An effective theory of Feshbach resonances and many-body properties of Fermi gases

TL;DR

This paper develops an effective theory for Feshbach resonances in Fermi gases, highlighting strong many-body effects in systems like $^{6}$Li and $^{40}$K, and calculating properties such as quasiparticle effective mass and lifetime.

Contribution

It introduces a new effective theory parameterized by atom-molecule coupling and molecular magnetic moment, capturing many-body effects in Fermi gases near Feshbach resonances.

Findings

Strong many-body effects are present even at large resonance energies.

Calculated quasiparticle effective mass and lifetime in Fermi gases.

Resonance parameters significantly influence many-body properties.

Abstract

For calculating low-energy properties of a dilute gas of atoms interacting via a Feshbach resonance, we develop an effective theory in which the parameters that enter are an atom-molecule coupling strength and the magnetic moment of the molecular resonance. We demonstrate that for resonances in the fermionic systems $^{6}$Li and $^{40}$K that are under experimental investigation, the coupling is so strong that many-body effects are appreciable even when the resonance lies at an energy large compared with the Fermi energy. We calculate a number of many-body effects, including the effective mass and the lifetime of atomic quasiparticles in the gas.