Sample-dependent Dirac point gap in MnBi${}_2$Te${}_4$ and its response to the applied surface charge: a combined photoemission and ab initio study

Abstract

Recently discovered intrinsic antiferromagnetic topological insulator MnBi${}_2$Te${}_4$ presents an exciting platform for realization of the quantum anomalous Hall effect and a number of related phenomena at elevated temperatures. An important characteristic making this material attractive for applications is its predicted large magnetic gap at the Dirac point (DP). However, while the early experimental measurements reported on large DP gaps, a number of recent studies claimed to observe a gapless dispersion of the MnBi${}_2$Te${}_4$ Dirac cone. Here, using micro($\mu$)-laser angle-resolved photoemission spectroscopy, we study the electronic structure of 15 different MnBi${}_2$Te${}_4$ samples, grown by two different chemists groups. Based on the careful energy distribution curves analysis, the DP gaps between 15 and 65 meV are observed, as measured below the Néel temperature at about 10-16 K. At that, roughly half of the studied samples show the DP gap of about 30 meV, while for a quarter of the samples the gaps are in the 50 to 60 meV range. Summarizing the results of both our and other groups, in the currently available MnBi${}_2$Te${}_4$ samples the DP gap can acquire an arbitrary value between a few and several tens of meV. Further, based on the density functional theory, we discuss a possible factor that might contribute to the reduction of the DP gap size, which is the excess surface charge that can appear due to various defects in surface region. We demonstrate that the DP gap is influenced by the applied surface charge and even can be closed, which can be taken advantage of to tune the MnBi${}_2$Te${}_4$ DP gap size.

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Cited by in corpus (32)

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• Large Itinerant Electron Exchange Coupling in the Magnetic Topological Insulator MnBi2Te4
• Intrinsic Magnetic Topological Materials
• Delicate Ferromagnetism in MnBi${}_6$Te${}_{10}$
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• The elusive quantum anomalous Hall effect in MnBi2Te4: a materials perspective
• Intrinsic magnetic topological insulators of the MnBi${}_2$Te${}_4$ family
• Fabrication-induced even-odd discrepancy of magnetotransport in few-layer MnBi${}_2$Te${}_4$
• On the topological surface states of the intrinsic magnetic topological insulator Mn-Bi-Te family
• Ubiquitous order-disorder transition in the Mn antisite sublattice of the (MnBi${}_2$Te${}_4$)(Bi${}_2$Te${}_3$)${}_n$ magnetic topological insulators
• Dynamical properties of magnetic topological insulator $T$Bi${}_2$Te${}_4$ ($T=$Mn, Fe): phonons dispersion, Raman active modes, and chiral phonons study
• Anti-site defect-induced disorder in compensated topological magnet MnBi${}_{2-x}$Sb${}_x$Te${}_4$
• Role of Magnetic Defects and Defect-engineering of Magnetic Topological Insulators
• Magnetic warping in topological insulators
• Layer-by-layer disentanglement of Bloch states via frequency-domain photoemission
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• Momentum-inversion symmetry breaking on the Fermi surface of magnetic topological insulators
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