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Polarization switching and electrical control of interlayer excitons in two-dimensional van der Waals heterostructures

Nature Photonics volume 13, pages 131–136 (2019)Cite this article

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Abstract

The long-lived interlayer excitons in van der Waals heterostructures based on transition-metal dichalcogenides, together with unique spin–valley physics, make them promising for next-generation photonic and valleytronic devices. Although the emission characteristics of interlayer excitons have been studied, efficient manipulation of their valley states, a necessary requirement for information encoding, is still lacking. Here, we demonstrate comprehensive electrical control of interlayer excitons in a MoSe2/WSe2 heterostructure. Encapsulation of our well-aligned stack with hexagonal boron nitride (h-BN) allows us to resolve two separate narrow interlayer transitions with opposite helicities under circularly polarized excitation, either preserving or reversing the polarization of incoming light. By electrically controlling their relative intensities, we realize a polarization switch with tunable emission intensity and wavelength. Finally, we observe large g-factors of these two transitions on application of an external magnetic field. These results are interpreted within the picture of moiré-induced brightening of forbidden optical transitions. The ability to control the polarization of interlayer excitons is a step towards the manipulation of the valley degree of freedom in realistic device applications.

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Fig. 1: Device characterization.
Fig. 2: Electrical control of interlayer excitons.
Fig. 3: Electrical control of polarization.
Fig. 4: Polarization switching action.
Fig. 5: Magnetic field effect on interlayer excitons.

Data availability

The data that support the findings of this study are available from the corresponding author on reasonable request.

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Acknowledgements

We acknowledge W. Yao, A. Chernikov and B. Urbaszek for discussions. We thank Z. Benes of CMi for help with electron beam lithography. D.U., A.C., A.A. and A.K. acknowledge support by the Swiss National Science Foundation (grant 153298), H2020 European Research Council (ERC, grant 682332), and Marie Curie-Sklodowska-Curie Actions (COFUND grant 665667). A.K. acknowledges funding from the European Union’s Horizon H2020 Future and Emerging Technologies under grant agreements 696656 and 785219 (Graphene Flagship). K.W. and T.T. acknowledge support from the Elemental Strategy Initiative conducted by MEXT, Japan, and from JSPS KAKENHI grant numbers JP15K21722 and JP25106006.

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Author notes

  1. These authors contributed equally: Alberto Ciarrocchi, Dmitrii Unuchek.

Authors and Affiliations

  1. Electrical Engineering Institute, École Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland

    Alberto Ciarrocchi, Dmitrii Unuchek, Ahmet Avsar & Andras Kis

  2. Institute of Materials Science and Engineering, École Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland

    Alberto Ciarrocchi, Dmitrii Unuchek, Ahmet Avsar & Andras Kis

  3. National Institute for Materials Science, 1–1 Namiki, Tsukuba, Japan

    Kenji Watanabe & Takashi Taniguchi

Authors
  1. Alberto Ciarrocchi
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  2. Dmitrii Unuchek
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Contributions

A.K. initiated and supervised the project. A.C. fabricated the devices. K.W. and T.T. grew the h-BN crystals. D.U. performed the optical measurements, assisted by A.C. A.C. and D.U. analysed the data with input from A.A. and A.K. All authors contributed to the writing of the manuscript.

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Correspondence to Andras Kis.

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Ciarrocchi, A., Unuchek, D., Avsar, A. et al. Polarization switching and electrical control of interlayer excitons in two-dimensional van der Waals heterostructures. Nature Photon 13, 131–136 (2019). https://doi.org/10.1038/s41566-018-0325-y

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