Gapless States Localized along a Staircase Edge in Second-Order Topological Insulators

Yuki Nagasato, Yositake Takane, Yukinori Yoshimura +2

A second-order topological insulator on a two-dimensional square lattice hosts zero-dimensional states inside a band gap. They are localized near $90^{\circ }$ and $270^{\circ }$ cor…