Room-temperature superfluidity in a polariton condensate

Abstract

Superfluidity—the suppression of scattering in a quantum fluid at velocities below a critical value—is one of the most striking manifestations of the collective behaviour typical of Bose–Einstein condensates1. This phenomenon, akin to superconductivity in metals, has until now been observed only at prohibitively low cryogenic temperatures. For atoms, this limit is imposed by the small thermal de Broglie wavelength, which is inversely related to the particle mass. Even in the case of ultralight quasiparticles such as exciton-polaritons, superfluidity has been demonstrated only at liquid helium temperatures2. In this case, the limit is not imposed by the mass, but instead by the small binding energy of Wannier–Mott excitons, which sets the upper temperature limit. Here we demonstrate a transition from supersonic to superfluid flow in a polariton condensate under ambient conditions. This is achieved by using an organic microcavity supporting stable Frenkel exciton-polaritons at room temperature. This result paves the way not only for tabletop studies of quantum hydrodynamics, but also for room-temperature polariton devices that can be robustly protected from scattering.

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Figure 1: Optical set-up and sample dispersion.
Figure 2: Superfluid behaviour.
Figure 3: Excitation spectrum and power dependence.
Figure 4: Time-resolved interferograms.
Figure 5: Influence of the polariton group velocity.

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Acknowledgements

This work was funded by the ERC project POLAFLOW (grant no. 308136). F.B. and S.K.-C. acknowledge funding from the NSERC Discovery Grant and the Canada Research Chair Program. S.A.M acknowledges the Leverhulme Trust and EPSRC Active Plasmonics Programme and K.S.D. acknowledges funding from the Academy of Finland through its Centers of Excellence Programme (2012–2017) under project No. 284621 and the European Research Council (ERC-2013-AdG-340748-CODE).

Author information

G.L. conceived and performed the optical measurements with assistance from A.F.; K.S.D. fabricated the sample and F.B. performed the simulations. G.L., D.B., F.B., K.S.D., S.K.-C. and D.S. co-wrote the manuscript. All authors contributed to the data analysis. S.K.-C. supervised the fabrication and simulation work and D.S. supervised the measurements and coordinated the project.

Correspondence to Dario Ballarini or Stéphane Kéna-Cohen or Daniele Sanvitto.

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The authors declare no competing financial interests.

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Lerario, G., Fieramosca, A., Barachati, F. et al. Room-temperature superfluidity in a polariton condensate. Nature Phys 13, 837–841 (2017). https://doi.org/10.1038/nphys4147

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