Laboratoire de Physique Théorique
Toulouse - UMR 5152

There is certainly a link between superfluidity and Bose-Einstein condensation, but this link is difficult to state with precision in situations that involve low dimensions, strong interactions, temperatures close to critical, or sources of disorder. In this talk, I will describe our approach, via inhomogeneous Bogoliubov theory, to calculate the condensate fraction, the coherent fraction, and finally the superfluid fraction of cold bosons in random potentials [1]. These analytical, but perturbative results for weak disorder are complemented by a generalised Josephson relation that is expected to be valid also under critical conditions [2].

[1] C. A. Müller, C. Gaul, "Condensate deformation and quantum depletion of Bose-Einstein condensates in external potentials”, New J. Phys. 14, 075025 (2012)

[2] C. A. Müller, "Josephson relation for disordered superfluids”, Phys. Rev. A 91, 023602 (2015)