Thickness-Dependent Magnetism and Topological Properties of EuSn₂As₂

Rare-earth magnetic compounds, known as conventional magnetic materials and magnetic topological materials, provide a platform for exploring prominent physics phenomena and designing topological spintronic devices. EuSn2As2, as a candidate of intrinsic antiferromagnetic (AFM) topological insulator, has recently attracted considerable attention in experiment. Here, by using density functional theory to systematically investigate the structure, magnetic, electronic, and topological properties, we demonstrate that the interlayer coupling, magnetic order, and spin orientation strongly influence the electronic and topological properties of EuSn2As2. The EuSn2As2 monolayer (1L) is a topological trivial ferromagnetic semiconductor. Increasing the thickness can lead to the appearance of interlayer AFM in the 2L and insulator to metal transition in the 3L one, respectively. Moreover, the nontrivial surface states that resulted from the band inversion between Sn p and As p orbitals can be obtained in the 4L one. Our study reveals the spin textured band effect, i.e., spin-orientation-controlled band structure effect, in EuSn2As2, and also evidence the importance of dimensional effect for the electronic properties and magnetic behaviors of this material as van der Waals AFM topological insulators.