Search for Axionlike Dark Matter Using Solid-State Nuclear Magnetic Resonance

We report the results of an experimental search for ultralight axionlike dark matter in the mass range 162-166 neV. The detection scheme of our Cosmic Axion Spin Precession Experiment is based on a precision measurement of Pb207 solid-state nuclear magnetic resonance in a polarized ferroelectric crystal. Axionlike dark matter can exert an oscillating torque on Pb207 nuclear spins via the electric dipole moment coupling gd or via the gradient coupling gaNN. We calibrate the detector and characterize the excitation spectrum and relaxation parameters of the nuclear spin ensemble with pulsed magnetic resonance measurements in a 4.4 T magnetic field. We sweep the magnetic field near this value and search for axionlike dark matter with Compton frequency within a 1 MHz band centered at 39.65 MHz. Our measurements place the upper bounds |gd|<9.5×10-4 GeV-2 and |gaNN|<2.8×10-1 GeV-1 (95% confidence level) in this frequency range. The constraint on gd corresponds to an upper bound of 1.0×10-21 e cm on the amplitude of oscillations of the neutron electric dipole moment and 4.3×10-6 on the amplitude of oscillations of CP-violating θ parameter of quantum chromodynamics. Our results demonstrate the feasibility of using solid-state nuclear magnetic resonance to search for axionlike dark matter in the neV mass range.