Josephson device with well-defined and low critical points

Two different basic types of switching behavior of Josephson interferometers are possible: a vortex-to-vortex and a vortex-to-voltage transition. Both transition types are separated by the so-called critical points on the threshold curve of the device. For critical points, in general, no analytic expression is available. Therefore, the position of the critical points can only be determined by numerical solutions. In the designs known, the critical points are very sensitlve with respect to parameter variations, which makes LSI design very difficult. In this paper, the design and the experimental results of an asymmetric Josephson interferometer with one well-defined and low critical point are described. This well-defined critical point corresponds to the tip point of the threshold characteristic, which is defined by an analytical expression. The practical consequence for the design of Josephson circuits will be indicated. The dynamic switching behavior of the asymmetric interferometer with respect to the critical points will be discussed extensively in the phase plane, together with the potential energy.