Interplay between potential and magnetic disorder in a quasi-one- dimensional system

We investigate transmission and weak localization of electrons in quasi-one-dimensional systems with a combination of a quenched disordered potential and a random distribution of magnetic fluxes. The underlying physics is basically a competition between two effects. On the one hand, there is the trend of the magnetic field to increase the conductance due to the breakdown of time-reversal symmetry. On the other hand, there is an attenuation of the conductance due to the additional disorder introduced through the randomness in the magnetic field. Although the effect of magnetic randomness on the localization length is found to be not universal, the magnetoconductance is always positive. The ratio of the localization length in the presence of magnetic disorder and the one without such disorder is smaller than is found at constant magnetic field. Thus, the effect of time-reversal violation on localization is weaker if the average field is zero. Consequently, the response to disorder is not determined solely by the universality class of the pertinent transfer matrices. The magnetoconductance of a disordered quasi-1D system under the influence of the inhomogeneous magnetic field of a uniformly distributed array of quantized flux tubes is also investigated. We find the response of the quasi-1D system to be compatible with a linear dependence of the magnetoconductance on the magnetic field as was established in a recent experiment for a 2D system under the aforementioned conditions.