Note to users. If you're seeing this message, it means that your browser cannot find this page's style/presentation instructions -- or possibly that you are using a browser that does not support current Web standards. Find out more about why this message is appearing, and what you can do to make your experience of our site the best it can be.

Science 27 January 2006:
Vol. 311. no. 5760, p. 432
DOI: 10.1126/science.311.5760.432c
Prev | Table of Contents | Next

This Week in Science

The pairing of fermions lies at the heart of superconductivity in metals and superfluidity in helium-3, where the spin populations are generally equal. Exotic pairing states are expected to arise for imbalanced spin populations, such as in the pairing of quark matter in neutron stars and in strongly magnetized superconductors, but such systems are difficult to realize experimentally. The availability of cold atom clouds of mixed atomic spin states has allowed the crossover regime between Bose-Einstein condensates of molecules and Bardeen-Cooper-Schrieffer superfluids to be probed experimentally. Two studies now address the quantum nature and the phase transition of interacting Fermi gases of lithium-6 in which unbalanced populations of two different spins states are prepared (see the 23 December 2005 news story by Cho). Zwierlein et al. (p. 492, published online 22 December 2005) examined the condensate fraction and superfluidity as a function of spin imbalance and found that superfluidity is remarkably stable against population imbalance. Partridge et al. (p. 503, published online 22 December 2005) detail the spatial structure and polarization of the mixed spin system.




To Advertise     Find Products

Science. ISSN 0036-8075 (print), 1095-9203 (online)