Signatures of strong exciton-surface plasmon coupling in monolayer transition metal dichalcogenide gold heterostructures

The strong light-matter interactions of excitons in the monolayer W- and Mo- transition metal dichalcogenides has led them to be among the most well-studied semiconductor excitations in recent years. Many rich phenomena has been revealed including multi-body exciton species as well as quantum confined excitons in strain potentials [1].  In addition, strong exciton-photon coupling inside optical cavities has been extensively studied, however their strong coupling with metal plasmons remains relatively unexplored. In this presentation, we will show recent work on the study of strong coupling signatures between excitons in monolayer WSe₂ 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.

[1] Darlington, T.P., Carmesin, C., Florian, M. et al. Nat. Nanotechnol. 15, 854–860 (2020). https://doi.org/10.1038/s41565-020-0730-5