Classification of Chern numbers based on high-symmetry points

The Chern number is a crucial topological invariant for distinguishing the phases of Chern insulators. Here, we find that for Chern insulators with inversion symmetry, the Chern number alone is insufficient to fully characterize their topology. Specifically, distinct topological phases can be differentiated based on skyrmions at different high-symmetry points. Interfaces between these topological phases exhibit gapless helical states, which provide counterpropagating transport channels and robust quantized transport. Additionally, we identify topological transitions that do not involve changes in the Chern number but can be characterized by transitions of skyrmions between high-symmetry points. These transitions arise due to the toroidal structure of the two-dimensional Brillouin zone, which is generally applicable to two-dimensional periodic lattice systems. Our research introduces different degrees of freedom for controlling topological optical transport and deepens the understanding of Chern insulators with inversion symmetry.