Dynamical delocalization in one-dimensional disordered systems with oscillatory perturbation

The effect of dynamical perturbation on the quantum localization phenomenon in a one-dimensional disordered quantum system (1DDS) is investigated systematically by a numerical method. The dynamical perturbation is modeled by an oscillatory driving force containing M independent (mutually incommensurate) frequency components. For M greater than or equal to 2 a diffusive behavior emerges and in the presence of the finite localization length of the asymptotic wave packet can no longer be detected numerically. The diffusive motion obeys a subdiffusion law characterized by the exponent alpha as xi(t)(2)proportional to t(alpha), when xi(t)(2) is the mean square displacement of the wave packet at time t. With an increase in M and/or the perturbation strength, the exponent a rapidly approaches 1, which corresponds to normal diffusion. Moreover, the space-time (x-t) dependence of the distribution function P(x,t) is reduced to a scaled form decided by a and another exponent P such that P(x,t)similar to exp{-constx(\x\/t(alpha/2))(beta)}, which contains the two extreme limits, i.e., the localization limit (alpha = 0, beta = 1) and the normal-diffusion limit (alpha = 1, beta = 2) in a unified manner. Some 1DDSs driven by the oscillatory perturbation in different ways an examined and compared. [S1063-651X(99)05304-0].