Researchers demonstrated quite dramatically nearly 10 years ago that bosonic atoms (those with integer spin) can collapse into a common ground state, known as a Bose–Einstein condensate (BEC), in which all the atoms march in lock step. This strange state is reached when the gas is so cold that the separate atomic wavefunctions overlap. It was natural, then, to look for the equivalent of BEC in a gas of fermionic atoms (with half-integer spin). Of course, the Pauli exclusion principle prevents even two fermions from occupying the same ground state, but there are ways around this quantum restriction.
One way is to combine fermionic atoms into bosonic molecules and then cool such molecules into a condensate. In fact, it has proved easier to create a BEC from molecules made of fermions than from molecules made of bosons, because the former have longer lifetimes. (See Physics Today, Physics Today 0031-9228...
