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1.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Aplesnin S. S.
Заглавие : A study of anisotropic Heisenberg antiferromagnet with S=1/2 on a square lattice by Monte-Carlo method
Место публикации : Phys. Status Solidi B. - 1998. - Vol. 207, Is. 2. - P.491-498. - ISSN 0370-1972, DOI 10.1002/(SICI)1521-3951(199806)207:2491::AID-PSSB4913.0.CO;2-G
Примечания : Cited References: 24
Предметные рубрики: EU2CUO4
LA2CUO4
ORDER
MODEL
STATE
Аннотация: The two-dimensional (2D) Heisenberg model (J 0) with anisotropic exchange Delta = 1-J(X)/J(Z) greater than or equal to 0 and with S = 1/2 is studied by the quantum Monte-Carlo method. Energy, susceptibility, specific heat, spin-spin correlation functions, and correlation radius are calculated. The dependence of the Neel temperature T(N)/J = 2/ln(11/Delta) on the exchange anisotropy is determined. The static magnetic factor is very slowly decreased for T/J 0.4. It is assumed to realize topological excitations in the range of these temperatures. The correlation radius of the isotropic Heisenberg model is fitted by the dependence 1/xi = 2.05T(1.0(6))/exp (1.0(4)/T).The temperature behavior of the static structural magnetic factor in La(2)CuO(4) and Er(2)CuO(4) for T T(N) is in agreement with the MC calculations.
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2.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Petrov M. I., Balaev D. A., Gokhfeld D. M.
Заглавие : Andreev reflection and experimental temperature dependences of the critical current in heterogeneous high-temperature superconductors (polycrystals and related composites)
Место публикации : Phys. Solid State: MAIK NAUKA/INTERPERIODICA/SPRINGER, 2007. - Vol. 49, Is. 4. - P619-626. - ISSN 1063-7834, DOI 10.1134/S106378340704004X
Примечания : Cited References: 41
Предметные рубрики: CURRENT-VOLTAGE CHARACTERISTICS
NORMAL-METAL
WEAK LINKS
JOSEPHSON-JUNCTIONS
MODEL
SCATTERING
TRANSPORT
DISSIPATION
HYSTERESIS
Аннотация: The temperature dependences of the critical current of Y3/4Lu1/4Ba2Cu3O7 polycrystalline high-temperature superconductors subjected to annealing for different times and those of Y3/4Lu1/4Ba2Cu3O7 + BaPbO3 composites were measured. The results obtained were analyzed in terms of the Gunsenheimer-Schussler-Kummler theory considering the Andreev reflection of carriers in a "superconductor-normal metal-superconductor" (S-N-S) junction. Good agreement between the experimental and theoretical temperature dependences of the critical current over a wide temperature range for polycrystals with both natural and artificially created boundaries (composites) made it possible to estimate the effective length of grain boundaries in the high-temperature superconductors. It was revealed that the critical current density measured at 4.2 K is an exponential function of the length of grain boundaries in samples of both types.
