A Landau level (which is a flat band) forms only when a magnetic flux with non-zero total flux threads a system. In fact the degeneracy at the flat band is proportional to the flux. So no flat band can form when the magnetic flux averages to zero. We will discuss this and then show otherwise. This is relevant to time reversal symmetric systems that form flat bands such as magic-angle twisted bilayer graphene. In this talk the magic behind those systems will be revealed through the simplest model that gives rise to magical behaviour.

Time permitting, I will shortly introduce the concept of Abelianization by which a non-Abelian theory can break into corresponding Abelian ones.

Pizza and drinks will be served after the seminar in ATL 2117.