Dynamical magnetoelectric coupling in axion insulator thin films

Abstract

Axion insulator is an exotic magnetic topological insulator with zero Chern number but a nonzero quantized Chern-Simons magnetoelectric coupling. A conclusive experimental evidence for axion insulators is still lacking due to the small signal of topological magnetoelectric effect (TME). Here we show that the dynamical magnetoelectric coupling can be induced by the \emph{out-of-plane} surface magnetization dynamics in axion insulator thin films, which further generates a polarization current in the presence of an external magnetic field in the same direction. Such a current is finite in the bulk and increases as the film thickness $d$ decreases, in opposite to TME current which decreases as $d$ decreases. Remarkably, the current in thin films at magnetic resonance is at least ten times larger than that of TME, and thus may serve as a smoking gun signature for axion insulators.

5 pages, 4 figures

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• Topological Field Theory of Time-Reversal Invariant Insulators
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• Higher-order Topology of Axion Insulator EuIn${}_2$As${}_2$
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Cited by in corpus (5)

• Observation of the Axion quasiparticle in 2D MnBi${}_2$Te${}_4$
• Dynamical Piezomagnetic Effect in Time-Reversal Invariant Weyl Semimetals with Axionic Charge-Density Waves
• Pseudo-gauge Fields in Dirac and Weyl Materials
• Unoccupied Topological Surface State in MnBi${}_2$Te${}_4$
• Edge optical effect as a probe of chiral topological superconductors