Abstract

For sufficiently strong interparticle interactions ultracold Fermi gases display universal properties where the macroscopic parameters become independent of the microscopic details of of the interatomic potential. We will describe the application of Bragg spectroscopy to probe the dynamic density response and spin response of a strongly interacting two-component Fermi gas of lithium-6 atoms confined in an optical dipole trap. The density response and spin response allow full characterisation of the spin-parallel and spin-antiparallel components of the dynamic and static structure factors. Bragg spectra taken close to unitarity show that short-range pair correlations remarkably follow a simple universal law based on a single short-range parameter, the ‘contact’, over a broad range of momenta and interaction strengths and that these pair correlations persist well above the superfluid transition temperature. Finally, we will report on results for the crossover from three to two dimensions for the case of a weakly interacting Fermi gas of lithium-6 atoms confined in a single ‘pancake’ dipole trap