CPM Seminar

Repelled, yet attracted: the case of strongly correlated superconductivity

André-Marie Tremblay

Université de Sherbrooke

Band theory and BCS theory are, arguably, the most successful theories of condensed matter. Yet, both of them fail miserably for some materials. In particular, high-temperature superconductors and layered organic superconductors cannot be explained by these theories. In this talk, I show that several conceptual and computational advances have allowed to demonstrate that the simplest model that accounts for competition between the wave and particle properties of electrons in solids, namely the Hubbard model, contains much of the physics of these puzzling materials. In particular, we can understand how electrons can bind and superconduct in the presence of strong repulsion thanks to retardation and superexchange. In the normal state, at finite doping, a first-order transition between a metal and a pseudogap ends at a critical point. In the supercritical region, a Widom line and its precursor determine the crossovers seen experimentally in both types of materials. The whole phase diagram is controlled by this first-order transition, a finite-doping signature of the Mott transition.