Laboratoire de Physique Théorique
Toulouse - UMR 5152

In a recent letter published in Phys. Rev. Lett. 107, 037203 (2011), Nicolas Laflorencie from LPT and Frédéric Mila from EPFL have shown that Bose-Einstein Condensation and Superfluidity may not appear simultaneously due to a frustrated proximity effect.

Since the discovery of superfluidity in He and Landau’s phenomenological theory, the relationship between Bose condensation and superfluidity has been intensely debated. He is known by now to be both superfluid and condensed at low temperature, and more generally, in dimension D2, all superfluid bosonic models realized in experiments are condensed in their ground-state, the most recent example being provided by ultracold bosonic atoms trapped in an optical lattice. In this paper, it is shown that a 2D gas of bosons which is not condensed at can be achieved by populating a layer through a frustrated proximity effect from a superfluid reservoir. This condensate-free bosonic fluid is further shown to be a superfluid with incommensurate correlations.