Prediction and observation of an antiferromagnetic topological insulator

By M. Otrokov, I. Klimovskikh, H. Bentmann, D. Estyunin, A. Zeugner, Z. Aliev, Sebastian Gass, A. Wolter, A. Koroleva, A. Shikin and 34 more. Nature, 2018

1,064 citations recorded by the source corpus.

Magnetic topological insulators are narrow-gap semiconductor materials that combine non-trivial band topology and magnetic order1. Unlike their nonmagnetic counterparts, magnetic topological insulators may have some of the surfaces gapped, which enables a number of exotic phenomena that have potential applications in spintronics1, such as the quantum anomalous Hall effect2 and chiral Majorana fermions3. So far, magnetic topological insulators have only been created by means of doping nonmagnetic topological insulators with 3d transition-metal elements; however, such an approach leads to strongly inhomogeneous magnetic4 and electronic5 properties of these materials, restricting the observation of important effects to very low temperatures2,3. An intrinsic magnetic topological insulator—a stoichiometric well ordered magnetic compound—could be an ideal solution to these problems, but no such material has been observed so far. Here we predict by ab initio calculations and further confirm using various experimental techniques the realization of an antiferromagnetic topological insulator in the layered van der Waals compound MnBi2Te4. The antiferromagnetic ordering that MnBi2Te4 shows makes it invariant with respect to the combination of the time-reversal and primitive-lattice translation symmetries, giving rise to a ℤ2 topological classification; ℤ2 = 1 for MnBi2Te4, confirming its topologically nontrivial nature. Our experiments indicate that the symmetry-breaking (0001) surface of MnBi2Te4 exhibits a large bandgap in the topological surface state. We expect this property to eventually enable the observation of a number of fundamental phenomena, among them quantized magnetoelectric coupling6–8 and axion electrodynamics9,10. Other exotic phenomena could become accessible at much higher temperatures than those reached so far, such as the quantum anomalous Hall effect2 and chiral Majorana fermions3. An intrinsic antiferromagnetic topological insulator, MnBi2Te4, is theoretically predicted and then realized experimentally, with implications for the study of exotic quantum phenomena.

Subfields: Atomic and Molecular Physics, and Optics, Condensed Matter Physics, Materials Chemistry

View Paper: https://www.semanticscholar.org/paper/99a88bd704723c21a44b08f8686319fa88fc4451

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Citations in the corpus

Dirac Surface States in Intrinsic Magnetic Topological Insulators EuSn2As2 and MnBi2nTe3n+1 (2019, methodology): “ 7]. The introduction of magnetism into the Z 2 TIs can produce more exotic topological quantum phenomena, such as the quantum anomalous Hall effect [8, 9, 10, 11, 12, 13, 14], axion insulator states [15, 16, 17, 18, 19, 20, 21] and chiral Majorana fermions [22]. The quantum anomalous Hall effect ha”
High-temperature quantum anomalous Hall regime in a MnBi2Te4/Bi2Te3 superlattice (2020, background): “[32] Otrokov, M.”
Colloquium : Quantum anomalous Hall effect (2022, background): “12(b)] (Li et al., 2019b; Otrokov et al., 2019a; Zhang et al., 2019a).”