Why only half of the fermionic atoms were converted to molecules by a Feshbach resonance?

Hui Hu, Feng Yuan, Shaojin Qin

In some recent experiments an ultracold gas of ${}^{40}$K${}_2$ (or ${}^6$Li${}_2$) molecules has been produced from a degenerate two-component Fermi gas of ${}^{40}$K (or ${}^6$Li) atoms…