Understanding the Superfluid phase diagram in trapped Fermi gases

P. Brussaard, M.A. Baranov, M. Yu. Kagan +2 more

Qijin Chen, Cindy A. Regal, Markus Greiner +2 more

Trapped ultracold Fermi gases provide a system that can be tuned between the BCS and Bose-Einstein condensation regimes by means of a magnetic-field Feshbach resonance. Condensation of fermionic atom pairs in a $^{40}\mathrm{K}$ gas was demonstrated experimentally by a sweep technique that pairwise projects fermionic atoms onto molecules. In this paper, we examine previous data obtained with this technique that probed the phase boundary in the temperature-magnetic field plane. Comparison of the $^{40}\mathrm{K}$ data to a theoretically computed phase diagram demonstrates good agreement between the two.

Wolfgang Ketterle

Chih-Chun Chien, Qijin Chen, Yan He +1 more

We present phase diagrams for population-imbalanced, trapped Fermi superfluids near unitarity. In addition to providing quantitative values for the superfluid transition temperature, the pairing onset temperature, and the transition line (separating the Sarma and phase separation regimes), we study experimental signatures of these transitions based on density profiles and density differences at the center. Predictions on the BCS side of resonance show unexpected behavior, which should be searched for experimentally.

M. A. Baranov, Ł. Dobrek, Maciej Lewenstein

We derive the phase diagram for ultracold trapped dipolar Fermi gases. Below the critical value of the dipole-dipole interaction energy, the BCS transition into a superfluid phase ceases to exist. The critical dipole strength is obtained as a function of the trap aspect ratio. Alternatively, for a given dipole strength there is a critical value of the trap anisotropy for the BCS state to appear. The order parameter exhibits a novel nonmonotonic behavior at the criticality.

Andrew J. Robertson, Victor M. Galitski