Superfluid fermions in a slowly rotating trap

Michael Urban

IPN, Bat. 100, 15, rue Georges Clemenceau, 91406 Orsay Cedex, France

We propose the moment of inertia as a possible observable for the unambigious experimental determination whether a trapped Fermi system has reached the BCS transition or not. The temperature dependence of the moment of inertia below the critical temperature Tc is described in detail. Special care is taken to account for the small size of the system, i.e., for the fact that the level spacing of the trapping potential is of the same order of magnitude as the gap. The usual transport approach, corresponding to the leading order in an expansion in powers of h, is not accurate in this case. It turns out that the moment of inertia decreases continuously when the temperature falls below Tc. Qualitatively this behavior can be explained within the two-fluid model, which again corresponds to the leading order in h. Quantitatively we find substantial deviations from the two-fluid model due to the small system size.