Chaotic walking of atoms in an optical lattice

We treat nonlinear dynamics of two-level atoms in an optical lattice taking into account photon recoil effect caused by spontaneous emission that is considered as random events to be incorporated in the equations of motion by a Monte Carlo method. The light-induced mechanical effects — acceleration, deceleration and velocity grouping of atoms — are simulated with the equations of motion. A new effect of chaotic walking of atoms in an optical lattice is found and shown to have anomalous statistical properties.