Title: Ultracold Fermion Mixtures: Interactions make them strong

Abstract:
The tunability of interactions via Feshbach resonances has been a gamechanger in the field of ultracold fermionic quantum gases. After a brief historic review on the emergence of strongly interacting Fermi gases, I will discuss two major research lines pursued in Innsbruck. Using potassium atoms immersed in a Fermi sea of lithium-6, we study the properties of quasiparticles in the Fermi sea, known as “Fermi polarons”. In current work, we focus on mediated interactions between impurities. In another experiment, we are aiming at novel superfluid states expected in a mass-imbalanced fermion mixture. Our mixture is realized with dysprosium and potassium atoms, and we have identified suitable Feshbach resonance. We demonstrate deep hydrodynamic behavior in a resonant mixture as precursor of superfluidity.