Magnetic second-order topological physics in two-dimensional NiZrI6

Two-dimensional (2D) nonmagnetic second-order topological insulators (SOTIs) have been exhaustively studied, whereas 2D magnetic SOTIs have received little attention from researchers. In this work, we have demonstrated using first-principles calculations that the 2D NiZrI6 monolayer is a 2D magnetic SOTI with a ferromagnetic ground state. Two spin channels in the 2D NiZrI6 monolayer exhibit nontrivial gaps. According to the higher-order bulk-boundary correspondence, the 2D NiZrI6 monolayer shows topologically protected corner states with quantized fractional charge (e/3) that are spin-polarized and pinned at the sample's corners in real space. In addition, the zero-dimensional corner states of the 2D NiZrI6 monolayer are resistant to spin–orbit coupling (SOC) effects. It is anticipated that 2D NiZrI6 monolayer with magnetic higher-order topology will contribute to topo-spintronics advancement.