We study the finite temperature-density phase diagram of an attractive fermionic system that supports two-body (dimer) and three-body (trimer) bound states in free space. Using interactions characteristic for nuclear systems, we obtain the critical temperature $T_{c2}$ for the superfluid phase transition and the limiting temperature $T_{c3}$ for the extinction of trimers. The phase diagram features a Cooper-pair condensate in the high-density, low-temperature domain which, with decreasing density, crosses over to a Bose condensate of strongly bound dimers. The high-temperature, low-density domain is populated by trimers whose binding energy decreases toward the density-temperature domain occupied by the superfluid and vanishes at a critical temperature $T_{c3}>T_{c2}$.

• Received 28 November 2005

DOI:https://doi.org/10.1103/PhysRevC.73.035803