Scientists at JILA, a joint laboratory of the Department of Commerce’s National Institute of Standards and Technology (NIST) and the University of Colorado at Boulder (CU-Boulder) report the first observation of a “fermionic condensate” formed from pairs of atoms in a gas, a long-sought, novel form of matter. The team hopes that such condensates eventually will help unlock the mysteries of high-temperature superconductivity, a phenomenon with the potential to improve energy efficiency dramatically across a broad range of applications.
For many decades, physicists have proposed that superconductivity (which involves fermions) and Bose-Einstein condensates (BEC) are closely linked. Theorists have hypothesized that superconductivity and BEC are two extremes of superfluid behavior, an unusual state where matter shows no resistance to flow. Superfluid liquid helium, for example, when poured into the center of an open container, will spontaneously flow up and over the sides of the container.
In the current experiment, a gas of 500,000 potassium atoms was cooled to temperatures below 50 billionths of a degree Celsius above absolute zero (minus 459 degrees Fahrenheit) and then a magnetic field was applied near a special “resonance” strength. This magnetic field coaxed the fermion atoms to match up into pairs, akin to the pairs of electrons that produce superconductivity, the phenomenon in which electricity flows with no resistance. The Jin group detected this pairing and the formation of a fermionic condensate for the first time on Dec. 16, 2003.
The temperature at which metals or alloys become superconductors depends on the strength of the “pairing” interaction between their electrons. The highest known temperature at which superconductivity occurs in any material is about minus 135 degrees Celsius (minus 216 degrees Fahrenheit).
Funding for the research was provided by NIST, the National Science Foundation, and the Hertz Foundation of Livermore, Calif.