Orbital magnetoelectric coupling of three dimensional Chern insulators

TL;DR

This paper introduces a new quantization rule for the orbital magnetoelectric response in 3D Chern insulators, demonstrating its topological origin and robustness through theoretical and numerical analysis, with potential experimental observation.

Contribution

It proposes a novel quantization rule for orbital magnetoelectric coupling in 3D Chern insulators with nonzero Chern numbers, expanding understanding of topological effects.

Findings

Quantized orbital magnetoelectric response in 3D Chern insulators.

Robustness against disorder and symmetry breaking.

Potential for experimental detection in new materials.

Abstract

Orbital magnetoelectric effect is closely related to the band topology of bulk crystalline insulators. Typical examples include the half quantized Chern-Simons orbital magnetoelectric coupling in three dimensional (3D) axion insulators and topological insulators, which are the hallmarks of their nontrivial bulk band topology. While the Chern-Simons coupling is well defined only for insulators with zero Chern number, the orbital magnetoelectric effects in 3D Chern insulators with nonzero (layer) Chern numbers are still open questions. In this work, we propose a never-mentioned quantization rule for the orbital magnetoelectric response in 3D Chern insulators, the spatial gradient of which is exactly quantized in unit of $e^2/h$. By theoretical analysis and numerical simulations, we demonstrate that such quantized orbital magnetoelectric response is exact for various types of interlayer hoppings and stackings, and remains robust even against disorder and lack of crystalline symmetries. We argue that the exact quantization has a topological origin and is protected by Chern number. Furthermore, we propose two promising material platforms to observe the proposed quantized orbital magnetoelectric response thanks to recent experimental developments in detecting spatial magnetic-field distributions in device systems.