Strongly Gapped Topological Surface States on Protected Surfaces of Antiferromagnetic MnBi$_4$Te$_7$ and MnBi$_6$Te$_{10}$

Kyle N. Gordon; Hongyi Sun; Chaowei Hu; A. Garrison Linn; Haoxiang Li; Yuntian Liu; Pengfei Liu; Scott Mackey; Qihang Liu; Ni Ni; Dan Dessau

arXiv · 1910.13943

Strongly Gapped Topological Surface States on Protected Surfaces of Antiferromagnetic MnBi$_4$Te$_7$ and MnBi$_6$Te$_{10}$

Kyle N. Gordon·Hongyi Sun·Chaowei Hu·A. Garrison Linn·Haoxiang Li·Yuntian Liu·Pengfei Liu·Scott Mackey·Qihang Liu·Ni Ni·Dan Dessau

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Abstract

The search for materials to support the Quantum Anomalous Hall Effect (QAHE) have recently centered on intrinsic magnetic topological insulators (MTIs) including MnBi$_2$Te$_4$ or heterostructures made up of MnBi$_2$Te$_4$ and Bi$_2$Te$_3$. While MnBi$_2$Te$_4$ is itself a MTI, most recent ARPES experiments indicate that the surface states on this material lack the mass gap that is expected from the magnetism-induced time-reversal symmetry breaking (TRSB), with the absence of this mass gap likely due to surface magnetic disorder. Here, utilizing small-spot ARPES scanned across the surfaces of MnBi$_4$Te$_7$ and MnBi$_6$Te$_{10}$, we show the presence of large mass gaps (~ 100 meV scale) on both of these materials when the MnBi$_2$Te$_4$ surfaces are buried below one layer of Bi$_2$Te$_3$ that apparently protects the magnetic order, but not when the MnBi$_2$Te$_4$ surfaces are exposed at the surface or are buried below two Bi$_2$Te$_3$ layers. This makes both MnBi$_4$Te$_7$ and MnBi$_6$Te$_{10}$ excellent candidates for supporting the QAHE, especially if bulk devices can be fabricated with a single continuous Bi$_2$Te$_3$ layer at the surface.

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Kyle N. Gordon, Hongyi Sun, Chaowei Hu, A. Garrison Linn, Haoxiang Li, Yuntian Liu, Pengfei Liu, Scott Mackey, Qihang Liu, Ni Ni, Dan Dessau. 2019-10-30. Strongly Gapped Topological Surface States on Protected Surfaces of Antiferromagnetic MnBi$_4$Te$_7$ and MnBi$_6$Te$_{10}$. https://arxiv.org/abs/1910.13943

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