Crossover from Coulomb-blockade to ohmic conduction in small tunnel junctions

We discuss the suppression of Coulomb effects in the low temperature conductance g(T) of small tunnel junctions with increasing dissipation or bare conductance g. The conductance is expressed in terms of the spin correlation fuction of a classical one dimensional XY-model with ferromagnetic nearest neighbor plus inverse square interaction. It is shown that at low temperatures the conductance vanishes asymptotically like T² instead of exponentially. A Coulomb gap in the sense of a thermally activated contribution to g(T) is present only for bare conductances smaller than g_c∼1. A simple model for the spin correlation functions is compared with experiments.