Collective Behavior in Few-Fermion Systems

This thesis reports on the exploration of collective behavior in a system of few fermionic atoms. Access to both real- and momentum space observables in combination with a high degree of control over both particle number and interaction strength allows us to explore the emergence of collective behavior from the bottom up - atom by atom. Inspired by observations in high-energy physics, where hydrodynamic behavior is present in absence of a separation of scales, we explore interaction-driven elliptic flow which is commonly considered a smoking-gun of hydrodynamic behavior. Our measurements reveal elliptic flow in systems of only six constituents. Motivated by the formation of pairs of fermionic particles in system with broken translational symmetry (such as atomic nuclei or ’dirty’ superconductors), where BCS theory does not apply, we investigate how a spatially varying potential affects pair formation. By altering interaction strength and particle number, we observe a transition from a regime in which pair formation is determined by the discrete level structure of the potential to a regime in which the potential only influences pairing by altering the local density.