Phase Coherence and Critical Resistance in a Natwork of Small Josephson Junctions

Abstract

Two-dimensional random Josephson networks consisting of small Sn particles with light oxidation on the surface were prepared by repeating vacuum evaporation and oxidation. The size of the particles was about three hundred angstrom in diameter, and the strength of the Josephson coupling was controlled by changing the degree of oxidation. With decreasing temperature below T c , the samples with normal sheet resistance larger than about 4 kohm showed insulating behavior, while those with less than 4 kohm behaved as usual superconducting thin films. This resistance is close to h/4 e 2 , of which the physical importance is currently discussed.