Sign of tunnel coupling in barrier-separated Bose-Einstein condensates and stability of double-ring systems
arXiv:0805.4447 · doi:10.1103/PhysRevA.81.025602
Abstract
We revisit recent claims about the instability of non-rotating tunnel coupled annular Bose-Einstein condensates leading to the emergence of angular-momentum Josephson oscillation [Phys. Rev. Lett. 98, 050401 (2007), arXiv:quant-ph/0609133v2]. It was predicted that all stationary states with uniform density become unstable in certain parameter regimes. By careful analysis, we arrive at a different conclusion. We show that there is a stable non-rotating and uniform ground state for any value of the tunnel coupling and repulsive interactions. The instability of an excited state with phase difference between the condensates can be interpreted in terms of the familiar snake instability. We further discuss the sign of the tunnel coupling through a separating barrier, which carries significance for the nature of the stationary states. It is found to always be negative for physical reasons.
4 pages, comment on Phys. Rev. Lett. 98, 050401 (2007) [arXiv:quant-ph/0609133v2]
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