Realizing gapped surface states in magnetic topological insulator MnBi${}_{2-x}$Sb${}_x$Te${}_4$

Abstract

The interplay between magnetism and non-trivial topology in magnetic topological insulators (MTI) is expected to give rise to a variety of exotic topological quantum phenomena, such as the quantum anomalous Hall (QAH) effect and the topological axion states. A key to assessing these novel properties is to tune the Fermi level in the exchange gap of the Dirac surface band. MnBi${}_2$Te${}_4$ possesses non-trivial band topology with intrinsic antiferromagnetic (AFM) state that can enable all of these quantum states, however, highly electron-doped nature of the MnBi${}_2$Te${}_4$ crystals obstructs the exhibition of the gapped topological surface states. Here, we tailor the material through Sb-substitution to reveal the gapped surface states in MnBi${}_{2-x}$Sb${}_x$Te${}_4$ (MBST). By shifting the Fermi level into the bulk band gap of MBST, we access the surface states and show a band gap of 50 meV at the Dirac point from quasi-particle interference (QPI) measured by scanning tunneling microscopy/spectroscopy (STM/STS). Surface-dominant conduction is confirmed below the Néel temperature through transport spectroscopy measured by multiprobe STM. The surface band gap is robust against out-of-plane magnetic field despite the promotion of field-induced ferromagnetism. The realization of bulk-insulating MTI with the large exchange gap offers a promising platform for exploring emergent topological phenomena.

arXiv comment19 pages, 4 figures

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• Spectroscopic realization of large surface gap in a doped magnetic topological insulator
• Experimental evidence on the dissipationless transport of chiral edge state of the high-field Chern insulator in MnBi2Te4 nanodevices
• Local manifestations of thickness dependent topology and axion edge state in topological magnet MnBi${}_2$Te${}_4$
• Quantum Oscillations in the Field-induced Ferromagnetic State of MnBi${}_{2-x}$Sb${}_x$Te${}_4$
• Optical Responses of Chiral Majorana Edge States in Two-Dimensional Topological Superconductors
• Dynamical properties of magnetic topological insulator $T$Bi${}_2$Te${}_4$ ($T=$Mn, Fe): phonons dispersion, Raman active modes, and chiral phonons study
• Observation of magnetism induced topological edge state in antiferromagnetic topological insulator MnBi4Te7
• Anti-site defect-induced disorder in compensated topological magnet MnBi${}_{2-x}$Sb${}_x$Te${}_4$
• Topological Electronic Structure Evolution with Symmetry Breaking Spin Reorientation in (Fe${}_{1-x}$Co${}_x$)Sn
• Extracting unconventional spin texture in two dimensional topological crystalline insulator bismuthene via tuning bulk-edge interactions
• Infrared study of the layered, magnetic insulator Mn(Bi${}_{0.07}$Sb${}_{0.93}$)${}_2$Te${}_4$ at low temperatures
• Optical study of the charge dynamics evolution in the topological insulators MnBi${}_2$Te${}_4$ and Mn(Bi${}_{0.74}$Sb${}_{0.26}$)${}_2$Te${}_4$ under high pressure
• Evolution of the optical response of the magnetic topological insulators Mn(Bi${}_{1-x}$Sb${}_x$)${}_2$Te${}_4$ with Sb content
• Defect-induced displacement of topological surface state in quantum magnet MnBi${}_2$Te${}_4$