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

paper

Strongly Gapped Topological Surface States on Protected Surfaces of Antiferromagnetic MnBi $_{4}$ Te $_{7}$ and MnBi $_{6}$ Te $_{10}$

arXiv:1910.13943

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.

17 pages, 4 figures

Strongly Gapped Topological Surface States on Protected Surfaces of Antiferromagnetic MnBi4​Te7​ and MnBi6​Te10​

Abstract

Strongly Gapped Topological Surface States on Protected Surfaces of Antiferromagnetic MnBi $_{4}$ Te $_{7}$ and MnBi $_{6}$ Te $_{10}$