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Electrically switchable anisotropic polariton propagation in a ferroelectric van der Waals semiconductor


Tailoring of the propagation dynamics of exciton-polaritons in two-dimensional quantum materials has shown extraordinary promise to enable nanoscale control of electromagnetic fields. Varying permittivities along crystal directions within layers of material systems, can lead to an in-plane anisotropic dispersion of polaritons. Exploiting this physics as a control strategy for manipulating the directional propagation of the polaritons is desired and remains elusive. Here we explore the in-plane anisotropic exciton-polariton propagation in SnSe, a group-IV monochalcogenide semiconductor that forms ferroelectric domains and shows room-temperature excitonic behaviour. Exciton-polaritons are launched in SnSe multilayer plates, and their propagation dynamics and dispersion are studied. This propagation of exciton-polaritons allows for nanoscale imaging of the in-plane ferroelectric domains. Finally, we demonstrate the electric switching of the exciton-polaritons in the ferroelectric domains of this complex van der Waals system. The study suggests that systems such as group-IV monochalcogenides could serve as excellent ferroic platforms for actively reconfigurable polaritonic optical devices.

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Fig. 1: Abundant FE domains in the SnSe multilayer plate.
Fig. 2: Near-field nano-imaging of the FE domains.
Fig. 3: Near-field nano-imaging of EPs on SnSe.
Fig. 4: Anisotropy of EPs in SnSe.
Fig. 5: Electrically switching an EP in SnSe with metal electrodes.
Fig. 6: Electrically switching an EP in SnSe with graphene/h-BN electrodes.

Data availability

The data that support the plots within this paper and other finding of this study are available at the online depository Zenodo (


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We thank A. Akey and J. Gardener at the Centre for Nanoscale Systems (CNS) at Harvard University for the TEM sample preparation and imaging. We thank Y. Han at Rice University for the helpful discussion on the TEM results. Part of the work was performed at CNS support by the National Science Foundation (NSF) under award no. ECCS-2025158. Y.L. was supported by the US Department of Energy under award no. DE-SC0019300. N.M. and J.K acknowledge the support by the US Department of Energy, Office of Science, Basic Energy Sciences under award no. DE-SC0020042 and the support from the STC Center for Integrated Quantum Materials, NSF grant number DMR-1231319. X.J. and J.K. acknowledge the support from the US Army Research Office (ARO) MURI project under grant number W911NF-18-1-0432. D.D., H.P. and P.K. acknowledge support from US Air Force Office of Scientific Research grants (nos. FA2386-21-1-4086 for P.K. and FA9550-17-1-0002 for H.P.). H.P. and P.K. acknowledge support from Department of Defense Vannevar Bush Faculty Fellowship (grant nos. N00014-16-1-2825 for H.P. and N00014-18-1-2877 for P.K.), Samsung Electronics and the NSF (PHY-1506284 for H.P.)

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Y.L., N.M. and W.L.W. conceived the experiment, Y.L., N.M., J.K. and W.L.W. planned the investigations. N.M., M.H-.C. and X.J. fabricated the pristine SnSe samples and carried out preliminary characterizations with J.K. and V.T. D.D. and Y.L. fabricated the device samples. Y.L. carried out the s-SNOM and LPFM experiments and analysed the data with N.M., J.K. and W.L.W. D.D. and Y.L. carried out the transport measurements under supervision of P.K. and H.P. Y.L. performed theoretical calculations and finite-difference time domain simulations. K.W and T.T provided the h-BN crystal. All authors discussed results and wrote the manuscript.

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Correspondence to William L. Wilson.

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Nature Nanotechnology thanks Cheng-Wei Qiu and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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Luo, Y., Mao, N., Ding, D. et al. Electrically switchable anisotropic polariton propagation in a ferroelectric van der Waals semiconductor. Nat. Nanotechnol. (2023).

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