Deformed Fermi surfaces in ultracold Fermi gases

Jordi Mur Petit

Dept. Estructura i Constituents de la Materia, Universitat de Barcelona, Avda. Diagonal 647, E-08028 Barcelona, Spanien

The superfluid transition in an ultracold two-component atomic Fermi gas is analyzed in the case where the two components have different densities. We describe a superfluid state which spontaneously breaks the rotational-symmetry by deforming the Fermi surfaces of both species into ellipsoidal form. At relatively large hyperfine-spin asymmetries, this deformation is shown to help the appearance of pairing, which in the rotationally-symmetric (BCS) case would be forbidden by Pauli blocking. The prospects for experimental detection of such a deformed Fermi surface phase in systems of ultracold fermionic gases are discussed.