  Detection of parity (P) and time-reversal (T) symmetry-odd electric dipole
moments (EDMs) within currently achievable resolution would evidence physics
beyond the Standard Model of particle physics. Via the CPT-theorem, which
includes charge conjugation (C), such low-energy searches complement
high-energy physics experiments that probe 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 P,T-violation due to
enhancement effects that increase steeply with increasing nuclear charge number
$Z$. However, different P,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 P,T-violation on a fundamental level.
Consequently, several experiments of complementary sensitivity to these
individual P,T-odd sources are required for this purpose. Herein, a
simply-applicable qualitative model is developed for global analysis of the
P,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 $Z\leq54$
can be of great value to tighten global bounds on P,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
P,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 PaF$^{3+}$.
