We investigate the stability of an attractive Bose-Einstein condensate in amoving 1D optical lattice in the presence of transverse confinement. By meansof a Bogoliubov linear stability analysis we find that the system isdynamically unstable for low quasimomenta and becomes stable near the bandedge, in a specular fashion with respect to the repulsive case. For lowinteractions the instability occurs via long wavelength excitations that arenot sufficient for spoiling the condensate coherence, producing instead anoscillating density pattern both in real and momentum space. This behaviour isillustrated by simulations for the expansion of the condensate in a movinglattice.
展开▼
