474 research outputs found
Topological Vortex Formation in BEC under Gravitational Field
Topological phase imprinting is a unique technique for vortex formation in a
Bose-Einstein condensate (BEC) of alkali metal gas, in that it does not involve
rotation: BEC is trapped in a quadrupole field with a uniform bias field which
is reversed adiabatically leading to vortex formation at the center of the
magnetic trap. The scenario has been experimentally verified by MIT group
employing Na atoms. Recently similar experiments have been conducted at
Kyoto University, in which BEC of Rb atoms has been used. In the latter
experiments they found that the fine-tuning of the field reverse time is required to achieve stable vortex formation. Otherwise, they often
observed vortex fragmentations or a condensate without a vortex. It is shown in
this paper that this behavior is attributed to the heavy mass of the Rb atom.
The confining potential, which depends on the eigenvalue of the hyperfine
spin \bv{F} along the magnetic field, is now shifted by the gravitational
field perpendicular to the vortex line. Then the positions of two
weak-field-seeking states with and 2 deviate from each other. This
effect is more prominent for BEC with a heavy atomic mass, for which the
deviation is greater and, moreover, the Thomas-Fermi radius is smaller. We
found, by solving the Gross-Pitaevskii equation numerically, that two
condensates interact in a very complicated way leading to fragmentation of
vortices, unless is properly tuned.Comment: 7 pages, 3 figures submitted to PR
Can Spinor Dipolar Effects be Observed in Bose-Einstein Condensates?
Weak dipolar effects in atomic Bose-Einstein condensates (BECs) have recently
been predicted to develop spin textures. However, observation of these effects
requires magnetic field as low as G for spin-1 alkali BECs, so
that they are not washed out by the Zeeman effect. We present a scheme to
observe the magnetic dipole-dipole interaction in alkali BECs under a realistic
magnetic field of mG. Our scheme enables us to extract genuine
dipolar effects and should apply also to Cr BECs.Comment: 4 pages, 3 figure
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