Differences between random-potential and random-magnetic-field localization in quasi-one-dimensional systems

We study electron localization of quasi-one-dimensional random-potential and random-magnetic-field systems with and without a uniform external magnetic field. We find that in a random-magnetic-field (RMF) system the localization length is not a monotonic decreasing function of magnetic-field randomness delta in contrast to a random-potential system in which the localization length is a monotonic decreasing function of the randomness w. We observed that, in both random-potential and RMF systems, the localization length can both increase and decrease with a uniform external magnetic field depending on the energy of a state. The crossover occurs when the electron energy is dose to the band edge in a random-potential system. In a RMF system, the magnetoproperty of the localization length is complicated. ii band edge effect is proposed to explain the anomalous numerical results. We also find that the inverse of the localization length of a quasi-one-dimensional disordered system peaks at certain energies inside the energy band. These peaks can be understood by the branch edge effect.