FLOATING OF EXTENDED STATES AND LOCALIZATION TRANSITION IN A WEAK MAGNETIC-FIELD

We report results of a numerical study of noninteracting electrons mov ing in a random potential in two dimensions in the presence of a weak perpendicular magnetic field. We study the topological properties of t he electronic eigenstates within a tight binding model. We find that i n the weak magnetic field or strong randomness limit extended states f loat up in energy. Further, the localization length is found to diverg e at the insulator phase boundary with the same exponent nu as that of the isolated lowest Landau band (high magnetic field limit).