Editing Fermionic condensate (section)

==Background==

===Superfluidity===
Fermionic condensates are attained at lower temperatures than Bose–Einstein condensates. Fermionic condensates are a type of [[superfluid]]. As the name suggests, a superfluid possesses fluid properties similar to those possessed by ordinary [[liquid]]s and [[gas]]es, such as the lack of a definite shape and the ability to flow in response to applied forces. However, superfluids possess some properties that do not appear in ordinary matter. For instance, they can flow at high velocities without dissipating any energy—i.e. zero [[viscosity]]. At lower velocities, energy is dissipated by the formation of [[quantized vortex|quantized vortices]], which act as "holes" in the medium where superfluidity breaks down. Superfluidity was originally discovered in liquid [[helium-4]] whose atoms are [[boson]]s, not fermions.

=== Fermionic superfluids ===
It is far more difficult to produce a fermionic superfluid than a bosonic one, because the [[Pauli exclusion principle]] prohibits fermions from occupying the same [[quantum state]]. However, there is a well-known mechanism by which a superfluid may be formed from fermions: That mechanism is the [[BCS theory|BCS transition]], discovered in 1957 by [[John Bardeen|J.&nbsp;Bardeen]], [[Leon Neil Cooper|L.N.&nbsp;Cooper]], and [[John Robert Schrieffer|R.&nbsp;Schrieffer]] for describing superconductivity. These authors showed that, below a certain temperature, electrons (which are fermions) can pair up to form bound pairs now known as [[Cooper pair]]s. As long as collisions with the ionic lattice of the solid do not supply enough energy to break the Cooper pairs, the electron fluid will be able to flow without dissipation. As a result, it becomes a superfluid, and the material through which it flows a superconductor.

The BCS theory was phenomenally successful in describing superconductors. Soon after the publication of the BCS paper, several theorists proposed that a similar phenomenon could occur in fluids made up of fermions other than electrons, such as [[helium-3]] atoms. These speculations were confirmed in 1971, when experiments performed by [[Douglas D. Osheroff|D.D.&nbsp;Osheroff]] showed that helium-3 becomes a superfluid below 0.0025&nbsp;K. It was soon verified that the superfluidity of helium-3 arises from a BCS-like mechanism.{{efn|The theory of superfluid helium-3 is a little more complicated than the BCS theory of superconductivity. These complications arise because helium atoms repel each other much more strongly than electrons, but the basic idea is the same.}}

=== Condensates of fermionic atoms ===
When [[Eric Cornell]] and [[Carl Wieman]] produced a Bose–Einstein condensate from [[rubidium]] [[atom]]s in 1995, there naturally arose the prospect of creating a similar sort of condensate made from fermionic atoms, which would form a superfluid by the BCS mechanism. However, early calculations indicated that the temperature required for producing Cooper pairing in atoms would be too cold to achieve. In 2001, Murray Holland at [[JILA]] suggested a way of bypassing this difficulty. He speculated that fermionic atoms could be coaxed into pairing up by subjecting them to a strong [[magnetic field]].

In 2003, working on Holland's suggestion, [[Deborah S. Jin|Deborah Jin]] at JILA, [[Rudolf Grimm]] at the [[University of Innsbruck]], and [[Wolfgang Ketterle]] at [[MIT]] managed  to coax fermionic atoms into forming molecular bosons, which then underwent Bose–Einstein condensation. However, this was not a true fermionic condensate. On December 16, 2003, Jin managed to produce a condensate out of fermionic atoms for the first time. The experiment involved 500,000&nbsp;[[potassium]]-40 atoms cooled to a temperature of 5×10<sup>−8</sup>&nbsp;K, subjected to a time-varying magnetic field.<ref name=":0">{{Cite journal |last1=Regal |first1=C.A. |last2=Greiner |first2=M. |last3=Jin |first3=D.S. |date=2004-01-28 |df=dmy-all |title=Observation of resonance condensation of Fermionic atom pairs|journal=Physical Review Letters |volume=92 |issue=4 |pages=040403 |doi=10.1103/PhysRevLett.92.040403 |pmid=14995356 |arxiv=cond-mat/0401554|bibcode=2004PhRvL..92d0403R |s2cid=10799388 }}</ref>