MEASUREMENTS OF CHARGE SOLITON MOTION IN 2-DIMENSIONAL ARRAYS OF ULTRASMALL JOSEPHSON-JUNCTIONS

We have measured two-dimensional arrays of Josephson junctions where the charging energy E(c) dominates the Josephson coupling energy E(J) by as much as a factor of 33. In this system, an added charge polarizes neighboring islands, creating a soliton. Instead of the predicted Kosterlitz-Thouless-Berezinskii phase transition for unbinding soliton-antisoliton pairs, we find that our linear conductance data are better described by a simple Arrhenius form, with an activation energy of approximately 0.23E(c) in the normal state and approximately 0.23E(c) plus the superconducting energy gap in the superconducting state.