Effects of periodic potentials on the critical velocity of superfluid Fermi gases in the BCS-BEC crossover

Journal Article · Tue Mar 15 00:00:00 EDT 2011 · Physical Review. A

DOI:https://doi.org/10.1103/PHYSREVA.83.033621· OSTI ID:21541348

Watanabe, Gentaro ^[1]; Dalfovo, Franco; Stringari, Sandro ^[2]; Pitaevskii, Lev P ^[2]

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1. Asia Pacific Center for Theoretical Physics (APCTP), POSTECH, San 31, Hyoja-dong, Nam-gu, Pohang, Gyeongbuk 790-784 (Korea, Republic of)
2. INO-CNR BEC Center and Department of Physics, University of Trento, I-38123 Povo (Italy)

We study the effects of an external periodic potential on the critical velocity of a superfluid Fermi gas in the crossover between the Bardeen-Cooper-Schrieffer (BCS) phase and Bose-Einstein condensation (BEC). We numerically solve the Bogoliubov-de Gennes equations to model a three-dimensional gas of ultracold atoms in the superfluid phase flowing through a one-dimensional optical lattice. We find that when the recoil energy is comparable to the Fermi energy, the presence of the periodic potential reduces the effect of pair-breaking excitations. This behavior is a consequence of the peculiar band structure of the quasiparticle energy spectrum in the lattice. When the lattice height is much larger than the Fermi energy, the periodic potential makes pairs of atoms to be strongly bound, even in the BCS regime, and pair-breaking excitations are further suppressed. We have also found that when the recoil energy is comparable to or larger than the Fermi energy, the critical velocity due to long-wavelength phonon excitations shows a nonmonotonic behavior along the BCS-BEC crossover.

• OSTI ID: 21541348
• Journal Information: Physical Review. A, Vol. 83, Issue 3; Other Information: DOI: 10.1103/PhysRevA.83.033621; (c) 2011 American Institute of Physics; ISSN 1050-2947
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
74 ATOMIC AND MOLECULAR PHYSICS
ATOMS
BCS THEORY
BOGOLYUBOV METHOD
BOSE-EINSTEIN CONDENSATION
CRITICAL VELOCITY
ENERGY SPECTRA
EXCITATION
FERMI GAS
ONE-DIMENSIONAL CALCULATIONS
PERIODICITY
PHONONS
POTENTIALS
RECOILS
SUPERFLUIDITY
THREE-DIMENSIONAL CALCULATIONS
WAVELENGTHS
CALCULATION METHODS
ENERGY-LEVEL TRANSITIONS
QUASI PARTICLES
SPECTRA
VARIATIONS
VELOCITY