Merits of heavy-heavy diatomic molecules for electron electric-dipole-moment searches

Abstract

The electric dipole moment of the electron (eEDM) and the Scalar-PseudoScalar (S-PS) interaction are probes of new physics beyond the standard model of elementary particles, but experiments to observe them using atoms and molecules are still in progress. Molecules that have a large effective electric field (Eeff), S-PS coefficient (Ws), and permanent electric dipole moment (PDM) are in principle favorable candidates for such experiments, and hence, it is necessary to analyze these properties. In this work, we calculate Eeff, Ws, and PDM for Ra systems; RaF, RaX (X = Cl, Br, I, and At) and RaY (Y = Cu, Ag, and Au) using the Dirac-Fock and the relativistic coupled-cluster methods. We find that RaX and RaY have larger Eeff and Ws,Ra than RaF. We explain this finding by taking into consideration the large s-p mixing for RaX and RaY, similar to what we had done in our previous work using hydrides and fluorides (A. Sunaga et al., Phys. Rev. A 95, 012502 (2017)). We also discuss the suitability of RaX and RaY molecules for eEDM experiments from the viewpoint of their large PDM and small polarizing electric field (Epol).

Theoretical Aspects of Radium-Containing Molecules Amenable to Assembly from Laser-Cooled Atoms for New Physics Searches

“…An explanation for this observation in terms of s-pmixing matrix elements and relevant spinor energies has been attempted in Ref. [35]. We refrain from delving into a deeper analysis of the related trends for E eff (R) in coinage-metal-Ra molecules since, as explained below, neither Cu nor Au atoms have significant advantages, relative to Ag, for use in an ultracold assembled molecule EDM We also consider a further important aspect for experimental feasibility: the external electric field E pol = 2B e /D required for fully polarizing the molecule.…”

“…Because the values of the P, T -odd constants scale roughly as Z 3 (where Z is the atomic number) [32][33][34], at least one of the atoms should be very heavy to maximize their values. Though less critical, it is experimentally convenient to use species that can be strongly polarized in small electric fields; this can be enabled by a large molecular dipole moment and/or small molecular rotational splitting [35].…”

“…Large molecular dipole moments in Ra-coinage metal molecules, discussed here, have also been found in Refs. [35,44]. Sunaga et al [35] discussed properties of radium-A molecules-where A is a halogen or a coinage-metal atom-relevant to molecular electron EDM searches.…”

“…[35,44]. Sunaga et al [35] discussed properties of radium-A molecules-where A is a halogen or a coinage-metal atom-relevant to molecular electron EDM searches. A more encompassing view on the possibilities of using ultracold diatomic molecules assembled from laser-coolable atoms, however, was not discussed in that paper.…”

Towards CP Violation Studies on Superheavy Molecules: Theoretical and Experimental Perspective

“…Recent advances in studies on heavy molecular systems are enabling new opportunities in fundamental physics [1][2][3][4][5][6][7][8][9][10][11][12][13]. Symmetry-violating properties of nuclei and fundamental particles can be highly enhanced in certain molecules.…”