Observation of proximity effect in YBCO/Au bilayer films by microwave surface resistance measurements

Abstract Measurements of surface resistance R s for YBCO films covered with thin Au layer of thickness d are carried out at 67 GHz in the temperature range 100–60 K. Measured R s ( d ) dependence exhibits a large maximum at small d ≈20 nm which cannot be explained by the simple model of normal metal–HTSC bilayer surface resistance. The difference is attributed to the proximity effects at the YBCO/Au interface.