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Spatial period-doubling in Bose-Einstein condensates in an optical lattice

M. Machholm·A. Nicolin·C. J. Pethick·H. Smith
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Abstract

We demonstrate that there exist stationary states of Bose-Einstein condensates in an optical lattice that do not satisfy the usual Bloch periodicity condition. Using the discrete model appropriate to the tight-binding limit we determine energy bands for period-doubled states in a one-dimensional lattice. In a complementary approach we calculate the band structure from the Gross-Pitaevskii equation, considering both states of the usual Bloch form and states which have the Bloch form for a period equal to twice that of the optical lattice. We show that the onset of dynamical instability of states of the usual Bloch form coincides with the occurrence of period-doubled states with the same energy. The period-doubled states are shown to be related to periodic trains of solitons.

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M. Machholm, A. Nicolin, C. J. Pethick, H. Smith. 2003-11-14. Spatial period-doubling in Bose-Einstein condensates in an optical lattice. https://doi.org/10.1103/physreva.69.043604

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