Nous passons en revue quelques questions théoriques non résolues dans les gaz tridimensionnels de fermions à deux composantes, en nous inspirant des expériences réalisées récemment sur les atomes froids dans des pièges immatériels près d’une résonance de Feshbach magnétique. Nous distinguons successivement (i) les questions ouvertes apparaissant dans le problème à petit nombre de corps avec interactions de contact dites de Wigner–Bethe–Peierls — essentiellement la stabilité du gaz vis-à-vis de l’effet Efimov et le calcul des coefficients d’amas (ou du viriel), (ii) celles relevant de la théorie effective de basse énergie dite hydrodynamique quantique de Landau et Khalatnikov — essentiellement l’amortissement des modes de phonons et le temps de cohérence du condensat de paires liées, et enfin (iii) les questions nécessitant une résolution complète, microscopique, du problème à N corps, comme les propriétés précises de la branche d’excitation sonore (de Goldstone) du condensat de paires, ou de sa branche d’excitation collective (de Higgs) dans le continuum de paire brisée.
We review some unresolved theoretical issues in three-dimensional two-component Fermi gases, drawing on recent experiments on cold atoms in immaterial traps close to a magnetic Feshbach resonance. We distinguish successively (i) the open questions arising in the few-body problem with Wigner–Bethe–Peierls contact interactions—essentially the stability of the gas with respect to the Efimov effect and the calculation of the cluster (or virial) coefficients, (ii) those arising in the effective low-energy theory of Landau and Khalatnikov quantum hydrodynamics—essentially the damping of phonon modes and the coherence time of the condensate of pairs, and finally (iii) questions requiring a complete, microscopic solution of the many-body problem, such as the specific properties of the acoustic excitation branch (Goldstone) of the condensate of pairs, or its collective excitation branch (Higgs) in the broken-pair continuum.
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Keywords: Fermi gases, Quantum hydrodynamics, Efimov effect, Unitary limit, Contact interactions, Cluster or virial expansion, Higgs mode
Yvan Castin 1

@article{CRPHYS_2025__26_G1_393_0, author = {Yvan Castin}, title = {Questions ouvertes pour les gaz de fermions en interaction forte et de port\'ee nulle}, journal = {Comptes Rendus. Physique}, pages = {393--461}, publisher = {Acad\'emie des sciences, Paris}, volume = {26}, year = {2025}, doi = {10.5802/crphys.244}, language = {fr}, }
Yvan Castin. Questions ouvertes pour les gaz de fermions en interaction forte et de portée nulle. Comptes Rendus. Physique, Volume 26 (2025), pp. 393-461. doi : 10.5802/crphys.244. https://comptes-rendus.academie-sciences.fr/physique/articles/10.5802/crphys.244/
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