Macroscopic quantum interference effects in superconducting multiterminal microstructures

We review the macroscopic quantum phenomena in superconducting microstructu res based on multiterminal junctions. The multiterminal Josephson junction presents a system in which the weak coupling takes place between several ma ssive superconducting banks (terminals). Compared with the conventional (tw o-terminal) junctions such systems have additional degrees of freedom and a corresponding set of control parameters, preset transport currents and (or ) applied magnetic fluxes. The general phenomenological theory of multiterm inal Josephson junctions is presented. The specific multichannel interferen ce effects (studied theoretically and experimentally) are described for two microstructures: the four-terminal SQUID and a system consisting of two we akly coupled superconducting rings. (C) 1999 Academic Press.