Self-trapping and self-focusing of a coherent atomic beam

Light-induced dipole-dipole interaction in a coherent atomic-field results in an effective nonlinearity for atoms. This nonlinearity can induce self-trapping and self-focusing of a coherent atomic beam undergoing propagation through a traveling-wave laser beam. we show how such a scheme could be realized and evaluate the critical density required for atomic self-trapping and self-focusing. An analogy to optical self-trapping and self-focusing is discussed.