Quantum degenerate Fermi and Bose gases

Recent experiments performed with fermionic ⁶Li and ⁴⁰K atoms, which possess both Feshbach resonances at convenient magnetic fields are discussed. When ⁴⁰K is mixed with a Bose-Einstein condensate of ⁸⁷Rb, for sufficient atom numbers of both species, a collapse of the Fermi gas is observed. This is the result of the strong interspecies attractive interaction which overcomes the Fermi pressure in the quantum degenerate regime. As for the case of phonon-induced interaction between electrons in superconductors, it is predicted that the boson-fermion attractive interaction favors Cooper pairing of fermions when prepared in a mixture of two states.