Universal thermodynamics of strongly interacting Fermi gases


Strongly interacting Fermi gases are of great current interest. Not only are fermions the most common particles in the universe, but they are also thought to have a universal thermodynamic behaviour for strong interactions1,2,3. Recent experiments on ultracold Fermi gases provide an unprecedented opportunity to test universality in the laboratory4,5,6,7,8. In principle this allows—for example—the interior properties of hot, dense neutron stars to be investigated on earth. Here we carry out a detailed test of this prediction. We analyse results from three ultracold fermion experiments involving two completely distinct atomic species in different kinds of atomic-trap environment6,7,8. The data are compared with the predictions of a recent strong-interaction theory9,10. Excellent agreement is obtained, with no adjustable parameters. By extrapolating to zero temperature, we show that the experimental measurements yield a many-body parameter β−0.59±0.07, describing the universal energy of strongly interacting Fermi gases.

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Figure 1: Illustration of the universal thermodynamics of a strongly interacting Fermi gas.
Figure 2: Analysis of the 40K experiment in JILA.
Figure 3: Analysis of the 6Li experiment at Duke.


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We are extremely grateful to J. E. Thomas and B. Clancy for many helpful discussions, and for sharing their data before publication. We also thank D. S. Jin and J. T. Stewart for communications on their data, and R. G. Hulet et al. for explaining their temperature measurements. This work was supported by an Australian Research Council Center of Excellence grant, the National Natural Science Foundation of China Grant No. NSFC-10574080, and the National Fundamental Research Program Grants Nos 2006CB921404 and 2006CB921306.

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Correspondence to Peter D. Drummond.

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Hu, H., Drummond, P. & Liu, X. Universal thermodynamics of strongly interacting Fermi gases. Nature Phys 3, 469–472 (2007). https://doi.org/10.1038/nphys598

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