Landau and dynamical instabilities of the superflow of Bose-Einstein condensates in optical lattices - art. no. 061603

The superfluidity of Bose-Einstein condensates (BECs) in optical lattices i s investigated. Apart from the usual Landau instability, which occurs when a BEC flows faster than the speed of sound, the BEC can also suffer a dynam ical instability, resulting in period doubling and other sorts of symmetry breaking of the system. Such an instability plays a crucial role in the dis sipative motion of a trapped BEC in an optical lattice recently observed.