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Realization of an intrinsic ferromagnetic topological state in MnBi₈Te₁₃.

ABSTRACT: Novel magnetic topological materials pave the way for studying the interplay between band topology and magnetism. However, an intrinsically ferromagnetic topological material with only topological bands at the charge neutrality energy has so far remained elusive. Using rational design, we synthesized MnBi8Te13, a natural heterostructure with [MnBi₂Te₄] and [Bi₂Te₃] layers. Thermodynamic, transport, and neutron diffraction measurements show that despite the adjacent [MnBi₂Te₄] being 44.1 Å apart, MnBi₈Te₁₃ manifests long-range ferromagnetism below 10.5 K with strong coupling between magnetism and charge carriers. First-principles calculations and angle-resolved photoemission spectroscopy measurements reveal it is an axion insulator with sizable surface hybridization gaps. Our calculations further demonstrate the hybridization gap persists in the two-dimensional limit with a nontrivial Chern number. Therefore, as an intrinsic ferromagnetic axion insulator with clean low-energy band structures, MnBi₈Te₁₃ serves as an ideal system to investigate rich emergent phenomena, including the quantized anomalous Hall effect and quantized magnetoelectric effect.

SUBMITTER: Hu C

PROVIDER: S-EPMC7375807 | biostudies-literature | 2020 Jul

REPOSITORIES: biostudies-literature

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Realization of an intrinsic ferromagnetic topological state in MnBi8Te13.

Hu Chaowei C Ding Lei L Gordon Kyle N KN Ghosh Barun B Tien Hung-Ju HJ Li Haoxiang H Linn A Garrison AG Lien Shang-Wei SW Huang Cheng-Yi CY Mackey Scott S Liu Jinyu J Reddy P V Sreenivasa PVS Singh Bahadur B Agarwal Amit A Bansil Arun A Song Miao M Li Dongsheng D Xu Su-Yang SY Lin Hsin H Cao Huibo H Chang Tay-Rong TR Dessau Dan D Ni Ni N

Science advances 20200722 30

Novel magnetic topological materials pave the way for studying the interplay between band topology and magnetism. However, an intrinsically ferromagnetic topological material with only topological bands at the charge neutrality energy has so far remained elusive. Using rational design, we synthesized MnBi8Te13, a natural heterostructure with [MnBi2Te4] and [Bi2Te3] layers. Thermodynamic, transport, and neutron diffraction measurements show that despite ...[more]

PMID: 32743072

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Project description:This work aims to study the conditions of topological phase transition (TPT) between the topological and trivial states in the antiferromagnetic topological insulator (AFM TI) MnBi[Formula: see text]Te[Formula: see text] and propose some theory about the relationship of this TPT with the possibility of axion-like state realization in this material. Using the density functional approach we have analyzed the changes in the electronic and spin structure of topological surface states (TSSs) and the nearest conduction and valence bands (CB and VB) including the changes in the bulk band gap as well as the Dirac point (DP) gap in TSSs under variation of the spin-orbit coupling strength in the region of the TPT for infinite crystal and slab with a surface both. We have shown that in both cases the TPT occurs with inversion of the contributions of the Bi-[Formula: see text] and Te-[Formula: see text] states of different parity at the gap edges related to change in the gap sign. In the case of surface calculations, the Bi-[Formula: see text] and Te-[Formula: see text] states at the edges of the bulk band gap and their inversion at the TPT point are transformed into the TSSs with an energy gap at the DP. In this case the TPT takes place without closing the band gap, i.e. with a "jump" through zero and the formation of the nonzero gap during such a transition. Our calculations show that the TPT point is also characterized by an inversion of the out-of-plane spin polarization [Formula: see text] at the [Formula: see text] point for lower and upper parts of the Dirac cone and a significant spatial redistribution of the TSSs between the surface and the bulk. We suppose that the nonzero Dirac gap can have some relationship with the formation of the axion-like state, which presumably couples nonmagnetic spin-orbit and magnetic contributions at the boundary between the topological and trivial phases for a system with parameters close to the TPT conditions. A practically realized system is proposed - the AFM TI with a stoichiometry close to that of MnBi[Formula: see text]Te[Formula: see text]Se[Formula: see text] with partial (about 50%) substitution of Te atoms for Se atoms in MnBi[Formula: see text]Te[Formula: see text] which can be an experimental platform for the implementation and experimental analysis of the TPT and the corresponding possibility of the axion-like state realization in Condensed Matter. Besides, such system could serve as a good platform for studying the dynamic axion effect, where the axion field fluctuations are maximised when a small external field is applied to the system which state is close to the TPT.

Dataset Information

Realization of an intrinsic ferromagnetic topological state in MnBi₈Te₁₃.

Publications

Realization of an intrinsic ferromagnetic topological state in MnBi<sub>8</sub>Te<sub>13</sub>.

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