Optical cycling and sensitivity to the electron's electric dipole moment in gold-containing molecules

We propose diatomic molecules built from gold and carbon-group atoms as promising candidates for optical cycling and precision measurements. We show that this class of molecules ($\mathrm{Au}X,X=\mathrm{C},\mathrm{Si},\mathrm{Ge},\mathrm{Sn},\mathrm{Pb}$) features laser-accessible electronic transitions with nearly diagonal Franck-Condon factors. The $^{2}\mathrm{\ensuremath{\Pi}}_{1/2}$ ground states can be easily polarized in the laboratory frame and have near-zero magnetic moments, valuable features for quantum science and precision measurement applications. The sensitivities of $\mathrm{Au}X$ molecules to the electron electric dipole moment (EDM) are found to be favorable, with effective electric fields of 10--30 GV/cm. Together these features imply that $\mathrm{Au}X$ molecules may enable significantly improved searches for time-reversal symmetry violation.