Interactions in an Ultracold Mixture of Rb and Cs Atoms

The project combines the scientific expertise of the applicant in the field of ultracold atomic mixtures with the one available at the Innsbruck University in the domain of ultracold molecules. The project is focused on the interaction properties in a Bose-Bose ultracold mixture composed of 87Rb and 133 Cs atoms. The two main goals are the characterization of the unknown Rb-Cs interactions and the creation of RbCs Feshbach molecules. Heteronuclear systems promise to open new unexplored domains of investigation, such as new quantum phases of matter, superfluid-to-Mott transition, repulsively bound pairs, geometric scattering resonances in optical lattices. The applicant intents to perform extensive magnetic Feshbach spectroscopy on an ultracold Rb-Cs mixture. The location of the interspecies resonances will be exploited to unambiguously determine the collisional parameters of the mixture, such as the singlet and triplet interspecies scattering length, and to identify the most suited entrance channels for molecule association. The applicant proposes to create heteronuclear RbCs molecules via Feshbach association. A study on atom-dimer and dimer-dimer collisions will also be performed. This investigation is needed to improve the molecule lifetime and to reveal possible more complex molecular structures, such as three-body Efimov states which have been recently observed on a Cs sample in Innsbruck. Moreover, the applicant plans to combine the heteronuclear molecules with optical lattices.