Coexistence\nof Chiral Edge and Localized States in\na High Chern Number Topological Photonic Alloy

Recently, a topological photonic alloy with a Chern number\nof 1\nhas been proposed and experimentally verified. Here, we create a substitutional-type\ntopological photonic alloy system with a high Chern number of 2 coexisting\nwith a Chern number of −1, based on the random mixing of nonmagnetized\nand magnetized yttrium iron garnet (YIG) rods. Interestingly, we find\nlocalized states in the topological gap with a high Chern number of\n2, which is different from that of −1. These localized states\nfill the topological gap statistically, indicating that the gap with\na high Chern number of 2 is not a density of states (DOS) gap. By\nfurther investigating the transport behavior of the chiral edge state\n(CES) in the topological gap, we find that the transport is unaffected.\nHowever, as observed through electromagnetic field inspections, the\nCESs may couple with these localized states during propagation. Our\nwork deepens the understanding and further enriches the topological\nphotonic alloy system.