Observing the emergence of many body physics, atom by atom

We prepare samples of up to 20 fermionic atoms with ultralow entropies in a two-dimensional configuration. We developed a single atom and spin sensitive imaging technique that allows us to detect all atoms of a samlpe either in real, or in momentum space. From such measurements we can infer correlations in the system. In our fermonic system, these are present already in a noninteracting sample and give rise to so-called Pauli Crystals [1]. More interesting correlations arise as soon as interactions in the system are turned on. Now, Cooper pairs and a BCS-like system can be observed to form with p,-p - correlations emerging at the Fermi surface [3]. In our trapped finite system, pairing occurs only at a finite attraction strength, which results in the precursor of a quantum phase transition [2]. To further understand the emergence of many body physics from the few-body limit we are currently exploring a single impurity in a finite Fermi sea to observe the transition from a molecular to a polaronic state. We will present progress on our quest to understand the polaron from the correlations between its constituents.