Seminarium Optyczne

Studies of fundamental physical phenomena with ultracold atoms, from superfluidity, through quantum simulators, to degenerate gases of polar molecules, require exquisite knowledge of collisional properties of atoms used in experiments. Theoretical predictions are usually based on scarce spectroscopic data and even for molecules like KCs, which have been extensively studied in hot vapors, theoretical understanding of ultracold properties of these molecules is rarely satisfactory. This necessitates the development of efficient cooling methods and extensive experimental studies of fine details of interactions between atoms to provide data for theoretical modeling.In the first part of the talk I will introduce our state-of-the-art experimental setup designed to study ultracold mixtures of cesium and potassium. The versatility of the apparatus will be demonstrated by individually cooling 39K, 40K, 41K, and 133Cs atoms as well as their mixtures. I will compare these findings with state of the art results from other research groups and highlight our achievement of the world’s first 39K-40K and 41K-133Cs mixtures. The second part of the talk will focus on Feshbach resonances spectroscopy of 39K-133Cs and 41K-133Cs mixtures. For 39K-133Cs, we provide the first independent verification of the 2017 results obtained by the group of H.-C. Nägerl (University of Innsbruck). The Feshbach spectrum of 41K-133Cs is demonstrated for the first time, showing significant disagreement with theoretical predictions. These results are vital for a deeper understanding of the collisional properties of cesium and potassium mixtures and are a prerequisite for advancing toward the formation of ultracold polar ground state molecules of KCs.