Bloch oscillations and mean-field effects of Bose-Einstein condensates in 1D optical lattices - art. no. 140402

We have loaded Bose-Einstein condensates into one-dimensional, off-resonant optical lattices and accelerated them by chirping the frequency difference between the two lattice beams. For small values of the lattice well depth, Bloch oscillations were observed. Reducing the potential depth further, La ndau-Zener tunneling out of the lowest lattice band, leading to a breakdown of the oscillations, was also studied and used as a probe for the effectiv e potential resulting from mean-field interactions as predicted by Choi and Niu [Phys. Rev. Lett. 82, 2022 (1999)]. The effective potential was measur ed for various condensate densities and trap geometries, yielding good qual itative agreement with theoretical calculations.