Heat Capacity of a Strongly-Interacting Fermi Gas

We have measured the heat capacity of an optically-trapped, strongly-interacting Fermi gas of atoms. A precise input of energy to the gas is followed by single-parameter thermometry, which determines the empirical temperature parameter $\tilde{T}$ of the gas cloud. Our measurements reveal a clear transition in the heat capacity. The energy and the spatial profile of the gas are computed using a theory of the crossover from Fermi to Bose superfluids at finite temperature. The theory calibrates $\tilde{T}$, yields excellent agreement with the data, and predicts the onset of superfluidity at the observed transition point.