Improved limits on axion-like-particle-mediated P,T-violating interactions between electrons and nucleons from electric dipole moments of atoms and molecules

TL;DR

This paper calculates how axion-like particles could induce electric dipole moments in atoms and molecules, and uses experimental data to set new, stronger limits on P,T-violating interactions mediated by these particles across a range of masses.

Contribution

It provides detailed calculations of axion-mediated atomic EDMs and derives improved experimental bounds on P,T-violating interactions for a broad axion mass range.

Findings

New limits on P,T-violating interactions surpass previous bounds for axion masses above 0.01 eV.

Analytical estimates clarify the dependence of EDMs on axion mass and atomic properties.

Constraints on CP violation in relaxion models are also established.

Abstract

In the presence of P,T-violating interactions, the exchange of axion-like particles between electrons and nucleons in atoms and molecules induces electric dipole moments (EDMs) of atoms and molecules. We perform calculations of such axion-exchange-induced atomic EDMs using the relativistic Hartree-Fock-Dirac method including electron core polarisation (RPA) corrections. We present analytical estimates to explain the dependence of these induced atomic EDMs on the axion mass and atomic parameters. From the experimental bounds on the EDMs of atoms and molecules, including $^{133}$Cs, $^{205}$Tl, $^{129}$Xe, $^{199}$Hg, $^{171}$Yb$^{19}$F, $^{180}$Hf$^{19}$F$^+$ and $^{232}$Th$^{16}$O, we constrain the P,T-violating scalar-pseudoscalar nucleon-electron and electron-electron interactions mediated by a generic axion-like particle of arbitrary mass. Our limits improve on existing laboratory bounds from other experiments by many orders of magnitude for $m_a \gtrsim 10^{-2}~\textrm{eV}$. We also place constraints on CP violation in certain types of relaxion models.