Transport in atomically engineered BiSrCaCuO multilayers

We have utilized atomic layer deposition to synthesize single crystal thin films of cuprate superconductors, as well as a variety of superlattices and multilayer heterostructures with atomically abrupt interfaces. For example, we made trilayer structures with the top and the bottom BiSrCaCuO electrodes separated by titanate barriers that were only 4 Å thick and yet free of pinholes over macroscopic areas. This unique synthetic capability made it possible to study transport in the c-axis direction under controlled and systematically varied conditions. Taken together, these experiments provide a picture of the c-axis transport in 2201, 2212, and various heterostructures under study. In particular, they suggest presence of a large density of localized states near the Fermi level and thus support a two-component description of the electron system in these compounds.