Barrier parameters and superconducting gap structure of the etched surface of Y-Ba-Cu-O by scanning tunnelling spectroscopy

Using a scanning tunnelling microscope, the tunnelling current vs. voltage is measured between a gold tip and the chemically etched (001) surface of YBa2Cu8Ox crystals at room temperature. The tunnelling barrier height and thickness are derived by modelling the system in the normal state as a conventional N-I-N junction. The I(V) and G(V) curves are computed for the same junction in the superconducting state (N-I-S junction). The predicted gap structure for a single BCS-Dynes-like gap is simple and has low zero-bias conductance. The complex G(V) spectra measured below T(c) on the etched junctions with approximately 50% zero-bias conductance suggest a possible multilayer contribution in the unit cell.