Strongly Interacting Polarized Fermi Gases

20 July 2007

Recently, the superfluidity in trapped ultracold Fermi gases becomes the hot point in physics. Particularly, Fermi gases with unequal spin populations have been the subject of considerable experimental and theoretical interest. This is a new area of research which has attracted a great amount of interest from widely varying fields such as condensed matter physics, atomic molecular and optical physics, to particle and astro physics. Since the BCS pairing requires an equal number of atoms in each spin state, the presence of spin population imbalance leads to some exotic forms of pairing. The recent experimental observations by MIT and Rice University open up the intriguing possibilities for resolving this long-standing problem.

Motivated by these significant experimental developments, the theory group at ACQAO at the University of Queensland explores the phase diagram, vortex bound states and thermodynamic properties of imbalanced Fermi gases near the broad Feshbach resonance. One paper describing the one-dimensional phase diagram entitled “Phase diagram of a strongly interacting polarized Fermi gas in one dimension” was published in Physical Review Letters 98, 070403 (2007) by Hui Hu, Xia-Ji Liu and Peter D. Drummond. Another paper about vortex states entitled “Visualization of vortex bound state in polarized Fermi gases in unitarity” was also published in Physical Review Letters 98, 060406 (2007) by Hui Hu, Xia-Ji Liu and Peter D. Drummond. For more information please see these papers.

Figure 1

The sudden rise of density difference at the core center at low temperatures provides a way to visualize the lowest bound state using phase contrast imaging.

Figure 2

Density profiles show two exotic phase separation states. These phases can be diagnosed by measuring the lowest density compressional mode.