Merits of Heavy-Heavy Molecules for Electron Electric Dipole Moment Searches

TL;DR

This study evaluates heavy-heavy molecules like RaX and RaY for electron EDM experiments, finding they have larger effective electric fields and S-PS coefficients than RaF, making them promising candidates for new physics searches.

Contribution

The paper provides detailed calculations of Eeff, Ws, and PDM for RaX and RaY molecules using relativistic methods, highlighting their potential advantages over previously studied molecules.

Findings

RaX and RaY have larger Eeff and Ws than RaF.

Large s-p mixing explains the increased Eeff and Ws.

RaX and RaY have favorable PDM and Epol for eEDM experiments.

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).