Optical Traps for Sympathetic Cooling of Ions with Ultracold Neutral Atoms.

We report the trapping of ultracold neutral Rb atoms and Ba^{+} ions in a common optical potential in absence of any radio frequency (rf) fields. We prepare Ba^{+} at 370 µK and demonstrate efficient sympathetic cooling by 100 µK after one collision. Our approach is currently limited by the Rb density and related three-body losses, but it overcomes the fundamental limitation in rf traps set by rf-driven, micromotion-induced heating. It is applicable to a wide range of ion-atom species, and may enable novel ultracold chemistry experiments and complex many-body dynamics.