Instabilities of bose-einstein condensates in optical lattices

W. H. Kuan*, Tsin-Fu Jiang, Szu Cheng Cheng

*Corresponding author for this work

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We study the instabilities, Landau and dynamical instabilities, that are two mechanisms responsible for the breakdown of superfluidity in Bose-Einstein condensates interacting with a one-dimensional optical lattice. An effective-mass Gross-Pitaevskii equation was used to calculate the excitation spectrum and the condensate density of Bose-Einstein condensates in a weak periodic potential. After the condensate velocities greater than the speed of sound, we observe a decreasing of the condensate density, which is the onset of Landau instability. The condensate is dissipated, but not completely, from colliding with the thermal atom cloud. For even higher velocities of the condensate, we find a fast decreasing of the condensate density until full removal of the condensate. The regime of totally removing of the condensate is happened at the inverse effective mass of the condensate becoming zero or negative, where the condensate is on the dynamical instability.

Original languageEnglish
Pages (from-to)219-229
Number of pages11
JournalChinese Journal of Physics
Issue number2 II
StatePublished - 1 Apr 2007

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    Kuan, W. H., Jiang, T-F., & Cheng, S. C. (2007). Instabilities of bose-einstein condensates in optical lattices. Chinese Journal of Physics, 45(2 II), 219-229.