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3.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Muzalevskiy K. V., Zeyliger, Anatoly
Заглавие : Application of Sentinel-1B polarimetric observations to soil moisture retrieval using neural networks: Case study for bare Siberian chernozem soil
Коллективы : Russian Foundation for Basic ResearchRussian Foundation for Basic Research (RFBR) [19-29-05261 mk]; Ministry of Science and Higher Education of the Russian Federation [0287-2021-0034]
Место публикации : Remote Sens. - 2021. - Vol. 13, Is. 17. - Ст.3480. - ISSN 2072-4292(eISSN), DOI 10.3390/rs13173480
Примечания : Cited References: 21. - This work was supported by the Russian Foundation for Basic Research (grant No. 19-29-05261 mk). The field experiment and EC-5 Decagon sensor calibration in laboratory conditions were carried out with the support of Ministry of Science and Higher Education of the Russian Federation, project No. 0287-2021-0034 (basic state assignment)
Предметные рубрики: SURFACE
MODEL
PARAMETERS
ROUGHNESS
INVERSION
DUBOIS
IEM
OH
Аннотация: Sentinel-1 is currently the only synthetic-aperture radar, which radar measurements of the earth’s surface to be carried out, regardless of weather conditions, with high resolution up to 5–40 m and high periodicity from several to 12 days. Sentinel-1 creates a technological platform for the development of new globally remote sensing algorithms of soil moisture, not only for hydrological and climatic model applications, but also on a single field scale for individual farms in precision farming systems used. In this paper, the potential of soil moisture remote sensing using polarimetric Sentinel-1B backscattering observations was studied. As a test site, the fallow agricultural field with bare soil near the Minino village (56.0865°N, 92.6772°E), Krasnoyarsk region, the Russian Federation, was chosen. The relationship between the cross-polarized ratio, reflectivity, and the soil surface roughness established Oh used as a basis for developing the algorithm of soil moisture retrieval with neural networks (NNs) computational model. Two NNs is used as a universal regression technique to establish the relationship between scattering anisotropy, entropy and backscattering coefficients measured by the Sentinel-1B on the one hand and reflectivity on the other. Finally, the soil moisture was found from the soil reflectivity in solving the inverse problem using the Mironov dielectric model. During the field campaign from 21 May to 25 August 2020, it was shown that the proposed approach allows us to predict soil moisture values in the layer thickness of 0.00–0.05 m with the root-mean-square error and determination coefficient not worse than 3% and 0.726, respectively. The validity of the proposed approach needs additional verification on a wider dataset using soils of different textures, a wide range of variations in soil surface roughness, and moisture.
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4.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Val'kov V. V., Dzebisashvili D. M., Barabanov A. F.
Заглавие : Basis states and collective excitations of nonlocal three-spin polarons over the singlet phase of the CuO2 plane
Место публикации : JETP Letters. - 2012. - Vol. 95, Is. 4. - P.206-212. - ISSN 0021-3640, DOI 10.1134/S0021364012040091
Примечания : Cited References: 15. - This work was supported by the Presidium of the Russian Academy of Sciences (program "Quantum Physics of Mesoscopic and Disordered Systems"), the Russian Foundation for Basic Research (project nos. 10-02-00251 and 11-02-98007-r-sibir'), and the Ministry of Education and Science of the Russian Federation (federal program "Human Capital for Science and Education in Innovative Russia" for 2009-2013).
Предметные рубрики: HEISENBERG-ANTIFERROMAGNET
SQUARE LATTICE
SPIN-POLARON
MODEL
Аннотация: An orthonormalized basis describing the single-hole states of the CuO2 plane has been constructed exactly taking into account the p-d exchange coupling between the spins of a hole and the two nearest copper ions. The introduced basis makes it possible to include the effects caused by the dependence of the Heisenberg interaction between the nearest copper ions on the occupation of the intermediate oxygen ion by the hole in the calculation of the spectrum of the collective excitations of nonlocal three-spin polarons. The inclusion of this correlation, as well as the nonlocality of the p-d exchange coupling, is the main difference of the developed approach to the description of the energy structure from the calculations with the use of the Zhang-Rice singlet.
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5.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Kolovsky A. R.
Заглавие : Bose-Hubbard Hamiltonian: Quantum chaos approach
Место публикации : Int. J. Mod. Phys. B: World Scientific Publishing, 2016. - Vol. 30, Is. 10. - Ст.1630009. - ISSN 0217-9792, DOI 10.1142/S0217979216300097. - ISSN 1793-6578(eISSN)
Примечания : Cited References:42
Предметные рубрики: Optical lattice
Dynamics
Atoms
States
Model
Ключевые слова (''Своб.индексиров.''): cold atoms in optical lattices--quantum transport--nonlinear dynamics and chaos
Аннотация: We discuss applications of the theory of quantum chaos to one of the paradigm models of many-body quantum physics - the Bose-Hubbard (BH) model, which describes, in particular, interacting ultracold Bose atoms in an optical lattice. After preliminary, pure quantum analysis of the system we introduce the classical counterpart of the BH model and the governing semiclassical equations of motion. We analyze these equations for the problem of Bloch oscillations (BOs) of cold atoms where a number of experimental results are available. The paper is written for nonexperts and can be viewed as an introduction to the field.
