211 research outputs found
Topological coupling of dislocations and magnetization vorticity in Spin Density Waves
The rich order parameter of Spin Density Waves allows for an unusual object
of a complex topological nature: a half-integer dislocation combined with a
semi-vortex of the staggered magnetization. It becomes energetically preferable
to ordinary dislocation due to enhanced Coulomb interactions in the
semiconducting regime. Generation of these objects changes the narrow band
noise frequency.Comment: To be published in Proceedings of ECRYS-99, J. de Physique, Coll.,
December 1999. http://ipnweb.in2p3.fr/~lptms/membres/brazov
Theory of plastic flows of CDWs in application to the current conversion
We suggest a theoretical picture for distributions of plastic deformations
experienced by a sliding Charge Density Wave in the course of the conversion
from the normal current at the contact to the collective one in the bulk.
Several mechanisms of phase slips via creation and proliferation of
dislocations are compared. The results are applied to space resolved X-ray,
multi-contact and optical studies. Numerical simulations are combined with
model independent relations.Comment: To be published in Proceedings of ECRYS-99, J. de Physique, Coll.,
December 1999. 7 pages, 3 figure
Topological Defects in Spin Density Waves
The rich order parameter of Spin Density Waves allows for unusual object of a
complex topological nature: a half-integer dislocation combined with a
semi-vortex of a staggered magnetization. It becomes energetically preferable
to ordinary dislocation due to enhanced Coulomb interactions in the
semiconducting regime. Generation of these objects changes e.g. the narrow band
noise frequency.Comment: 9 pages, 2 figure
Observation of correlations up to the micrometer scale in sliding charge-density waves
High-resolution coherent x-ray diffraction experiment has been performed on
the charge density wave (CDW) system KMoO. The satellite
reflection associated with the CDW has been measured with respect to external
dc currents. In the sliding regime, the satellite reflection displays
secondary satellites along the chain axis which corresponds to correlations up
to the micrometer scale. This super long range order is 1500 times larger than
the CDW period itself. This new type of electronic correlation seems inherent
to the collective dynamics of electrons in charge density wave systems. Several
scenarios are discussed.Comment: 4 pages, 3 figures Typos added, references remove
Multi-vortex dynamics in junctions of charge density waves
Ground state reconstruction by creation of topological defects in junctions
of CDWs is a convenient playground for modern efforts of field-effect
transformations in strongly correlated materials with spontaneous symmetry
breakings. Being transient, this effect contributes also to another new science
of pump-induced phase transitions. We present a dynamical model for behavior of
the CDW in restricted geometries of junctions under an applied voltage or a
passing current. The model takes into account multiple interacting fields: the
amplitude and the phase of the CDW complex order parameter, distributions of
the electric field, the density and the current of various normal carriers. A
particular challenge was to monitor the local conservation of the condensed and
the normal charge densities. That was done easily invoking the chiral
invariance and the associated anomaly, but prize is an unconventional
Ginsburg-Landau type theory which is not analytic with respect to the order
parameter. The numerical modeling poses unusual difficulties but still can
demonstrate that vortices are nucleated at the junction boundary when the
voltage across, or the current through, exceed a threshold.Comment: To be published in proceedings of the conference SUPERSTRIPES-2014,
A. Bianconi ed., J. Supercond. Nov. Mag., (2015
Coulomb interaction and electron-hole asymmetry in cyclotron resonance of bilayer graphene in high magnetic field
Inter-Landau-level transitions in the bilayer graphene at high perpendicular
magnetic field at the filling-factor v<<1 have been studied. The
next-nearest-neighbor transitions, energy difference between dimer and
non-dimer sites and layer asymmetry are included. The influence of Coulomb
interaction is taken into account. The magnetoplasmon excitations in bilayer
graphene at small momenta are considered in the frame of the Hartree-Fock
approximation. It is shown that asymmetry in cyclotron resonance of clean
bilayer graphene depends on magnetic field. At lower magnetic fields the energy
splitting in the spectrum is due to electron-hole one-particle asymmetry, at
higher magnetic fields the energy splitting in the spectrum is due to Coulomb
interaction. For the fullsymmetric case with half-filled zero-energy levels the
energy splitting proportional to the energy of Coulomb interaction is found
both for bilayer and monolayer graphene.Comment: 6 pages, 2 figure
METHOD OF ESTIMATION OF ENVIRONMENTAL HAZARD OF URBAN LAND USING FOR VITAL ACTIVITY OF POPULATION
