39 research outputs found
Dipolar Drag in Bilayer Harmonically Trapped Gases
We consider two separated pancake-shaped trapped gases interacting with a
dipolar (either magnetic or electric) force. We study how the center of mass
motion propagates from one cloud to the other as a consequence of the
long-range nature of the interaction. The corresponding dynamics is fixed by
the frequency difference between the in-phase and the out-of-phase center of
mass modes of the two clouds, whose dependence on the dipolar interaction
strength and the cloud separation is explicitly investigated. We discuss Fermi
gases in the degenerate as well as in the classical limit and comment on the
case of Bose-Einsten condensed gases.Comment: Submitted to EPJD, EuroQUAM special issue "Cold Quantum Matter -
Achievements and Prospects
Counter-flow instability of a quantum mixture of two superfluids
We study the instability of a mixture of two interacting counter-flowing
superfluids. For a homogeneous system, we show that superfluid hydrodynamics
leads to the existence of a dynamical instability at a critical value of the
relative velocity . When the interspecies coupling is small the
critical value approaches the value , given by the sum of the
sound velocities of the two uncoupled superfluids, in agreement with the recent
prediction of [1] based on Landau's argument. The crucial dependence of the
critical velocity on the interspecies coupling is explicitly discussed. Our
results agree with previous predictions for weakly interacting Bose-Bose
mixtures and applies to Bose-Fermi superfluid mixtures as well. Results for the
stability of transversally trapped mixtures are also presented.Comment: 5 pages, 2 figue
Destroying superfluidity by rotating a Fermi gas at unitarity
We study the effect of the rotation on a harmonically trapped Fermi gas at
zero temperature under the assumption that vortices are not formed. We show
that at unitarity the rotation produces a phase separation between a non
rotating superfluid (S) core and a rigidly rotating normal (N) gas. The
interface between the two phases is characterized by a density discontinuity
, independent of the angular velocity. The depletion
of the superfluid and the angular momentum of the rotating configuration are
calculated as a function of the angular velocity. The conditions of stability
are also discussed and the critical angular velocity for the onset of a
spontaneous quadrupole deformation of the interface is evaluated.Comment: 5 pages, 4 figures; comments added; 2 figures changed according to
new results; inset Fig.2 corrected; accepted for publication in Phys. Rev.
Let
Collisional Properties of a Polarized Fermi Gas with Resonant Interactions
Highly polarized mixtures of atomic Fermi gases constitute a novel Fermi
liquid. We demonstrate how information on thermodynamic properties may be used
to calculate quasiparticle scattering amplitudes even when the interaction is
resonant and apply the results to evaluate the damping of the spin dipole mode.
We estimate that under current experimental conditions, the mode would be
intermediate between the hydrodynamic and collisionless limits.Comment: 4 pages, 2 figures. Nordita preprint 2008-14. Paper slightly revise