HIGH-FIELD VS LOW-FIELD MAGNETOTRANSPORT IN A PERCOLATING MEDIUM

Recent theoretical and numerical work on high-field magneto-transport in a percolating medium is described and compared to earlier work on w eak-field magneto-transport in such systems. While the weak-field beha vior is well described by the simple nodes-links picture, which ignore s blobs and loops on a scale smaller than the percolation correlation length xi(p), the strong-field behavior is extremely sensitive to thos e features. The critical behavior at strong magnetic fields H near the percolation threshold is governed by a competition between the usual H = 0 fixed point and a new H = infinity fixed point. Which of those f ixed points dominates the behavior is determined by the relative sizes of two characteristic lengths: the percolation correlation length xi( p) and a new, magnetic field dependent length xi(H).