Locality of topological dynamics in Chern insulators

A system having macroscopic patches in different topological phases has no well-defined global topological invariant. To treat such a case, the quantities labeling different areas of the sample according to their topological state are used, dubbed local topological markers. Here we study their dynamics. We concentrate on two quantities, namely the local Chern marker and the on-site charge induced by an applied magnetic field. The first one provides the correct information about the system’s topological properties, the second can be readily measured in experiment. We demonstrate that the time-dependent local Chern marker is a much more non-local object than the equilibrium one. Surprisingly, large samples driven out of equilibrium lead to a simple description of the local Chern marker’s dynamics by a local continuity equation. Also, we argue that the connection between the local Chern marker and magnetic-field induced charge known in static holds out of equilibrium in some experimentally relevant systems as well. This gives a clear physical description of the marker’s evolution and provides a simple recipe for experimental estimation of the topological marker’s value.