Electron transport in granular metals.

We consider thermodynamic and transport properties of a long granular array with strongly connected grains (intergrain conductance g>>1). We find that the system's conductance and differential capacitance exhibits activated behavior, approximately exp([-T(*)/T]. The gap T(*) represents the energy needed to create a long single-electron charge soliton propagating through the array. This scale is parametrically larger than the energy at which conventional perturbation theory breaks down.