Quantum fluctuations in the superfluid state of the BCS-BEC crossover

Journal Article · Fri Feb 15 00:00:00 EST 2008 · Physical Review. A

DOI:https://doi.org/10.1103/PHYSREVA.77.023626· OSTI ID:21140547

Diener, Roberto B; Sensarma, Rajdeep; Randeria, Mohit ^[1]

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1. Department of Physics, Ohio State University, Columbus, Ohio 43210 (United States)

We determine the effects of quantum fluctuations about the T=0 mean-field solution of the BCS-BEC crossover in a dilute Fermi gas using the functional integral method. These fluctuations are described in terms of the zero-point motion of collective modes and the virtual scattering of gapped quasiparticles. We calculate their effects on various measurable properties, including chemical potential, ground-state energy, the gap, the speed of sound and the Landau critical velocity. At unitarity, we find excellent agreement with quantum Monte Carlo and experimental results. In the BCS limit, we show analytically that we obtain Fermi liquid interaction corrections to thermodynamics including the Hartree shift. In the Bose-Einstein condensation (BEC) limit, we show that the theory leads to an approximate description of the reduction of the scattering length for bosonic molecules and also obtain quantum depletion of the Lee-Yang form. At the end of the paper, we describe a method to include feedback of quantum fluctuations into the gap equation, and discuss the problems of self-consistent calculations in satisfying Goldstone's theorem and obtaining ultraviolet finite results at unitarity.

• OSTI ID: 21140547
• Journal Information: Physical Review. A, Vol. 77, Issue 2; Other Information: DOI: 10.1103/PhysRevA.77.023626; (c) 2008 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
BCS THEORY
BOSE-EINSTEIN CONDENSATION
FERMI GAS
FLUCTUATIONS
FUNCTIONAL ANALYSIS
GROUND STATES
LEE-YANG THEORY
MATHEMATICAL SOLUTIONS
MEAN-FIELD THEORY
MONTE CARLO METHOD
POTENTIALS
QUASI PARTICLES
SCATTERING
SCATTERING LENGTHS
SOUND WAVES
SUPERFLUIDITY
TEMPERATURE RANGE 0000-0013 K
THERMODYNAMICS