Current–voltage characteristics of break junctions of high-Tc superconductors

The current–voltage (I–V) characteristics of break junctions of polycrystalline La1.85Sr0.15CuO4, Y0.75Lu0.25Ba2Cu3O7−δ, Bi1.8Pb0.3Sr1.9Ca2Cu3Ox and composite YBa2Cu3O7−δ + Ag are investigated. The experimental I–V curves exhibit the specific peculiarities of superconductor/normal-metal/superconductor junctions. The relation between an I–V characteristic of network of weak links and I–V dependencies of typical weak links is suggested to describe the experimental data. The I–V curves of typical weak links are calculated by the Kümmel–Gunsenheimer–Nicolsky model considering the multiple Andreev reflections.