Events at Physics
I will present our experiments of immersing single and few Cs atoms into an ultracold, thermal Rb cloud. We observe the sympathetic cooling of the impurity atoms, where the temperature is limited only by the temperature of the Rb gas. The thermalization dynamics can be understood in terms of the well-known elastic interspecies s-wave scattering length. Inelastic three-body collisions are studied with atomic resolution, allowing to unambiguously assign losses to Rb-Rb-Cs three-body recombination and permitting a precise determination of the loss coefficient, which is not directly possible in balanced mixtures. In all experiments, the ultracold Rb gas remains unaffected by the interaction with the Cs impurity atoms, demonstrating the feasibility of using single atoms as probes for a many-body system. The obtained results for the interaction properties of the two sub-systems are a significant step toward a coherently interacting hybrid system of individually controllable impurities in a quantum many-body system.