Experiments with Interacting Fermi Gases

D. S. Jin, Cindy A. Regal

John E. Thomas

This program explores fundamental interactions in multi-component Fermi gases. Since single component Fermi gases do not interact at low temperatures as a consequence of the Pauli exclusion principle, it is necessary to trap and cool more than one fermionic species in order to study interactions. In current experiments, 40K and 6Li are considered particularly promising for observation of superfluidity in a Fermi gases, because these atoms exhibit magnetically tunable Feshbach resonances in their scattering interactions. The predicted superfluidity is an atomic gas analog of a superconducting transition. For systems with resonant interactions, transition temperatures of up to half the Fermi temperature are predicted. This would make these atomic systems the highest temperature superconductors ever studied, in units of the Fermi temperature. However, the most interesting mixtures of these Fermi gases must be confined in an all-optical trap, because the states of interest are repelled from magnetic traps.

Giovanni Carlo Modugno

We report on the first experiments with atomic Fermi gases in optical lattices. We have studied the properties of non interacting fermions and of an interacting boson‐fermion mixture in a 1D lattice in presence of additional linear or harmonic potentials. These systems have allowed to study for the first time the fundamental quantum transport properties of a perfect crystal and to confirm the role of interactions in real crystals. We have found that the combination of Fermi gases and optical lattices can also have important applications, such as high‐resolution force sensing.

John E. Thomas, Le Luo, Bason E. Clancy +5 more

S. Laalitya Uppalapati, Daniel E. Sheehy

H. Bantilan, Jasmine Brewer, Takaaki Ishii +2 more

Very different strongly interacting quantum systems such as Fermi gases, quark-gluon plasmas formed in high-energy ion collisions, and black holes studied theoretically in string theory are known to exhibit quantitatively similar damping of hydrodynamic modes. It is not known if such similarities extend beyond the hydrodynamic limit. Do nonhydrodynamic collective modes in Fermi gases with strong interactions also match those from string theory calculations? In order to answer this question, we use calculations based on string theory to make predictions for modes outside the hydrodynamic regime in trapped Fermi gases. These predictions are amenable to direct testing with current state-of-the-art cold atom experiments.