Zero-Temperature Properties of a Strongly Interacting Superfluid Fermi Gas in the BCS–BEC Crossover Region
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We investigate thermodynamic properties and effects of quantum fluctuations in the Bardeen–Cooper–Schrieffer (BCS)–Bose–Einstein condensation (BEC) crossover region of a superfluid Fermi gas in the low-temperature limit. Including strong-coupling corrections within the framework of an extended T-matrix approximation, we numerically compute the isothermal compressibility \(\chi _n\). While quantum fluctuation effects on \(\chi _n\) in the strong-coupling BEC regime are explained by the quantum depletion due to a repulsive interaction between tightly bound molecules, effects of self-energy shift on the Fermi chemical potential are found to enhance \(\chi _n\) in the weak-coupling BCS region. We also show that the calculated \(\chi _n\) agrees well with the recent experiment on a \(^6\)Li Fermi gas done from the weak-coupling region to the unitarity limit. Our result would be useful for the study of many-body quantum corrections in the BCS–BEC crossover region of a strongly interacting Fermi superfluid.
KeywordsUltracold Fermi gas BCS–BEC crossover Quantum fluctuations
We thanks to M. Matsumoto for useful discussions. This work was supported by KiPAS project in Keio University. H.T. and R.H. were supported by a grant-in-aid for JSPS fellows. D.I. was supported by grant-in-aid for Young Scientists (B) from JSPS in Japan (No.16K17773). M.H. was supported by grant-in-aid for Scientific Research on Innovative Areas (No. 24105006) and grant-in-aid for Young Scientists (A) from JSPS in Japan (No. 23684033). Y.O. was supported by grant-in-aid for Scientific Research from MEXT and JSPS in Japan (No.15H00840,No.15K00178,No.16K05503).
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