Ballistic four-terminal Josephson junction: bistable states and magnetic flux transfer

The macroscopic quantum interference effects in the ballistic Josephson microstructures are investigated. The studied system comprises four hulk superconductors (terminals) which are weakly coupled through a mesoscopic rectangular normal metal layer (two-dimensional electron gas). We show that nonlocal electrodynamics of ballistic systems lead to specific current-phase relations for the mesoscopic multiterminal Josephson junction. The nonlocal coupling of supercurrents produces a "dragging" effect for phases of the superconducting order parameter in different terminals. The composite Josephson junction, based on this effect, exhibits the two-level system behaviour controlled by the external magnetic flux. The effect of magnetic flux transfer in a system of nonlocally coupled superconducting rings is also studied. (C) 2000 Elsevier Science B.V. All rights reserved.