Detection of axion dark matter heavier than a meV is hindered by its small wavelength, which limits the useful volume of traditional experiments. This problem can be avoided by directly detecting in-medium excitations, whose ∼meV−eV energies are decoupled from the detector size. We show that for any target inside a magnetic field, the absorption rate of electromagnetically-coupled axions into in-medium excitations is determined by the dielectric function. As a result, the plethora of candidate targets previously identified for sub-GeV dark matter searches can be repurposed as broadband axion detectors. We find that a kg⋅yr exposure with noise levels comparable to recent measurements is sufficient to probe parameter space currently unexplored by laboratory tests. Noise reduction by only a few orders of magnitude can enable sensitivity to the QCD axion in the ∼10meV−10eV mass range.
@article{arxiv.2305.05681,
title = {Absorption of Axion Dark Matter in a Magnetized Medium},
author = {Asher Berlin and Tanner Trickle},
journal= {arXiv preprint arXiv:2305.05681},
year = {2025}
}