Collective excitations in magnetic topological insulators and axion dark matter search

TL;DR

This paper studies collective excitations in magnetic topological insulators, identifying an axionic quasi-particle and analyzing its electromagnetic coupling, which impacts axion dark matter detection sensitivity.

Contribution

It formulates the effective action of magnons and amplitude modes in magnetic TIs, revealing a suppressed axion coupling that alters detection prospects.

Findings

Identified an axionic quasi-particle in magnetic TIs.

Found the axion-electromagnetic coupling is significantly suppressed.

Implications for axion dark matter search sensitivity.

Abstract

We investigate collective excitations in magnetic topological insulators (TIs) and their impact on axion detection. In the three-dimensional TI model with the Hubbard term, the effective action of magnons and amplitude modes is formulated by dynamical susceptibility under the antiferromagnetic and ferromagnetic states. One of the amplitude modes is identified as ``axionic'' quasi-particle and its effective coupling to the electromagnetic fields turns out to be roughly unchanged, or suppressed by up to two orders of magnitude, compared to the previous estimate, which may drastically change the sensitivity of the axion search using``axion' in magnetic TIs.