Evolution of wave packets in quasi-one-dimensional and one-dimensional random media: Diffusion versus localization

We study numerically the evolution of wave packets in quasi-one-dimensional random systems described by a tight-binding Hamiltonian with long-range random interactions. Results are presented for the scaling properties of the width of packets in three time regimes: ballistic, diffusive, and localized. Particular attention is given to the fluctuations of packet widths in both the diffusive and localized regime. Scaling properties of the steady-state distribution are also analyzed and compared with a theoretical expression borrowed from the one-dimensional Anderson theory. Analogies and differences with the kicked rotator model and the one-dimensional localization are discussed.