Absorption of Axion Dark Matter in a Magnetized Medium. (arXiv:2305.05681v1 [hep-ph])
<a href="http://arxiv.org/find/hep-ph/1/au:+Berlin_A/0/1/0/all/0/1">Asher Berlin</a>, <a href="http://arxiv.org/find/hep-ph/1/au:+Trickle_T/0/1/0/all/0/1">Tanner Trickle</a>

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 $sim
text{meV} – text{eV}$ 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 $text{kg} cdot text{yr}$ 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
$sim 10 text{meV} – 10 text{eV}$ mass range.

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 $sim
text{meV} – text{eV}$ 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 $text{kg} cdot text{yr}$ 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
$sim 10 text{meV} – 10 text{eV}$ mass range.

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