Large Dynamical Axion Field in Topological Antiferromagnetic Insulator Mn₂Bi₂Te₅

Abstract

The dynamical axion field is a new state of quantum matter where the magnetoelectric response couples strongly to its low-energy magnetic fluctuations. It is fundamentally different from an axion insulator with a static quantized magnetoelectric response. The dynamical axion field exhibits many exotic phenomena such as axionic polariton and axion instability. However, these effects have not been experimentally confirmed due to the lack of proper topological magnetic materials. Combining analytic models and first-principles calculations, here we predict a series of van der Waals layered Mn2Bi2Te5-related topological antiferromagnetic materials that could host the long-sought dynamical axion field with a topological origin. We also show that a large dynamical axion field can be achieved in antiferromagnetic insulating states close to the topological phase transition. We further propose the optical and transport experiments to detect such a dynamical axion field. Our results could directly aid and facilitate the search for topological-origin large dynamical axion field in realistic materials.

Axion dark matter: What is it and why now?

“…The existence of the axion quasiparticle requires the breaking of time reversal symmetry and is provided by magnetic ions and antiferromagnetic order. Candidate materials to host the axion quasiparticle include Bi(Fe) 2 Se 3 and Mn 2 Bi 2 Te 5 (74,75). The axion quasiparticle has yet to be observed in the laboratory, although various experiments have been designed to hunt for it, and there is growing interest in these candidate materials with possible applications to high-speed computer memory (76).…”

Intrinsic magnetic topological insulators

“…68 In addition to the (MnBi 2 Te 4 )(Bi 2 Te 3 ) n family, the intrinsic van der Waals material Mn 2 Bi 2 Te 5 -as a sister compound of MBT-has also been predicted to be a topological AFM material, one that could host the long-sought dynamical axion field. 81 Unlike AFM MBT, in which a certain symmetry fixes the axion field q to a quantized value (q = p), in Mn 2 Bi 2 Te 5 q becomes a bulk dynamical field from magnetic fluctuations and varies from zero to p because of the breaking of both time-reversal and inversion symmetries. 81 Such a dynamical axion field could induce novel phenomena, such as axionic polaritons 82 and nonlinear electromagnetic effects induced by axion instability.…”

“…81 Unlike AFM MBT, in which a certain symmetry fixes the axion field q to a quantized value (q = p), in Mn 2 Bi 2 Te 5 q becomes a bulk dynamical field from magnetic fluctuations and varies from zero to p because of the breaking of both time-reversal and inversion symmetries. 81 Such a dynamical axion field could induce novel phenomena, such as axionic polaritons 82 and nonlinear electromagnetic effects induced by axion instability. 83 A similar dynamical axion insulator state was also predicted in an (MnBi 2 Te 4 ) 2 (Bi 2 Te 3 ) heterostructure.…”

Vapor transport growth of MnBi2Te4 and related compounds

“…nMnTe.Bi 2 Te 3 , with more than one MnTe sheet inserted into Bi 2 Te 3 , might show complex magnetism and host novel topological properties [36][37][38]. A recent study reports the successful growth of n=2 member, Mn 2 Bi 2 Te 5 , by flux method [2].…”