https://doi.org/10.1140/epjs/s11734-025-02021-z
Regular Article
Precision thermodynamics of the strongly interacting Fermi gas in two dimensions
1
Center for Theoretical Physics, Sloane Physics Laboratory, Yale University, 06520, New Haven, Connecticut, USA
2
Department of Physics and Astronomy, University of Louisville, 40292, Louisville, Kentucky, USA
a
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Received:
11
August
2025
Accepted:
10
October
2025
Published online:
28
October
2025
Abstract
The two-species cold atomic Fermi gas with attractive short-range interactions in two spatial dimensions undergoes a Bardeen–Cooper–Schrieffer (BCS) to a Bose–Einstein condensate (BEC) crossover as a function of 
, where a is the scattering length. However, the nature of this crossover in the strong coupling regime, 
, remains poorly understood. In this work, we use canonical ensemble auxiliary-field quantum Monte Carlo methods on discrete lattices to calculate several thermodynamical quantities in the strongly interacting regime, and eliminate systematic errors by extrapolating to continuous time and taking the continuum limit. In particular, we present results for the condensate fraction, spin susceptibility, contact, energy equation of state, and the free energy staggering gap. We identify signatures of a pseudogap regime, in which pairing correlations survive above the critical temperature for superfluidity, in the spin susceptibility and in the free energy staggering gap. These results can be used as a benchmark for future experiments.
Supplementary Information The online version contains supplementary material available at https://doi.org/10.1140/epjs/s11734-025-02021-z.
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© The Author(s), under exclusive licence to EDP Sciences, Springer-Verlag GmbH Germany, part of Springer Nature 2025
Springer Nature or its licensor (e.g. a society or other partner) holds exclusive rights to this article under a publishing agreement with the author(s) or other rightsholder(s); author self-archiving of the accepted manuscript version of this article is solely governed by the terms of such publishing agreement and applicable law.
