An ultracold, optically trapped mixture of Rb-87 and metastable He-4 atoms

We report on the realization of an ultracold (< 25 mu K) mixture of rubidium (Rb-87) and metastable triplet helium (He-4) in an optical dipole trap. Our scheme involves laser cooling in a dual-species magneto-optical trap, simultaneous MW- and RF-induced forced evaporative cooling in a quadrupole magnetic trap, and transfer to a single-beam optical dipole trap. We observe long trapping lifetimes for the doubly spin-stretched spin-state mixture and measure much shorter lifetimes for other spin-state combinations. We discuss prospects for realizing quantum degenerate mixtures of alkali-metal and metastable helium atoms.