Chapter 2 - CP-violating Magnetic Moments of Atoms and Molecules

Abstract

Abstract We develop a theory of electric-field-induced magnetization of a medium. The relevant polarizability, β CP , simultaneously violates the inversion symmetry (parity), the time-reversal symmetry, and the combined CP symmetry. We focus on two fundamental mechanisms mediating the appearance of β CP —the electric dipole moment of the electron (eEDM) and the electron-nucleus pseudo-scalar weak neutral currents. Measuring β CP may reveal so-far elusive eEDM and these neutral currents. We start with computing β CP for rare-gas atoms and demonstrate that β CP scales steeply as Z 5 with the nuclear charge Z . Further, we show that β CP manifests itself in permanent CP-violating magnetic moments of molecules. A macroscopic sample of polarized molecules would exhibit a magnetization correlated with the direction of externally-applied polarizing electric field. We numerically estimate this unconventional moment for diamagnetic molecules. Finally, we introduce a thermally-induced CP-violating magnetization of a sample of paramagnetic molecules. In all cases, we evaluate the feasibility of an experimental search for eEDM. We find that paramagnetic molecules HgH embedded in a rare-gas matrix at a temperature of a few Kelvin have a remarkable sensitivity to eEDM. We conclude, that experiments with such “artificial solids” can push the current limit on the eEDM by several orders of magnitude, deep into the domain of predictions of competing extensions to the Standard Model of elementary particles.