The CASPEr-e Search for Axion-like Dark Matter Using Solid-state Nuclear Magnetic Resonance*

We present the results of an experimental search for axion-like dark matter in the mass range 162 neV to 166 neV. The detection scheme of our Cosmic Axion Spin Precession Experiment (CASPEr) is based on a precision measurement of $^{207}$Pb nuclear magnetic resonance in a polarized ferroelectric crystal [D. Budker, et al., Phys. Rev. X 4, 021030] at 4.4 T field with a resonant circuit coupled to a low-noise amplifier. Our measurements place upper bounds on the electric-dipole moment coupling $|g_d|<7.0\times10^{-4}\mathrm{GeV}^{-2}$ and the gradient coupling $|g_{\mathrm{aNN}}|<2.1\times10^{-1}\mathrm{GeV}^{-1}$ of axion-like dark matter with 95\% confidence level in the searched mass range [D. Aybas, et al., arXiv:2101.01241].