Charge dynamics in junction arrays

2D Junction arrays with nearest neighbour capacitance larger than the self capacitance are a physical realization of the 2D Coulomb gas. One therefore expects a Kosterlitz-Thouless-Berezinskii (KTB) transition, where charge dipoles dissociate. We performed simulations of the charge dynamics in such arrays, based on tunnel rates for single electrons and Cooper pairs. The resulting I-V curves clearly show the Coulomb gap at low temperatures, while at higher temperatures one finds effects of the KTB transition.