Experimental realization of the axion insulator that exhibits the intriguing topological magnetoelectric effect has remained a challenge since it was theoretically predicted in three-dimensional (3D) topological insulators (TIs) a decade ago. One of the primary experimental difficulties is to break time-reversal symmetry with a special configuration of magnetization that points inwards or outwards over the whole surface of 3D TIs. Here, we propose that axion insulator state can show up in a ferromagnetic insulator/3D-TI/antiferromagnet insulator heterostructure. Importantly, its appearance only depends on the magnetization of the ferromagnetic insulator. Therefore, the axion insulator state in such heterostructure can be more easily observed by experiments. Remarkably, it is exemplified that the ferromagnetic insulator MnBi2Se4/Bi2Se3/antiferromagnetic insulator Mn2Bi2Se5 heterostructure manifests axion insulator state indeed. Our work thus sheds new light onto the exploration of axion insulator state in the heterostructures formed by magnetic insulators and 3D TIs.
Published in: "arXiv Material Science".