Observation of the BEC-BCS crossover in a degenerate Fermi gas of lithium atoms

doi:10.1088/1674-1056/ac0dae

Abstract We observe characteristic atomic behaviors in the Bose-Einstein-condensation-Bardeen-Cooper-Schrieffer (BEC-BCS) crossover, by accurately tuning the magnetic field across the Feshbach resonance of lithium atoms. The magnetic field is calibrated by measuring the Zeeman shift of the optical transition. A non-monotonic anisotropic expansion is observed across the Feshbach resonance. The density distribution is explored in different interacting regimes, where a condensate of diatomic molecules forms in the BEC limit with the indication of a bimodal distribution. We also measure the three-body recombination atom loss in the BEC-BCS crossover, and find that the magnetic field of the maximum atom loss is in the BEC limit and gets closer to the Feshbach resonance when decreasing the atom temperature, which agrees with previous experiments and theoretical prediction. This work builds up a controllable platform for the study on the strongly interacting Fermi gas.

Keywords: BEC-BCS crossover three-body recombination anisotropic expansion

Received: 19 May 2021
Revised: 31 May 2021
Accepted manuscript online: 23 June 2021

PACS:	67.85.-d	(Ultracold gases, trapped gases)
	03.75.Ss	(Degenerate Fermi gases)
	67.10.Db	(Fermion degeneracy)

Fund: This work has been supported by the National Key Research and Development Program of China (Grant No. 2016YFA0301503), the National Natural Science Foundation of China (Grant Nos. 11674358, 11434015, and 11974384), Chinese Academy of Sciences (Grant No. YJKYYQ20170025), and K.C. Wong Education Foundation (Grant No. GJTD-2019-15)).

Corresponding Authors: Da-Li Sun, Da-Li Sun
E-mail: dlsun@wipm.ac.cn;kjjiang@wipm.ac.cn

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Xiang-Chuan Yan(严祥传), Da-Li Sun(孙大立), Lu Wang(王璐), Jing Min(闵靖), Shi-Guo Peng(彭世国), and Kai-Jun Jiang(江开军) Observation of the BEC-BCS crossover in a degenerate Fermi gas of lithium atoms 2022 Chin. Phys. B 31 016701

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