Optically Trapped Gas Offers Superconductivity Test Bed

According to researchers at Duke University in Durham, N.C., optically trapped atomic Fermi gases with magnetically tunable strong interactions have the potential to form the basis of a desktop laboratory for testing nonperturbative theories in systems ranging from superconductors to neutron stars. In research detailed in the Nov. 7 edition of Science, they cooled a fermionic gas of ⁶Li atoms to degeneracy in an optical trap by applying a 910-G magnetic field. This induced strong interactions that reportedly exhibit behavior universal to all fermionic systems.

Using forced evaporation in the optical trap, the scientists cooled 1.5 x 10⁵ atoms to a temperature of less than 1.5 µK in 3.5 s. The final temperature is low compared with the Fermi temperature of 8 µK, at which degeneracy first occurs. Release from the cigar-shaped optical trap produces anisotropic expansion that recent predictions indicate is a signature of superfluidity, where the Fermi gas becomes an analog of a high-temperature superconductor.