Frequency-dependent conduction in disordered composites: A percolative study

In a recent paper [Phys. Rev. B 57, 3375 (1998)], we examined in detail the nonlinear (electrical) de response of a random resistor cum tunneling bond network (RRTN) (introduced by us elsewhere to explain nonlinear response of metal-insulator type mixtures). In this work which is a sequel to that paper, we consider the ac response of the RRTN-based correlated RC (CRC) model. Numerical solutions of the Kirchoff's laws for the CRC model give a power-law exponent (=0.7 near p=p(c)) of the modulus of the complex ac conductance at moderately low frequencies, in conformity with experiments on various types of disordered systems. But, at very low frequencies, it gives a simple quadratic or linear dependence on the frequency depending upon whether the system is percolating or not. We do also discuss the effective medium approximation (EMA) of our CRC and the traditional random RC network model, and discuss their comparative successes and shortcomings. [S0163-1829(99)07813-3].