420 research outputs found
Globalization of the world economic- innovative processes and its effect on the cluster policy of the russian federation in the field of formation of spatial organization of the territory = Глобализация мировых экономико-инновационных процессов и его влияние на кластерную политику РФ формирования пространственной организации территории
The article considers the strategies of state economic development implemented through
cluster policy, which are one of the most effective methods of smoothing regional disparities in the formationof developmen
Field-induced spin density wave in (TMTSF)NO
Interlayer magnetoresistance of the Bechgaard salt (TMTSF)NO is
investigated up to 50 teslas under pressures of a few kilobars. This compound,
the Fermi surface of which is quasi two-dimensional at low temperature, is a
semi metal under pressure. Nevertheless, a field-induced spin density wave is
evidenced at 8.5 kbar above 20 T. This state is characterized by a
drastically different spectrum of the quantum oscillations compared to the low
pressure spin density wave state.Comment: to be published in Phys. Rev. B 71 (2005
THE ROLE OF RESPIRATORY DISEASE IN CAUSES OF MORTALITY IN THE IRKUTSK REGION
We present the results of assessment of mortality key elements and trends concerning respiratory diseases in the Irkutsk region in comparison with Siberian District and whole Russian Federation during 1992-2009 years. It was found that the bronchial-pulmonary pathology is ranked first in the pattern of mortality from cancer and. infectious diseases. Also it was established that in recent years morbidity and mortality from pneumonia of the population of the Irkutsk region increased
Orientational order parameters of a de Vries–type ferroelectric liquid crystal obtained by polarized Raman spectroscopy and x-ray diffraction
The orientational order parameters 〈P2〉 and 〈P4〉 of the ferroelectric, de Vries–type liquid crystal 9HL have been determined in the SmA* and SmC* phases by means of polarized Raman spectroscopy, and in the SmA* phase using x-ray diffraction. Quantum density functional theory predicts Raman spectra for 9HL that are in good agreement with the observations and indicates that the strong Raman band probed in the experiment corresponds to the uniaxial, coupled vibration of the three phenyl rings along the molecular long axis. The magnitudes of the orientational order parameters obtained in the Raman and x-ray experiments differ dramatically from each other, a discrepancy that is resolved by considering that the two techniques probe the orientational distributions of different molecular axes. We have developed a systematic procedure in which we calculate the angle between these axes and rescale the orientational order parameters obtained from x-ray scattering with results that are then in good agreement with the Raman data. At least in the case of 9HL, the results obtained by both techniques support a “sugar loaf” orientational distribution in the SmA* phase with no qualitative difference to conventional smectics A. The role of individual molecular fragments in promoting de Vries–type behavior is considered
Collective modes in a system with two spin-density waves: the `Ribault' phase of quasi-one-dimensional organic conductors
We study the long-wavelength collective modes in the magnetic-field-induced
spin-density-wave (FISDW) phases experimentally observed in organic conductors
of the Bechgaard salts family, focusing on phases that exhibit a sign reversal
of the quantum Hall effect (Ribault anomaly). We have recently proposed that
two SDW's coexist in the Ribault phase, as a result of Umklapp processes. When
the latter are strong enough, the two SDW's become circularly polarized
(helicoidal SDW's). In this paper, we study the collective modes which result
from the presence of two SDW's. We find two Goldstone modes, an out-of-phase
sliding mode and an in-phase spin-wave mode, and two gapped modes. The sliding
Goldstone mode carries only a fraction of the total optical spectral weight,
which is determined by the ratio of the amplitude of the two SDW's. In the
helicoidal phase, all the spectral weight is pushed up above the SDW gap. We
also point out similarities with phase modes in two-band or bilayer
superconductors. We expect our conclusions to hold for generic two-SDW systems.Comment: Revised version, 25 pages, RevTex, 7 figure
A study on correlation effects in two dimensional topological insulators
We investigate correlation effects in two dimensional topological insulators
(TI). In the first part, we discuss finite size effects for interacting systems
of different sizes in a ribbon geometry. For large systems, there are two pairs
of well separated massless modes on both edges. For these systems, we analyze
the finite size effects using a standard bosonization approach. For small
systems, where the edge states are massive Dirac fermions, we use the
inhomogeneous dynamical mean field theory (DMFT) combined with iterative
