1,228 research outputs found
On the internal modes in sine-Gordon chain
We address the issue of internal modes of a kink of a discrete sine-Gordon
equation. The main point of the present study is to elucidate how the
antisymmetric internal mode frequency dependence enters the quasicontinuum
spectrum of nonlocalized waves. We analyze the internal frequency dependencies
as functions of both the number of cites and discreteness parameter and explain
the origin of spectrum peculiarity which arises after the frequency dependence
of antisymmetric mode returns back to the continuous spectrum at some nonzero
value of the intersite coupling.Comment: 5 pages, 3 figure
Iron Displacements and Magnetoelastic Coupling in the Spin-Ladder Compound BaFe2Se3
We report long-range ordered antiferromagnetism concomitant with local iron
displacements in the spin-ladder compound BaFeSe. Short-range magnetic
correlations, present at room temperature, develop into long-range
antiferromagnetic order below T = 256 K, with no superconductivity down to
1.8 K. Built of ferromagnetic Fe plaquettes, the magnetic ground state
correlates with local displacements of the Fe atoms. These iron displacements
imply significant magnetoelastic coupling in FeX-based materials, an
ingredient hypothesized to be important in the emergence of superconductivity.
This result also suggests that knowledge of these local displacements is
essential for properly understanding the electronic structure of these systems.
As with the copper oxide superconductors two decades ago, our results highlight
the importance of reduced dimensionality spin ladder compounds in the study of
the coupling of spin, charge, and atom positions in superconducting materials
Nonlinear acoustic waves in channels with variable cross sections
The point symmetry group is studied for the generalized Webster-type equation
describing non-linear acoustic waves in lossy channels with variable cross
sections. It is shown that, for certain types of cross section profiles, the
admitted symmetry group is extended and the invariant solutions corresponding
to these profiles are obtained. Approximate analytic solutions to the
generalized Webster equation are derived for channels with smoothly varying
cross sections and arbitrary initial conditions.Comment: Revtex4, 10 pages, 2 figure. This is an enlarged contribution to
Acoustical Physics, 2012, v.58, No.3, p.269-276 with modest stylistic
corrections introduced mainly in the Introduction and References. Several
typos were also correcte
Elementary excitations in the hybrid Bose-Fermi system induced by circularly polarized light in a two-dimensional gas of charge carriers with different masses
We developed a theory describing elementary excitations in the Bose-Fermi
system induced by circularly polarized light in a two-dimensional (2D) gas of
charge carriers with different masses. In such a hybrid system, the Fermi
subsystem is a degenerate Fermi gas, whereas the Bose subsystem is a condensate
of the light-induced composite bosons consisting of two fermions (electrons or
holes) with different effective masses. The interaction of the single-particle
excitations and the collective excitations (plasmons) in the Fermi subsystem
with the Bogoliubov collective modes (bogolons) in the Bose subsystem is
analyzed. The renormalization and damping (lifetime) of the excitations are
calculated, and the possibility of their experimental observation is discussed.
The developed theory can be applied to describe 2D condensed-matter structures
containing charge carriers with different effective masses, including
transition metal dichalcogenide monolayers and semiconductor quantum wells.Comment: Published versio
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