Fig. 1: Fractional mass-kink induced topological corner state with a fractional charge of e/4.
From: Antiferromagnetic second-order topological insulator with fractional mass-kink
Schematic mass distribution along the edge (red line) and localized domain wall state (blue line) for a mass-inversion, b fractional mass-kink. The mass M is defined in edge state space, m is mass-intensity, θ is mass-angle, Δθ is phase shift across the domain wall, τx and τy are Pauli matrix of the edge state. c Schematic checkerboard AFM order in monolayer FeSe cluster and the gapless topological edge states. d Schematic real-space distribution of gapless topological edge state (QSH edge state), showing the propagating direction (arrow) and spin (red and blue color). e Schematic canted checkerboard AFM order in monolayer FeSe cluster and the gapped topological edge states. Each corner is connected by two ferromagnetic edges with the same spin. The adjacent edges have a different mass-angle of θ and θ + π/2. f Schematic real-space distribution of in-gap topological corner state, holding a fractional charge of e/4.
