhanced quantum plasmonics. In addition to improving the spatial resolution, we use the scanning probe to control the optoelectronic response of monolayer WS2 by varying the neutral/charged exciton ratio via charge tunneling in Au-Ag picocavity. We observe trion “hot spots” generated by varying the picometer-scale probe-sample distance and show the effects of weak and strong coupling, which depend on the spatial location. Our experimental results are in agreement with simulations and open an unprecedented view of a new range of quantum plasmonic phenomena with 2D materials that will help to design new quantum optoelectronic devices.
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    Quantum plasmonic hot-electron injection in lateral WSe2/MoSe2heterostructures
    (American Physical Society, 2018) Tang, Chenwei; He, Zhe; Chen, Weibing; Jia, Shuai; Lou, Jun; Voronine, Dmitri V.
    Lateral two-dimensional (2D) transition-metal dichalcogenide (TMD) heterostructures have recently attracted wide attention as promising materials for optoelectronic nanodevices. Due to the nanoscale width of lateral heterojunctions, the study of their optical properties is challenging and requires using subwavelength optical characterization techniques. We investigated the photoresponse of a lateral 2D WSe2/MoSe2 heterostructure using tip-enhanced photoluminescence (TEPL) with nanoscale spatial resolution and with picoscale tip-sample distance dependence. We demonstrate the observation of quantum plasmonic effects in 2D heterostructures on a nonmetallic substrate, and we report the nano-optical measurements of the lateral 2D TMD heterojunction width of ∼150 nm and the charge tunneling distance of ∼20 pm. Controlling the plasmonic tip location allows for both nano-optical imaging and plasmon-induced hot-electron injection into the heterostructure. By adjusting the tip-sample distance, we demonstrated the controllability of the hot-electron injection via the competition of two quantum plasmonic photoluminescence (PL) enhancement and quenching mechanisms. The directional charge transport in the depletion region leads to the increased hot-electron injection, enhancing the MoSe2 PL signal. The properties of the directional hot-electron injection in the quantum plasmonic regime make the lateral 2D MoSe2/WSe2 heterostructures promising for quantum nanodevices with tunable photoresponse.