Proximity effects with the cuprates

In view of the problems encountered in manufacturing S/I/S Josephson junctions with cuprates, S/N/S junctions represent an interesting alternative. However, when designing such junctions, one must take into account the specific characteristics of the cuprates, mainly a very short coherence length and a low carrier density. When N is a conventional normal metal such as Ag or Au, these specific characteristics lead to a strong depression of the pair amplitude in N at the interface, and thus to low I_cR products. We show that large I_cR products can be obtained by using for N a low carrier density metal or a heavily doped semiconductor. This prediction is compared with recent experimental results. Grain boundary junctions are also discussed in the same general framework.