Superfluidity and collective modes in a uniform gas of Fermi atoms with a Feshbach resonance

Journal Article · Sun Jun 01 00:00:00 EDT 2003 · Physical Review. A

DOI:https://doi.org/10.1103/PhysRevA.67.063612· OSTI ID:20639805

Ohashi, Y ^[1]; Griffin, A ^[2]

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1. Institute of Physics, University of Tsukuba, Ibaraki 305, (Japan)
2. Department of Physics, University of Toronto, Toronto, Ontario, Canada M5S 1A7 (Canada)

We investigate strong-coupling superfluidity in a uniform two-component gas of ultracold Fermi atoms attractively interacting via quasimolecular bosons associated with a Feshbach resonance. This interaction is tunable by the threshold energy 2{nu} of the Feshbach resonance, becoming large as 2{nu} is decreased (relative to 2{epsilon}{sub F}, where {epsilon}{sub F} is the Fermi energy of one component). In recent work, we showed that the enhancement of this tunable pairing interaction naturally leads to the BCS-BEC (Bose-Einstein condensation) crossover, where the character of the superfluid phase transition changes from the BCS type to a BEC of composite bosons consisting of preformed Cooper-pairs and Feshbach-induced molecules. In this paper, we extend our previous work and study both the quasiparticles and the collective dynamics of the superfluid phase below the phase-transition temperature T{sub c}, limiting ourselves to a uniform gas. We show how the superfluid order parameter changes from the Cooper-pair amplitude {delta} to the square root of the number of condensed molecules ({phi}{sub m}) associated with the Feshbach resonance, as the threshold energy 2{nu} is lowered. In the intermediate coupling regime, the superfluidity is shown to be characterized by an order parameter consisting of a superposition of {delta} and {phi}{sub m}. We also discuss the Goldstone mode associated with superfluidity, and show how its character smoothly changes from the Anderson-Bogoliubov phonon in the BCS regime to the Bogoliubov phonon in the BEC regime in the BCS-BEC crossover. The velocity of this Goldstone phonon mode is shown to strongly depend on the value of 2{nu}. We also show that this Goldstone mode appears as a resonance in the spectrum of the density-density correlation function, which is experimentally accessible.

• OSTI ID: 20639805
• Journal Information: Physical Review. A, Vol. 67, Issue 6; Other Information: DOI: 10.1103/PhysRevA.67.063612; (c) 2003 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA); ISSN 1050-2947
• Country of Publication: United States
• Language: English

Related Subjects

74 ATOMIC AND MOLECULAR PHYSICS
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
AMPLITUDES
ATOMS
BOSE-EINSTEIN CONDENSATION
COOPER PAIRS
CORRELATION FUNCTIONS
DENSITY
FERMIONS
INTERMEDIATE COUPLING
MOLECULES
ORDER PARAMETERS
PAIRING INTERACTIONS
PHASE TRANSFORMATIONS
PHONONS
RADIATION PRESSURE
RESONANCE
SUPERFLUIDITY
THRESHOLD ENERGY
TRANSITION TEMPERATURE