Small-capacitance Josephson Junctions: One-dimensional Arrays and Single Junctions

Small-capacitance superconducting tunnel junctions provide an ideal system for studying the interplay between the Josephson phase and the charge on the junction electrode, which are quantum mechanically conjugate to each other. This interplay can be probed through the superconductor-insulator (SI) transition [1], which is a quantum phase transition occurring at T = 0. The SI transition has been extensively studied in two-dimensional (2D) systems. Experiments have been carried out on granular [2, 3, 4, 5] and homogeneous films [6, 7]. Theoretical studies have modeled the films as 2D arrays of small-capacitance Josephson junctions (JJs) [8,9,10,11,12], and experiments with such arrays have also been reported [13,14]. In 1D, however, experimental study of the SI transition in JJ arrays has been less extensive, while the theoretical investigation has been done [1, 8, 15, 16, 17, 18, 19, 20]. Experimental data on long and narrow films are available [22, 21]. In contrast to films, JJ arrays can be fabricated with a