The electromagnetic field confinement and amplification typical of nano-sized metallic objects supporting localized surface plasmon resonances, i.e., light-induced collective electronic oscillations, can significantly strengthen the interaction of light with atomically thin transition metal dichalcogenides. In view of the realization of plasmon-enhanced devices, it is crucial to investigate the effects induced by light confinement within metallic nanostructures on the excitonic properties of these materials at the nanoscale. Here, we exploit tip-enhanced photoluminescence spectroscopy to locally control the excitons of monolayer molybdenum disulfide (MoS2) coupled with gold nanotriangles in the quantum tunneling regime. The spatial resolution of 10 nm in the tip-enhanced photoluminescence measurements made it possible to image the light-emission related properties of monolayer MoS2 across one single metallic nanostructure and to investigate the effect of the plasmonic enhancement on its photoluminescence peak. Moreover, by taking advantage of the degree of freedom given by the tuning of the tip-sample distance; it was possible to probe the effect of the plasmonic pico-cavity size on the photoluminescence quenching rate of monolayer MoS2.

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