Tunable second-order topological corner states induced by interlayer coupling in twisted bilayer Chern insulators

We propose a theory for tunable second-order topological corner states induced by interlayer coupling in bilayer Chern insulators with opposite Chern numbers. We demonstrate that the existence of the topological corner state is determined by the relationship between the twist angle of the bilayer Chern insulators and the normal angles of the two sides of the corner. In addition, the position of these corner states can be sensitively controlled by the twist angle, as confirmed by a rigorous analysis of edge state theory. Our findings serve as a theoretical guide, opening avenues for the design and realization of higher-order topological materials.