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Optically active quantum dots in monolayer WSe2

Nature Nanotechnology volume 10, pages 491–496 (2015)Cite this article

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Abstract

Semiconductor quantum dots have emerged as promising candidates for the implementation of quantum information processing, because they allow for a quantum interface between stationary spin qubits and propagating single photons1,2,3. In the meantime, transition-metal dichalcogenide monolayers have moved to the forefront of solid-state research due to their unique band structure featuring a large bandgap with degenerate valleys and non-zero Berry curvature4. Here, we report the observation of zero-dimensional anharmonic quantum emitters, which we refer to as quantum dots, in monolayer tungsten diselenide, with an energy that is 20–100 meV lower than that of two-dimensional excitons. Photon antibunching in second-order photon correlations unequivocally demonstrates the zero-dimensional anharmonic nature of these quantum emitters. The strong anisotropic magnetic response of the spatially localized emission peaks strongly indicates that radiative recombination stems from localized excitons that inherit their electronic properties from the host transition-metal dichalcogenide. The large ∼1 meV zero-field splitting shows that the quantum dots have singlet ground states and an anisotropic confinement that is most probably induced by impurities or defects. The possibility of achieving electrical control in van der Waals heterostructures5 and to exploit the spin–valley degree of freedom6 renders transition-metal-dichalcogenide quantum dots interesting for quantum information processing.

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Figure 1: Photoluminescence of monolayer WSe2 flakes.
Figure 2: Photon correlations and photoluminescence lifetimes of quantum dots.
Figure 3: Stability of emission and spectral wandering of quantum dots.
Figure 4: Magnetic field dependence of quantum dot photoluminescence.

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Acknowledgements

This work is supported by NCCR Quantum Science and Technology (NCCR QSIT), a research instrument of the Swiss National Science Foundation (SNSF).

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Author notes

  1. Ajit Srivastava and Meinrad Sidler: These authors contributed equally to this work

Authors and Affiliations

  1. Institute of Quantum Electronics, ETH Zurich, Zurich, CH-8093, Switzerland

    Ajit Srivastava, Meinrad Sidler & A. Imamoğlu

  2. Electrical Engineering Institute, Ecole Polytechnique Federale de Lausanne (EPFL), CH-1015, Switzerland

    Adrien V. Allain, Dominik S. Lembke & Andras Kis

Authors
  1. Ajit Srivastava
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  6. A. Imamoğlu
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Contributions

A.S. and M.S. carried out the optical measurements. A.V.A., D.S.L. and A.K. prepared the samples. A.S. and A.I. supervised the project and analysed the experimental data. All authors contributed extensively to this work.

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Correspondence to Ajit Srivastava or A. Imamoğlu.

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The authors declare no competing financial interests.

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Srivastava, A., Sidler, M., Allain, A. et al. Optically active quantum dots in monolayer WSe2. Nature Nanotech 10, 491–496 (2015). https://doi.org/10.1038/nnano.2015.60

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