CKM benchmarks for electron electric dipole moment experiments

All current experiments searching for an electron electric dipole moment (EDM) dₑ are performed with atoms and diatomic molecules. Motivated by significant recent progress in searches for an EDM-type signal in diatomic molecules with an uncompensated electron spin, we provide an estimate for the expected signal in the Standard Model due to the Cabibbo-Kobayashi-Maskawa (CKM) phase. We find that the main contribution originates from the effective electron-nucleon operator ēiγ₅eN̄N, induced by a combination of weak and electromagnetic interactions at O(GF²α²), and not by the CKM-induced electron EDM itself. When the resulting atomic $P,T$-odd mixing is interpreted as an equivalent electron EDM, this estimate leads to the benchmark dₑequiv(CKM)~10^-38 ecm.