Electrical Transport and Noise Properties of [100]-Tilt YBa2Cu3O7−x Grain-Boundary Junctions With High IcRn Product

We have studied electrical transport and low-frequency noise properties of [100]-tilt bicrystal YBa₂Cu₃O_7-x junctions, which show a lower degree of structural disorder and higher characteristic voltages I_cR_nmiddot in comparison with conventional [001]-tilt grain-boundary junctions. The oxygen content of the junction barrier was varied by an annealing in atomic oxygen and by aging in molecular oxygen. The modification of the I-V curves and low-frequency noise were monitored. The terahertz losses in the junctions were derived and were shown to decrease with the increase of the oxygen content. It was found that the resistance and critical current fluctuations are completely antiphase correlated and intensities of normalized resistance and critical current low-frequency fluctuations are equal in these junctions. Consequently, quasiparticles and Cooper pairs in the [100]-tilt junctions tunnel directly through the same parts of the barrier, and a band-bending model with the charge fluctuations at the barrier can applied to explain the modification of the [100]-tilt grain-boundary junctions after oxygen loading and aging.