Strongly Gapped Topological Surface States on Protected Surfaces of Antiferromagnetic MnBi4Te7 and MnBi6Te10
Abstract
The search for materials to support the Quantum Anomalous Hall Effect (QAHE) have recently centered on intrinsic magnetic topological insulators (MTIs) including MnBi2Te4 or heterostructures made up of MnBi2Te4 and Bi2Te3. While MnBi2Te4 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 MnBi4Te7 and MnBi6Te10, we show the presence of large mass gaps (~ 100 meV scale) on both of these materials when the MnBi2Te4 surfaces are buried below one layer of Bi2Te3 that apparently protects the magnetic order, but not when the MnBi2Te4 surfaces are exposed at the surface or are buried below two Bi2Te3 layers. This makes both MnBi4Te7 and MnBi6Te10 excellent candidates for supporting the QAHE, especially if bulk devices can be fabricated with a single continuous Bi2Te3 layer at the surface.
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