Nano-optical activation of tightly localized bound excitons in monolayer WSe₂ at room temperature

Bound excitons confined to nanobubbles in monolayer (ML) WSe₂, are efficient quantum light sources at cryogenic temperatures. However, when temperature is increased the bound excitons are suppressed, posing a significant challenge to realizing such single-photon emitters in practical devices. Using a model plasmonic-2D semiconductor architecture, we demonstrate that a nano-optical antenna activates optical emission from bound excitons in nanobubbles of ML-WSe₂ at room-temperature. The activation is attributed to Purcell enhancement, potential charge transfer, and local strain and exemplifies how the combination of a nano-optical antenna with a 2D semiconductors can enable novel phenomena. Further, bound exciton emission from single nanobubbles is imaged with sub-diffraction resolution, and multiple distinct states that are separated by distances as small as 50 nm are resolved. Analysis that extracts the strain profile from topography reveals a strong correlation of the bound excitons with local strain extrema within the nanobubble, directly visualizing how strain controls excitonic phenomena on nanoscale dimensions. Utilizing nano-optics to enable room-temperature emission of localized excitons is a critical step towards realizing room-temperature quantum emitters in ML-WSe₂.