Optical lattice clocks with weakly bound molecules

Abstract

Optical molecular clocks promise unparalleled sensitivity to the temporal variation of the electron-to-proton mass ratio and insight into possible new physics beyond the Standard Model. We propose to realize a molecular clock with bosonic $^{174}$Yb$_2$ molecules, where the forbidden $^1$S$_0$$\rightarrow$$^3$P$_0$ clock transition would be induced magnetically. The use of a bosonic species avoids possible complications due to hyperfine structure present in fermionic species. While direct clock line photoassociation would be challenging, weakly bound ground state molecules could be produced by STIRAP and used instead. The recent scattering measurements [L. Franchi, et al. New J. Phys 19, 103037 (2017)] enable us to determine the positions of target $^1$S$_0$+$^3$P$_0$ vibrational levels and calculate the Franck-Condon factors for clock transitions between ground and excited molecular states. The resulting magnetically induced Rabi frequencies are similar to those for atoms hinting that an experimental realization is feasible. A successful observation could pave the way towards Hz-level molecular spectroscopy.