Measurements of the dc Josephson current in proximity systems

Junctions modeled as S-N/I/S and S-N/I/N-S proximity systems (where S, I, and N indicate a superconductor, an insulator, and a normal metal, respectively) are widely discussed in literature from both the experimental and theoretical point of view. In the present paper experimental aspects concerning Nb/Nb junctions including a proximity bilayer are considered. Nb-M/I/Nb and M-Nb/I/Nb structures (where M is a normal metal, a semimetal, or a superconductor) are investigated by using a semimetal (bismuth) and a superconductor (aluminum) as the M layer. In particular, how the deposition of a back layer influences the behavior of Nb/I/Nb high-quality junctions is discussed, focusing the interest on measurements of the temperature dependence of the maximum dc Josephson current. Experimental data are discussed in the framework of Kresin's theoretical calculations based on the thermodynamic Green's function method.