3,581 research outputs found
A Tale of Two Distributions: From Few To Many Vortices In Quasi-Two-Dimensional Bose-Einstein Condensates
Motivated by the recent successes of particle models in capturing the
precession and interactions of vortex structures in quasi-two-dimensional
Bose-Einstein condensates, we revisit the relevant systems of ordinary
differential equations. We consider the number of vortices as a parameter
and explore the prototypical configurations ("ground states") that arise in the
case of few or many vortices. In the case of few vortices, we modify the
classical result of Havelock [Phil. Mag. , 617 (1931)] illustrating
that vortex polygons in the form of a ring are unstable for .
Additionally, we reconcile this modification with the recent identification of
symmetry breaking bifurcations for the cases of . We also briefly
discuss the case of a ring of vortices surrounding a central vortex (so-called
configuration). We finally examine the opposite limit of large and
illustrate how a coarse-graining, continuum approach enables the accurate
identification of the radial distribution of vortices in that limit.Comment: 15 pages, 2 figure
Multiquantum well spin oscillator
A dc voltage biased II-VI semiconductor multiquantum well structure attached
to normal contacts exhibits self-sustained spin-polarized current oscillations
if one or more of its wells are doped with Mn. Without magnetic impurities, the
only configurations appearing in these structures are stationary. Analysis and
numerical solution of a nonlinear spin transport model yield the minimal number
of wells (four) and the ranges of doping density and spin splitting needed to
find oscillations.Comment: 11 pages, 2 figures, shortened and updated versio
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