The locking of the electron spin to the valley degree of freedom in transition metal dichalcogenide (TMD) monolayers has seen these materials emerge as a promising platform in valleytronics1,2. When embedded in optical microcavities, the large oscillator strengths of excitonic transitions in TMDs allow the formation of polaritons that are part-light part-matter quasiparticles3,4,5,6,7. Here, we report that polaritons in MoSe2 show an efficient retention of the valley pseudospin contrasting them with excitons and trions in this material. We find that the degree of the valley pseudospin retention is dependent on the photon, exciton and trion fractions in the polariton states. This allows us to conclude that in the polaritonic regime, cavity-modified exciton relaxation inhibits loss of the valley pseudospin. The valley-addressable exciton-polaritons and trion-polaritons presented here offer robust valley-polarized states with the potential for valleytronic devices based on TMDs embedded in photonic structures and valley-dependent nonlinear polariton–polariton interactions.

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  1. 1.

    , , , & Coupled spin and valley physics in monolayers of MoS2 and other group-VI dichalcogenides. Phys. Rev. Lett. 108, 196802 (2012).

  2. 2.

    , , & Control of valley polarization in monolayer MoS2 by optical helicity. Nat. Nanotech. 7, 494–498 (2012).

  3. 3.

    et al. Strong light–matter coupling in two-dimensional atomic crystals. Nat. Photon. 9, 30–34 (2015).

  4. 4.

    et al. Exciton–polaritons in van der Waals heterostructures embedded in tunable microcavities. Nat. Commun. 6, 8579 (2015).

  5. 5.

    et al. Room-temperature exciton-polaritons with two-dimensional WS2. Sci. Rep. 6, 33134 (2016).

  6. 6.

    et al. Fermi polaron-polaritons in charge-tunable atomically thin semiconductors. Nat. Phys. 13, 255–261 (2017).

  7. 7.

    et al. Room-temperature Tamm-plasmon exciton-polaritons with a WSe2 monolayer. Nat. Commun. 7, 13328 (2016).

  8. 8.

    , , , & Atomically thin MoS2: a new direct-gap semiconductor. Phys. Rev. Lett. 105, 136805 (2010).

  9. 9.

    , & Theory of neutral and charged excitons in monolayer transition metal dichalcogenides. Phys. Rev. B 88, 045318 (2013).

  10. 10.

    et al. Giant bandgap renormalization and excitonic effects in a monolayer transition metal dichalcogenide semiconductor. Nat. Mater. 13, 1091–1095 (2014).

  11. 11.

    et al. Bose–Einstein condensation of exciton polaritons. Nature 443, 409–414 (2006).

  12. 12.

    et al. Superfluidity of polaritons in semiconductor microcavities. Nat. Phys. 5, 805–810 (2009).

  13. 13.

    et al. Exciton–polariton spin switches. Nat. Photon. 4, 361–366 (2010).

  14. 14.

    et al. Realization of an all optical exciton-polariton router. Appl. Phys. Lett. 107, 201115 (2015).

  15. 15.

    et al. Ultra-low-power hybrid light–matter solitons. Nat. Commun. 6, 8317 (2015).

  16. 16.

    , , & Valley excitons in two-dimensional semiconductors. Natl Sci. Rev. 2, 57–70 (2014).

  17. 17.

    , & Exciton spin dynamics in quantum wells. Phys. Rev. B 47, 15776 (1993).

  18. 18.

    et al. Exciton fine structure and spin decoherence in monolayers of transition metal dichalcogenides. Phys. Rev. B 89, 201302 (2014).

  19. 19.

    , , , & Dirac cones and Dirac saddle points of bright excitons in monolayer transition metal dichalcogenides. Nat. Commun. 5, 3876 (2014).

  20. 20.

    et al. Motional narrowing in semiconductor microcavities. Phys. Rev. Lett. 77, 4792–4795 (1996).

  21. 21.

    et al. Polarization and time-resolved photoluminescence spectroscopy of excitons in MoSe2 monolayers. Appl. Phys. Lett. 106, 112101 (2015).

  22. 22.

    et al. Topographic control of open-access microcavities at the nanometer scale. Opt. Express 23, 17205–17216 (2015).

  23. 23.

    et al. Negatively charged polaritons in a semiconductor microcavity. Phys. Rev. B 63, 235310 (2001).

  24. 24.

    , & Optical spin Hall effect. Phys. Rev. Lett. 95, 136601 (2005).

  25. 25.

    et al. Strong exciton-photon coupling in open semiconductor microcavities. Appl. Phys. Lett. 104, 192107 (2014).

  26. 26.

    et al. Exciton and trion dynamics in atomically thin MoSe2 and WSe2: effect of localization. Phys. Rev. B 94, 165301 (2016).

  27. 27.

    et al. Intrinsic homogeneous linewidth and broadening mechanisms of excitons in monolayer transition metal dichalcogenides. Nat. Commun. 6, 8315 (2015).

  28. 28.

    , & Optical valley Hall effect based on transitional metal dichalcogenide cavity polaritons. Preprint at (2016).

  29. 29.

    et al. Polarization bistability and resultant spin rings in semiconductor microcavities. Phys. Rev. Lett. 105, 216402 (2010).

  30. 30.

    et al. Electronic properties of graphene encapsulated with different two-dimensional atomic crystals. Nano Lett. 14, 3270–3276 (2014).

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We thank the financial support of the Graphene Flagship under grant agreement 696656, the Engineering and Physical Sciences Research Council (EPSRC) grants EP/M012727/1 and EP/J007544/1, European Research Council (ERC) Advanced Grant EXCIPOL no. 320570, and Marie Sklodowska-Curie network Spin-NANO under grant agreement 676108. A.A.P.T., D.N.K. and J.M.S. acknowledge support from the Leverhulme Trust. F.W. acknowledges support from the Royal Academy of Engineering, and K.S.N. from the Royal Society, EPSRC, US Army Research Office and ERC Grant Hetero2D.

Author information


  1. Department of Physics and Astronomy, University of Sheffield, Sheffield S3 7RH, UK

    • S. Dufferwiel
    • , T. P. Lyons
    • , S. Schwarz
    • , M. S. Skolnick
    • , D. N. Krizhanovskii
    •  & A. I. Tartakovskii
  2. Institut Pascal, University Clermont Auvergne and CNRS, 24 Avenue Blaise Pascal, 63178 Aubiere Cedex, France

    • D. D. Solnyshkov
    •  & G. Malpuech
  3. Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH, UK

    • A. A. P. Trichet
    •  & J. M. Smith
  4. School of Physics and Astronomy, University of Manchester, Manchester M13 9PL, UK

    • F. Withers
    •  & K. S. Novoselov
  5. Centre for Graphene Science, CEMPS, University of Exeter, Exeter EX4 4QF, UK

    • F. Withers


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S.D, and T.P.L. carried out optical investigations with a contribution from S.S. A.A.P.T. designed and fabricated the concave mirrors. F.W. fabricated the MoSe2 samples. D.D.S. and G.M. carried out theoretical analysis. S.D. analysed the data and prepared the manuscript with contributions from all co-authors. J.M.S., K.S.N., M.S.S., D.N.K. and A.I.T. provided management of various aspects of the project. D.N.K. proposed the idea of using an open-access microcavity system, developed by his group, for polariton studies with TMD monolayers. S.D. and A.I.T. conceived the project. A.I.T. oversaw the project.

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The authors declare no competing financial interests.

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Correspondence to S. Dufferwiel or A. I. Tartakovskii.

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