Chiral channel network from magnetization textures in two-dimensional <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi>MnBi</mml:mi><mml:mn>2</mml:mn></mml:msub><mml:msub><mml:mi>Te</mml:mi><mml:mn>4</mml:mn></mml:msub></mml:mrow></mml:math>
Chengxin Xiao, Jianju Tang, Pei Zhao, Qingjun Tong, Wang Yao
Abstract
When an atomically thin van der Waals magnet forms a 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 two-dimensional (2D) magnets. The recent discovery of 2D magnetic topological insulators such as ${\mathrm{MnBi}}_{2}{\mathrm{Te}}_{4}$ 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 ${\mathrm{MnBi}}_{2}{\mathrm{Te}}_{4}$. 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.