THERMAL NOISE IN HIGH-TEMPERATURE SUPERCONDUCTING-NORMAL-SUPERCONDUCTING STEP-EDGE JOSEPHSON-JUNCTIONS

We have fabricated YBa2Cu3O7-delta-normal metal-YBa2Cu3O7-delta step-e dge Josephson junctions that fit the resistively shunted junction mode l with Johnson-Nyquist thermal noise. The I- V curves are well fit ove r a large temperature range for junctions of varying critical current values. There is good agreement between the fitted thermal noise tempe rature and the measured ambient temperature. This is strong evidence t hat these junctions are not dominated by superconducting shorts longer than the superconducting coherence length.