PHASE-COHERENT CONDUCTANCE OF A SUPERCONDUCTOR NORMAL-METAL QUANTUM INTERFEROMETER

A theory of the subgap conductance of a hybrid superconductor-normal-m etal (S/N) quantum interferometer consisting of two tunnel junctions ( S/N) in contact with an N layer is developed. The oscillatory dependen ce of the conductance of the system G on the phase difference between superconductors phi is shown to be due to the proximity effect, i.e., to the penetration of the condensate into the N region. The G(phi) dep endence is found for the cases of both weak and strong proximity effec ts. This dependence can radically change its shape form qualitatively when the voltage is varied. The amplitude of the conductance oscillati ons appears to be large in the case of strong proximity effect. Differ ent layouts are considered including the cases when there is the third tunnel junction or point contact between the N conductor and the N el ectrode.