  We study the problem of two interacting particles in the classical Harper
model in the regime when one-particle motion is absolutely bounded inside one
cell of periodic potential. The interaction between particles breaks
integrability of classical motion leading to emergence of Hamiltonian dynamical
chaos. At moderate interactions and certain energies above the mobility edge
this chaos leads to a chaotic propulsion of two particles with their diffusive
spreading over the whole space both in one and two dimensions. At the same time
the distance between particles remains bounded by one or two periodic cells
demonstrating appearance of new composite quasi-particles called chaons. The
effect of chaotic delocalization of chaons is shown to be rather general being
present for Coulomb and short range interactions. It is argued that such
delocalized chaons can be observed in experiments with cold atoms and ions in
optical lattices.
