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arXiv:1304.5143 · Physical Review A

Instability crossover of helical shear flow in segregated Bose-Einstein condensates

Shinsuke Hayashi, Makoto Tsubota, Hiromitsu Takeuchi

Published Jun 24, 2013• 25 citations
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Abstract

We theoretically study the instability of helical shear flows, in which one fluid component flows along the vortex core of the other, in phase-separated two-component Bose-Einstein condensates at zero temperature. The helical shear flows are hydrodynamically classified into two regimes: (1) a helical vortex sheet, where the vorticity is localized on the cylindrical interface and the stability is described by an effective theory for ripple modes, and (2) a core-flow vortex with the vorticity distributed in the vicinity of the vortex core, where the instability phenomena are dominated only by the vortex-characteristic modes (Kelvin and varicose modes). The helical shear-flow instability shows remarkable competition among different types of instabilities in the crossover regime between the two regimes.

DOI
10.1103/physreva.87.063628

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A two-component Bose–Einstein condensate of cold atoms with a strong intercomponent repulsion leading to the spatial separation of the components has been numerically studied. Configurations with a multiple quantized vortex in one component, where the vortex core is filled with the other component, are considered. The effective radius of the core can exceed the width of the transition layer between components, and then an analogy with a filled cylindrical vortex in the classical hydrodynamics of two immiscible ideal fluids appears. This analogy allows one to analyze the longitudinal “sausage” instability and the transverse instability of the filled vortex in the condensate caused by the “tangential discontinuity,” as well as the stable regime in the parametric gap between them. The presence of long-lived coherent structures formed in some cases at the nonlinear stages of both instabilities is numerically discovered.
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