Ultracold Fermion Cooling Cycle using Heteronuclear Feshbach Resonances
  We consider an ideal gas of Bose and Fermi atoms in a harmonic trap, with a Feshbach resonance in the interspecies atomic scattering that can lead to formation of fermionic molecules. We map out the phase diagram for this three-component mixture in chemical and thermal equilibrium. Considering adiabatic association and dissociation of the molecules, we identify a possible cooling cycle, which in ideal circumstances can yield an exponential increase of the phase-space density. 
M. A. Morales, N. Nygaard, J. E. Williams and Charles W. Clark