Critical velocity of superfluid flow through single barrier and periodic potentials

Abstract

We investigate the problem of an ultracold atomic gas in the superfluid phase flowing in the presence of a potential barrier or a periodic potential. We use a hydrodynamic scheme in the local density approximation (LDA) to obtain an analytic expression for the critical current as a function of the barrier height or the lattice intensity, which applies to both Bose and Fermi superfluids. In this scheme, the stationary flow becomes energetically unstable when the local superfluid velocity is equal to the local sound velocity at the point where the external potential is maximum. We compare this prediction with the results of the numerical solutions of the Gross-Pitaevskii and Bogoliubov-de Gennes equations. We discuss the role of long wavelength excitations in determining the critical velocity. Our results allow one to identify the different regimes of superfluid flow, namely, the LDA hydrodynamic regime, the regime of quantum effects beyond LDA for weak barriers and the regime of tunneling between weakly coupled superfluids for strong barriers. We finally discuss the relevance of these results in the context of current experiments with ultracold gases.

10 pages, 6 figures; appendix extended, to appear in Phys. Rev. A

References in corpus (10)

• Theory of ultracold Fermi gases
• Observation of persistent flow of a Bose-Einstein condensate in a toroidal trap
• Optical ferris wheel for ultracold atoms
• Critical velocity for superfluid flow across the BEC-BCS crossover
• Bose-Einstein condensates in 1D optical lattices: compressibility, Bloch bands and elementary excitations
• The Josephson effect throughout the BCS-BEC crossover
• DC Josephson Effect with Fermi gases in the Bose-Einstein regime
• Collective modes and superflow instabilities of strongly correlated Fermi superfluids
• Stability of Superflow for Ultracold Fermions in Optical Lattices
• Equation of state and effective mass of the unitary Fermi gas in a 1D periodic potential

Cited by in corpus (14)

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• The critical velocity in the BEC-BCS crossover
• Connecting dissipation and phase slips in a Josephson junction between fermionic superfluids
• Temperature induced decay of persistent currents in a superfluid ultracold gas
• Instability of the superfluid flow as black-hole lasing effect
• Effects of periodic potentials on the critical velocity of superfluid Fermi gases in the BCS-BEC crossover
• Cubic-quintic nonlinearity in superfluid Bose-Bose mixtures in optical lattices: Heavy solitary waves, barrier-induced criticality, and current-phase relations
• Critical velocity for superfluidity in the one-dimensional mean-field regime: From matter to light quantum fluids
• Time-resolved density correlations as probe of squeezing in toroidal Bose-Einstein condensates
• Quantum analog to flapping of flags: interface instability for co-flow binary superfluids
• Collective excitation and stability of flow-induced gapless Fermi superfluids
• Parity Symmetry Breaking and Topological Phases in a Superfluid Ring
• Increasing the stability of a superfluid in a rotating necklace potential
• Anomalous minimization for critical velocity of superflow along a step potential