Abstract

We demonstrate that deviations from a harmonic periodic potential may lead to dramatic changes in the band gap structure and nature of the gap solitons and Bloch waves of a Bose-Einstein condensate in a lattice. We reveal that the relative widths of the band gaps may be strongly modified even leading to closure of the higher gaps. We show that changing the shape of the potential may change the symmetry of the gap-edge Bloch waves and so affect the symmetry of the higher-gap solitons. Finally we introduce a new type of mixed-gap state existing in two different gaps simultaneously.

© 2007 Optical Society of America