SINGLE-PARTICLE MOTION IN A RANDOM MAGNETIC-FLUX

The motion of a quantum particle in a random magnetic flux in two dime nsions is investigated. Two situations are distinguished, a ''Debye'' phase where the fluxes are uncorrelated, and a ''Meissner'' phase wher e the fluxes-appear as neutral pairs. A geometrical interpretation of effective single-particle action in these phases is emphasized. Result s are discussed for (a) a continuum white-noise model where we employ a trial-action method, (b) a continuum model with randomly distributed flux tubes where we obtain the form of the Lifschitz tail, and (c) a lattice model, where numerical results for the density of states and d iamagnetic response of Debye and Meissner phases are given. An importa nt conclusion is that the density of states in the Debye phase exhibit s a sharp peak at an effective band edge.