Time Reversal Symmetry Violation in Neutral Systems: The Nuclear Schiff Moment and Atomic EDM

The electric dipole moment (EDM) is the “smoking gun” of time reversal symmetry violation. For a neutral atom, the nuclear EDM is screened by the atomic electrons. To recover from this shielding, an additional parity and time reversal violating (𝑃,𝑇 -odd) nuclear moment is required to induce an EDM in the electron cloud. This moment is called the nuclear Schiff moment and is necessarily the product of 𝑃,𝑇 -odd nuclear forces. Interest in EDMs is motivated by an effort to explain the cosmological baryon asymmetry (or matter-antimatter asymmetry) problem. The violation of the combination charge conjugation-parity symmetry (𝐶𝑃 violation) is expected to play a role in explaining the baryon asymmetry. Assuming 𝐶𝑃𝑇 symmetry, 𝑇 violation is equivalent to 𝐶𝑃 violation making 𝑇 -odd phenomena useful proxies. In this work, we calculated Schiff moments of the ²⁰⁵Tl nucleus using self-consistent mean-field theory in the Skyrme-Hartree-Fock-Bogoliubov code HFODD in collaboration with the Cold molecule Nuclear Time-Reversal EXperiment (CeNTREX). These calculations were performed with several Skyrme interactions to estimate uncertainties and are presented here.

David Stilwell

University of North Carolina at Chapel Hill