Unitary Fermi superfluid near the critical temperature: Thermodynamics and sound modes from elementary excitations

Year: 2022

Authors: Bighin G., Cappellaro A., Salasnich L.

Autors Affiliation: Heidelberg Univ, Inst Theoret Phys, Philosophenweg 19, D-69120 Heidelberg, Germany; Inst Sci & Technol Austria ISTA, Campus 1, A-3400 Klosterneuburg, Austria; Univ Padua, Dipartimento Fis Galileo Galilei, Via Marzolo 8, I-35122 Padua, Italy; Univ Padua, QTech, Via Marzolo 8, I-35122 Padua, Italy; Ist Nazl Fis Nucl, Sez Padova, Via Marzolo 8, I-35131 Padua, Italy; CNR, Ist Nazl Ott, Via Carrara 2, I-50019 Sesto Fiorentino, Italy.

Abstract: We compare recent experimental results [Science 375, 528 (2022)] of the superfluid unitary Fermi gas near the critical temperature with a thermodynamic model based on the elementary excitations of the system. We find good agreement between experimental data and our theory for several quantities such as first sound, second sound, and superfluid fraction. We also show that mode mixing between first and second sound occurs. Finally, we characterize the response amplitude to a density perturbation: Close to the critical temperature both first and second sound can be excited through a density perturbation, whereas at lower temperatures only the first sound mode exhibits a significant response.

Journal/Review: PHYSICAL REVIEW A

Volume: 105 (6)      Pages from: 63329-1  to: 63329-6

More Information: The authors gratefully acknowledge stimulating discussions with T. Enss, and thank an anonymous referee for suggestions and remarks that allowed us to improve the original manuscript. This work is supported by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) under Germany’s Excellence Strategy EXC2181/1-390900948 (the Heidelberg STRUCTURES Excellence Cluster).
KeyWords: 2nd Sound; Universal Thermodynamics; Bose-condensation; Viscosity; Crossover; Gas; State
DOI: 10.1103/PhysRevA.105.063329

Citations: 3
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