Abstract
Disorder, topology, symmetry breaking, and dimensionality intertwine to form a rich and enigmatic landscape in condensed matter physics. In this seminar, I will provide an overview of the basic concepts of quantum anomalies and Anderson transitions, with a focus on magnetic topological insulator films that have attracted particular interest. I will then present our numerical investigation of the parity-anomalous semimetal (PAS) under disorder. Starting from the clean limit, I will trace how its electronic spectrum and transport properties evolve as disorder increases. Our simulations show that the characteristic half-quantized Hall response remains robust against weak disorder. With increasing disorder, the PAS evolves through an intermediate marginal metallic regime before eventually entering an Anderson-insulating phase. More remarkably, disorder does not merely destroy this novel gapless phase; it can also induce a PAS in a system that is topologically trivial in the clean limit, revealing an unexpected route from disorder to anomaly-related transport. These results provide a global picture of how the PAS emerges, persists, and disappears across different disorder regimes. I will conclude the seminar by discussing open questions and possible future directions.
Anyone interested is welcome to attend.