Evolution of the vortex state in the BCS-BEC crossover of a quasi two-dimensional superfluid Fermi gas

doi:10.1088/1674-1056/25/11/110306

Abstract We use the path-integral formalism to investigate the vortex properties of a quasi-two dimensional (2D) Fermi superfluid system trapped in an optical lattice potential. Within the framework of mean-field theory, the cooper pair density, the atom number density, and the vortex core size are calculated from weakly interacting BCS regime to strongly coupled while weakly interacting BEC regime. Numerical results show that the atoms gradually penetrate into the vortex core as the system evolves from BEC to BCS regime. Meanwhile, the presence of the optical lattice allows us to analyze the vortex properties in the crossover from three-dimensional (3D) to 2D case. Furthermore, using a simple re-normalization procedure, we find that the two-body bound state exists only when the interaction is stronger than a critical one denoted by G_c which is obtained as a function of the lattice potential's parameter. Finally, we investigate the vortex core size and find that it grows with increasing interaction strength. In particular, by analyzing the behavior of the vortex core size in both BCS and BEC regimes, we find that the vortex core size behaves quite differently for positive and negative chemical potentials.

Keywords: ultra-cold quantum gases superconductivity/superfluidity vortex BCS-BEC crossover

Received: 30 March 2016
Revised: 28 June 2016
Accepted manuscript online:

PACS:	03.75.Ss	(Degenerate Fermi gases)
	03.75.Lm	(Tunneling, Josephson effect, Bose-Einstein condensates in periodic potentials, solitons, vortices, and topological excitations)
	37.10.Jk	(Atoms in optical lattices)

Fund: Project supported by the National Natural Science Foundation of China (Grant Nos. 51331006, 51590883, and 11204321) and the Project of Chinese Academy of Sciences (Grant No. KJZD-EW-M05-3).

Corresponding Authors: Kezhao Zhou
E-mail: kezhaozhou@gmail.com

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Xuebing Luo(罗学兵), Kezhao Zhou(周可召), Zhidong Zhang(张志东) Evolution of the vortex state in the BCS-BEC crossover of a quasi two-dimensional superfluid Fermi gas 2016 Chin. Phys. B 25 110306

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Evolution of the vortex state in the BCS-BEC crossover of a quasi two-dimensional superfluid Fermi gas

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