Ultrasensitive optomechanical detection of an axion-mediated force based
  on a sharp peak emerging in probe absorption spectrum
  Axion remains the most convincing solution to the strong-CP problem and a
well-motivated dark matter candidate, causing the search for axions and
axion-like particles(ALPs) to attract attention continually. The exchange of
such particles may cause anomalous spin-dependent forces, inspiring many
laboratory ALP searching experiments based on the detection of macroscopic
monopole-dipole interactions between polarized electrons/nucleons and
unpolarized nucleons. Since there is no exact proof of the existence of these
interactions, to detect them is still of great significance. In the present
paper, we study the electron-neucleon monopole-dipole interaction with a new
method, in which a hybrid spin-nanocantilever optomechanical system consisting
of a nitrogen-vacancy(NV) center and a nanocantilever resonator is used. With a
static magnetic field and a pump microwave beam and a probe microwave beam
applied, a probe absorption spectrum could be obtained. Through specific peaks
appearing in the spectrum, we can identify this monopole-dipole interaction.
And we also provide a prospective constraint to constrain the interaction.
Furthermore, because our method can also be applied to the detection of some
other spin-dependent interactions, this work provides new ideas for the
experimental searches of the anomalous spin-dependent interactions.
