Abstract
Thin films of magnetic topological insulators (TIs) are expected to exhibit a quantized anomalous Hall effect when the magnetizations on the top and bottom surfaces are parallel and a quantized topological magnetoelectric effect when the magnetizations have opposite orientations. Progress in the observation of these quantum effects was achieved earlier in the films with modulated magnetic doping. On the other hand, the molecular-beam-epitaxy technique allowing the growth of stoichiometric magnetic van der Waals blocks in combination with blocks of topological insulator was developed. This approach should allow the construction of modulated heterostructures with the desired architecture. In the present paper, based on the first-principles calculations, we study the electronic structure of symmetric thin film heterostructures composed of magnetic MnBi2Se4 blocks (septuple layers, SLs) and blocks of Bi2Se3 TI (quintuple layers, QLs) in dependence on the depth of the magnetic SLs relative to the film surface and the TI spacer between them. Among considered heterostructures we have revealed those characterized by nontrivial band topology.
Highlights
The combination of nontrivial band topology and magnetism gives rise to novel spintronic phenomena, such as the quantum anomalous Hall effect and the topological magnetoelectric effect
We found that thin film heterostructures, in which the magnetic SL blocks are placed on top of or near the surface with at least a 3QL thick topological insulators (TIs) spacer, are potential candidates for realizing topological edge states within a relatively large band gap
We consider heterostructures consisting of MnBi2 Se4 and Bi2 Se3 blocks stacked along the [0001] direction with MnBi2 Se4 SLs located at different depths from the surface
Summary
The combination of nontrivial band topology and magnetism gives rise to novel spintronic phenomena, such as the quantum anomalous Hall effect and the topological magnetoelectric effect. It was reported that the QAH effect was observed at 1 K, which was achieved by the construction of modulated thin TI films where magnetic doping (Cr) was organized only in certain quintuple layers (QLs) of (Bi1−y Sby ) Te3 [10]. Such modulated doping enhanced the magnetically induced gap in the TI surface Dirac state due to a higher Cr doping concentration as well as the reduction of the doping induced disorder on the TI surface. The axion insulator state was realized in the modulation-doped magnetic heterostructures prepared by the layer-by-layer MBE with Cr in the vicinity of the top and bottom surfaces of the (Bi1−y Sby ) Te3 with the asymmetric location of the magnetic layer [15] and in asymmetric films where a nonmagnetic layer of (Bi1−y Sby ) Te3 is sandwiched by a Cr-doped and V-doped layers [16]
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