Comment on "Absence of Topological Protection of the Interface States in ${\mathbb{Z}}_2$ Photonic Crystals"

Xing-Xiang Wang, Toshikaze Kariyado, Xiao Hu

In the Letter, Xu et al. reported that edge modes disappear in the expanded structure of Wu-Hu model characterized by ${\mathbb{Z}}_2$ topological index, while appear in the trivial…