Compressing ultracold Fermi gases to new regimes

We report on the highest densities achieved with ultracold Fermi gases, by combining sympathetic cooling with tight compression of lithium-6 atoms in an optical potential. In contrast to the usual notion of non-interacting spin-polarized fermions, we observe elastic and inelastic p-wave collisions far away from any Feshbach resonance. We realize p-wave evaporation that reaches a temperature of T/T_F =0.42, and also obtain the first experimental measurement of a p-wave background scattering volume, determined to be Vp=(39 a₀)³. The record Fermi energy obtained, combined with the high optical densities, will allow to study light scattering in new regimes, where one can expect to observe superradiance and Pauli blocking of light scattering.