The intrinsic magnetic topological insulators MnBi2Te4 and MnBi2Se4 support novel topological states related to symmetry breaking by magnetic order. Unlike MnBi2Te4, the study of MnBi2Se4 has been inhibited by the lack of bulk crystals, as the van der Waals (vdW) crystal is not the thermodynamic equilibrium phase. In this study, we report the layer-by-layer synthesis of vdW MnBi2Se4 crystals using nonequilibrium molecular beam epitaxy. Atomic-resolution scanning transmission electron microscopy and scanning tunneling microscopy identify a well-ordered vdW crystal with septuple-layer base units. The magnetic properties agree with the predicted layered antiferromagnetic ordering but disagree with its predicted out-of-plane orientation. Instead, our samples exhibit an easy-plane anisotropy, which is explained by including dipole–dipole interactions. Angle-resolved photoemission spectroscopy reveals the gapless Dirac-like surface state, which demonstrates that MnBi2Se4 is a topological insulator above the magnetic-ordering temperature. These studies show that MnBi2Se4 is a promising candidate for exploring rich topological phases of layered antiferromagnetic topological insulators.
Zhu, Tiancong, et al. "Synthesis, Magnetic Properties, and Electronic Structure of Magnetic Topological Insulator MnBi<sub>2</sub>Se<sub>4</sub>." Nano Letters, vol. 21, no. 12, Jun. 2021. https://doi.org/10.1021/acs.nanolett.1c00141
Zhu, Tiancong, Bishop, Alexander J., Zhou, Tong, Zhu, Menglin, O’Hara, Dante J., Baker, Alexander A., Cheng, Shuyu, Walko, Robert C., Repicky, Jacob J., Liu, Tao, Gupta, Jay A., Jozwiak, Chris M., Rotenberg, Eli, Hwang, Jinwoo, Žutić, Igor, & Kawakami, Roland K. (2021). Synthesis, Magnetic Properties, and Electronic Structure of Magnetic Topological Insulator MnBi<sub>2</sub>Se<sub>4</sub>. Nano Letters, 21(12). https://doi.org/10.1021/acs.nanolett.1c00141
Zhu, Tiancong, Bishop, Alexander J., Zhou, Tong, et al., "Synthesis, Magnetic Properties, and Electronic Structure of Magnetic Topological Insulator MnBi<sub>2</sub>Se<sub>4</sub>," Nano Letters 21, no. 12 (2021), https://doi.org/10.1021/acs.nanolett.1c00141
@article{osti_1807756,
author = {Zhu, Tiancong and Bishop, Alexander J. and Zhou, Tong and Zhu, Menglin and O’Hara, Dante J. and Baker, Alexander A. and Cheng, Shuyu and Walko, Robert C. and Repicky, Jacob J. and Liu, Tao and others},
title = {Synthesis, Magnetic Properties, and Electronic Structure of Magnetic Topological Insulator MnBi<sub>2</sub>Se<sub>4</sub>},
annote = {The intrinsic magnetic topological insulators MnBi2Te4 and MnBi2Se4 support novel topological states related to symmetry breaking by magnetic order. Unlike MnBi2Te4, the study of MnBi2Se4 has been inhibited by the lack of bulk crystals, as the van der Waals (vdW) crystal is not the thermodynamic equilibrium phase. In this study, we report the layer-by-layer synthesis of vdW MnBi2Se4 crystals using nonequilibrium molecular beam epitaxy. Atomic-resolution scanning transmission electron microscopy and scanning tunneling microscopy identify a well-ordered vdW crystal with septuple-layer base units. The magnetic properties agree with the predicted layered antiferromagnetic ordering but disagree with its predicted out-of-plane orientation. Instead, our samples exhibit an easy-plane anisotropy, which is explained by including dipole–dipole interactions. Angle-resolved photoemission spectroscopy reveals the gapless Dirac-like surface state, which demonstrates that MnBi2Se4 is a topological insulator above the magnetic-ordering temperature. These studies show that MnBi2Se4 is a promising candidate for exploring rich topological phases of layered antiferromagnetic topological insulators.},
doi = {10.1021/acs.nanolett.1c00141},
url = {https://www.osti.gov/biblio/1807756},
journal = {Nano Letters},
issn = {ISSN 1530-6984},
number = {12},
volume = {21},
place = {United States},
publisher = {American Chemical Society},
year = {2021},
month = {06}}
Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States); Univ. at Buffalo, NY (United States)
Sponsoring Organization:
US Air Force Office of Scientific Research (AFOSR); USDOE National Nuclear Security Administration (NNSA); USDOE Office of Science (SC), Basic Energy Sciences (BES)