Magnetic domain walls in antiferromagnetic topological insulator heterostructures

We explore the emergence of spin-polarized flat bands at head-to-head domain walls (DWs) in topological insulator heterostructures with in-plane magnetization and interlayer antiferromagnetic coupling. We show in the framework of quantum well physics that, by tuning the width of a DW, one can control the functional form of the bound states appearing across it. Furthermore, we demonstrate the effect that the parity of the number of layers in a multilayer sample has on the electronic dispersion. The alignment of the magnetization vectors on the top and bottom surfaces of odd-layer samples affords particle-hole symmetry, leading to the presence of linearly dispersing topologically nontrivial states around E=0. By contrast, the lack of particle-hole symmetry in even-layer samples results in a gapped system, with spin-polarized flat bands appearing on either side of a band gap, with a characteristic energy well within terahertz energy scales. Such a system is a versatile platform for the development of spintronic devices and proposes one use in reconfigurable magnetic memory.