Global analysis of $$ \mathcal{CP} $$-violation in atoms, molecules and role of medium-heavy systems

Abstract

Abstract Detection of parity $$ \left(\mathcal{P}\right) $$ P and time-reversal $$ \left(\mathcal{T}\right) $$ T symmetry-odd electric dipole moments (EDMs) within currently achievable resolution would evidence physics beyond the Standard Model of particle physics. Via the $$ \left(\mathcal{CPT}\right) $$ CPT -theorem, which includes charge conjugation $$ \left(\mathcal{C}\right) $$ C , such low-energy searches complement high-energy physics experiments that probe $$ \left(\mathcal{CP}\right) $$ CP -violation up to the TeV scale. Heavy-elemental atoms and molecules are considered to be among the most promising candidates for a first direct detection of $$ \mathcal{P} $$ P , $$ \mathcal{T} $$ T -violation due to enhancement effects that increase steeply with increasing nuclear charge number Z. However, different $$ \mathcal{P} $$ P , $$ \mathcal{T} $$ T -odd sources on the subatomic level can contribute to molecular or atomic EDMs, which are target of measurements, and this complicates obtaining rigorous bounds on $$ \mathcal{P} $$ P , $$ \mathcal{T} $$ T -violation on a fundamental level. Consequently, several experiments of complementary sensitivity to these individual $$ \mathcal{P} $$ P , $$ \mathcal{T} $$ T -odd sources are required for this purpose. Herein, a simply-applicable qualitative model is developed for global analysis of the $$ \mathcal{P} $$ P , $$ \mathcal{T} $$ T -odd parameter space from an electronic-structure theory perspective. Rules of thumb are derived for the choice of atoms and molecules in terms of their angular momenta and nuclear charge number. Contrary to naive expectations from Z-scaling laws, it is demonstrated that medium-heavy molecules with Z ≤ 54 can be of great value to tighten global bounds on $$ \mathcal{P} $$ P , $$ \mathcal{T} $$ T -violating parameters, in particular, if the number of complementary experiments increases. The model is confirmed by explicit density functional theory calculations of all relevant $$ \mathcal{P} $$ P , $$ \mathcal{T} $$ T -odd electronic structure parameters in systems that were used in past experiments or are of current interest for future experiments, respectively: the atoms Xe, Cs, Yb, Hg, Tl, Ra, Fr and the molecules CaOH, SrOH, YO, CdH, BaF, YbF, YbOH, HfF+, WC, TlF, PbO, RaF, ThO, ThF+ and PaF3+.