We numerically investigate vortex lattices in rotating two-component Bose-Einstein condensates in which the two components have unequal atomic masses and interact attractively with each other. For sufficiently strong attraction, the system is found to exhibit exotic ground-state structures in a harmonic trap, such as lattices having a square geometry or consisting of two-quantum vortices. The obtained states satisfy the Feynman relation, and they can be realized with current experimental techniques.Comment: 7 pages, 4 color figures; the content of v2 is identical to the published articl

Recently, Freilich et al. [Science 329, 1182 (2010)] experimentally discovered stationary states of vortex dipoles, pairs of vortices of opposite circulation, in dilute Bose-Einstein condensates. To explain their observations, we perform simulations based on the Gross-Pitaevskii equation and obtain excellent quantitative agreement on the size of the stationary dipole. We also investigate how their imaging method, in which atoms are repeatedly extracted from a single condensate, affects the vortex dynamics. We find that it mainly induces isotropic size oscillations of the condensate without otherwise disturbing the vortex trajectories. Thus, the imaging technique appears to be a promising tool for studying real-time superfluid dynamics.Comment: 4 pages, 3 figure

No abstract

We study the splitting of multiply quantized vortices with large quantum numbers in dilute nonrotated Bose-Einstein condensates in the zero-temperature limit. The splitting is observed to result in vortex-free condensate fragments which are separated by vortex sheets. The number of these fragments is found to be equal to the angular-momentum quantum number of the Bogoliubov excitation mode responsible for the splitting, although the formulation of the fragments cannot be described by small-amplitude excitations. Thus, the realization of an isolated giant vortex and the observation of its splitting would provide a means to directly relate the experimental data to discrete theoretical quantities.Comment: 8 pages, 6 figures (color

Motivated by a recent demonstration of cyclic addition of quantized vorticity into a Bose-Einstein condensate, the vortex pump, we study dynamical instabilities and core sizes of giant vortices. The core size is found to increase roughly as a square-root function of the quantum number of the vortex, whereas the strength of the dynamical instability either saturates to a fairly low value or increases extremely slowly for large quantum numbers. Our studies suggest that giant vortices of very high angular momenta may be achieved by gradually increasing the operation frequency of the vortex pump.