Scientific Report - BEC

Ultracold gases in optical lattices 46Figure 1: Stability diagrams as a function of the quasimomentap and q of the condensate and the excitations, for differentvalues of the lattice intensity s and interaction strenghtg. Colored regions indicate where the system is dynamicallyunstable. The colour scale corresponds to the growth rate ofthe unstable modes for a given p, q. The solid and dashedlines in (a), (b) and (c) correspond to analytic predictions fors = 0, whereas the bold line in (g), (h) and (i) refer to thecase g = 0 (see [3]). Light shaded area: energetic instability.Dotted region in (g), (h), and (i): regimes of DI for therepulsive case.