Proximity effect in gold-coated YBa2Cu3O7-δ films studied by scanning tunneling spectroscopy -: art. no. 017003

Scanning tunneling spectroscopy on gold layers overcoating c-axis YBa2Cu3O7-delta (YBCO) films reveals proximity-induced gap structures. The gap size reduces exponentially with the distance from a-axis facets, indicating that the proximity effect is primarily due to the (100) YBCO facets. The penetration depth of superconductivity into the gold is similar to30 nm, in good agreement with estimations for the dirty limit. The extrapolated gap at the interface is similar to15 meV, similar to the value of an s-wave component of the order parameter measured at the YBCO surface in recent point-contact experiments.