Direct Observation Of The Proximity Effect In The N Layer In A Multi-Terminal SINIS Josephson Junction

It is found that the lateral conductivity of a thin N layer inside a multi-terminal SINIS device (at temperatures down to 1.8 K) is dissipative with a small coherent contribution near zero voltage, which can be suppressed with a small parallel magnetic field; here S, I, and N denote a superconductor (Nb), an insulator (A10X), and a normal metal (A1) respectively. It is suggested that this contribution is due to the proximity effect through the tunnel barriers, involving the superconducting fluctuations in A1. At the same time, a high Josephson current can flow normal to the structure, which we propose is due to a direct Josephson coupling between the external S electrodes.