Superconductor-insulator crossover in Josephson junction arrays due to reduction from two to one dimension

摘要

We investigated the dimensionality effect on electrical properties of small-capacitance Josephson junction arrays (JJAs). A one-dimensional JJA and several two-dimensional JJAs with different array widths were fabricated on a substrate simultaneously so that they would have nominally the same junction parameters. As the array width decreases, the current-voltage characteristics show a crossover from a superconducting behavior with a dc Josephson-current-like branch to an insulating one with a Coulomb blockade gap of Cooper pairs. The superconductor-insulator crossover is explained in terms of enhanced quantum fluctuations of superconducting phase variables due to a dimensional reduction.