Dynamical delocalization of one-dimensional disordered system with lattice vibration

Effect of dynamical perturbation on quantum localization phenomenon in one-dimensional disordered quantum system 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 the presence of finite localization length 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), where xi(t)(2) is the mean square displacement of the wave packet. With increase in M and/or the perturbation strength, the exponent a approaches rapidly to 1 which corresponds to the normal-diffusion. Moreover, the space(x)-time(t) dependence of the distribution function P(x,t) is reduced to a scaled form decided by or and an another exponent P such that P(x,t) similar to exp { - const.(\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. (C) 1999 Elsevier Science B.V. All rights reserved.