Severe dirac mass gap suppression in Sb 2 Te 3-based quantum anomalous Hall materials
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Date
2020-09-28
Authors
Chong, Yi Xue
Liu, Xiaolong
Sharma, Rahul
Kostin, Andrey
Gu, Genda
Fujita, K.
Davis, J. C. Séamus
Sprau, Peter O.
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American Chemical Society
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Abstract
The quantum anomalous Hall (QAH) effect appears in ferromagnetic topological insulators (FMTIs) when a Dirac mass gap opens in the spectrum of the topological surface states (SSs). Unaccountably, although the mean mass gap can exceed 28 meV (or ∼320 K), the QAH effect is frequently only detectable at temperatures below 1 K. Using atomic-resolution Landau level spectroscopic imaging, we compare the electronic structure of the archetypal FMTI Cr0.08(Bi0.1Sb0.9)1.92Te3 to that of its nonmagnetic parent (Bi0.1Sb0.9)2Te3, to explore the cause. In (Bi0.1Sb0.9)2Te3, we find spatially random variations of the Dirac energy. Statistically equivalent Dirac energy variations are detected in Cr0.08(Bi0.1Sb0.9)1.92Te3 with concurrent but uncorrelated Dirac mass gap disorder. These two classes of SS electronic disorder conspire to drastically suppress the minimum mass gap to below 100 μeV for nanoscale regions separated by <1 μm. This fundamentally limits the fully quantized anomalous Hall effect in Sb2Te3-based FMTI materials to very low temperatures.
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Keywords
Dirac mass gap , Quantum anomalous Hall effect , Disorder , Ferromagnetic topological insulator , Surface state
Citation
Chong, Y. X., Liu, X., Sharma, R., Kostin, A., Gu, G., Fujita, K., Davis, J. C. S. and Sprau, P. O. (2020) 'Severe dirac mass gap suppression in Sb 2 Te 3-based quantum anomalous Hall materials', Nano Letters, 20(11), 8001-8007. doi: 10.1021/acs.nanolett.0c02873
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© 2020 American Chemical Society. This document is the Accepted Manuscript version of a Published Work that appeared in final form in Nano Letters, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see https://pubs.acs.org/doi/10.1021/acs.nanolett.0c02873