Tunneling Spectroscopy Study of YBa2Cu3O7 Thin Films Using a Cryogenic Scanning Tunneling Microscope.

摘要

We have measured reproducible tunneling spectra on YBa2Cu307 thin films with a cryogenic scanning tunneling microscope. We find that the I-V curves are generally of three types. The most common type, featured in a large majority of the data, shows a region of high conductance at zero bias. The amplitude of this region is inversely proportional to the tunneling resistance between the tip and sample. It is possible that this can be explained in terms of Josephson effects with the films, although an alternative is given based on electronic self-energy corrections. Data showing capacitive charging steps are analyzed in terms of two ultrasmall tunnel junctions in series.