TaN, a molecular system for probing ${\cal{P,T}}$-violating hadron physics

TL;DR

This study uses advanced relativistic quantum chemistry methods to analyze the TaN molecule, providing key parameters for its use in probing fundamental ${ m P,T}$-violating physics beyond the Standard Model.

Contribution

The paper introduces a comprehensive all-electron Dirac-Coulomb CI approach to calculate ${ m P,T}$-odd effects in TaN, including a new method for nuclear magnetic-quadrupole interaction constants.

Findings

${ m P,T}$-odd effective electric field: 36.0 GV/cm

Scalar-pseudoscalar interaction constant: 32.8 kHz

Large molecule-frame electric dipole moment: -4.91 Debye

Abstract

All-electron configuration interaction theory in the framework of the Dirac-Coulomb Hamiltonian has been applied to the TaN molecule, a promising candidate in the search for Beyond-Standard-Model physics in both the hadron and the lepton sector of matter. We obtain in the first excited {$^3\Delta_1$} state a ${\cal{P,T}}$-odd effective electric field of $36.0 \left[\frac{\rm GV}{\rm cm}\right]$, a scalar-pseudoscalar ${\cal{P,T}}$-odd interaction constant of $32.8$ [kHz], and a nuclear magnetic-quadrupole moment interaction constant of $0.74$ [$\frac{10^{33} {\text{Hz}}}{e\, {\text{cm}}^2}$]. The latter interaction constant has been obtained with a new approach which we describe in detail. Using the same highly correlated all-electron wavefunctions with up to $2.5$ billion expansion terms, we obtain a parallel magnetic hyperfine interaction constant of $-2954$ [MHz] for the $\rm {^{181}{T}a}$ nucleus, a very large molecule-frame electric dipole moment of $-4.91$ [Debye], and spectroscopic constants for the four lowest-lying electronic states of the molecule.