3 years ago

Room-temperature superfluidity in a polariton condensate

Room-temperature superfluidity in a polariton condensate
Konstantinos S. Daskalakis, Stefan A. Maier, Lorenzo Dominici, Antonio Fieramosca, Stéphane Kéna-Cohen, Milena De Giorgi, Giuseppe Gigli, Dario Ballarini, Giovanni Lerario, Daniele Sanvitto, Fábio Barachati
First observed in liquid helium below the lambda point, superfluidity manifests itself in a number of fascinating ways. In the superfluid phase, helium can creep up along the walls of a container, boil without bubbles, or even flow without friction around obstacles. As early as 1938, Fritz London suggested a link between superfluidity and Bose–Einstein condensation (BEC)3. Indeed, superfluidity is now known to be related to the finite amount of energy needed to create collective excitations in the quantum liquid4, 5, 6, 7, and the link proposed by London was further evidenced by the observation of superfluidity in ultracold atomic BECs1, 8. A quantitative description is given by the Gross–Pitaevskii (GP) equation9, 10 (see Methods) and the perturbation theory for elementary excitations developed by Bogoliubov11. First derived for atomic condensates, this theory has since been successfully applied to a variety of systems, and the mathematical framework of the GP equation naturally leads to important analogies between BEC and nonlinear optics12, 13, 14. Recently, it has been extended to include condensates out of thermal equilibrium, like those composed of interacting photons or bosonic quasiparticles such as microcavity exciton-polaritons and magnons14, 15. In particular, for exciton-polaritons, the observation of many-body effects related to condensation and superfluidity such as the excitation of quantized vortices, the formation of metastable currents and the suppression of scattering from potential barriers2, 16, 17, 18, 19,

Publisher URL: http://dx.doi.org/10.1038/nphys4147

DOI: 10.1038/nphys4147

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