Superconducting proximity effect in Y 1Ba 2Cu 3O 7-δ - Ag-Pb trilayer structures

We have studied the superconducting critical current I _c for Y ₁Ba ₂Cu ₃O _7-δ (123) - Ag - Pb proximity structures as a function of temperature and magnetic field. The temperature dependence of I _c is in agreement with the theory of de Gennes; the magnitude of the critical current density is as large as 1.7 × 10 ⁵ A/cm ² at 4.0 K which indicates strong proximity coupling. The decrease of I _c with magnetic field is explained by the reduction of the normal metal (Ag) coherence length by the field.