Ultracold $^{88}\rm{Sr}_2$ molecules in the absolute ground state

Abstract

We report efficient all-optical creation of an ultracold gas of alkalineearth-metal dimers, 88 Sr 2 , in their absolute ground state. Starting with weakly bound singlet molecules formed by narrow-line photoassociation in an optical lattice, followed by stimulated Raman adiabatic passage (STIRAP) via a singlet-dominant channel in the (1)0 + u excited potential, we prepare pure samples of more than 5500 molecules in X 1 Σ + g (v = 0, J = 0). We observe two-body collisional loss rates close to the universal limit for both the least bound and most bound vibrational states in X 1 Σ + g . We demonstrate the enhancement of STIRAP efficiency in a magic-wavelength optical lattice where thermal decoherence is eliminated. Our results pave the way for the use of alkaline-earth-metal dimers for high-precision spectroscopy, and indicate favorable prospects for robust quantum state preparation of ultracold molecules involving closedshell atoms, as well as molecule assembly in deep optical traps tuned to a magic wavelength.

Collisional losses of ultracold molecules due to intermediate complex formation

“…Experimental proposal. We suggest that recently produced ultracold ground-state strontium dimers [65] are a suitable system for further studies and verification of the importance of the nuclear spin-spin and quadrupole couplings for the dynamics of intermediate complexes. Depending on the isotope, the Bose-Bose dimers do not have a hyperfine structure, while Fermi-Fermi dimers have spin-spin and nuclear quadrupole couplings.…”