Alireza Parhizkar
University of Maryland
Magic revealed: How flat bands appear and disappear in moiré materials
Location: 1080 Physics Research Building
Faculty Host: Brian Skinner
Abstract: Flat bands are puzzling occurrences where electrons cease to propagate across a system. In this talk, I will show that these occurrences are linked to the realizability of a timeless version of the system, and that the self-consistency condition for this realization takes on a topological form in two-dimensional materials. Moiré structures come with an additional twist: The emergence of flat bands in these structures is related to the behavior of a particle in an inhomogeneous magnetic field with zero total flux. We will explore why perfectly flat bands are generally impossible in this context but how introducing a “non-Abelian component”—a spin field with zero total curvature—can achieve perfect localization. Since there is a lot of material to cover in this talk, I will try to present the bird’s-eye view and descend to technical details whenever necessary. I will, however, quickly review the path integral approach to quantum anomalies, as it is going to be used in the talk, and, time permitting, introduce the process of Abelianization through which the non-Abelian theory transforms to its Abelian version.
