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Séminaire Théorie : vendredi 22 septembre 2023 à 11h00

Andrea Tononi (Université Paris-Saclay, CNRS, LPTMS)

Titre : Self-bound fermionic mixtures in low dimensions

LPMMC, Salle G421


Résumé : Self-binding in Bose-Bose mixtures has received lots of theoretical [1] and experimental [2] attention in the recent years, and a few studies also discussed Bose-Fermi droplets [3]. Fermi-Fermi mixtures with zero-range interspecies attraction, however, are not expected to display self-bound states, since the fermions of one species should overcome a strong Pauli pressure to bind the fermions of the other. This repulsion is, in fact, the fundamental mechanism that provides stability of Fermi mixtures along the BCS-BEC crossover, in which the dimers repel and do not form larger clusters [4]. In our work [5], we find that a 1D Fermi-Fermi mixture with sufficiently large mass imbalance can form a self-bound state in the thermodynamic limit. This result elaborates our previous few-body analyses [6], and is based on a mean-field theory in which the heavy fermions are described within the Thomas-Fermi approximation, which is exact in the limit of large mass ratios. We are also extending our theory towards the 2D case, which is complicated by the same scaling with length of the kinetic energy and of the interaction energy of the system [7]. Our work sets the basis for understanding liquid-like states in fermionic gases.


[1] D. S. Petrov, Quantum Mechanical Stabilization of a Collapsing Bose-Bose Mixture, Phys. Rev. Lett. 115, 155302 (2015).

[2] C. R. Cabrera, et al., Quantum liquid droplets in a mixture of Bose-Einstein condensates, Science 359, 301 (2018).

[3] D. Rakshit, et al., Self-bound Bose–Fermi liquids in lower dimensions, New J. Phys. 21, 073027 (2019); T. Karpiuk, et al., Bistability of Bose–Fermi mixtures, New J. Phys. 22, 103025 (2020).

[4] D. S. Petrov, C. Salomon, and G. V. Shlyapnikov, Weakly bound dimers of fermionic atoms, Phys. Rev. Lett. 93, 090404 (2004).

[5] J. Givois, A. Tononi, and D. S. Petrov, Self-binding of one-dimensional fermionic mixtures with zero-range interspecies attraction, arXiv:2207.04742 , accepted for publication on SciPost Physics.

[6] A. Tononi, J. Givois, and D. S. Petrov, Binding of heavy fermions by a single light atom in one dimension, Phys. Rev. A 106, L011302 (2022).

[7] J. Givois, A. Tononi and D. S. Petrov, in preparation (2023).