We investigate the phase diagram and the BCS-BEC crossover of a homogeneous three-component ultracold Fermi gas with a U(3)-invariant attractive interaction. We show that the system at sufficiently low temperatures exhibits population imbalance as well as fermionic pairing. We describe the crossover in this system, connecting the weakly interacting BCS regime of the partially population-imbalanced fermion pairing state and the BEC limit with three weakly interacting species of molecules, including pairing fluctuations within a $t$-matrix calculation of the particle self-energies.

• Received 1 November 2010

DOI:https://doi.org/10.1103/PhysRevA.82.063615