Critical velocity of superfluid flow through single-barrier and periodic potentials

Physical Review A - Atomic, Molecular, and Optical Physics

Volumn 80, Issue 5, 2009, Pages

  Watanabe, Gentaro ^a,b   Dalfovo, F ^a   Piazza, F ^a   Pitaevskii, L P ^a,c   Stringari, S ^a  

^a UNIVERSITY OF TRENTO   (Italy)

^b RIKEN   (Japan)

^c KAPITZA INSTITUTE FOR PHYSICAL PROBLEMS   (Russian Federation)

Author keywords

[No Author keywords available]

Indexed keywords

ANALYTIC EXPRESSIONS; ATOMIC GAS; BARRIER HEIGHTS; BOGOLIUBOV-DE GENNES EQUATIONS; CRITICAL VELOCITIES; EXTERNAL POTENTIAL; FERMI SUPERFLUIDS; HYDRODYNAMIC REGIME; LONG WAVELENGTH; NUMERICAL SOLUTION; PERIODIC POTENTIALS; POTENTIAL BARRIERS; QUANTUM EFFECTS; SOUND VELOCITIES; STATIONARY FLOW; SUPERFLUID FLOWS; SUPERFLUID PHASE; SUPERFLUID VELOCITY; ULTRA-COLD; ULTRACOLD GAS;

FLUID DYNAMICS; HYDRODYNAMICS; QUANTUM ELECTRONICS;

VELOCITY;

EID: 70350776521     PISSN: 10502947     EISSN: 10941622     Source Type: Journal    
DOI: 10.1103/PhysRevA.80.053602     Document Type: Article

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56. In general, there are also cases where Pc is outside the first Brillouin zone, as we have seen for bosons when the energy exhibits swallow tails. In Appendix, we do not consider this case for simplicity, but the procedure for calculating Pc is the same.
57. Note that in this work we always consider a flow along the direction of the 1D lattice. It is worth noticing here that the critical velocity of the superfluid flowing instead along the transverse direction can be larger than the sound velocity for the uniform system cs (0). In fact, since the system is translationally invariant in the transverse direction, one has m□ =m, ∂n ∂ P□ e= P□ /m, and κ does not depend on the transverse momentum P□. On the other hand, due to the periodic potential, κ-1 can be larger than that of the uniform system with the same average density (Refs.). Under these conditions, both the sound velocity in the lattice and the critical velocity, vc = ∂n2 e ∂P2 e = κ-1 /m, are larger than cs (0).