ABSTRACT
Recent experimental advances in ultracold Fermi gases allow for exploring response functions under different dynamical conditions. In particular, the issue of obtaining a "quasirepulsive" regime starting from a Fermi gas with an attractive interparticle interaction while avoiding the formation of the two-body bound state is currently debated. Here, we provide a calculation of the density and spin response for a wide range of temperature and coupling both in the attractive and quasirepulsive regime, whereby the system is assumed to evolve nonadiabatically toward the "upper branch" of the Fermi gas. A comparison is made with the available experimental data for these two quantities.
ABSTRACT
Wave-vector resolved radio frequency spectroscopy data for an ultracold trapped Fermi gas are reported for several couplings at T(c), and extensively analyzed in terms of a pairing-fluctuation theory. We map the evolution of a strongly interacting Fermi gas from the pseudogap phase into a fully gapped molecular Bose gas as a function of the interaction strength, which is marked by a rapid disappearance of a remnant Fermi surface in the single-particle dispersion. We also show that our theory of a pseudogap phase is consistent with a recent experimental observation as well as with quantum Monte Carlo data of thermodynamic quantities of a unitary Fermi gas above T(c).