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arXiv · 2603.08691

Fermi-pressure-assisted cavity superradiance in a mesoscopic Fermi gas

Francesca Orsi·Ekaterina Fedotova·Rohit Prasad Bhatt·Mae Eichenberger·Léa Dubois·Jean-Philippe Brantut
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Abstract

We study the superradiant phase transition of a mesoscopic Fermi gas comprising between a few tens and a few thousand $^6$Li atoms in a high-finesse cavity across a wide range of densities. We observe a non-monotonic variation of the superradiant threshold as a function of density, with a minimum reached when the Fermi and recoil wavevectors are comparable. The minimum corresponds to a crossover between Fermi pressure-assisted ordering and Pauli blocking of photon scattering, in good agreement with theory. This interpretation is confirmed by a study of the atom-number dependence of the ordering threshold and photon number scaling. Lastly, we demonstrate the operation of our mesoscopic system in a regime where light-induced forces are opposite for the two spin components, leading to an ordered phase with a spin-density-wave character. Our system opens the perspective of studying few-fermion systems with strong and coherent light-matter coupling.

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Francesca Orsi, Ekaterina Fedotova, Rohit Prasad Bhatt, Mae Eichenberger, Léa Dubois, Jean-Philippe Brantut. 2026-03-09. Fermi-pressure-assisted cavity superradiance in a mesoscopic Fermi gas. https://arxiv.org/abs/2603.08691

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