Department of Physics Colloquium, Abhay Pasupathy, Columbia University. Refreshments at 3:30pm.
Abstract: Superconductivity in traditional materials like aluminum and lead is suppressed by the introduction of magnetic order. We have an intuitive picture of why this happens - magnetism breaks the degeneracy between up and down spins and thus hinders the formation of superconducting Cooper pairs. However, in a large number of recently discovered superconductors, it is observed that the superconducting phase of the material lies in close proximity to a magnetic phase. There is significant experimental evidence and theoretical speculation that magnetic fluctuations are actually responsible for superconductivity in these materials, but the issue is by no means settled. I will describe recent scanning tunneling microscopy measurements on the iron pnictide superconductors that give us insight into the nature of magnetism at the atomic scale and its relationship to superconductivity in these materials.