Kinetic phenomena and charge discreteness effects in granulated media

An approach to the problem of charge transport in a system of small metallic particles coupled by tunnel interactions is proposed. The system Hamiltonian is represented in the form H = Ho+Hv+ HT where Hv takes into account electrostatic effects due to charge accumulation in the granules and the discrete character of the charge, and HT is the tunnel Hamiltonian. Owing to the electrostatic threshold at low temperatures the conductivity a is asymptotically proportional to T. The important role of the specific granule charge fluctuations due to the discrete character of the charge is demonstrated. The fluctuations are manifested by the characteristic oscillations of a number of physical characteristics of granulated media. Some features of the conductivity of M-G-M and ~G-S tunnel junctions containing granules of a metal G in an oxide layer (M is the normal metal and S the superconductor) are investigated.