In monolayer transition metal dichalcogenides, quantum emitters are associated with localized strain that can be deterministically applied to create designer nano-arrays of single photon sources. Here, nano-optical imaging of nanobubbles in low-defect monolayers of WSe2 reveal localized excitons and quantum-dot-like states at room temperature, providing key insights of how strain-induced confinement—without crystalline defects—can efficiently localize excitons on length scales commensurate with exciton size. We are now investigating the strong coupling signatures between these states and Au surface plasmon-polaritons, so-called plexciton states. Using tip-enhanced photoluminescence, we see peak splitting of strain localized excitons in WSe2 nanobubbles coupled to gap-mode plasmons between an Au probe and substrate. Further, using WSe2 nanobubbles as a reporter, we observe signs of propagating surface plasmon-exciton in the spatial signal of the recorded photoluminescence. Our results highlight the promise of engineering plexcitons for use in the next generation of on-chip opto-electronic devices and quantum circuitry.

Signatures of quantum-dot-like states and strong exciton-plasmon coupling in monolayer WSe2-gold heterostructures

ACS Spring 2022

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