One of the top ten Physics stories in 2007* was the finding of Cooper (electron) pairs in thin film insulators by the Brown University team of Stewart, Yin, Xu and Valles. While the existence of paired electrons in insulators has been postulated before, the Brown team performed a definitive experiment that used "nanohoneycomb" thin films of amorphous bismuth that undergo a thickness-tuned insulator-superconductor transition.
These films were formed on anodic aluminum oxide nanopore array membranes, fabricated in the laboratory of Jimmy Xu, Professor of Engineering and Physics, by vapor deposition of bismuth to produce amorphous bismuth layers with 27 nm diameter hole arrays (see Figure, panel B). The ordered hole array leads to magneto-oscillations, and the nanoscale dimension of the array is believed to enhance the localization and correlation of Cooper pairs. This interdisciplinary project demonstrates how new methods of nanopatterning can enable breakthroughs in fundamental condensed-matter physics.
* named by the American Institute of Physics