Coherent Behavior in Josephson Junction Arrays

Abstract

Experiments on arrays of Josephson junctions seem to indicate coherent behavior.¹ In the present work we describe experiments on an array made by compressing small particles, which apparently shows cooperative behavior. Perhaps the most surprising observation is that of a steady zero-bias dc voltage across the sample when rf power is incident on it. Because this voltage can have either sign and only appears below the T _c , of the array, we do not think it can be explained by rectification in the junctions. This phenomenon has been observed in a single junction,² but the zero-bias voltage was found to switch between different quantum states. This seems analogous to the case of a single spin which would have no preferred direction, whereas an assembly of spins would make a transition to a state of fixed magnetization.

This work was performed under the auspices of the U.S. Atomic Energy Commission.