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arXiv:0910.2775 · Physical Review A

Stable fractional vortices in the cyclic states of Bose-Einstein condensates

J. A. M. Huhtamäki, Tapio Simula, M. Kobayashi, K. Machida

Published Nov 4, 2009• 35 citations
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Abstract

We propose methods to create fractional vortices in the cyclic state of an $F=2$ spinor Bose-Einstein condensate by manipulating its internal spin structure using pulsed microwave and laser fields. The stability of such vortices is studied as a function of the rotation frequency of the confining harmonic trap both in pancake- and cigar-shaped condensates. We find a range of parameters for which the so-called $\frac{1}{3}$ vortex state is energetically favorable. Such fractional vortices could be created in condensates of $^{87}\text{R}\text{b}$ atoms using current experimental techniques facilitating probing of topological defects with non-Abelian statistics.

DOI
10.1103/physreva.80.051601

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In this paper we first derive a general method which enables one to create expressions for vortices and monopoles. By using this method we construct several order-parameters describing the vortices and monopoles of Bose–Einstein condensates with hyperfine spin F = 1 and F = 2. We concentrate on defects which are topologically stable in the absence of an external magnetic field. In particular we show that in a ferromagnetic condensate there can be a vortex which does produce any superfluid flow. We also point out that the order-parameter space of the cyclic phase of F = 2 condensate consists of two disconnected sets. Finally we examine the effect of an external magnetic field on the vortices of a ferromagnetic F = 1 condensate and discuss the experimental preparation of a vortex in this system.
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