Severe Dirac Mass Gap Suppression in Sb2Te3-Based Quantum Anomalous Hall Materials

Yi Xue Chong; Xiaolong Liu; Rahul Sharma; Andrey Kostin; Genda Gu; K. Fujita; J. C.Séamus Davis; Peter O. Sprau

doi:10.1021/acs.nanolett.0c02873

Severe Dirac Mass Gap Suppression in Sb₂Te₃-Based Quantum Anomalous Hall Materials

Yi Xue Chong
, Xiaolong Liu
, Rahul Sharma
, Andrey Kostin
, Genda Gu
, K. Fujita
, J. C.Séamus Davis
, Peter O. Sprau

School of Physics

Research output: Contribution to journal › Article › peer-review

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 Cr_0.08(Bi_0.1Sb_0.9)_1.92Te₃to that of its nonmagnetic parent (Bi_0.1Sb_0.9)₂Te₃, to explore the cause. In (Bi_0.1Sb_0.9)₂Te₃, we find spatially random variations of the Dirac energy. Statistically equivalent Dirac energy variations are detected in Cr_0.08(Bi_0.1Sb_0.9)_1.92Te₃with 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.

Original language	English
Pages (from-to)	8001-8007
Number of pages	7
Journal	Nano Letters
Volume	20
Issue number	11
DOIs	https://doi.org/10.1021/acs.nanolett.0c02873
Publication status	Published - 11 Nov 2020

Keywords

Dirac mass gap
disorder
ferromagnetic topological insulator
Quantum anomalous Hall effect
surface state

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10.1021/acs.nanolett.0c02873

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title = "Severe Dirac Mass Gap Suppression in Sb2Te3-Based Quantum Anomalous Hall Materials",

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)1.92Te3to 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)1.92Te3with 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.",

keywords = "Dirac mass gap, disorder, ferromagnetic topological insulator, Quantum anomalous Hall effect, surface state",

author = "Chong, \{Yi Xue\} and Xiaolong Liu and Rahul Sharma and Andrey Kostin and Genda Gu and K. Fujita and Davis, \{J. C.S{\'e}amus\} and Sprau, \{Peter O.\}",

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doi = "10.1021/acs.nanolett.0c02873",

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AU - Chong, Yi Xue

AU - Liu, Xiaolong

AU - Sharma, Rahul

AU - Kostin, Andrey

AU - Gu, Genda

AU - Fujita, K.

AU - Davis, J. C.Séamus

AU - Sprau, Peter O.

PY - 2020/11/11

Y1 - 2020/11/11

N2 - 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)1.92Te3to 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)1.92Te3with 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.

AB - 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)1.92Te3to 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)1.92Te3with 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.

KW - Dirac mass gap

KW - disorder

KW - ferromagnetic topological insulator

KW - Quantum anomalous Hall effect

KW - surface state

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Severe Dirac Mass Gap Suppression in Sb₂Te₃-Based Quantum Anomalous Hall Materials

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