It is noted that the global updating of the ecological problems at the end of the XX - the beginning of the XXI centuries, the undeniable importance of the ecological component of human existence, causes the urgent need for a balanced, holistic, integrated approach to the analysis and solution of issues of ensuring the ecological safety of the vital activities of the population, including the city. At the same time, at the legislative level, environmental safety is identified as one of the priority tasks in the state policy of Ukraine in order to achieve sustainable development. It is proved that the provision of environmental safety remains the main way of solving ecological problems, which guarantees citizens the development and living in harmony with the environment and opens up new opportunities for other forms of activity in the field of nature management, in particular, political, economic, social, etc. The methodical approach to an estimation of ecological danger of urban land use for vital activity of the population and typification of land use of green plantings is grounded. An assessment of the state of ecological danger for the city of Kiev is given. On the basis of the proposed methodical approach, it is justified that today there are threats to the ecological stability of land use, and accordingly, environmental insecurity of land use, which indicates a lack of change in the structure of land use for many years
TRANSFORMATION OF THE RUSSIAN TAX SYSTEM IN THE CONTEXT OF ESTABLISHMENT OF THE DIGITAL ECONOMY
The controversial issues of a new approach to solving the problem of transformation of the tax system of the Russian Federation in the context of establishment of the digital economy have been considered. The problems of converting the tax system of the Russian Federation in digital reality and search for approaches to their solution have been identified. The methods of systematic approach, analysis and synthesis, as well as abstraction and generalization have been used. Due to the use of modern business models, carrying- out business activities without registration and the actual presence in the country, tax risks of tax evasion are increasing. The conclusions have been made about the need to identify new emerging economic relations and their legal consolidation, development and implementation of effective tax policy, and on its basis the transformation of the tax system
Probing Spin-Charge Relation by Magnetoconductance in One-Dimensional Polymer Nanofibers
Polymer nanofibers are one-dimensional organic hydrocarbon systems containing
conducting polymers where the non-linear local excitations such as solitons,
polarons and bipolarons formed by the electron-phonon interaction were
predicted. Magnetoconductance (MC) can simultaneously probe both the spin and
charge of these mobile species and identify the effects of electron-electron
interactions on these nonlinear excitations. Here we report our observations of
a qualitatively different MC in polyacetylene (PA) and in polyaniline (PANI)
and polythiophene (PT) nanofibers. In PA the MC is essentially zero, but it is
present in PANI and PT. The universal scaling behavior and the zero (finite) MC
in PA (PANI and PT) nanofibers provide evidence of Coulomb interactions between
spinless charged solitons (interacting polarons which carry both spin and
charge)
Wigner crystallization in a polarizable medium
We present a variational study of the 2D and 3D Wigner crystal phase of large
polarons. The method generalizes that introduced by S. Fratini,P.\
Qu{\'{e}}merais [Mod. Phys. Lett. B {\bf 12} 1003 (1998)]. We take into account
the Wigner crystal normal modes rather than a single mean frequency in the
minimization procedure of the variational free energy. We calculate the
renormalized modes of the crystal as well as the charge polarization
correlation function and polaron radius. The solid phase boundaries are
determined via a Lindemann criterion, suitably generalized to take into account
the classical-to-quantum cross-over.
In the weak electron-phonon coupling limit, the Wigner crystal parameters are
renormalized by the electron-phonon interaction leading to a stabilization of
the solid phase for low polarizability of the medium. Conversely, at
intermediate and strong coupling, the behavior of the system depends strongly
on the polarizability of the medium.
For weakly polarizable media, a density crossover occurs inside the solid
phase when the renormalized plasma frequency approaches the phonon frequency.
At low density, we have a renormalized polaron Wigner crystal, while at higher
densities the electron-phonon interaction is weakened irrespective of the {\it
bare} electron-phonon coupling.
For strongly polarizable media, the system behaves as a Lorentz lattice of
dipoles. The abrupt softening of the internal polaronic frequency predicted by
Fratini and Quemerais is observed near the actual melting point only at very
strong coupling, leading to a possible liquid polaronic phase for a wider range
of parameters.Comment: 24 pages, 13 figures v1.
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