Seminar by Mathias Scheurer
Condensed Matter Seminar Series
University of Innsbruck
More moiré is better: many-body physics in several twisted graphene systems
When two layers of graphene are stacked on top of each other with a finite relative angle of rotation, a moiré pattern forms. Most strikingly, at so-called “magic angles”, the largest of which is around 1 degree, the bands around the Fermi surface become very flat; this enhances the density of states and the impact of electron-electron interactions. Soon after the experimental discovery in 2018 that this enhancement can induce superconductivity and insulating phases, it became clear that twisted bilayer graphene is only one example of an engineered graphene-based moiré system with a complex phase diagram akin to other strongly correlated materials. In this talk, I will provide an introduction to the rich set of possibilities provided by graphene-based moiré superlattices to create and study interesting many-body physics at the intersection of strong correlations and topology. Involving a combination of analytics, numerics, and experimental insights, some of our recent efforts to elucidate their complex phase diagrams will be presented. Specifically, I will discuss nematicity in twisted double-bilayer graphene, instabilities in twisted trilayer graphene, and, if time permits, a possible topological origin of superconductivity in twisted bilayer graphene.