Quantum transport in long-range random magnetic fields

The frequency dependence of the ac conductivity for a two-dimensional electron system subject to a long-range random magnetic field (RMF) with zero mean is numerically investigated. It is found that the ac conductivity (Tuv) increases in the frequency regime lower than a crossover frequency omega(c) and linearly decreases for to omega much greater than omega(c). The crossover frequency is governed by the localization length of the electron eigenstate at the Fermi energy. These facts indicate that quantum-interference effects are crucial for ac transport in the long-range RMF in conflict with the recent analytical argument. (C) 2001 Elsevier Science B.V. All rights reserved.