8,910 research outputs found
Bright-like soliton solution in quasi-one-dimensional BEC in third order on interaction radius
Nonlinear Schr\"{o}dinger equations and corresponding quantum hydrodynamic
(QHD) equations are widely used in studying ultracold boson-fermion mixtures
and superconductors. In this article, we show that a more exact account of
interaction in Bose-Einstein condensate (BEC), in comparison with the
Gross-Pitaevskii (GP) approximation, leads to the existence of a new type of
solitons. We use a set of QHD equations in the third order by the interaction
radius (TOIR), which corresponds to the GP equation in a first order by the
interaction radius. The solution for the soliton in a form of expression for
the particle concentration is obtained analytically. The conditions of
existence of the soliton are studied. It is shown what solution exists if the
interaction between the particles is repulsive. Particle concentration of order
of - has been achieved experimentally for the BEC,
the solution exists if the scattering length is of the order of 1 m, which
can be reached using the Feshbach resonance. It is one of the limit case of
existence of new solution. The corresponding scattering length decrease with
the increasing of concentration of particles. The investigation of effects in
the TOIR approximation gives a more detail information on interaction
potentials between the atoms and can be used for a more detail investigation
into the potential structure.Comment: 7 pages, 3 figure
Semiclassical Approach to Competing Orders in Two-leg Spin Ladder with Ring-Exchange
We investigate the competition between different orders in the two-leg spin
ladder with a ring-exchange interaction by means of a bosonic approach. The
latter is defined in terms of spin-1 hardcore bosons which treat the N\'eel and
vector chirality order parameters on an equal footing. A semiclassical approach
of the resulting model describes the phases of the two-leg spin ladder with a
ring-exchange. In particular, we derive the low-energy effective actions which
govern the physical properties of the rung-singlet and dominant vector
chirality phases. As a by-product of our approach, we reveal the mutual
induction phenomenon between spin and chirality with, for instance, the
emergence of a vector-chirality phase from the application of a magnetic field
in bilayer systems coupled by four-spin exchange interactions.Comment: 15 pages, 9 figure
Non-divergent pseudo-potential treatment of spin-polarized fermions under 1D and 3D harmonic confinement
Atom-atom scattering of bosonic one-dimensional (1D) atoms has been modeled
successfully using a zero-range delta-function potential, while that of bosonic
3D atoms has been modeled successfully using Fermi-Huang's regularized s-wave
pseudo-potential. Here, we derive the eigenenergies of two spin-polarized 1D
fermions under external harmonic confinement interacting through a zero-range
potential, which only acts on odd-parity wave functions, analytically. We also
present a divergent-free zero-range potential treatment of two spin-polarized
3D fermions under harmonic confinement. Our pseudo-potential treatments are
verified through numerical calculations for short-range model potentials.Comment: 9 pages, 4 figures (subm. to PRA on 03/15/2004
Re-entrant localization of single particle transport in disordered Andreev wires
We study effects of disorder on the low energy single particle transport in a
normal wire surrounded by a superconductor. We show that the heat conductance
includes the Andreev diffusion decreasing with increase in the mean free path
and the diffusive drift produced by a small particle-hole asymmetry,
which increases with increasing . The conductance thus has a minimum as a
function of which leads to a peculiar re-entrant localization as a
function of the mean free path.Comment: 4 pages, 2 figure
A quantum hydrodynamics approach to the formation of new types of waves in polarized two-dimension systems of charged and neutral particles
In this paper we explicate a method of quantum hydrodynamics (QHD) for the
study of the quantum evolution of a system of polarized particles. Though we
focused primarily on the two-dimension physical systems, the method is valid
for three-dimension and one-dimension systems too. The presented method is
based upon the Schr\"{o}dinger equation. Fundamental QHD equations for charged
and neutral particles were derived from the many-particle microscopic
Schr\"{o}dinger equation. The fact that particles possess the electric dipole
moment (EDM) was taken into account. The explicated QHD approach was used to
study dispersion characteristics of various physical systems. We analyzed
dispersion of waves in a two-dimension (2D) ion and hole gas placed into an
external electric field which is orthogonal to the gas plane. Elementary
excitations in a system of neutral polarized particles were studied for 1D, 2D
and 3D cases. The polarization dynamics in systems of both neutral and charged
particles is shown to cause formation of a new type of waves as well as changes
in the dispersion characteristics of already known waves. We also analyzed wave
dispersion in 2D exciton systems, in 2D electron-ion plasma and 2D
electron-hole plasma. Generation of waves in 3D system neutral particles with
EDM by means of the beam of electrons and neutral polarized particles is
investigated.Comment: 15 pages, 7 figure
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