Tue February 27, 2018 4:10 pm
Exciting an ultracold Fermi gas
Location:Harvard Jefferson 250
Dr. Chris Vale,
Swinburne University of Technology
Ultracold Fermi gases with tunable scattering properties provide a versatile testbed for developing quantitative understandings of strongly-coupled fermions. In this talk I will present measurements of the excitation spectra of strongly interacting Fermi gases at both low and high momentum using focused beam Bragg spectroscopy. At low momentum, below the superfluid transition temperature, the Bogoliubov-Anderson phonon mode is the dominant low energy excitation. For energies larger than twice the pairing gap, the single-particle continuum becomes visible. The frequencies of the phonon mode and the onset of single-particle excitations provide direct measures of the speed of sound and pairing gap, respectively. At high momentum, focused beam Bragg spectroscopy allows the determination of Tan’s universal contact parameter and the internal energy via the application of sum-rules. These allow us to probe the temperature dependence of the contact and energy for gases with resonantly enhanced elastic collisions.