Hunting axion dark matter with anti-ferromagnets: a case study with nickel oxide

TL;DR

This paper proposes using nickel oxide, an anti-ferromagnet, as a novel target to detect axion dark matter in the meV mass range through its interactions with collective excitations, expanding the search parameter space.

Contribution

It introduces a universal effective field theory for axion interactions with nickel oxide and explores its potential for broad and narrowband axion detection channels.

Findings

Nickel oxide can detect axions with masses down to fractions of an meV.

External magnetic field variation enhances detection prospects.

Nickel oxide is a promising multi-purpose target for light dark matter searches.

Abstract

We show that nickel oxide, which is already a very promising target to look for sub-MeV dark matter scattering, can be employed to hunt axion dark matter, with masses in the meV range and couplings to electrons allowing them to potentially be QCD axions. We describe the interactions between axions and the collective excitations of nickel oxide in terms of a universal effective field theory, built solely out of symmetry arguments. The processes of conversion into one or two excitations provide, respectively, a narrowband and a broadband channel for the axion search, and the possibility of varying an external magnetic field up to a phase transition point allows to cover a large portion of a yet unexplored parameter space, reaching axion masses down to few fractions of an meV. Our results underline nickel oxide as an ideal candidate for a multi-purpose target for light dark matter searches.