Supersonic rotation of a superfluid: a long-lived dynamical ring

The recent results of the BEC group were published in Physical Review Letters this January 2020. The letter presents the experimental realization of a long-lived superfluid flow of a quantum gas rotating in an anharmonic potential, sustained by its own angular momentum. The gas is set into motion by rotating an elliptical deformation of the trap. An evaporation selective in angular momentum yields an acceleration of rotation until the density vanishes at the trap center, resulting in a dynamical ring with with 350 hbar of angular momentum per particle. The density profile of the ring corresponds to the one of a quasi two-dimensional superfluid, with a linear velocity reaching Mach 18 and a rotation lasting more than a minute.   Here you can find the whole article in arXiv and in the PRL journal.The article was selected as an Editor’s suggestion by PRL   The article gave place to a synopsis by APS. You can read the whole synopsis here.
(a) Computed density contour (red annulus) of the dynamical ring rotating in the shell trap (gray ellipsoid). (b) Experimental density profile of the annular superfluid rotating at supersonic speed (Mach 15 for these data). Photo credits : (a) Hélène Perrin, LPL, (b) Romain Dubessy, LPL