TRANSPORT-PROPERTIES BETWEEN QUANTUM HALL PLATEAUS

We propose a unified transport theory for the two-dimensional electron gas (2DEG) in the dissipative quantum Hall regime in the presence of a long-range disorder. We find that the evolution of the longitudinal conductivity peaks as a function of the disorder can be described by a single parameter beta-1 which is determined by the typical gradient o f the electron density fluctuations. In the case of relatively strong disorder we utilize the edge states network model to describe transpor t in a half-filled Landau level. In the fractional quantum Hall regime we apply the network model to the system of composite fermions findin g universal values of the resistivity at even-denominator filling frac tions. The breakdown of the network model takes place at weak disorder because the edge channels develop into wide compressible strips and a t strong disorder because of the destruction of the incompressible str ips, isolating the edge channels. We find the limits of the applicabil ity of the network model in terms of beta. In the limit of very weak d isorder the system is effectively a Fermi-liquid of composite fermions . We calculate the conductivity in this regime by considering the moti on of non-interacting fermions in a spatially varying magnetic field a rising from the density fluctuations. The resistivity is found to scal e linearly with the magnetic field with the slope given by beta-1. Alt hough the presence of the non-local transport makes measurements of th e resistivity difficult, we find qualitative and in some cases quantit ative agreement with experiment.