Crossover exponents in percolating nonlinear normal conductor/insulator random networks

The critical exponents of crossover electric field and current density in n onlinear normal conductor/insulator random network above the percolation th reshold are investigated within a "Links-Nodes-Blobs'' picture. We assume t hat the normal conductor obeys the nonlinear current (i)-voltage (v) respon se v = ri(alpha 1) + bi(alpha 2). As the percolation threshold p(e) is appr oached from above, the crossover electric field and current density are fou nd to have the powerlaw dependences \J(e)\ similar to (p - p(e))(H) and \E- e similar to (p - p(e))(M) with H and M given by H = v(d)(d - 1) and M = v( d) - 1, independent of the nonlinearities alpha(1) and alpha(2). The effect of dimensionality d on these crossover exponents is investigated in detail , interesting behaviour is found in the two-dimensional case.