Dimers of ultracold two-component Fermi gases on magnetic-field Feshbach resonance

TL;DR

This paper investigates the equilibrium properties of fermionic atom and dimer mixtures near a magnetic-field Feshbach resonance in the unitarity limit, providing theoretical insights that align with recent experimental observations.

Contribution

It introduces a simple theoretical model for the mixture of fermionic atoms and dimers at unitarity, explaining experimental results on molecule fractions and collective mode frequencies.

Findings

The dimer fraction matches experimental high zero-momentum molecule observations.

The model explains the observed radial breathing mode frequency.

The equilibrium state minimizes Gibbs free energy in the unitarity limit.

Abstract

At the location of a magnetic-field Feshbach resonance, a mixture gas of fermionic atoms and dimers of fermionic atom pairs is investigated in the unitarity limit where the absolute value of the scattering length is much larger than the mean distance between atoms. The dynamic equilibrium of the mixture gases is characterized by the minimum of the Gibbs free energy. For the fermionic atoms and dimers with divergent scattering length, it is found that the fraction of the dimers based on a very simple theory agrees with the high fraction of zero-momentum molecules observed in a recent experiment (M. W. Zwierlein et al, Phys. Rev. Lett. 92, 120403 (2004)). The dimeric gas can be also used to interpret the frequency of the radial breathing mode observed in the experiment by J. Kinast et al (Phys. Rev. Lett. 92, 150402 (2004)).