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Open AccessArticle

BCS-BEC Crossover and Pairing Fluctuations in a Two Band Superfluid/Superconductor: A T Matrix Approach

1
Department of Mathematics and Physics, Kochi University, Kochi 780-8520, Japan
2
Quantum Hadron Physics Laboratory, RIKEN Nishina Center, Wako, Saitama 351-0198, Japan
3
School of Pharmacy, Physics Unit, Università di Camerino, 62032 Camerino (MC), Italy
4
School of Science and Technology, Physics Division, Università di Camerino, 62032 Camerino (MC), Italy
5
INFN, Sezione di Perugia, 06123 Perugia (PG), Italy
*
Author to whom correspondence should be addressed.
Condens. Matter 2020, 5(1), 10; https://doi.org/10.3390/condmat5010010
Received: 5 December 2019 / Revised: 7 January 2020 / Accepted: 16 January 2020 / Published: 21 January 2020
We investigate pairing fluctuation effects in a two band fermionic system, where a shallow band in the Bardeen–Cooper–Schrieffer–Bose–Einstein condensation (BCS-BEC) crossover regime is coupled with a weakly interacting deep band. Within a diagrammatic T matrix approach, we report how thermodynamic quantities such as the critical temperature, chemical potential, and momentum distributions undergo the crossover from the BCS to BEC regime by tuning the intraband coupling in the shallow band. We also generalize the definition of Tan’s contact to a two band system and report the two contacts for different pair-exchange couplings. The present results are compared with those obtained by the simpler Nozières–Schmitt–Rink approximation. We confirm a pronounced enhancement of the critical temperature due to the multiband configuration, as well as to the pair-exchange coupling.
Keywords: multi-band superconductivity; BCS-BEC crossover; ultracold Fermi gases multi-band superconductivity; BCS-BEC crossover; ultracold Fermi gases
MDPI and ACS Style

Tajima, H.; Perali, A.; Pieri, P. BCS-BEC Crossover and Pairing Fluctuations in a Two Band Superfluid/Superconductor: A T Matrix Approach. Condens. Matter 2020, 5, 10.

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