Axion Insulator State in Hundred-Nanometer-Thick Magnetic Topological Insulator Sandwich Heterostructures

Abstract

An axion insulator is a three-dimensional (3D) topological insulator (TI), in which the bulk maintains the time-reversal symmetry or inversion symmetry but the surface states are gapped by surface magnetization. The axion insulator state has been observed in molecular beam epitaxy (MBE)-grown magnetically doped TI sandwiches and exfoliated intrinsic magnetic TI MnBi2Te4 flakes with an even number layer. All these samples have a thickness of ~10 nm, near the 2D-to-3D boundary. The coupling between the top and bottom surface states in thin samples may hinder the observation of quantized topological magnetoelectric response. Here, we employ MBE to synthesize magnetic TI sandwich heterostructures and find that the axion insulator state persists in a 3D sample with a thickness of ~106 nm. Our transport results show that the axion insulator state starts to emerge when the thickness of the middle undoped TI layer is greater than ~3 nm. The 3D hundred-nanometer-thick axion insulator provides a promising platform for the exploration of the topological magnetoelectric effect and other emergent magnetic topological states, such as the high-order TI phase.

arXiv comment25 pages, 5 figures. Comments are very much welcome

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Cited by in corpus (7)

• Intrinsic magnetic topological insulators of the MnBi${}_2$Te${}_4$ family
• Even-Odd Layer-Dependent Exchange Bias Effect in MnBi2Te4 Chern Insulator Devices
• Evidence for Half-Quantized Chiral Edge Current in a C = 1/2 Parity Anomaly State
• Engineering Plateau Phase Transition in Quantum Anomalous Hall Multilayers
• Absence of Parity Anomaly in Massive Dirac Fermions on a Lattice
• The electronic structure of intrinsic magnetic topological insulator MnBi2Te4 quantum wires
• Interlayer Exchange Coupling-Induced Critical-Metal-to-Insulator Phase Transition in Quantum Anomalous Hall Insulators