{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,10,31]],"date-time":"2025-10-31T01:37:58Z","timestamp":1761874678974,"version":"build-2065373602"},"reference-count":37,"publisher":"MDPI AG","issue":"11","license":[{"start":{"date-parts":[[2025,10,30]],"date-time":"2025-10-30T00:00:00Z","timestamp":1761782400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"ANID\/FONDECYT","award":["1251928"],"award-info":[{"award-number":["1251928"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Entropy"],"abstract":"<jats:p>We investigate the thermal evolution of fermionic pairings in a finite-size SU(2) \u00d7 SU(2) complex model, drawing an analogy to the BCS-BEC crossover in interacting quantum gases. Unlike the conventional crossover, which is driven by tuning the interaction strength, our study suggests that temperature alone can induce a smooth transition from weakly bound Cooper pairs (BCS-like state) to tightly bound dimers (BEC-like state). Using an exactly solvable model with a finite number of fermions, we analyze the structure of eigenstates, pairing correlations, and thermodynamic response functions. We demonstrate that different multiplet structures, characterized by distinct quasi-spin quantum numbers, become thermally accessible, effectively mimicking the crossover behavior seen in ultracold Fermi gases. Our results provide new insights into the role of thermal fluctuations in quantum pairing phenomena and suggest alternative routes for exploring crossover physics in mesoscopic and strongly correlated systems.<\/jats:p>","DOI":"10.3390\/e27111116","type":"journal-article","created":{"date-parts":[[2025,10,31]],"date-time":"2025-10-31T01:23:59Z","timestamp":1761873839000},"page":"1116","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Thermal BCS-BEC Crossovers in Finite Systems"],"prefix":"10.3390","volume":"27","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-5934-2783","authenticated-orcid":false,"given":"Angelo","family":"Plastino","sequence":"first","affiliation":[{"name":"Instituto de F\u00edsica La Plata\u2013CCT-CONICET, Universidad Nacional de La Plata, C.C. 727, La Plata 1900, Argentina"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Flavia","family":"Pennini","sequence":"additional","affiliation":[{"name":"Departamento de F\u00edsica, Universidad Cat\u00f3lica del Norte, Av. Angamos 0610, Antofagasta 1270709, Chile"},{"name":"Departamento de F\u00edsica, Facultad de Ingenieria, Universidad Nacional de Mar del Plata (UNMDP), CONICET, Av. J.B. Justo 4302, Mar del Plata CP 7600, Argentina"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Victor","family":"Apel","sequence":"additional","affiliation":[{"name":"Departamento de F\u00edsica, Universidad Cat\u00f3lica del Norte, Av. Angamos 0610, Antofagasta 1270709, Chile"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2025,10,30]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","unstructured":"Parish, M.M. (2014). 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