Atomic CP-violating polarizability

Searches for CP-violating effects in atoms and molecules provide important constrains on competing extensions to the standard model of elementary particles. In particular, CP violation in an atom leads to the CP-odd (T,P-odd) polarizability β^CP: a magnetic moment μ^CP is induced by an electric field E₀ applied to an atom, μ^CP=β^CPE₀. We estimate the CP-violating polarizability for rare-gas (diamagnetic) atoms He through Rn. We relate β^CP to the permanent electric dipole moment (EDM) of the electron and to the scalar constant of the CP-odd electron-nucleus interaction. The analysis is carried out using the third-order perturbation theory and the Dirac-Hartree-Fock formalism. We find that, as a function of nuclear charge Z, β^CP scales steeply as Z⁵R(Z), where slowly varying R(Z) is a relativistic enhancement factor. Finally, we evaluate the feasibility of setting a limit on electron EDM by measuring CP-violating magnetization of liquid Xe. We find that such an experiment could provide competitive bounds on electron EDM only if the present level of experimental sensitivity to ultraweak magnetic fields [ Kominis et al. Nature 422 596 (2003)] is improved by several orders of magnitude.