Chiral channel network from magnetization textures in 2D MnBi2Te4

TL;DR

This paper explores how moiré-patterned magnetization textures in 2D MnBi2Te4 create chiral channels at domain walls, leading to novel miniband structures and potential spintronic applications.

Contribution

It introduces a minimal model showing how magnetization textures induce chiral channels and minibands in 2D MnBi2Te4, linking magnetic textures with topological surface states.

Findings

Chiral channels form at magnetization domain walls.

Superlattice minibands can be gapped or gapless depending on domain geometry.

Spin and current density textures reveal spin-momentum locking.

Abstract

When atomically thin van der Waals (vdW) magnet forms long-period moir\'e pattern with a magnetic substrate, the sensitive dependence of interlayer magnetic coupling on the atomic registries can lead to moir\'e defined magnetization textures in the two-dimensional (2D) magnets. The recent discovery of 2D magnetic topological insulators such as MnBi2Te4 leads to the interesting possibility to explore the interplay of such magnetization textures with the 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 close loops of chiral channels, while in magnetization textures with open domain wall geometries, gapless mini-Dirac cone is found instead. The miniband Bloch states feature a spatial texture of spin and local current density, which are clear manifestation of the spin-momentum locked chiral channels at the domain walls. The results suggest a new platform to engineer spin and current flows through the manipulation of magnetization domains for spintronic devices.