No abstract

Systems of fermions with multiple internal states, such as quarks in quantum chromodynamics and nucleons in nuclear matter, are at the heart of some of the most complex quantum many-body problems. The stability of such many-body multi-component systems is crucial to understanding, for instance, baryon formation and the structure of nuclei, but these fermionic problems are typically very challenging to tackle theoretically. Versatile experimental platforms on which to study analogous problems are thus sought after. Here, we report the creation of a uniform gas of three-component fermions. We characterize the decay of this system across a range of interaction strengths and observe nontrivial competition between two-and three-body loss processes. We observe anomalous decay of the polarized (i.e. spin-population imbalanced) gas, in which the loss rates of each component unexpectedly differ. We introduce a generalized three-body rate equation which captures the decay dynamics, but the underlying microscopic mechanism is unknown.

We report the creation and the study of the stability of a repulsive quasi-homogeneous spin-1/2 Fermi gas with contact interactions. For the range of scattering lengths a explored, the dominant mechanism of decay is a universal three-body recombination towards a Feshbach bound state. We observe that the recombination coefficient K3 ∝ kina 6 , where the first factor, the average kinetic energy per particle kin, arises from a three-body threshold law, and the second one from the universality of recombination. Both scaling laws are consequences of Pauli blocking effects in three-body collisions involving two identical fermions. As a result of the interplay between Fermi statistics and the momentum dependence of the recombination process, the system exhibits non-trivial temperature dynamics during recombination, alternatively heating or cooling depending on its initial quantum degeneracy. The measurement of K3 provides an upper bound for the interaction strength achievable in equilibrium for a uniform repulsive Fermi gas.