A generalized molecule approach capturing the Feshbach-induced pairing physics in the BEC-BCS crossover

By including the effect of a trap with characteristic energy given by the Fermi temperature T-F in a two-body two-channel model for Feshbach resonances, we reproduce the measured binding energy of ultracold molecules in a K-40 atomic Fermi gas. We also reproduce the experimental closed-channel fraction Z across the BEC-BCS crossover and into the BCS regime of a Li-6 atomic Fermi gas. We obtain the expected behavior Z proportional to root T-F at unitarity, together with the recently measured proportionality constant. Our results are also in agreement with recent measurements of the Z dependency on T-F on the BCS side, where a significant quantitative discrepancy between experimental data and theory's predictions has been repeatedly reported. In order to contrast with future experiments we report the proportionality constant at unitarity between Z and root T-F predicted by our model for a K-40 atomic Fermi gas.

Automated summary

By incorporating the effect of a trap with characteristic energy given by the Fermi temperature TF into a two-channel model for Feshbach resonances, the study successfully reproduces the binding energy of ultracold molecules and closed-channel fraction Z in atomic Fermi gases. The results are consistent with the expected behavior of Z proportional to root TF at unitarity, as well as recent measurements of the Z dependency on TF, providing valuable insights for future experiments.