From Efimov Physics to Polarons in an Ultracold Mixture of Li and Cs Atoms

This thesis reports on the reconstruction and improvement of a quantum gas experiment for studying Bose polarons as well as on theoretical investigations at the interface between Efimov physics and Fermi polarons. In both experiment and theory an ultracold mixture of fermionic 6Li and bosonic 133Cs with a large mass ratio is considered. With the improved experimental setup we realize Bose-Einstein condensates (BEC) of 133Cs with N = 10^4 atoms and molecular BECs of 6Li2 with N = 10^5 dimers. For the creation of Bose polarons we trap a small number of Li atoms in a tightly confined optical dipole trap and propose a scheme to combine them with the 133Cs BEC. In a theoretical study, employing the Born-Oppenheimer approximation, we calculate Efimov bound state energies (E 0) we calculate the induced scattering length between two 133Cs atoms mediated by the Fermi sea, and find resonant behavior. We find that for large mass ratios bound states can persist at positive energies to form quasibound states