Low-frequency noise due to site energy fluctuations in hopping conductivity

The noise in hopping conductivity arising due to hopping sites energy fluctuations (as suggested by Shlimak et al., Solid State Commun., 93, 829, 1995) is considered. The fluctuations are related to changes of local potentials resulting due to hops within some pairs of sites not incorporated into the percolation cluster; such pairs can be identified as ''electronic two-level systems'' or ''fluctuators''. A dependence of the noise on both fluctuators statistics and percolation cluster morphology is analyzed. An analog of Hooge relation for the mechanism discussed is derived. For the case of nearest neighbor hopping an independence of relative noise power from temperature is predicted in agreement with recent experimental results by Shlimak et al.