Mode Analysis of Fluctuations in Two-Species Bose-Einstein Condensates of Atomic Gases with a Vortex for a Component : Characteristic Features of Compressive and Sliding Motions

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Characterislic features of fluctuations of Bose-Einstein condensations for systems of two-components in gas phases of alkali-metal atoms trapped by spherical harmonic potentials are discussed on the basis of numerical calculations. We concentrate our attention on the phases in which the spherical state Ψ_1 without vortex is surrounded by Ψ_2 with a vortex for the unit circulation q=1. These states are expressed by Gross-Pitaevskii equation, where a vortex-core is along the z-axis. We investigate properties of collective excitations by the linear analysis for bosonic excitations described as Bogoliubov equations. The behavior of each mode is discussed in relation with the role of inlerspecies repulsion in addition to that of intraspecies one. We point out the role of the new compressive mode which has two nodes on z-axis, in addition to that of the core mode without a node which have been previously discussed in the single-component system. Furthermore, we would like to emphasize that sliding modes show the branching features into in- and out-of-phase motions with increasing interspecies interaction. The dependence of those branchings on interspecies repulsion is explained by spatial shapes of relevant modes.
社団法人日本物理学会の論文
2003-04-15