Room-temperature superfluidity in a polariton condensate

5 years ago

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 liquid^{4, 5, 6, 7}, and the link proposed by London was further evidenced by the observation of superfluidity in ultracold atomic BECs^{1, 8}. A quantitative description is given by the Gross–Pitaevskii (GP) equation^{9, 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 optics^{12, 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 magnons^{14, 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 barriers^{2, 16, 17, 18, 19, Publisher URL: http://dx.doi.org/10.1038/nphys4147
DOI: 10.1038/nphys4147}