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Radiative control of dark excitons at room temperature by nano-optical antenna-tip Purcell effect

TitleRadiative control of dark excitons at room temperature by nano-optical antenna-tip Purcell effect
Publication TypeJournal Article
Year of Publication2018
AuthorsPark, K-D, Jiang, T, Clark, G, Xu, X, Raschke, MB
JournalNature Nanotechnology
Pagination59 - 64
Date PublishedJan-01-2018
KeywordsNanophotonics and plasmonics, Two-dimensional materials

Excitons, Coulomb-bound electron–hole pairs, are elementary photo-excitations in semiconductors that can couple to light through radiative relaxation. In contrast, dark excitons (XD) show anti-parallel spin configuration with generally forbidden radiative emission. Because of their long lifetimes, these dark excitons are appealing candidates for quantum computing and optoelectronics. However, optical read-out and control of XD states has remained challenging due to their decoupling from light. Here, we present a tip-enhanced nano-optical approach to induce, switch and programmably modulate the Xemission at room temperature. Using a monolayer transition metal dichalcogenide (TMD) WSe2 on a gold substrate, we demonstrate ~6 × 105-fold enhancement in dark exciton photoluminescence quantum yield achieved through coupling of the antenna-tip to the dark exciton out-of-plane optical dipole moment, with a large Purcell factor of ≥2 × 103 of the tip–sample nano-cavity. Our approach provides a facile way to harness excitonic properties in low-dimensional semiconductors offering new strategies for quantum optoelectronics.


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