37,868 research outputs found
Collective oscillations of dipolar Bose-Einstein condensates and accurate comparison between contact and dipolar interaction
We propose a scheme for the measurement of the s-wave scattering length
of an atom or molecule with significant dipole-dipole interaction with an
accuracy at the percent level. The frequencies of the collective oscillations
of a Bose-Einstein condensate are shifted by the magnetic dipole interaction.
The shift is polarization dependent and proportional to the ratio
of dipolar and s-wave coupling constants. Measuring the
differences in the frequencies for different polarization we can extract the
value of and thus measure . We calculate the frequency
shifts for a large variety of non-axisymmetric harmonic traps in the
Thomas-Fermi limit and find optimal trapping geometries to maximize the shifts.Comment: 4 pages, brief repor
Calibrating dipolar interaction in an atomic condensate
We revisit the topic of a dipolar condensate with the recently derived more
rigorous pseudo-potential for dipole-dipole interaction [A. Derevianko, Phys.
Rev. A {\bf 67}, 033607 (2003)]. Based on the highly successful variational
technique, we find that all dipolar effects estimated before (using the bare
dipole-dipole interaction) become significantly larger, i.e. are amplified by
the new velocity-dependent pseudo-potential, especially in the limit of large
or small trap aspect ratios. This result points to a promising prospect for
detecting dipolar effects inside an atomic condensate.Comment: 5 figures, to be publishe
Novel vortex structures in dipolar condensates
We investigate the properties of single vortices and of vortex lattice in a
rotating dipolar condensate. We show that vortices in this system possess many
novel features induced by the long-range anisotropic dipolar interaction
between particles. For example, when the dipoles are polarized along the
rotation axis, vortices may display a crater-like structure; when dipoles are
polarized orthogonal to the rotation axis, vortex cores takes an elliptical
shape and the vortex lattice no longer possesses hexagonal symmetry.Comment: 4 pages, 5 figure
Thermodynamic properties of a dipolar Fermi gas
Based on the semi-classical theory, we investigate the thermodynamic
properties of a dipolar Fermi gas. Through a self-consistent procedure, we
numerically obtain the phase space distribution function at finite temperature.
We show that the deformations in both momentum and real space becomes smaller
and smaller as one increases the temperature. For homogeneous case, we also
calculate pressure, entropy, and heat capacity. In particular, at low
temperature limit and in weak interaction regime, we obtain an analytic
expression for the entropy, which agrees qualitatively with our numerical
result. The stability of a trapped gas at finite temperature is also explored
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