Figure 7. Temperature dependence.

(a) Field measured at the centre of the UD layer: as a single layer (open symbols) or as a barrier with thickness of 46 nm in the trilayer (filled symbols). In the latter case the average local field is diamagnetically shifted up to T_eff≅22 K. Above this temperature its value is within the experimental error equal to the applied field. No shift is observed for a single UD layer. (b) Temperature dependence of the magnetic penetration depths in the barrier (black triangles, λ′) and in the electrode layer (red circles, λ) compared with typical behaviour in optimally doped crystals (blue line) obtained from ref. 17. Error bars give the fit errors. The dashed lines are guides to the eyes. The divergent behaviour of λ′ close to 22 K indicates the disappearance of the long-range phase coherence in the barrier at that temperature. The temperature dependence indicates that the induced superfluid density in the barrier layer is more sensitive to thermal excitation than in a bulk superconductor.