Tunable interlayer magnetism and band topology in van der Waals heterostructures of Mn Bi2Te4 -family materials

Manipulating interlayer magnetic coupling (IMC) of van der Waals (vdW) magnets is the key to tailoring material properties for various electronic applications and fundamental studies. Using Mn Bi₂Te₄ -family materials as examples, we systematically investigate the constituent-element dependence of IMC by first-principles calculations and attribute the IMC to unusual long-range superexchange interactions mediated by the p orbitals across the vdW gap. Remarkably, a simple, universal rule is proposed to determine the sign of IMC (ferromagnetic or antiferromagnetic) by d -orbital occupation, and guidance is provided to achieve extraordinarily strong or stacking-dependent IMC by element engineering. Furthermore, several magnetic topological states are designed by heterostructuring, including ferromagnetic Weyl semimetals, high-order topological insulators, and unusual kinds of quantum anomalous Hall insulators. The findings enable us to engineer the magnetic and topological properties of Mn Bi₂Te₄ -family materials as well as other vdW magnetic materials and heterostructures.