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Optical control of room-temperature valley polaritons

Abstract

The formation of half-light half-matter quasiparticles under strong coupling results in properties unique from those of the constituent components. Fingerprints of both light and matter are imprinted on the new quasiparticles, called polaritons. In the context of two-dimensional (2D) materials, this opens up the possibility of exploiting the intriguing spin–valley physics of a bare semiconductor combined with the light mass of the photonic component for possible quantum technologies. Specifically, the valley degree of freedom1,2, which remained largely unexplored until the advent of these materials, is highly attractive in this context as it provides an optically accessible route for the control and manipulation of electron spin. Here, we report the observation of room-temperature strongly coupled light–matter quasiparticles that are valley polarized because of the coupling of photons with specific helicity to excitons that occupy quantum mechanically distinct valleys in momentum space. The realization of valley polaritons in 2D semiconductor microcavities presents the first step towards engineering valley-polaritonic devices.

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Figure 1: Schematic of the valley polariton phenomena.
Figure 2: Dispersion of the microcavity.
Figure 3: Helicity of the polariton emission.
Figure 4: Helicity of polariton emission under the resonant pump (Pump 2).
Figure 5: Theoretical simulation of the angle dependence of helicity.

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Acknowledgements

Work at the City University of New York was supported by the National Science Foundation (NSF) under the EFRI 2-DARE program EFMA-1542863 (Z.Sun, A.G., M.D., B.C., P.G. and V.M.M.), NSF-ECCS-1509551 (J.G. and C.R.C.), NSF MRSEC program DMR-1420634 (Z.Shotan) and by the Army Research Office W911NF-16-1-0256 (X.L. and V.M.M.). S.K.-C. acknowledges support by the Natural Sciences and Engineering Research Council Discovery grant program.

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Contributions

V.M.M., Z.Sun and X.L. initiated the project. Z.Sun, S.K.-C. and V.M.M. designed the experiments. Z.Sun, C.R.C. and M.D. fabricated the microcavity samples, Z.Sun, J.G., B.C. and Z.Shotan collected the optical characterization data, and Z.Sun, J.G. and B.C. analysed the data. A.G., P.G. and S.K.-C. carried out the theoretical modelling. All the authors contributed to the discussion of the results and writing the manuscript.

Corresponding author

Correspondence to Vinod M. Menon.

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The authors declare no competing financial interests.

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Sun, Z., Gu, J., Ghazaryan, A. et al. Optical control of room-temperature valley polaritons. Nature Photon 11, 491–496 (2017). https://doi.org/10.1038/nphoton.2017.121

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