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

Nature Nanotechnologyvolume 13pages5964 (2018) | Download Citation

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 (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 XD emission 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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Acknowledgements

The authors would like to thank M. D. Lukin for insightful discussions. K.-D.P., T.J. and M.B.R. acknowledge funding from the US Department of Energy, Office of Basic Sciences, Division of Material Sciences and Engineering, under award no. DE-SC0008807. G.C. and X.X. acknowledge support from NSF-EFRI-1433496. We also acknowledge support provided by the Center for Experiments on Quantum Materials (CEQM) of the University of Colorado.

Author information

Affiliations

  1. Department of Physics, University of Colorado, Boulder, CO, USA

    • Kyoung-Duck Park
    • , Tao Jiang
    •  & Markus B. Raschke
  2. Department of Chemistry, University of Colorado, Boulder, CO, USA

    • Kyoung-Duck Park
    • , Tao Jiang
    •  & Markus B. Raschke
  3. JILA, University of Colorado, Boulder, CO, USA

    • Kyoung-Duck Park
    • , Tao Jiang
    •  & Markus B. Raschke
  4. Center for Experiments on Quantum Materials, University of Colorado, Boulder, CO, USA

    • Kyoung-Duck Park
    • , Tao Jiang
    •  & Markus B. Raschke
  5. Department of Physics, University of Washington, Seattle, WA, USA

    • Genevieve Clark
    •  & Xiaodong Xu
  6. Department of Materials Science and Engineering, University of Washington, Seattle, WA, USA

    • Genevieve Clark
    •  & Xiaodong Xu

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Contributions

M.B.R. and K.-D.P. conceived the experiment. K.-D.P. performed the measurements and the FDTD simulations. K.-D.P. and M.B.R. designed the samples, and G.C. and X.X. prepared the samples. K.-D.P. and M.B.R. analysed the data, and all authors discussed the results. K.-D.P. and M.B.R. wrote the manuscript with contributions from all authors. M.B.R. supervised the project.

Competing interests

The authors declare no competing financial interests.

Corresponding author

Correspondence to Markus B. Raschke.

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DOI

https://doi.org/10.1038/s41565-017-0003-0

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