Tunable Topological Phases in a Natural MnSb2Te4/(Sb2Te3)2 superlattice

Intrinsic ferromagnetic materials with nontrivial topological properties provide a fertile ground to explore exotic quantum properties, such as the quantum anomalous Hall effect, large tunneling magnetoresistance, etc., which would have potential applications in next-generation spintronic devices. In this work, combining experimental and theoretical studies, we find that in a newly synthesized natural bulk van der Waals MnSb2Te4/(Sb2Te3)2 superlattice, the competing magnetic interactions give rise to a fragile ferromagnetic ground state, which whereas very easily enters into the antiferromagnetic states at higher temperatures. Moreover, the system can be forced into a ferromagnetic state by a very small vertical magnetic field. Especially, our calculations reveal that MnSb2Te4/(Sb2Te3)2 system in different magnetic configurations always keeps staying in the axion-insulator state. The axion-insulator state can be converted into a Weyl semimetal with hole doping, manifested by the notable intrinsic anomalous Hall effect. Our work thus provides an intrinsic ferromagnetic topological material which can be tuned into versatile topological phases by temperature, magnetic field, as well as carrier doping.