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| Format: | Preprint |
| Veröffentlicht: |
2026
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| Online-Zugang: | https://arxiv.org/abs/2604.18798 |
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| _version_ | 1866915946300440576 |
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| author | Filothodoros, Evangelos G. |
| author_facet | Filothodoros, Evangelos G. |
| contents | We study the BCS--BEC crossover of the large $N$ attractive Fermi-Hubbard model on a one-dimensional lattice using the mean field approximation in the presence of an imaginary chemical potential. We show that the crossover is governed by three parameters. The imaginary chemical potential $iθ$, the temperature via a thermal kernel $g(βE_k,βθ)$ and the parameter $δ_u$ whose sign controls the weak and strong coupling regimes. At the unitarity point ($U=U_c$), we find a thermal window $ϕ=βθ=2π/3,4π/3$ where the gap vanishes while the fermion number $N_f$, which quantifies the balance between particle-like and hole-like excitations, has a local maximum/minimum. Inside this thermal window BCS and BEC physics are await changes in the coupling to be selected as the dominant regime. We expect that our results will unveil a better understanding of pairing correlations in lattice many-body physics. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2604_18798 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | Thermal Phase Structure of the Attractive Fermi Hubbard Model with Imaginary Chemical Potential Filothodoros, Evangelos G. High Energy Physics - Theory Quantum Gases We study the BCS--BEC crossover of the large $N$ attractive Fermi-Hubbard model on a one-dimensional lattice using the mean field approximation in the presence of an imaginary chemical potential. We show that the crossover is governed by three parameters. The imaginary chemical potential $iθ$, the temperature via a thermal kernel $g(βE_k,βθ)$ and the parameter $δ_u$ whose sign controls the weak and strong coupling regimes. At the unitarity point ($U=U_c$), we find a thermal window $ϕ=βθ=2π/3,4π/3$ where the gap vanishes while the fermion number $N_f$, which quantifies the balance between particle-like and hole-like excitations, has a local maximum/minimum. Inside this thermal window BCS and BEC physics are await changes in the coupling to be selected as the dominant regime. We expect that our results will unveil a better understanding of pairing correlations in lattice many-body physics. |
| title | Thermal Phase Structure of the Attractive Fermi Hubbard Model with Imaginary Chemical Potential |
| topic | High Energy Physics - Theory Quantum Gases |
| url | https://arxiv.org/abs/2604.18798 |