Shift of the molecular bound state threshold in dense ultracold Fermi gases with Feshbach resonance

Abstract

We consider a dense ultracold Fermi gas in the presence of a Feshbach resonance. We investigate how the treshold for bound state formation, which is just at the Feshbach resonance for a dilute gas, is modified due to the presence of the Fermi sea. We make use of a preceding framework of handling this many-body problem. We restrict ourselves to the simple case where the chemical potential $\mu$ is negative, which allows us to cover in particular the classical limit where the effect is seen to disappear. We show that, within a simple approach where basically only the effect of Pauli exclusion is included, the Fermi sea produces a large shift of the threshold, which is of order of the width of the Feshbach resonance. This is in agreement with very recent experimental findings.

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• Atom Loss Maximum in Ultra-cold Fermi Gases
• Efimov three-body states on top of a Fermi sea
• Dressed-molecules in resonantly-interacting ultracold atomic Fermi gases
• Peaks and widths of radio-frequency spectra: An analysis of the phase diagram of ultra-cold Fermi gases