Sympathetic Cooling in an Optically Trapped Mixture of Alkali and Spin-Singlet Atoms

We report on the realization of a stable mixture of ultracold lithium and ytterbium atoms confined in a far-off-resonance optical dipole trap. We observe sympathetic cooling of Li-6 by Yb-174 and extract the s-wave scattering length magnitude vertical bar Li-a6-Yb-174 vertical bar = (13 +/- 3)a(0) from the rate of interspecies thermalization. Using forced evaporative cooling of Yb-174, we achieve reduction of the Li-6 temperature to below the Fermi temperature, purely through interspecies sympathetic cooling.