ИСТИНА

The phononless (resonance) AC hopping conductivity is evaluated in a wide frequency range for disordered nanogranular arrays. It is shown that in dense granular systems, where the grain size is much greater than the average edge-to-edge separation between neighboring grains, the prefactor of the transfer integral is strongly reduced. At low frequencies, the conventional behavior of the conductivity corresponding to a crossover from linear to quadratic frequency dependence is obtained. At higher frequencies, the frequency dependence of the conductivity may become nonmonotonic, and the conductivity saturates after passing over a maximum.