Physics & Astronomy Colloquium

3:30 PM, Friday, January 18, 2008
Room 155, Chem-Phys Building

Dr. James R. Thompson
Department of Physics and Astronomy
University of Tennessee, Knoxville
and
Materials Science and Technology Division
Oak Ridge National Laboratory

" Superconductivity and Large Macroscopic Currents in Nanoscale Metallic Films, Formed by Quantum Confinement''

Ultrathin films of Pb are intriguing materials. They are nearly ideal model systems for demonstrating how quantum mechanics can help in forming nano-materials and how superconductivity operates in extremely thin layers. We studied materials that are only a few atoms thick (5-18 monolayers), where quantum-confined growth enables formation of atomically smooth crystalline films over mesoscopic length scales. Films grow in bilayers, as shown by Scanning Tunneling Microscopy, because of the quantum nature of the film stability.
Superconductivity properties were investigated magnetically. Even the thinnest films (5 atoms thick) turn out to be quite robust superconductors. We’ll describe how superconductivity evolves from the thinnest films to bulk materials, and show that one can ``tune'' structural and superconductive properties by adding bismuth. These studies paint a conceptually appealing, elegant picture of a model nanoscale superconductor with calculable critical state properties and surprisingly strong phase coherence.
M.M. Özer et al., Nature Phys. 2, 173 (2006); Phys. Rev. B 74, 235427 (2006); and Science 316, 1594 (15 June 2007).

Refreshments will be served in CP 179 at 3:15 PM