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

Author
Abstract
Excitons, Coulomb-bound electron-hole pairs, are elementary photo-excitations in semiconductors that can couple to light through radiative relaxation. In contrast, dark excitons (X<sub>D</sub>) 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 X<sub>D</sub> 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 X<sub>D</sub>emission at room temperature. Using a monolayer transition metal dichalcogenide (TMD) WSe<sub>2</sub> on a gold substrate, we demonstrate ~6 x 10<sup>5</sup>-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 x 10<sup>3</sup> 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.
Year of Publication
2018
Journal
Nature Nanotechnology
Volume
13
Number of Pages
59-64
Date Published
2018-01
ISSN Number
1748-3387
URL
https://www.nature.com/articles/s41565-017-0003-0
DOI
10.1038/s41565-017-0003-0
JILA PI
Journal Article