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6.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Bulgakov E. N., Sadreev A. F.
Заглавие : Bound states in the continuum in photonic waveguides inspired by defects
Место публикации : Phys. Rev. B: AMER PHYSICAL SOC, 2008. - Vol. 78, Is. 7. - Ст.75105. - ISSN 1098-0121, DOI 10.1103/PhysRevB.78.075105
Примечания : Cited References: 53
Предметные рубрики: SCATTERING-THEORY
NUCLEAR REACTIONS
UNIFIED THEORY
TRANSMISSION
ELECTRON
MODEL
Аннотация: Photonic crystal with defect layer forms directed continuum for electromagnetic waves. Defect rods in the vicinity of the defect layer interact with the continuum and give rise to scattering of ingoing waves. We derive quantum-mechanical analog of the non-Hermitian Hamiltonian of the open system with complex eigenvalues, which describes a scattering of electromagnetic waves by the defect rods. In this formalism a bound state in the continuum (BIC) can be easily found by the condition that one of the complex eigenvalues becomes real for variation of dielectric constant of the defect rods. We numerically find BICs with discrete frequencies belong to the continuum for different arrangements of the defects and show that they are localized around the defects.
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7.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Arbuzov A. B., Barbashov B. M., Nazmitdinov R. G., Pervushin V. N., Borowiec A., Pichugin K. N., Zakharov A. F.
Заглавие : Conformal Hamiltonian dynamics of general relativity
Место публикации : Phys. Lett. B: ELSEVIER SCIENCE BV, 2010. - Vol. 691, Is. 5. - P230-233. - ISSN 0370-2693, DOI 10.1016/j.physletb.2010.06.042
Примечания : Cited References: 30
Предметные рубрики: COSMOLOGICAL CONSTANT
UNIVERSE
GRAVITATION
SUPERNOVAE
MODEL
Ключевые слова (''Своб.индексиров.''): general relativity--cosmology--dilaton gravity--cosmology--dilaton gravity--general relativity
Аннотация: The General Relativity formulated with the aid of the spin connection coefficients is considered in the finite space geometry of similarity with the Dirac scalar dilaton. We show that the redshift evolution of the General Relativity describes the vacuum creation of the matter in the empty Universe at the electroweak epoch and the dilaton vacuum energy plays a role of the dark energy. (C) 2010 Elsevier B.V. All rights reserved.
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8.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Kagan, M. Yu., Val'kov V. V., Aksenov S. V.
Заглавие : Coulomb interactions-induced perfect spin-filtering effect in a quadruple quantum-dot cell
Коллективы : Euro-Asian Symposium "Trends in MAGnetism", "Trends in MAGnetism", Euro-Asian Symposium, Институт физики им. Л.В. Киренского Сибирского отделения РАН
Место публикации : J. Magn. Magn. Mater.: Elsevier Science, 2017. - Vol. 440: EURO-Asian Symposium on Trends in Magnetism (EASTMAG) (AUG 15-19, 2016, Siberian Fed Univ, Krasnoyarsk, RUSSIA). - P.15-18. - ISSN 0304-8853, DOI 10.1016/j.jmmm.2016.12.106. - ISSN 1873-4766(eISSN)
Примечания : Cited References:29. - We acknowledge fruitful discussions with P.I. Arseyev, N.S. Maslova, V.N. Mantsevich and R.Sh. Ikhsanov. This work was supported by the Comprehensive programme SB RAS no. 0358-2015-0007, the Russian Foundation for Basic Research, Government of Krasnoyarsk Territory, Krasnoyarsk Region Science and Technology Support Fund to the research projects nos. 15-02-03082, 16-42-243056, 16-42-242036, 17-42-240441. M.Yu.K. thanks the Program of Basic Research of the National Research University Higher School of Economics for support.
