Pantheon SEMPARIS Le serveur des séminaires parisiens Paris

Status Confirmed
Seminar Series SEM-LPTMC
Subjects cond-mat
Date Monday 25 September 2023
Time 10:45
Institute LPTMC
Seminar Room campus Jussieu, couloir 12-13, 5ème, salle 5-23
Speaker's Last Name Kurkjian
Speaker's First Name Hadrien
Speaker's Email Address
Speaker's Institution LPT Toulouse
Title The normal Fermi gas: a Fermi liquid?
Abstract Landau's Fermi liquid theory provides an effective description of a low-temperature fermionic system in the form of a dilute gas of quasiparticles confined to the Fermi level. It remarkably applies to systems whose microscopic physics is poorly understood, such as Helium-3, and successfully describes their long wavelength collective modes, in particular the phononic ones. However, due to the difficulty of solving exactly the quasiparticle transport equation in the case of arbitrary interactions, Landau's theory is generally used only in the hydrodynamic or collisionless limiting cases. In the case of a two-component ultracold Fermi gas in its normal phase, the simplicity of contact interactions has allowed us to go further and describe the entire transition from the hydrodynamic to the collisionless regime. In the weakly-interacting limit, our results are in excellent quantitative agreement with density-density response measurements performed by the Yale group, where the resonance corresponding to the first sound emerges from the Lindhard function of the non-interacting gas. In time-of-flight images, which enable tomography of the Fermi liquid, this evolution corresponds to a drastic change in the distribution of quasiparticles on the Fermi sphere. While the density response thus seems to be very well described by Landau's theory, I will show that non-Fermi liquid properties appear in the pairing susceptibility, near the superfluid critical temperature.
arXiv Preprint Number

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