Role of fourth-order phase-space moments in collective modes of trapped Fermi gases

Abstract

We study the transition from hydrodynamic to collisionless behavior in collective modes of ultracold trapped Fermi gases. To that end, we solve the Boltzmann equation for the trapped Fermi gas via the moments method. We showed previously that it is necessary to go beyond second-order moments if one wants to reproduce the results of a numerical solution of the Boltzmann equation. Here, we will give the detailed description of the method including fourth-order moments. We apply this method to the case of realistic parameters, and compare the results for the radial quadrupole and scissors modes at unitarity to experimental data obtained by the Innsbruck group. It turns out that the inclusion of fourth-order moments clearly improves the agreement with the experimental data. In particular, the fourth-order moments reduce the effect of collisions and therefore partially compensate the effect of the enhanced in-medium cross section at low temperatures.

10 pages, 2 figures; published version

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• Collective modes of ultracold fermionic alkaline-earth gases with SU(N) symmetry
• Damping of the quadrupole mode in a two-dimensional Fermi gas
• Time-of-flight expansion of trapped dipolar Fermi gases: From the collisionless to the hydrodynamic regime
• Collective modes of an imbalanced unitary Fermi gas
• Shock waves in colliding Fermi gases at finite temperature
• Coupled oscillator model of a trapped Fermi gas at the BEC-BCS crossover
• Boltzmann equation with double-well potentials