Pseudogap Pairing of a Strongly Correlated Fermi Gas

22 June 2010

ACQAO theorists Hui Hu, Xia-Ji Liu, Peter D. Drummond, and visiting student Hui Dong at Swinburne University of Technology’s Centre for Atom Optics and Ultrafast Spectroscopy (CAOUS) have recently developed a new theoretical tool to elucidate the controversial pseudogap pairing in strongly correlated atomic Fermi gases.

This new theoretical framework is motived by a series of experiments at JILA (Colorado, USA), MIT (USA), Tokyo University (Japan) and SUT (Australia). All of these experiments focus on investigating the dynamical response of strongly-interacting ultra-cold Fermi gases to external fields. In this way, experimentalists have probed the dynamical structure of strongly correlated Fermi gases, to obtain information about mechanisms of pairing. Such questions have immediate relevance not just to ultra-cold atomic physics. They also help in the scientific understanding of other strongly interacting Fermi gases - from high-Tc superconductors to neutron stars - where there is a need to quantitatively decide which theoretical models are best.

This theoretical work is vitally important because, for the first time in this field, it was shown how to apply a high-temperature virial expansion to dynamical problems in this exciting research on ultra-cold Fermi gases. Such virial expansions have exceptional significance because they are free of the usual problem of unjustified theoretical approximations. In the past, this led to a plethora of competing theories, without any clear way to distinguish them. Instead, by the use of high temperature expansions, theorists are now able to make use of a small parameter, namely the inverse temperature. This still allows one to investigate the topical problem of pseudogap pairing above the critical point, and is an important step towards more extended use of this method.

This research shows an excellent agreement with recent experiments, where other methods have failed to obtain good agreement.

For more details, see:

Pseudogap Pairing in Ultracold Fermi Atoms.
Hui Hu, Xia-Ji Liu, Peter D. Drummond, and Hui Dong
Phys. Rev. Lett. 104, 240407 (2010)