JOSEPHSON-JUNCTION SINGLE PLAQUETTE AS A MODEL FOR THE HIGH-TC GRAIN-BOUNDARY JUNCTIONS

Abstract

We have calculated the widths of the integer and half-integer voltage steps in a square Josephson-junction single plaquette as a function of ac level for various filling factors f. The characteristic features of the step widths, corresponding to n = 0, 1/2, and 1, show clear differences between small and large values of f, and are in reasonable agreement with the results observed experimentally in high-T(c) single grain-boundary junctions. When the inhomogeneity in the critical current of the junctions parallel and perpendicular to the external current is introduced to the model the equations of motion for a single plaquette become equivalent to those of a dc superconducting quantum interference device in the limit of small loop inductance.