Phase diagram for superconductor-insulator transitions in two-dimensional network of small tunnel junctions

We have measured the temperature dependence of the resistance of insulating two-dimensional network of Josephson junctions. With decreasing temperature, the resistance grew faster than the Arrhenius type. We attributed the feature to the precursor of the Koseritz-Touless transition of charges as recently reported by Kanda ei al. We studied the K-T transition temperature as a function of the junction resistance. In the present stage the result was consistent with the theory that the transitions result from competing K-T transitions.