Atomic Physics Seminars

With the recent advances in cooling of heteronuclear dipolar molecules to their rovibrational ground state, the prospect of ultra-cold gases of fermionic dipoles in the lab is becoming realistic. Accordingly, the low energy collective excitations have been calculated for a uniform single-species polarized gas of fermionic dipoles below the superfluid critical temperature in the dilute BCS regime. Its behaviour differs strongly from the standard s-wave BCS gas due to a node line in its quasiparticle excitation spectrum that resembles that in the hypothetical polar phase of He-3 and exotic superconductors. One finds: (1) Appreciable damping of collective modes occurs even at T=0 and far below the sound velocity. (2) An ``aligned superfluid'' regime with no analogue in the s-wave-interacting gas, occurs for temperatures greater than the excitation energy. Here good quality superfluidity occurs only in directions concentrated broadly around the polarisation, whereas other directions are strongly damped. Furthermore, in the "good" direction, this aligned superfluidity is much less damped than at T=0.