Thermodynamics of ultracold fermions in traps in the strongly interacting regime

We discuss the entropy $S$, energy $E$ for trapped fermionic gases, over the entire range from BCS to BEC, and over all $T$ from below to above $T_c$. Our work, which is based on the conventional mean field ground state, shows that both ``bosonic" and fermionic excitations contribute to $S$, and that boson-fermion interactions are essential. Trap edge effects lead to low $T$ power law contributions for the fermions in the unitary and BCS regimes, while bosons contribute to $S$ with a $T^{3/2}$ dependence. Comparison with recent experiments by the Thomas group (cond-mat/0409283) shows very good quantitative agreement. This lays the groundwork for implementing thermometry in strongly interacting Fermi gases. \\ 1. Q.J. Chen, J. Stajic, and K. Levin, \textit{Thermodynamics of ultracold fermions in traps}, cond-mat/0411090; submitted to \textbf{Science}. \\ 2. J. Stajic, Q.J. Chen, K.Levin, \textit{Measuring condensates in fermionic superfluids via density profiles in traps}, cond-mat/0408104. \\ 3. Q.J. Chen, J. Stajic, S.N. Tan, K. Levin, \textit{BCS-BEC crossover: From high temperature superconductors to ultracold superfluids}, cond-mat/0404274.