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arXiv · 1901.11444

Enhanced critical temperature, pairing fluctuation effects, and BCS-BEC crossover in a two-band Fermi gas

Hiroyuki Tajima·Yuriy Yerin·Andrea Perali·Pierbiagio Pieri
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Abstract

We study the superfluid critical temperature in a two-band attractive Fermi system with strong pairing fluctuations associated with both interband and intraband couplings. We focus specifically on a configuration where the intraband coupling is varied from weak to strong in a shallow band coupled to a weakly-interacting deeper band. The whole crossover from the Bardeen-Cooper-Schrieffer (BCS) condensation of largely overlapping Cooper pairs to the Bose-Einstein condensation (BEC) of tightly bound molecules is covered by our analysis, which is based on the extension of the Nozières-Schmitt-Rink (NSR) approach to a two-band system. In comparison with the single-band case, we find a strong enhancement of the critical temperature, a significant reduction of the preformed pair region where pseudogap effects are expected, and the entanglement of two kinds of composite bosons in the strong-coupling BEC regime.

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Hiroyuki Tajima, Yuriy Yerin, Andrea Perali, Pierbiagio Pieri. 2019-05-28. Enhanced critical temperature, pairing fluctuation effects, and BCS-BEC crossover in a two-band Fermi gas. https://doi.org/10.1103/physrevb.99.180503

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