Quantum Degenerate Two-Species Fermi-Fermi Mixture Coexisting with a Bose-Einstein Condensate

We report on the generation of a quantum degenerate Fermi-Fermi mixture of two different atomic species. The quantum degenerate mixture is realized employing sympathetic cooling of fermionic ⁶Li and ⁴⁰K gases by an evaporatively cooled bosonic ⁸⁷Rb gas. We describe the combination of trapping and cooling methods that proved crucial to successfully cool the mixture. In particular, we study the last part of the cooling process and show that the efficiency of sympathetic cooling of the ⁶Li gas by ⁸⁷Rb is increased by the presence of ⁴⁰K through catalytic cooling. Because of the differing physical properties of the two components, the quantum degenerate ⁶Li-⁴⁰K Fermi-Fermi mixture is an excellent candidate for a stable, heteronuclear system allowing the study of several so far unexplored types of quantum matter.