CASPEr-Electric: second generation of low frequency search for axion-like dark matter using magnetic resonance

Axions were originally proposed to solve the strong CP problem but they have become one of the most promising candidates for dark matter as well. We present the latest results of the second generation of the CASPEr-Electric experiment which searches for ultralight axion-like dark matter in the neV mass range (below 1 MHz). The experiment is sensitive to the interaction of axions with nuclear spins: the axion dark matter field creates an oscillating electric dipole moment of a ²⁰⁷Pb nucleus in a PMN-PT ferroelectric crystal. This dipole moment gives rise to a torque on the nuclear spin, and the resulting transverse nuclear magnetization can be detected with a superconducting quantum interference device (SQUID). We calibrate the sensitivity of the experiment by solid-state magnetic resonance on ²⁰⁷Pb nuclei and detect the signal with a SQUID.