2003/06/30 by Biao Wu, Qian Niu · 17 citations
Physics and Astronomy · #Cold Atom Physics and Bose-Einstein Condensates #Quantum optics and atomic interactions #Strong Light-Matter Interactions #cond-mat.soft
paper · pdf · doi:10.1088/1367-2630/5/1/104
published as New Journal of Physics 5, 104 (2003) · A new section on tight-binding approximation is added with a new figure
arxiv created 2003/07/02 · openalex publication_date 2003/07/31 · arxiv updated 2009/11/30 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/30
Superflow of a Bose–Einstein condensate in an optical lattice is represented by a Bloch wave, a plane wave with periodic modulation of the amplitude. We review the theoretical results of the interaction effects in the energy dispersion of the Bloch waves and in the linear stability of such waves. For sufficiently strong repulsion between the atoms, the lowest Bloch band develops a loop at the edge of the Brillouin zone, with the dramatic consequence of a finite probability of Landau–Zener tunnelling even in the limit of a vanishing external force. Superfluidity can exist in the central region of the Brillouin zone in the presence of a repulsive interaction, beyond which Landau instability takes place where the system can lower its energy by making a transition into states with smaller Bloch wavenumbers. In the outer part of the region of Landau instability, the Bloch waves are also dynamically unstable in the sense that a small initial deviation grows exponentially in time. In the inner region of Landau instability, a Bloch wave is dynamically stable in the absence of persistent external perturbations. Experimental implications of our findings will be discussed.