Superconducting transport characteristics of YBa2Cu3O7-δ grain boundary junctions

The superconducting transport of YBa₂Cu₃O _7-δ grain boundary junctions (GBJs) fabricated by laser ablation deposition on SrTiO₃ bicrystals is discussed. For narrow GBJs with a width smaller than about four times their Josephson penetration depth, the current-voltage characteristics can be modeled closely by the resistively shunted junction (RSJ) model and the magnetic field dependence of the critical current is Fraunhofer-pattern-like. The temperature dependence of the critical current is proportional to (1-T/T_c)² close to T _c. The characteristic voltages V_c=J ^gb_cρ_N, where J^gb _c is the critical current density and ρ_N the normal resistance times unit area of the GBJs, range between 0.2 and 8 mV at 4.2 K and scale proportional to (1/ρ_N)^1.5 . The transport characteristics of the GBJs are in agreement with a SNINS-type junction model