Dynamical Axion Field in a Magnetic Topological Insulator Superlattice

TL;DR

This paper proposes a new way to realize a dynamical axion field in magnetic topological insulator superlattices, which could lead to observable axion electrodynamics effects without requiring long-range magnetic order.

Contribution

It introduces a condensed-matter platform for dynamical axion fields using magnetic topological insulators that do not need long-range magnetic order, unlike previous proposals.

Findings

Proposes magnetic topological insulator superlattices as dynamical axion hosts

Suggests experimental methods to detect the dynamical axion field

Demonstrates that uniform magnetization suffices for axion dynamics

Abstract

We propose that the dynamical axion field can be realized in a magnetic topological insulator superlattice or a topological paramagnetic insulator. The magnetic fluctuations of these systems produce a pseudoscalar field which has an axionic coupling to the electromagnetic field, and thus it gives a condensed-matter realization of the axion electrodynamics. Compared to the previously proposed dynamical axion materials where a long range antiferromagnetic order is required, the systems proposed here have the advantage that only a uniform magnetization or a paramagnetic state is needed for the dynamic axion. We further propose several experiments to detect such a dynamical axion field.