The interplay between topology and magnetism is essential for realizing novel topological states including the axion insulator, the magnetic Weyl semimetal, etc. An intrinsically ferromagnetic topological material with only the topological bands at the charge neutrality energy has so far remained elusive. By rationally designing the natural heterostructure consisting of [MnBi2Te4] septuple layers and [Bi2Te3] quintuple layers, we report MnBi8Te13 as the first intrinsic ferromagnetic topological material with clean low-energy band structure. Based on the thermodynamic, transport and neutron diffraction measurements, our data show that despite the adjacent [MnBi2Te4] being 44.1 {\AA} apart, MnBi8Te13 manifests long-range ferromagnetism below 10.5 K with strong coupling between magnetism and charge carriers. Our first-principles calculations and angle-resolved photoemission spectroscopy measurements further demonstrate that MnBi8Te13 is an intrinsic ferromagnetic axion state. Therefore, MnBi8Te13 serves as an ideal system to investigate rich emergent phenomena, including the quantized anomalous Hall effect and quantized topological magnetoelectric effect.
@article{arxiv.1910.12847,
title = {Realization of an intrinsic, ferromagnetic topological state in MnBi8Te13},
author = {Chaowei Hu and Lei Ding and Kyle N. Gordon and Barun Ghosh and Hung-Ju Tien and Haoxiang Li and A. Garrison Linn and Shang-Wei Lian and Cheng-Yi Huang and Scott Mackey. P. V. Sreenivasa Reddy and Bahadur Singh and Amit Agarwal and Arun Bansil and Miao Song and Dongsheng Li and Su-Yang Xu and Hsin Lin and Huibo Cao and Tay-Rong Chang and Dan Dessau and Ni Ni},
journal= {arXiv preprint arXiv:1910.12847},
year = {2021}
}