Proximity effect and Josephson current in clean strong/weak/strong superconducting trilayers

Abstract

Recent measurements of the Josephson critical current through LSCO/LCO/LSCO thin films showed an unusually large proximity effect. Using the Bogoliubov–de Gennes equations for a tight-binding Hamiltonian we describe the proximity effect in weak links between a superconductor with critical temperature Tc and one with critical temperature Tc′, where Tc>Tc′. The weak link (N′) is therefore a superconductor above its own critical temperature and the superconducting regions are considered to have either s-wave or d-wave symmetry. We note that the proximity effect is enhanced due to the presence of superconducting correlations in the weak link. The dc Josephson current is calculated, and we obtain a nonzero value for temperatures greater than Tc′ for sizes of the weak links that can be almost an order of magnitude greater than the conventional coherence length. Considering pockets of superconductivity in the N′ layer, we show that this can lead to an even larger effect on the Josephson critical current by effectively shortening the weak link.

Source-reported materials — not catalogue approval

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