Collective modes of low-dimensional superfluid Fermi gases in the BCS-BEC crossover: Time-dependent variational analysis

Journal Article · Thu Feb 15 00:00:00 EST 2007 · Physical Review. A

DOI:https://doi.org/10.1103/PHYSREVA.75.023611· OSTI ID:20982162

Zhou, Yu; Huang, Guoxiang ^[1]

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1. Department of Physics and Institute of Theoretical Physics, East China Normal University, Shanghai 200062 (China)

We investigate collective modes and free expansions of quasi-one- and quasi-two-dimensional (Q1D and Q2D) ultracold Fermi gases in the crossover from a Bardeen-Cooper-Schrieffer (BCS) superfluid to a Bose-Einstein condensate (BEC). We solve a superfluid order parameter equation valid for the BCS-BEC crossover by employing a time-dependent variational method. We take a trial wave function of hybrid Gaussian-parabolic type, which not only reflects the low-dimensional character of the system but also allows an essentially analytical approach for the problem. We present Q1D and Q2D criteria that are valid in various superfluid regimes and show clearly the relation between the maximum condensed particle number and the parameters of the trapping potential as well as the atom-atom interaction. We demonstrate that, due to the small particle number in Q1D and Q2D condensates, the contribution to oscillating frequencies of collective modes by the quantum pressure in the strong-confinement direction is significant and hence the Thomas-Fermi approximation cannot be used. We also show that the free expansion of Q1D and Q2D superfluid Fermi gases in the strong-confinement direction is much faster than that in the weak-confinement direction.

• OSTI ID: 20982162
• Journal Information: Physical Review. A, Vol. 75, Issue 2; Other Information: DOI: 10.1103/PhysRevA.75.023611; (c) 2007 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA); ISSN 1050-2947
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
APPROXIMATIONS
ATOMS
BCS THEORY
BOSE-EINSTEIN CONDENSATION
CONDENSATES
CONFINEMENT
EXPANSION
FERMI GAS
FERMIONS
PARTICLES
POTENTIALS
SUPERFLUIDITY
TEMPERATURE RANGE 0000-0013 K
THOMAS-FERMI MODEL
TIME DEPENDENCE
TRAPPING
TWO-DIMENSIONAL CALCULATIONS
VARIATIONAL METHODS
WAVE FUNCTIONS