Hybridization-Induced Gapped and Gapless States on the Surfaces of Magnetic Topological Insulators

Abstract

The layered MnBi2nTe3n+1 family represents the first intrinsic antiferromagnetic topological insulator (AFM TI, protected by a combination symmetry ) ever discovered, providing an ideal platform to explore novel physics such as quantum anomalous Hall effect at elevated temperature and axion electrodynamics. Recent angle-resolved photoemission spectroscopy (ARPES) experiments on this family have revealed that all terminations exhibit (nearly) gapless topological surface states (TSSs) within the AFM state, violating the definition of the AFM TI, as the surfaces being studied should be -breaking and opening a gap. Here we explain this curious paradox using a surface-bulk band hybridization picture. Combining ARPES and first-principles calculations, we prove that only an apparent gap is opened by hybridization between TSSs and bulk bands. The observed (nearly) gapless features are consistently reproduced by tight-binding simulations where TSSs are coupled to a Rashba-split bulk band. The Dirac-cone-like spectral features are actually of bulk origin, thus not sensitive to the-breaking at the AFM surfaces. This picture explains the (nearly) gapless behaviour found in both Bi2Te3- and MnBi2Te4-terminated surfaces and is applicable to all terminations of MnBi2nTe3n+1 family. Our findings highlight the role of band hybridization, superior to magnetism in this case, in shaping the general surface band structure in magnetic topological materials for the first time.

arXiv comment18 pages, 4 figures

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• Light-Tunable Surface State and Hybridization Gap in Magnetic Topological Insulator MnBi${}_8$Te${}_{13}$
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• Intrinsic Magnetic Topological Materials
• Delicate Ferromagnetism in MnBi${}_6$Te${}_{10}$
• On the topological surface states of the intrinsic magnetic topological insulator Mn-Bi-Te family
• An Integrated Quantum Material Testbed with Multi-Resolution Photoemission Spectroscopy
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• Magnetic warping in topological insulators
• Antiferromagnetic topological insulator with selectively gapped Dirac cones
• Three-Dirac-fermion approach to unexpected universal gapless surface states of van der Waals magnetic topological insulators
• Momentum-inversion symmetry breaking on the Fermi surface of magnetic topological insulators
• Facet dependent surface energy gap on magnetic topological insulators
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• Fate of surface gaps in magnetic topological insulators
• Defect-induced displacement of topological surface state in quantum magnet MnBi${}_2$Te${}_4$
• Resonantly enhanced photoemission from topological surface states in MnBi${}_6$Te${}_{10}$