A Reappraisal of the Electric Dipole Moment Enhancement Factor for Thallium

TL;DR

This paper recalculates the electric dipole moment enhancement factor for thallium using advanced relativistic coupled-cluster theory, providing a more accurate value that refines the upper limit for the electron EDM.

Contribution

It introduces a new calculation of the Tl EDM enhancement factor using relativistic coupled-cluster theory with triple excitations, reducing uncertainties in previous estimates.

Findings

EDM enhancement factor for Tl is -466

New upper limit for electron EDM is 2.0 x 10^-27 e·cm

All-order correlation effects are crucial and compared with other ab initio methods

Abstract

The electric dipole moment (EDM) enhancement factor of atomic Tl is of considerable interest as it has been used in determining the most accurate intrinsic electron EDM limit to date. However, the value of this quantity varies from $-179$ to $-1041$ in different approximations. In view of the large uncertainties associated with many of these calculations, we have employed the relativistic coupled-cluster theory with single and double excitations and a subset of leading triple excitations and obtained the EDM enhancement factor of Tl as $-466$, which in combination with the most accurate measured value of Tl EDM yields $2.0 \times 10^{-27}\,{\mathrm e\,cm}$ as the new upper limit for the EDM of the electron. The importance of all-order correlation effects is emphasized and their trends are compared with those of two other ab initio calculations.