Hu Chaowei, Ding Lei, Gordon Kyle N, Ghosh Barun, Tien Hung-Ju, Li Haoxiang, Linn A Garrison, Lien Shang-Wei, Huang Cheng-Yi, Mackey Scott, Liu Jinyu, Reddy P V Sreenivasa, Singh Bahadur, Agarwal Amit, Bansil Arun, Song Miao, Li Dongsheng, Xu Su-Yang, Lin Hsin, Cao Huibo, Chang Tay-Rong, Dessau Dan, Ni Ni
Department of Physics and Astronomy and California NanoSystems Institute, University of California, Los Angeles, Los Angeles, CA 90095, USA.
Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA.
Sci Adv. 2020 Jul 22;6(30):eaba4275. doi: 10.1126/sciadv.aba4275. eCollection 2020 Jul.
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 [MnBiTe] and [BiTe] layers. Thermodynamic, transport, and neutron diffraction measurements show that despite the adjacent [MnBiTe] being 44.1 Å apart, MnBiTe 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, MnBiTe serves as an ideal system to investigate rich emergent phenomena, including the quantized anomalous Hall effect and quantized magnetoelectric effect.
新型磁性拓扑材料为研究能带拓扑与磁性之间的相互作用铺平了道路。然而，迄今为止，一种在电荷中性能量处仅具有拓扑能带的本征铁磁拓扑材料仍然难以捉摸。通过合理设计，我们合成了MnBi8Te13，一种具有[MnBiTe]和[BiTe]层的天然异质结构。热力学、输运和中子衍射测量表明，尽管相邻的[MnBiTe]层间距为44.1 Å，但MnBiTe在10.5 K以下表现出长程铁磁性，且磁性与电荷载流子之间存在强耦合。第一性原理计算和角分辨光电子能谱测量表明，它是一种具有可观表面杂化能隙的轴子绝缘体。我们的计算进一步证明，杂化能隙在二维极限下仍然存在，且具有非平凡的陈数。因此，作为一种具有纯净低能能带结构的本征铁磁轴子绝缘体，MnBiTe是研究丰富的涌现现象（包括量子化反常霍尔效应和量子化磁电效应）的理想体系。
