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 ^207Pb solid-state nuclear magnetic resonance in a polarized ferroelectric crystal. Axionlike dark matter can exert an oscillating torque on ^207Pb nuclear spins via the electric dipole moment coupling g₃ or via the gradient coupling g₀₍₍. 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 |g₃|<9. 5×10^-4 GeV^-2 and |g₀₍₍|<2. 8×10^-1 GeV^-1 (95% confidence level) in this frequency range. The constraint on g₃ 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.