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Dipolar interactions between localized interlayer excitons in van der Waals heterostructures

Abstract

Although photons in free space barely interact, matter can mediate interactions between them resulting in optical nonlinearities. Such interactions at the single-quantum level result in an on-site photon repulsion, crucial for photon-based quantum information processing and for realizing strongly interacting many-body states of light. Here, we report repulsive dipole–dipole interactions between electric field-tuneable, localized interlayer excitons in the MoSe2/WSe2 heterobilayer. The presence of a single, localized exciton with an out-of-plane, non-oscillating dipole moment increases the energy of the second excitation by ~2 meV—an order of magnitude larger than the emission linewidth and corresponding to an inter-dipole distance of ~7 nm. At higher excitation power, multi-exciton complexes appear at systematically higher energies. The magnetic field dependence of the emission polarization is consistent with the spin-valley singlet nature of the dipolar molecular state. Our finding represents a step towards the creation of excitonic few- and many-body states such as dipolar crystals with spin-valley spinor in van der Waals heterostructures.

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Fig. 1: Interlayer exciton dipoles in MoSe2/WSe2 heterostructure.
Fig. 2: Excitons from MoSe2/WSe2 heterostructure at low temperature (~4 K).
Fig. 3: Signatures of localized interlayer biexcitons.
Fig. 4: Spin-valley structure of localized interlayer excitons and biexcitons under magnetic field.

Data availability

The data represented in Figs. 24 are provided with the paper as source data. All other data that support results in this article are available from the corresponding author on reasonable request.

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Acknowledgements

We thank A. Imamoğlu and M. Kroner for many enlightening discussions. We also thank R. Lemasters and H. Harutyunyan for assistance with atomic layer deposition. A.S. acknowledges support from the National Science Foundation through the EFRI programme, grant no. EFMA-1741691 and National Science Foundation DMR award no. 1905809.

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Contributions

A.S., W.L., X.L. and S.D. conceived the project. W.L., X.L., S.D. and L.D. carried out the measurements. W.L. performed the theoretical calculations. X.L., S.D. and L.D. prepared the samples. A.S. supervised the project. All authors were involved in analysis of the experimental data and contributed extensively to this work.

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Correspondence to Ajit Srivastava.

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Supplementary Information

Supplementary Figs. 1–16, Notes 1–6 and Table 1.

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Source Data Fig. 2

Raw data for Fig. 2.

Source Data Fig. 3

Raw data for Fig. 3.

Source Data Fig. 4

Raw data for Fig. 4.

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Li, W., Lu, X., Dubey, S. et al. Dipolar interactions between localized interlayer excitons in van der Waals heterostructures. Nat. Mater. 19, 624–629 (2020). https://doi.org/10.1038/s41563-020-0661-4

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