Fermion condensate
A fermion condensate (also Fermi condensate ) is a superfluid aggregate state in a system of fermions . The effect is based - analogous to the Bose-Einstein condensate of bosons - on the superposition of the wave functions of the fermions involved, whereupon these assume a uniform quantum state .
generation
Fermions do not line up ( Pauli principle ), so it's only by a degeneration in the spin - quantum number possible. This is achieved in that two fermions each (with spin ½) combine to form a boson (spin 1), which in turn condense to form a Bose-Einstein condensate.
One possibility for this is that molecules of two fermions form and behave as bosons. Bose-Einstein condensates of such molecules were first produced almost simultaneously in 2003 by the working groups led by Rudolf Grimm at the University of Innsbruck and Deborah Jin at the American National Institute of Standards and Technology .
In contrast to the formation of molecules from two fermions, it is also conceivable that the two fermions interact over greater distances, as occurs, for example, in the analogous case of electrons ( Cooper pairs ) in superconductors . First steps in this direction were taken in 2004 with an ultracold gas made of potassium atoms in the research group of Deborah Jin. A similar effect is also for the superfluidity of helium - isotope 3 responsible He.
All of these phenomena are only possible at extremely low temperatures.
See also
Web links
- Sixth physical state discovered , article at heise online from February 1, 2004
- Phil Schewe, James Riordon, Ben Stein: BEC Made From Fermion Molecules. In: Physics News Update 663 # 1. American Institute of Physics , November 25, 2003, archived from the original July 8, 2008 ; Retrieved July 10, 2016 (report on the first discoveries of the Bose-Einstein condensation of fermion pairs in ultracold gases).
- Observation of Resonance Condensation of Fermionic Atom Pairs , article in the Physical Review Letters of January 28, 2004 (full text only for subscribers to the journal, e.g. universities) (English)
- Phil Schewe, James Riordon, Ben Stein: Halfway Across the BEC-BCS Prairie. In: Physics News Update 671 # 1. American Institute of Physics , January 30, 2004, archived from the original October 1, 2009 ; Retrieved on July 10, 2016 (English, explanations for the article mentioned).