Electromagnetic effects induced by time-dependent axion field

TL;DR

This paper investigates how time-dependent axion-like fields in topological materials can induce unconventional electromagnetic effects, driven by magnetic configuration changes in a specially designed superlattice.

Contribution

It demonstrates a method to control the $ heta$-term dynamics in a magnetic superlattice, revealing new electromagnetic phenomena linked to topological and axion physics.

Findings

Magnetic field-induced charge currents generated by $ heta$-term dynamics

Control of $ heta$-term via magnetic configuration switching

Unconventional electromagnetic effects observed in topological superlattice

Abstract

We studied the dynamics of the so-called $\theta$-term, which exists in topological materials and is related to a hypothetical field predicted by Peccei-Quinn in particle physics, in a magnetic superlattice constructed using a topological insulator and two ferromagnetic insulators, where the ferromagnetic insulators had perpendicular magnetic anisotropies and different magnetic coercive fields. We examined a way to drive the dynamics of the $\theta$-term in the magnetic superlattice through changing the inversion symmetry (from an anti-parallel to a parallel magnetic configuration) using an external magnetic field. As a result, we found that unconventional electromagnetic fields, which are magnetic field-induced charge currents and vice versa, are generated by the nonzero dynamics of the $\theta$-term.