Low-frequency voltage noise and electrical transport in [100]-tilt YBa2Cu3O7−x grain-boundary junctions

We have fabricated [100]-tilt YBa2Cu3O7−x grain-boundary junctions with high characteristic voltages IcRn and studied their low-frequency voltage noise. The intensities of normalized resistance and critical current fluctuations have been found to be equal in these junctions and a complete antiphase correlation between these two fluctuations has been demonstrated. These results show that quasiparticles and Cooper pairs in the [100]-tilt junctions tunnel directly through the same parts of the barrier. The band-bending model with charge fluctuations at the structural interface is indicated to be adequate for understanding current transport and voltage noise in high-Tc grain-boundary junctions.