For our experiments with ultracold atoms and molecules we recently installed a commercial frequency comb system that can serve as a frequency reference for multiple application lasers. The system is operating in our lab and sharing the frequency comb with two other laboratories in CQT. We are using a sub-kiloherz linewidth diode laser stabilized to a highly stable optical reference resonator (design - courtesy by Max-Planck-Institute for Quantum Optics, Munich, Germany.) in order to improve the short time stability of the comb system.

We investigate s-wave interactions in a two-species Fermi-Fermi mixture of ⁶Li and ⁴⁰K. We develop for this case the method of cross-dimensional relaxation and find from a kinetic model, Monte Carlo simulations, and measurements that the individual relaxation rates differ due to the mass difference. The method is applied to measure the elastic cross section at the Feshbach resonance that we previously used for the production of heteronuclear molecules. Location (B₀=154.71(5) G) and width are determined for this resonance. This reveals that molecules are being produced on the atomic side of the resonance within a range related to the Fermi energies, therefore establishing the first observation of a many body effect in the crossover regime of a narrow Feshbach resonance.

In March 2010 we transfered the experimental setup from Munich to Singapore. The experiment had been developed in the group of Prof. Hänsch at the Ludwig-Maximilians-University of Munich.

We report on the first creation of ultracold bosonic heteronuclear molecules of two fermionic species, ⁶Li and ⁴⁰K, by a magnetic field sweep across an interspecies s-wave Feshbach resonance. This allows us to associate up to 4×10⁴ molecules with high efficiencies of up to 50%. Using direct imaging of the molecules, we measure increased lifetimes of the molecules close to resonance of more than 100ms in the molecule-atom mixture stored in a harmonic trap.

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.

We report on the simultaneous trapping of two fermionic species, ⁶Li and ⁴⁰K, and a bosonic species, ⁸⁷Rb demonstrating the first three-species magneto-optical trap: "Triple MOT". The apparatus including the atom sources and the three laser systems is described, and the single-species MOTs and the triple MOT are characterized. In triple MOT operation, typical atom numbers of 3.2×10⁷ for ⁶Li, 1.5×10⁷ for ⁴⁰K, and 5.4×10⁹ for ⁸⁷Rb were achieved. Trap loss due to interspecies collisions was observed.We describe our way to optimize the triple MOT and turn it into a suitable source for the goal to achieve quantum degeneracy by evaporative and sympathetic cooling.