Anomalous Bulk Current in Quantum Hall Systems with an Expanding Edge

Yuuki Sugiyama, Tokiro Numasawa

Published 2025-06-25Version 1

Understanding topological phases of matter is essential for advancing both the fundamental theory and practical applications of condensed matter physics. Recently, a theoretical framework for a quantum Hall system with an expanding edge state was proposed [Phys. Rev. D {\bf 105}, 105009 (2022)], revealing the existence of an energy flux analogous to Hawking radiation on the edge. Motivated by this work, we extend the analysis to a model of a $(2+1)$-dimensional spacetime that includes both the bulk and edge regions. Due to the presence of bulk and edges, we demonstrate that the covariant form of the gravitational anomaly appears on the edge via the anomaly-inflow mechanism. Then, we investigate the energy flux on the edge from the viewpoint of gravitational anomalies, such as covariant gravitational and Weyl anomalies. We also find that, due to the conservation of energy and momentum in the entire system, the presence of anomalous currents on the expanding edge induces non-trivial currents in the bulk originating from the expansion of the edge.