Collective modes of trapped Fermi gases with in-medium interaction

Abstract

Due to Pauli blocking of intermediate states, the scattering matrix (or $T$ matrix) of two fermionic atoms in a Fermi gas becomes different from that of two atoms in free space. This effect becomes particularly important near a Feshbach resonance, where the interaction in free space is very strong but becomes effectively suppressed in the medium. We calculate the in-medium $T$ matrix in ladder approximation and study its effects on the properties of collective modes of a trapped gas in the normal-fluid phase. We introduce the in-medium interaction on both sides of the Boltzmann equation, namely in the calculation of the mean field and in the calculation of the collision rate. This allows us to explain the observed upward shift of the frequency of the quadrupole mode in the collisionless regime. By including the mean field, we also improve considerably the agreement with the measured temperature dependence of frequency and damping rate of the scissors mode, whereas the use of the in-medium cross section deteriorates the description, in agreement with previous work.

17 pages

References in corpus (10)

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Cited by in corpus (6)

• Collective excitations of quasi-two-dimensional trapped dipolar fermions: transition from collisionless to hydrodynamic regime
• Heat and spin transport in a cold atomic Fermi gas
• Numerical solution of the Boltzmann equation for trapped Fermi gases with in-medium effects
• Trap anharmonicity and sloshing mode of a Fermi gas
• Dynamic Structure Factor of Normal Fermi Gas from Collisionless to Hydrodynamic Regime
• Effects of interaction on field-induced resonances in confined Fermi liquid