AC Properties of a Random Barrier Network

The ac properties of random barrier network are analyzed using the effective medium theory. At low frequencies σ m ∼ ω s and at high frequencies it saturates to the value determined by the conductivity of the bulk material. Below the percolation threshold s ≈ 0.8, at the threshold s ≈ 0.4, and above the threshold s still decreases. The effective dielectric constant ε m decreases with increasing frequency saturating to the bulk value at high frequencies. At the percolation threshold ε m shows a pronounced maximum exceeding by several orders of magnitude the bulk value.