230 research outputs found
Transport of the repulsive Bose-Einstein condensate in a double-well trap: interaction impact and relation to Josephson effect
Two aspects of the transport of the repulsive Bose-Einstein condensate (BEC)
in a double-well trap are inspected: impact of the interatomic interaction and
analogy to the Josephson effect. The analysis employs a numerical solution of
3D time-dependent Gross-Pitaevskii equation for a total order parameter
covering all the trap. The population transfer is driven by a time-dependent
shift of a barrier separating the left and right wells. Sharp and soft profiles
of the barrier velocity are tested. Evolution of the relevant characteristics,
involving phase differences and currents, is inspected. It is shown that the
repulsive interaction substantially supports the transfer making it possible i)
in a wide velocity interval and ii) three orders of magnitude faster than in
the ideal BEC. The transport can be approximately treated as the d.c. Josephson
effect. A dual origin of the critical barrier velocity (break of adiabatic
following and d.c.-a.c. transition) is discussed. Following the calculations,
robustness of the transport (d.c.) crucially depends on the interaction and
barrier velocity profile. Only soft profiles which minimize undesirable dipole
oscillations are acceptable.Comment: 10 pages, 8 figures, accepted by Laser Physis. arXiv admin note: text
overlap with arXiv:1312.2750 The replaced version has a few corrections and
additional reference
Dynamics of cluster deposition on Ar surface
Using a combined quantum mechanical/classical method, we study the dynamics
of deposition of small Na clusters on Ar(001) surface. We work out basic
mechanisms by systematic variation of substrate activity, impact energy,
cluster orientations, cluster sizes, and charges. The soft Ar material is found
to serve as an extremely efficient shock absorber which provides cluster
capture in a broad range of impact energies. Reflection is only observed in
combination with destruction of the substrate. The kinetic energy of the
impinging cluster is rapidly transfered at first impact. The distribution of
the collision energy over the substrate proceeds very fast with velocity of
sound. The full thermalization of ionic and atomic energies goes at a much
slower pace with times of several ps. Charged clusters are found to have a much
stronger interface interaction and thus get in significantly closer contact
with the surface.Comment: 10 pages, 6 figures, accepted in Euro. Phys. J.
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