328 research outputs found
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
Breaking of Chiral Symmetry and Spontaneous Rotation in a Spinor Bose-Einstein Condensate
We show that a spin-1 Bose-Einstein condensate with ferromagnetic
interactions spontaneously generates a topological spin texture, in which the m
= \pm 1 components of the magnetic sublevels form vortices with opposite
circulations. This phenomenon originates from an interplay between
ferromagnetic interactions and spin conservation.Comment: 5 pages, 4 figure
Einstein--de Haas Effect in Dipolar Bose-Einstein Condensates
The general properties of the order parameter for a dipolar spinor
Bose-Einstein condensate are discussed based on symmetries of interactions. An
initially spin-polarized dipolar condensate is shown to dynamically generate a
non-singular vortex via spin-orbit interactions -- a phenomenon reminiscent of
the Einstein--de Haas effect in ferromagnets.Comment: 4 pages, 4 figures; Final versio
Spontaneous Circulation in Ground-State Spinor Dipolar Bose-Einstein Condensates
We report on a study of the spin-1 ferromagnetic Bose-Einstein condensate
with magnetic dipole-dipole interactions. By solving the non-local
Gross-Pitaevskii equations for this system, we find three ground-state phases.
Moreover, we show that a substantial orbital angular momentum accompanied by
chiral symmetry breaking emerges spontaneously in a certain parameter regime.
We predict that all these phases can be observed in the spin-1 Rb
condensate by changing the number of atoms or the trap frequency.Comment: final versio
Symmetry Breaking in Bose-Einstein Condensates
A gaseous Bose-Einstein condensate (BEC) offers an ideal testing ground for
studying symmetry breaking, because a trapped BEC system is in a mesoscopic
regime, and situations exist under which symmetry breaking may or may not
occur. Investigating this problem can explain why mean-field theories have been
so successful in elucidating gaseous BEC systems and when many-body effects
play a significant role. We substantiate these ideas in four distinct
situations: namely, soliton formation in attractive BECs, vortex nucleation in
rotating BECs, spontaneous magnetization in spinor BECs, and spin texture
formation in dipolar BECs.Comment: Submitted to the proceedings of International Conference on Atomic
Physics 200
Topological defect formation in quenched ferromagnetic Bose-Einstein condensates
We study the dynamics of the quantum phase transition of a ferromagnetic
spin-1 Bose-Einstein condensate from the polar phase to the broken-axisymmetry
phase by changing magnetic field, and find the spontaneous formation of spinor
domain walls followed by the creation of polar-core spin vortices. We also find
that the spin textures depend very sensitively on the initial noise
distribution, and that an anisotropic and colored initial noise is needed to
reproduce the Berkeley experiment [Sadler et al., Nature 443, 312 (2006)]. The
dynamics of vortex nucleation and the number of created vortices depend also on
the manner in which the magnetic field is changed. We point out an analogy
between the formation of spin vortices from domain walls in a spinor BEC and
that of vortex-antivortex pairs from dark solitons in a scalar BEC.Comment: 10 pages, 11 figure
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