Thermodynamics of Interacting Fermions in Atomic Traps

We discuss the entropy $S$ for trapped Fermi gases as a function of temperature $T$ for a wide range of magnetic fields, using BCS--Bose-Einstein condensation (BEC) crossover theory and the BCS-Leggett mean field ground state. In the intermediate regime this approach has been shown to be in very good agreement with experiment. We demonstrate how, near unitarity, fermions at the trap edge dominate $S$, at all but $T \approx 0$ where bosonic contributions are more important. For general fields, these results provide a basis for thermometry, by enabling temperature estimates for regimes accessed adiabatically through field sweeps.