Disordered Parity Anomalous Semimetal

The parity anomalous semimetal is a topological state of matter characterized by its semi-metallic nature and a quantum Hall conductance of one-half e²/h  (e is the elementary charge and h is the Planck constant). Here we investigate the topological phase transition driven by disorder in a semi-magnetic structure of topological insulator, and narrow-gap weak topological insulator film. We demonstrate that strong disorder not only leads to a topological transition from the parity anomalous semimetal to a marginal metal with non-quantized anomalous Hall conductance, but also induces the topological phase in a trivial insulating phase. Our calculations of the local density of states provide clear picture for the formation of a single gapless Dirac fermion, which emerges as the disorder strength increases. The half quantized Hall effect is attributed to the existence of the gapless Dirac cone. Our findings of disorder-induced parity anomalous semimetal and marginal metal significantly advance our understanding of the disorder-driven topological phase transition in magnetic topological insulators, opening up new avenues for further exploration in the field of quantum materials.