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Microscopic description of the twist mode in normal and superfluid trapped Fermi gases
Grasso, Marcella; Urban, Michael; Viñas Gausí, Xavier
Universitat de Barcelona
We investigate the "twist" mode (rotation of the upper against the lower hemisphere) of a dilute atomic Fermi gas in a spherical trap. The normal and superfluid phases are considered. The linear response to this external perturbation is calculated within the microscopic Hartree-Fock-Bogoliubov approach. In the normal phase the excitation spectrum is concentrated in a rather narrow peak very close to the trapping frequency. In the superfluid phase the strength starts to be damped and fragmented and the collectivity of the mode is progressively lost when the temperature decreases. In the weak-pairing regime some reminiscence of the collective motion still exists, whereas in the strong-pairing regime the twist mode is completely washed out. The disappearance of the twist mode in the strong-pairing regime with decreasing temperature is interpreted in the framework of the two-fluid model.
Matèria condensada
Estructura nuclear
Models nuclears
Gas d'electrons
Teoria de l'aproximació
Condensed matter
Nuclear structure
Nuclear models
Electron gas
Approximation theory
(c) The American Physical Society, 2005
The American Physical Society

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