373 research outputs found
Energy spectrum of graphene multilayers in a parallel magnetic field
We study the orbital effect of a strong magnetic field parallel to the layers
on the energy spectrum of the Bernal-stacked graphene bilayer and multilayers,
including graphite. We consider the minimal model with the electron tunneling
between the nearest sites in the plane and out of the plane. Using the
semiclassical analytical approximation and exact numerical diagonalization, we
find that the energy spectrum consists of two domains. In the low- and
high-energy domains, the semiclassical electron orbits are closed and open, so
the spectra are discrete and continuous, correspondingly. The discrete energy
levels are the analogs of the Landau levels for the parallel magnetic field.
They can be detected experimentally using electron tunneling and optical
spectroscopy. In both domains, the electron wave functions are localized on a
finite number of graphene layers, so the results can be applied to graphene
multilayers of a finite thickness.Comment: 11 pages, 13 figures. Added to v.2: Appendix A, Fig. 13, Refs.
[18-23]. V.3: minor stylistic corrections from the published versio
Professional education in tourism: problems of the regional level
The article reveals the main problems of professional education in the sphere of tourism at the regional leve
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 Fractional Quantum Hall effect in an array of quantum wires
We demonstrate the emergence of the quantum Hall (QH) hierarchy in a 2D model
of coupled quantum wires in a perpendicular magnetic field. At commensurate
values of the magnetic field, the system can develop instabilities to
appropriate inter-wire electron hopping processes that drive the system into a
variety of QH states. Some of the QH states are not included in the
Haldane-Halperin hierarchy. In addition, we find operators allowed at any field
that lead to novel crystals of Laughlin quasiparticles. We demonstrate that any
QH state is the groundstate of a Hamiltonian that we explicitly construct.Comment: Revtex, 4 pages, 2 figure
Regional socio-economic-geographical systems: approaches to the definition
The article is devoted to the analyses of theoretical approaches towards the definition of the concept "region" in Russian and foreign researches. Research studies of a region as a socio-economic system appears to be sufficiently conventional within the modern socio-economic and geographic science, however the united approach towards theoretical evaluation of the category, its definition and its forming subsystems does not still exists. The authors put emphasis on a topological approach towards the definition of the concept "the regional social, economic and geographical system
Sensitivity of the interlayer magnetoresistance of layered metals to intralayer anisotropies
Many of the most interesting and technologically important electronic
materials discovered in the past two decades have two common features: a
layered crystal structure and strong interactions between electrons. Two of the
most fundamental questions about such layered metals concern the origin of
intralayer anisotropies and the coherence of interlayer charge transport. We
show that angle dependent magnetoresistance oscillations (AMRO) are sensitive
to anisotropies around an intralayer Fermi surface. Hence, AMRO can be a probe
of intralayer anisotropies that is complementary to angle-resolved
photoemission spectroscopy (ARPES) and scanning tunneling microscopy (STM).
However, AMRO are not very sensitive to the coherence of the interlayer
transport. We illustrate this with comparisons to recent AMRO experiments on an
overdoped cuprate.Comment: 7 pages, 3 figure
СПЕЦЫФІКА МАСТАЦКАГА ПЕРАКЛАДУ З БЛІЗКАРОДНАСНЫХ МОЎ: ТЭАРЭТЫЧНЫ АСПЕКТ
On the basis of the concepts of Western scientists Anton Popovich, Katarina Rice, Hans Fermeer, Edmund Husserl, Roman Ingarden et al., hard-to solve problems of literary translation from related languages are comprehended theoretically. The translation is a result of an original work of a translator who reproduces the original in the language of another nationality and for different social and cultural environment and is an indication of certain translation outlook and aesthetic position.В статье на основе концепций западноевропейских ученых Антона Поповича, Катарины Райс, Ханса Фермеера, Эдмунда Гуссерля, Романа Ингардена и других теоретически осмысливаются трудноразрешимые проблемы художественного перевода с близкородственных языков, который является результатом своеобразной работы переводчика над воспроизведением оригинала на языке другой национальности и для другой социокультурной среды, показателем определенного переводческого мировоззрения и эстетической позиции
Quantum Hall effect anomaly and collective modes in the magnetic-field-induced spin-density-wave phases of quasi-one-dimensional conductors
We study the collective modes in the magnetic-field-induced spin-density-wave
(FISDW) phases experimentally observed in organic conductors of the Bechgaard
salts family. In phases that exhibit a sign reversal of the quantum Hall effect
(Ribault anomaly), the coexistence of two spin-density waves gives rise to
additional collective modes besides the Goldstone modes due to spontaneous
translation and rotation symmetry breaking. These modes strongly affect the
charge and spin response functions. We discuss some experimental consequences
for the Bechgaard salts.Comment: Final version (LaTex, 8 pages, no figure), to be published in
Europhys. Let
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
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