From the zero-field metal-insulator transition in two dimensions to the quantum Hall transition: A percolation-effective-medium theory - art. no. 073108

Effective-medium theory is applied to the percolation description of the me tal-insulator transition in two dimensions with emphasis on the continuous connection between the zero-magnetic-field transition and the quantum Hall transition. In this model, the system consists of puddles connected via sad dle points, and there is loss of quantum coherence inside the puddles. The effective conductance of the network is calculated using appropriate integr ation over the distribution of conductances, leading to a determination of the magnetic-field dependence of the critical density. Excellent quantitati ve agreement is obtained with the experimental data, which allows an estima te of the puddle physical parameters.