Non-local sidewall response and deviation from exact quantization of the topological magnetoelectric effect in axion-insulator thin films

Abstract

Topological insulator (TI) thin films with surface magnetism are expected to exhibit a quantized anomalous Hall effect (QAHE) when the magnetizations on the top and bottom surfaces are parallel, and a quantized topological magnetoelectric (QTME) response when the magnetizations have opposing orientations (axion insulator phase) and the films are sufficiently thick. We present a unified picture of both effects that associates deviations from exact quantization of the QTME caused by finite thickness with non-locality in the side-wall current response function. Using realistic tight-binding model calculations, we show that in $B{i}_{2}S{e}_3$ TI thin films deviations from quantization in the axion insulator-phase are reduced in size when the exchange coupling of tight-binding model basis states to the local magnetization near the surface is strengthened. Stronger exchange coupling also reduces the effect of potential disorder, which is unimportant for the QAHE but detrimental for the QTME, which requires that the Fermi energy lie inside the gap at all positions.

5 pages, 4 figures

References in corpus (8)

• Topological Insulators with Inversion Symmetry
• Topological Field Theory of Time-Reversal Invariant Insulators
• Quantized Anomalous Hall Effect in Magnetic Topological Insulators
• Orbital magnetization in periodic insulators
• Tailoring tricolor structure of magnetic topological insulator for robust axion insulator
• Theory of orbital magnetoelectric response
• Large-gap magnetic topological heterostructure formed by subsurface incorporation of a ferromagnetic layer
• Large Anomalous Hall Effect in Topological Insulators with Proximitized Ferromagnetic Insulators

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• Magnetoelectricity in two-dimensional materials
• Engineering axion insulator phase in superlattices with inversion symmetry breaking
• Symmetry, topology, and geometry: The many faces of the topological magnetoelectric effect
• Capacitive scheme to detect the topological magnetoelectric effect
• Chiral edge transport along domain walls in magnetic topological insulator nanoribbons
• Surface Reconstructions in Thin-Films of Magnetic Topological Insulator MnBi${}_2$Te${}_4$
• Generalized method of image dyons for quasi-two dimensional slabs with ordinary-topological insulator interfaces