Abstract
The phenomenon of superfluidity is characterized by the frictionless flow of a fluid below a critical velocity. Initially observed in liquid helium at low temperatures, and later in ultracold atomic gases, superfluidity has also been demonstrated in polariton fluids and light fluids at room temperature. To quantify this phenomenon, we introduce the superfluid fraction, whose temperature dependence has been studied in various systems.
In this work, we focus on very low-temperature systems, in which the superfluid fraction is varied by applying external potentials. We experimentally determine this fraction using transport methods. More notably, we also show that, in the case of a Bose-Einstein condensate at equilibrium and in the weak interaction regime, the superfluid fraction can be extracted directly from a simple image of the fluid. This approach opens up particularly promising prospects for the study of supersolid phases highlighted in recent experiments.
References:
Chauveau et al. Phys. Rev. Lett. 130, 226003 (2023)
Rabec et al. Phys. Rev. Lett. 136, 133401 (2026)
