DIMENSIONAL CROSSOVER AND METAL-INSULATOR-TRANSITION IN QUASI-2-DIMENSIONAL DISORDERED CONDUCTORS

We study the metal-insulator transition in weakly coupled disordered p lanes on the basis of a nonlinear sigma model (NL sigma M). Using two different methods, a renormalization-group approach and an auxiliary-f ield method, we calculate the crossover length between a two-dimension al (2D) regime at small length scales and a 3D regime at larger length scales. The 3D regime is described by an anisotropic 3D NL sigma M wi th renormalized coupling constants. We obtain the critical value of th e single-particle interplane hopping, which separates the metallic and insulating phases. We also show that a strong parallel magnetic field favors the localized phase and derive the phase diagram.