Bose condensation, macroscopic quantum phenomena and atomic spatial correlations in superfluid He-4

Nikolay M. Blagoveshchenskii, Vladimir Anatolyevich Parfenov, Alexander V. Puchkov

Fernando Sols, Sigmund Kohler

Georgy V. Shlyapnikov

Hadiseh Alaeian, Mira Schedensack, Clara Bartels +2 more

Superfluidity and Bose–Einstein condensation are usually considered as two closely related phenomena. Indeed, in most macroscopic quantum systems, like liquid helium, ultracold atomic Bose gases, and exciton-polaritons, condensation and superfluidity occur in parallel. In photon Bose–Einstein condensates realized in the dye microcavity system, thermalization does not occur by direct interaction of the condensate particles as in the above described systems, i.e. photon–photon interactions, but by absorption and re-emission processes on the dye molecules, which act as a heat reservoir. Currently, there is no experimental evidence for superfluidity in the dye microcavity system, though effective photon interactions have been observed from thermo-optic effects in the dye medium. In this work, we theoretically investigate the implications of effective thermo-optic photon interactions, a temporally delayed and spatially non-local effect, on the photon condensate, and derive the resulting Bogoliubov excitation spectrum. The calculations suggest a linear photon dispersion at low momenta, fulfilling the Landau's criterion of superfluidity. We envision that the temporally delayed and long-range nature of the thermo-optic photon interaction offer perspectives for novel quantum fluid phenomena.

James F. Annett

Abstract Superconductivity, superfluidity, and Bose–Einstein condensation (BEC) are among the most fascinating phenomena in nature. Their strange and often surprising properties are direct consequences of quantum mechanics. This is why they only occur at low temperatures, and it is very difficult (but hopefully not impossible!) to find a room temperature superconductor. But, while most other quantum effects only appear in matter on the atomic or subatomic scale, superfluids and superconductors show the effects of quantum mechanics acting on the bulk properties of matter on a large scale. In essence they are macroscopic quantum phenomena.

J. Mayers