New Observables for Direct Detection of Axion Dark Matter
  We propose new signals for the direct detection of ultralight dark matter
such as the axion. Axion or axion like particle (ALP) dark matter may be
thought of as a background, classical field. We consider couplings for this
field which give rise to observable effects including a nuclear electric dipole
moment, and axial nucleon and electron moments. These moments oscillate rapidly
with frequencies accessible in the laboratory, ~ kHz to GHz, given by the dark
matter mass. Thus, in contrast to WIMP detection, instead of searching for the
hard scattering of a single dark matter particle, we are searching for the
coherent effects of the entire classical dark matter field. We calculate
current bounds on such time varying moments and consider a technique utilizing
NMR methods to search for the induced spin precession. The parameter space
probed by these techniques is well beyond current astrophysical limits and
significantly extends laboratory probes. Spin precession is one way to search
for these ultralight particles, but there may well be many new types of
experiments that can search for dark matter using such time-varying moments.