perturbation theory as an impurity solver to study interaction effects. We show
that the finite size gap in the edge states is renormalized for weak
interactions, which is consistent with a Fermi-liquid picture for small size
TIs. In the second part, we investigate phase transitions in finite size TIs at
zero temperature focusing on the effects of possible inter-edge Umklapp
scattering for the edge states within the inhomogeneous DMFT using the
numerical renormalization group. We show that correlation effects are
effectively stronger near the edge sites because the coordination number is
smaller than in the bulk. Therefore, the localization of the edge states around
the edge sites, which is a fundamental property in TIs, is weakened for strong
coupling strengths. However, we find no signs for "edge Mott insulating states"
and the system stays in the topological insulating state, which is
adiabatically connected to the non-interacting state, for all interaction
strengths smaller than the critical value. Increasing the interaction further,
a nearly homogeneous Mott insulating state is stabilized.Comment: 20 page
Sign reversals of the quantum Hall effect and helicoidal magnetic-field-induced spin-density waves in quasi-one-dimensional organic conductors
We study the effect of umklapp scattering on the magnetic-field-induced
spin-density-wave phases, which are experimentally observed in the
quasi-one-dimensional organic conductors of the Bechgaard salts family. Within
the framework of the quantized nesting model, we show that umklapp processes
may naturally explain sign reversals of the quantum Hall effect (QHE) observed
in these conductors. Moreover, umklapp scattering can change the polarization
of the spin-density wave (SDW) from linear (sinusoidal SDW) to circular
(helicoidal SDW). The QHE vanishes in the helicoidal phases, but a
magnetoelectric effect appears. These two characteristic properties may be
utilized to detect the magnetic-field-induced helicoidal SDW phases
experimentally.Comment: 4 pages, latex, 3 figure
Effect of umklapp scattering on the magnetic-field-induced spin-density waves in quasi-one-dimensional organic conductors
We study the effect of umklapp scattering on the magnetic-field-induced
spin-density-wave (FISDW) phases which are experimentally observed in the
quasi-one-dimensional organic conductors of the Bechgaard salts family. Within
the framework of the quantized nesting model, we show that the transition
temperature is determined by a modified Stoner criterion which includes the
effect of umklapp scattering. We determine the SDW polarization (linear or
circular) by analyzing the Ginzburg-Landau expansion of the free energy. We
also study how umklapp processes modify the quantum Hall effect (QHE) and the
spectrum of the FISDW phases. We find that umklapp scattering stabilizes phases
which exhibit a sign reversal of the QHE, as experimentally observed in the
Bechgaard salts. These ``negative'' phases are characterized by the
simultaneous existence of two SDWs with comparable amplitudes. As the umklapp
scattering strength increases, they may become helicoidal (circularly polarized
SDWs). The QHE vanishes in the helicoidal phases, but a magnetoelectric effect
appears. These two characteristic properties may be utilized to detect the
magnetic-field-induced helicoidal SDW phases experimentally.Comment: Revtex, 27 pages, 9 figure
Theory of Thermodynamic Magnetic Oscillations in Quasi-One-Dimensional Conductors
The second order correction to free energy due to the interaction between
electrons is calculated for a quasi-one-dimensional conductor exposed to a
magnetic field perpendicular to the chains. It is found that specific heat,
magnetization and torque oscillate when the magnetic field is rotated in the
plane perpendicular to the chains or when the magnitude of magnetic filed is
changed. This new mechanism of thermodynamic magnetic oscillations in metals,
which is not related to the presence of any closed electron orbits, is applied
to explain behavior of the organic conductor (TMTSF)ClO.Comment: 11 pages + 5 figures (included
Metals in high magnetic field: a new universality class of Fermi liquids
Parquet equations, describing the competition between superconducting and
density-wave instabilities, are solved for a three-dimensional isotropic metal
in a high magnetic field when only the lowest Landau level is filled. In the
case of a repulsive interaction between electrons, a phase transition to the
density-wave state is found at finite temperature. In the opposite case of
attractive interaction, no phase transition is found. With decreasing
temperature , the effective vertex of interaction between electrons
renormalizes toward a one-dimensional limit in a self-similar way with the
characteristic length (transverse to the magnetic field) decreasing as
( is a cutoff). Correlation functions have
new forms, previously unknown for conventional one-dimensional or
three-dimensional Fermi-liquids.Comment: 13 pages + 4 figures (included
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