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arXiv:2108.11134 · Physical Review A

Dynamics of large samples of repulsive Fermi gases at nonzero temperatures

Jarosław Ryszkiewicz, Mirosław Brewczyk, Tomasz Karpiuk

Published Feb 14, 2022• 2 citations
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Abstract

We develop a model of a binary fermionic mixture, consisting of a large number of atoms, applicable at nonzero temperatures, in the normal phase. We use this approach to study the dynamics of degenerate Fermi systems under various perturbations. For example, we analyze the spin-dipole oscillations of a two-component fermionic mixture, demonstrating that the ferromagnetic phase shows up at a stronger repulsion between components while the temperature rises. We study as well the radial oscillations of weakly interacting repulsive Fermi gases. We obtain a good agreement with experimental data when available. Otherwise, we compare our results with the outcome of the Hartree-Fock orbital calculations done for a system with a small number of fermions.

DOI
10.1103/physreva.105.023315

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We consider a mixture of two-component Fermi gases at low temperature. The density profile of this degenerate Fermi gas is calculated under the semiclassical approximation. The results show that the fermion-fermion interactions make a large correction to the density profile at low temperature. The phase separation of such a mixture is also discussed for both attractive and repulsive interatomic interactions, and the numerical calculations demonstrate the existance of a stable temperature region T c1 < T < T c2 for the mixture. In addition, we give the critical temperature of the BCS-type transition in this system beyond the semiclassical approximation.
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We examine the spin asymmetry of ground states for two-dimensional, harmonically trapped two-component gases of fermionic atoms at zero temperature with weakly repulsive short range interactions. Our main result is that, in contrast to the three-dimensional case, in two dimensions a non-trivial spin-asymmetric phase can only be caused by shell structure. A simple, qualitative description is given in terms of an approximate single particle model, comparing well to the standard results of Hartree-Fock or direct diagonalization methods.