Chiral channel network from magnetization textures in two-dimensional MnBi2Te4

Abstract

When an atomically thin van der Waals magnet forms a long-period moiré pattern with a magnetic substrate, the sensitive dependence of interlayer magnetic coupling on the atomic registries can lead to moiré-defined magnetization textures in two-dimensional (2D) magnets. The recent discovery of 2D magnetic topological insulators such as MnBi2Te4 leads to the interesting possibility of exploring the interplay of such magnetization textures with topological surface states, which we explore here with a minimal model established for 2D MnBi2Te4. The sign flip of the exchange gap across a magnetization domain wall gives rise to a single in-gap chiral channel on each surface. In the periodic magnetization textures, such chiral spin channels at the domain walls couple to form a network and superlattice minibands emerge. We find that in magnetization textures with closed domain-wall geometries, the formed superlattice miniband is a gapped Dirac cone featuring orbital magnetization from the current circulation in the closed loops of chiral channels, while in magnetization textures with open domain wall geometries, a gapless mini-Dirac cone is found instead. The miniband Bloch states feature a spatial texture of spin and local current densities, which are clear manifestations of the spin-momentum locked chiral channels at the domain walls. The results suggest a platform to engineer spin and current flows through the manipulation of magnetization domains for spintronic devices.