Polarised Fermi gases within the T-matrix approach
ABSTRACT :
With ultracold fermionic atoms one can realise the crossover from a Bose-Einstein condensate (BEC) of bound dimers to a superfluid of Cooper pairs (BCS phase). The critical temperature in the BEC-BCS crossover can be described by the Nozieres-Schmitt-Rink (NSR) theory based on the non-self-consistent T matrix (ladder approximation). However, in the polarised case (unequal population of the two spin states), the NSR theory fails, and actually it already fails in the calculation of the spin susceptibility of the unpolarised system. In this talk I will show that the inclusion of the quasiparticle energy shift in the T-matrix calculation helps to overcome these problems, although there remain still unsolved problems in the theoretical description of the phase diagram of the polarised Fermi gas.