DIFFERENCES BETWEEN RANDOM-POTENTIAL AND RANDOM-MAGNETIC-FIELD LOCALIZATION IN QUASI-ONE-DIMENSIONAL SYSTEMS

We study electron localization of quasi-one-dimensional random-potenti al and random-magnetic-held systems with and without a uniform externa l magnetic held. We find that in a random-magnetic-held (RMF) system t he localization length is not a monotonic decreasing function of magne tic-held randomness delta in contrast to a random-potential system in which the localization length is a monotonic decreasing function of th e randomness w. We observed that, in both random-potential and RMF sys tems, the localization length can both increase and decrease with a un iform external magnetic held depending on the energy of a state. The c rossover 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 invers e of the localization length of a quasi-one-dimensional disordered sys tem peaks at certain energies inside the energy band. These peaks can be understood by the branch edge effect.