LC Circuits for the Direct Detection of Ultralight Dark Matter
  Candidates
  Cosmological mechanisms that yield ultralight dark matter are insensitive to
the intrinsic parity of a bosonic dark matter candidate, but that same quantity
plays a crucial role in a direct detection experiment. The modification of
electrodynamics in the presence of ultralight axion-like dark matter is
well-known and has been used to realize sensitive probes of such sub-eV
mass-scale dark matter, and analogous studies exist for hidden-photon dark
matter as well. Here we reframe the modification of electrodynamics for
ultralight dark matter of positive intrinsic parity, with a focus on the scalar
case. In particular, we show that resonant LC circuit searches for axions can
be modified to detect scalar dark matter particles by exploiting the large
electric fields developed for use in neutron EDM experiments. Our proposed
experimental set-up can improve upon previous sensitive searches for scalar
particles from "light shining through a wall" experiments to probe
scalar-photon couplings some three orders of magnitude smaller in the $1\times
10^{-11} - \,4\times 10^{-8}$ eV mass ($2\, {\rm kHz} - 10\,{ \rm MHz}$
frequency) range.
