Achieving a BCS transition in an atomic Fermi gas

Lincoln D. Carr , Gora V. Shlyapnikov , Yvan Castin (1)

1 LKB (Lhomond) - Laboratoire Kastler Brossel

We consider a gas of cold fermionic atoms having two spin components with interactions characterized by their s-wave scattering length $a$. At positive scattering length the atoms form weakly bound bosonic molecules which can be evaporatively cooled to undergo Bose-Einstein condensation, whereas at negative scattering length BCS pairing can take place. It is shown that, by adiabatically tuning the scattering length $a$ from positive to negative values, one may transform the molecular Bose-Einstein condensate into a highly degenerate atomic Fermi gas, with the ratio of temperature to Fermi temperature $T/T_F \sim 10^{-2}$. The corresponding critical final value of $k_{F}|a|$ which leads to the BCS transition is found to be about one half, where $k_F$ is the Fermi momentum.

Domaines: Supraconductivité [cond-mat.supr-con]

Lincoln D. Carr, Gora V. Shlyapnikov, Yvan Castin. Achieving a BCS transition in an atomic Fermi gas. Physical Review Letters, 2004, 92, pp.150404. ⟨hal-00002433⟩