Application of the Finite Field Coupled Cluster Method to Calculate Molecular Properties Relevant to Electron Electric Dipole Moment Searches

TL;DR

This paper develops and applies a relativistic finite field coupled cluster method to accurately calculate molecular properties of heavy diatomic molecules, aiding electron EDM searches and exploring physics beyond the Standard Model.

Contribution

It introduces a finite field coupled cluster approach for relativistic calculations of molecular properties relevant to eEDM experiments, with detailed error analysis.

Findings

Calculated effective electric fields (Eeff) for target molecules.

Provided permanent electric dipole moments (PDM) for molecules of interest.

Achieved results with an error estimate including basis set and correlation effects.

Abstract

Heavy polar diatomic molecules are currently among the most promising probes of fundamental physics. Constraining the electric dipole moment of the electron (eEDM), in order to explore physics beyond the Standard Model, requires a synergy of molecular experiment and theory. Recent advances in experiment in this field have motivated us to implement a finite field coupled cluster approach (FFCC). This work has distinct advantages over the theoretical methods that we had used earlier in the analysis of eEDM searches. We used the relativistic FFCC to calculate molecular properties of interest to eEDM experiments, that is, the effective electric field (Eeff), and the permanent electric dipole moment (PDM). We theoretically determine these quantities for the alkaline earth monofluorides (AEMs), the mercury monohalides (HgX), and PbF. The latter two systems, as well as BaF from the AEMs, are of interest to eEDM searches. We also report the calculations of the properties using a relativistic coupled cluster approach with single, double, and partial triples' excitations, which is considered to be the gold standard of electronic structure calculations. We also present a detailed error estimate, including errors that stem from the choice of basis sets, and higher order correlation effects.