Ultracold atoms in modulated standing light waves

We discuss two different aspects of the dynamics of ultracold atoms in periodically driven optical lattices. We consider the reorganization of the quantum mechanical level structure brought about by a classical resonance in a weakly driven deep lattice, and point out that the collapse of the ground state quasienergy band in far-detuned, shallow optical lattices leads to dynamic localization. In addition, we suggest to realize Harper's model with atomic de Broglie waves in bichromatic standing light waves, and show that the corresponding metal-insulator transition can be controlled by varying the amplitude of an oscillating force. (C) 1997 Elsevier Science B.V.