Browsing by Author "Cui, Longji"

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    Molecular scale nanophotonics: hot carriers, strong coupling, and electrically driven plasmonic processes
    (De Gruyter, 2024) Zhu, Yunxuan; Raschke, Markus B.; Natelson, Douglas; Cui, Longji; Electrical and Computer Engineering; Materials Science and Nanoengineering; Physics and Astronomy
    Plasmonic modes confined to metallic nanostructures at the atomic and molecular scale push the boundaries of light–matter interactions. Within these extreme plasmonic structures of ultrathin nanogaps, coupled nanoparticles, and tunnelling junctions, new physical phenomena arise when plasmon resonances couple to electronic, exitonic, or vibrational excitations, as well as the efficient generation of non-radiative hot carriers. This review surveys the latest experimental and theoretical advances in the regime of extreme nano-plasmonics, with an emphasis on plasmon-induced hot carriers, strong coupling effects, and electrically driven processes at the molecular scale. We will also highlight related nanophotonic and optoelectronic applications including plasmon-enhanced molecular light sources, photocatalysis, photodetection, and strong coupling with low dimensional materials.
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    Tuning Light Emission Crossovers in Atomic-Scale Aluminum Plasmonic Tunnel Junctions
    (American Chemical Society, 2022) Zhu, Yunxuan; Cui, Longji; Abbasi, Mahdiyeh; Natelson, Douglas; Electrical and Computer Engineering; Materials Science and Nanoengineering; Physics and Astronomy
    Atomic-sized plasmonic tunnel junctions are of fundamental interest, with great promise as the smallest on-chip light sources in various optoelectronic applications. Several mechanisms of light emission in electrically driven plasmonic tunnel junctions have been proposed, from single-electron or higher-order multielectron inelastic tunneling to recombination from a steady-state population of hot carriers. By progressively altering the tunneling conductance of an aluminum junction, we tune the dominant light emission mechanism through these possibilities for the first time, finding quantitative agreement with theory in each regime. Improved plasmonic resonances in the energy range of interest increase photon yields by 2 orders of magnitude. These results demonstrate that the dominant emission mechanism is set by a combination of tunneling rate, hot carrier relaxation time scales, and junction plasmonic properties.