Spectroscopic realization of large surface gap in a doped magnetic topological insulator

Abstract

Realization of the quantum anomalous Hall effect and axion electrodynamics in topological materials are among the paradigmatic phenomena in condensed matter physics. Recently, signatures of both phases are observed to exist in thin films of MnBi${}_2$Te${}_4$, a stoichiometric antiferromagnetic topological insulator. Direct evidence of the bulk topological magnetoelectric response in an axion insulator requires an energy gap at its topological surface state (TSS). However, independent spectroscopic experiments revealed that such a surface gap is absent, or much smaller than previously thought, in MnBi${}_2$Te${}_4$. Here, we utilize angle resolved photoemission spectroscopy and density functional theory calculations to demonstrate that a sizable TSS gap unexpectedly exists in Sb-doped MnBi${}_2$Te${}_4$. This gap is found to be topologically nontrivial, insensitive to the bulk antiferromagnetic-paramagnetic transition, while enlarges along with increasing Sb concentration. Our work shows that Mn(Bi${}_{1-x}$Sb${}_x$)${}_2$Te${}_4$ is a potential platform to observe the key features of the high-temperature axion insulator state, such as the topological magnetoelectric responses and half-integer quantum Hall effects.

arXiv comment18 pages, 4 figures

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Cited by in corpus (20)

• Spectral signatures of the surface anomalous Hall effect in magnetic axion insulators
• Routes to realize the axion-insulator phase in MnBi${}_2$Te${}_4$(Bi${}_2$Te${}_3$)${}_n$ family: a perspective
• Origins of electronic bands in antiferromagnetic topological insulator MnBi${}_2$Te${}_4$
• Moiré disorder effect in twisted bilayer graphene
• Coexistence of Ferromagnetism and Topology by Charge Carrier Engineering in intrinsic magnetic topological insulator MnBi4Te7
• Intrinsic Magnetic Topological Materials
• Delicate Ferromagnetism in MnBi${}_6$Te${}_{10}$
• Quantum Oscillations in the Field-induced Ferromagnetic State of MnBi${}_{2-x}$Sb${}_x$Te${}_4$
• Controlling a quantum point junction on the surface of an antiferromagnetic topological insulator
• On the topological surface states of the intrinsic magnetic topological insulator Mn-Bi-Te family
• 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${}_4$
• Fabry-Pérot resonant vortices and magnetoconductance in topological insulator constrictions with magnetic barriers
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• Hedgehog-like spin texture in Sb-doped MnBi${}_2$Te${}_4$