Severe Dirac Mass Gap Suppression in Sb2Te3-Based Quantum Anomalous Hall Materials
- Yi Xue ChongYi Xue ChongLASSP, Department of Physics, Cornell University, Ithaca, New York 14853, United StatesCMPMS Department, Brookhaven National Laboratory, Upton, New York 11973, United StatesMore by Yi Xue Chong
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- Xiaolong LiuXiaolong LiuLASSP, Department of Physics, Cornell University, Ithaca, New York 14853, United StatesKavli Institute at Cornell, Cornell University, Ithaca, New York 14853, United StatesMore by Xiaolong Liu
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- Rahul SharmaRahul SharmaLASSP, Department of Physics, Cornell University, Ithaca, New York 14853, United StatesCMPMS Department, Brookhaven National Laboratory, Upton, New York 11973, United StatesMore by Rahul Sharma
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- Andrey KostinAndrey KostinLASSP, Department of Physics, Cornell University, Ithaca, New York 14853, United StatesMore by Andrey Kostin
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- Genda GuGenda GuCMPMS Department, Brookhaven National Laboratory, Upton, New York 11973, United StatesMore by Genda Gu
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- K. FujitaK. FujitaCMPMS Department, Brookhaven National Laboratory, Upton, New York 11973, United StatesMore by K. Fujita
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- J. C. Séamus Davis*J. C. Séamus Davis*Email: [email protected]LASSP, Department of Physics, Cornell University, Ithaca, New York 14853, United StatesDepartment of Physics, University College Cork, Cork T12R5C, IrelandClarendon Laboratory, University of Oxford, Oxford OX1 3PU, U.K.More by J. C. Séamus Davis
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- Peter O. SprauPeter O. SprauLASSP, Department of Physics, Cornell University, Ithaca, New York 14853, United StatesAdvanced Development Center, ASML, Wilton, Connecticut 06897, United StatesMore by Peter O. Sprau
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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