Topological heterostructure, in which two anomalous insulators (represented by A, top inset) surround a middle region whose gap size and topology is electrically reconfigurable (represented by S). Region A is a honeycomb network of circulators connected by transmission lines (TLs) of phase delay φ. Region S is similar to region A, except for the introduction of unitary scatterers at the middle of each TL (bottom inset, yellow boxes). The scattering amplitude of the scatterers is controlled by the parameter θ and proportional to an external DC voltage. This allows to reconfigure the topological phase of the region S from anomalous to Chern. When the region S is in anomalous phase, a wave input from the left (yellow arrow, VA) will tend to flow undisturbed along the edge, following the red signal path. In contrast, when S is switched to the Chern phase, the input meets an anomalous-Chern topological interface, and must go down the blue signal (VB).
