  Dynamics of an atomic wavepacket in an optical superlattice is considered. We
propose a simple scheme of wavepacket localization near the minima of the
optical potential. In our approach, a wavelike perturbation caused by an
additional lattice induces classical resonance which traps an atomic cloud.
Adiabatic phase modulation of the perturbation slowly shifts resonance zone in
phase space to the range of lower energies, retaining trapped atoms inside.
This phenomenon is a kind of autoresonance. Quantum computations agree well
with classical modelling.
