QUANTUM PHASE-TRANSITIONS IN JOSEPHSON-JUNCTION CHAINS

We investigate the quantum phase transition in a one-dimensional chain of ultrasmall superconducting grains, considering both the self-and j unction capacitances. At zero temperature, the system is transformed i nto a two-dimensional system of classical vortices, where the junction capacitance introduces anisotropy in the interaction between vortices . This leads to the superconductor-insulator transition of the Berezin skii-Kosterlitz-Thouless type, as the ratios of the Josephson coupling energy to the charging energies are varied. It is found that the junc tion capacitance plays a role similar to that of dissipation and tends to suppress quantum fluctuations; nevertheless the insulator region s urvives even for arbitrarily large values of the junction capacitance.