Enhanced Schiff and magnetic quadrupole moments in deformed nuclei and their connection to the search for axion dark matter

Deformed nuclei possess enhanced moments violating time reversal invariance (T ) and parity (P). Collective magnetic quadrupole moments (MQM) appear in nuclei with a quadrupole deformation (which have ordinary T, P-conserving collective electric quadrupole moments). Nuclei with an octupole deformation have a collective electric octupole moment, electric dipole moment (EDM), Schiff moment, and MQM in the intrinsic frame which rotates with the nucleus. In a state with definite angular momentum in the laboratory frame, these moments are forbidden by T and P conservation, meaning their expectation values vanish due to nuclear rotation. However, nuclei with an octupole deformation have doublets of close opposite parity rotational states with the same spin, which are mixed by T, P-violating nuclear forces. This mixing polarizes the orientation of the nuclear axis along the nuclear spin, and all moments existing in the intrinsic frame appear in the laboratory frame (provided the nuclear spin I is sufficiently large to allow such a moment). Such a mechanism produces enhanced T, P-violating nuclear moments. This enhancement also takes place in nuclei with a soft octupole vibration mode. In this paper we present updated estimates for the enhanced Schiff moment in isotopes of Eu, Sm, Gd, Dy, Er, Fr, Rn, Ac, Ra, Th, Pa, U, Np, and Pu in terms of the CP-violating pi-meson-nucleon interaction constants g over bar 0, g over bar 1, and g over bar 2, the quantum chromodynamics parameter theta over bar and the quark chromo-EDMs. The implications of the enhanced T, P-violating moments to the search for axion dark matter in solid state experiments are also discussed, with potential alternative candidate compounds in which we may expect enhanced effects suggested.

Automated summary

Deformed nuclei violate time reversal invariance and parity, resulting in enhanced magnetic quadrupole moments. Nuclei with octupole deformation have various electric moments, including octupole moment, electric dipole moment, Schiff moment, and magnetic quadrupole moment. These moments are forbidden by T and P conservation in the laboratory frame, but mixing of opposite parity rotational states in nuclei with octupole deformation allows these moments to appear. This mechanism produces enhanced T, P-violating nuclear moments. The paper also presents estimates for enhanced Schiff moments in various isotopes and discusses the implications for axion dark matter detection in solid state experiments.