@article{4193,
  keywords = {Nanophotonics and plasmonics, Two-dimensional materials},
  author = {Kyoung-Duck Park and Tao Jiang and Genevieve Clark and Xiaodong Xu and Markus Raschke},
  title = {Radiative control of dark excitons at room temperature by nano-optical antenna-tip Purcell effect},
  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 = {2018},
  journal = {Nature Nanotechnology},
  volume = {13},
  pages = {59-64},
  month = {2018-01},
  issn = {1748-3387},
  url = {https://www.nature.com/articles/s41565-017-0003-0},
  doi = {10.1038/s41565-017-0003-0},
}