Imaging strain-localized exciton states in nanoscale bubbles in monolayer transition metal dichalcogenides at room temperature

In monolayer transition metal dichalcogenides (1L-TMD’s), applied strain can deterministically create quantum emitters at arbitrary sites on-demand. Despite a robust empirical correlation with strain, the nanoscopic details of these quantum emitters are poorly understood. Here we combine room-temperature nano-optical imaging of excitons in nanobubbles in 1L-WSe₂ with atomistic structural models to elucidate how strain induces the nanoscale confinement potentials that give rise to highly localized exciton states in 2D semiconductors. Nano-optical imaging reveals localized excitons on length scales of ~10 nm at multiple sites along the periphery of individual nanobubbles, which is in stark contrast to predictions of continuum strain models. These results agree with theoretical confinement potentials derived from measured topographies of nanobubbles. We reproduce these findings in nanobubbles of low-defect WSe₂ and MoSe₂, suggesting our results are applicable to excitons in all the semiconducting 1L-TMD’s. Our results provide one-of-a-kind insight of how strain-induced confinement—without crystalline defects—can localize excitons on length scales commensurate with exciton size, providing key nanoscale structure-property information for quantum emitter phenomena in 1L-TMD’s.