Abstract: Quantum gases of atoms and molecules serve to realize paradigmatic models of many-body physics, enabling us to search for novel states of matter. In particular, strongly interacting fermionic atoms form superfluids in the crossover from Bose-Einstein condensation of tightly bound molecules to the Bardeen-Cooper-Schrieffer state of long-range Cooper pairs.

The thermodynamics of resonant Fermi gases constrain the equation of state of nuclear matter, and transport of spin, sound and heat feature low, quantum-limited damping. A direct way to measure heat transport in situ allowed us to reveal second sound in the superfluid Fermi gas, the wave-like propagation of heat. We recently realized a microscope enabling the observation of quantum gases in the continuum with single-atom resolution. We observed bosonic bunching in a Bose gas, fermionic anti-bunching and the formation of fermion pairs in a 2D Fermi gas.

Trapped in optical lattices, fermionic atoms realize the Hubbard model of strongly interacting electrons. For attractive interactions, we observe pairing to occur even above the superfluid transition, in the “pseudo-gap” regime of preformed pairs. With spin imbalance, we explore signatures of exotic pairing in the search for the long-sought Fulde-Ferrell-Larkin-Ovchinnikov state. Extensions of these atom-resolved studies are promising for the exploration of bosonic and fermionic quantum Hall states in rotating gases, as well as molecular gases with long-range dipolar interactions.