Physics Colloquium Series, Fall 2009 and beyond

If we deform a material and restore it precisely back to its starting point, our everyday intuition tells us that the material before and afterwards is identical. This is true classically, and was believed to be true quantum mechanically until recently. Even if all the atoms, electrons, and other ingredients are returned exactly to where they started, we now know that the restored material can differ from the undeformed material by nontrivial quantum mechanical phase factors. The importance of these so-called geometric or Berry phases has garnered increasing appreciation and attention in recent years. The quantum Berry phase can fundamentally alter the ground state of a system, lead to new states of quantum matter, and be exploited in quantum devices and topological quantum computing strategies This talk will overview new experiments, employing scanning tunneling microscopy and atomic manipulation, that directly visualize Berry's phase in nanostructures, graphene, and topological insulators.