Предметные рубрики: SPINTRONICS
TRANSPORT
MODEL
Ключевые слова (''Своб.индексиров.''): spin filter--quantum interference--fano-feshbach resonance--coulomb--correlations
Аннотация: A quadruple quantum-dot (QQD) cell is proposed as a spin filter. The transport properties of the QQD cell were studied in linear response regime on the basis of the equations of motion for retarded Green's functions. The developed approach allowed us to take into account the influence of both intra-and interdot Coulomb interactions on charge carriers' spin polarization. It was shown that the presence of the insulating bands in the conductance due to the Coulomb correlations results in the emergence of spin-polarized windows (SPWs) in magnetic field leading to the high spin polarization. We demonstrated that the SPWs can be effectively manipulated by gate fields and considering the hopping between central dots in both isotropic and anisotropic regimes.
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9.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Shneyder E. I., Spitaler J., Kokorina E. E., Nekrasov I. A., Gavrichkov V. A., Draxl C., Ovchinnikov S. G.
Заглавие : Coupling of Hubbard fermions with phonons in La2 CuO4: A combined study using density-functional theory and the generalized tight-binding method
Место публикации : J. Alloys Compd.: Elsevier, 2015. - Vol. 648. - P.258-264. - ISSN 0925-8388, DOI 10.1016/j.jallcom.2015.05.150
Примечания : Cited References: 60. - We acknowledge the stimulating discussions with V.V. Val'kov, D.M. Dzebisashvilly, M.M. Korshunov and I.S. Sandalov. E.I.S. and S.G.O. are thankful to the Russian Science Foundation (project No. 14-12-00061) for the support of the research given in Sections 2, 6 and 7. E.E.K. and I.A.N. are thankful to the State Contract No. 0389-2014-0001 and RFBR grant No. 14-02-00065 for the support of the research given in Section 5. Financial support of the research given in Sections 3 and 4 by the Austrian Federal Government (in particular from Bundesministerium fur Verkehr, Innovation und Technologie and Bundesministerium fur Wissenschaft, Forschung und Wirtschaft) represented by Osterreichische Forschungsforderungsgesellschaft mbH and the Styrian and the Tyrolean Provincial Government, represented by Steirische Wirtschaftsforderungsgesellschaft mbH and Standortagentur Tirol, within the framework of the COMET Funding Programme is gratefully acknowledged by C.D. and J.S.
Предметные рубрики: MEAN-FIELD THEORY
LINEAR-RESPONSE THEORY
CUPRATE SUPERCONDUCTORS
ELECTRONIC-STRUCTURE
CORRELATED SYSTEMS
LATTICE-DYNAMICS
BAND-STRUCTURE
LA2CUO4
MODEL
LA2-XSRXCUO4
Ключевые слова (''Своб.индексиров.''): high-temperature superconductivity--electron-phonon coupling--density-functional theory--generalized tight-binding approach
Аннотация: We present results for the electron-phonon interaction of the Γ-point phonons in the tetragonal high-temperature phase of La2 CuO4 obtained from a hybrid scheme, combining density-functional theory (DFT) with the generalized tight-binding approach. As a starting point, eigenfrequencies and eigenvectors for the Γ-point phonons are determined from DFT within the frozen phonon approach utilizing the augmented plane wave + local orbitals method. The so obtained characteristics of electron-phonon coupling are converted into parameters of the generalized tight-binding method. This approach is a version of cluster perturbation theory and takes the strong on-site electron correlations into account. The obtained parameters describe the interaction of phonons with Hubbard fermions which form quasiparticle bands in strongly correlated electron systems. As a result, it is found that the Γ-point phonons with the strongest electron-phonon interaction are the A2u modes (236 cm-1, 131 cm-1 and 476 cm-1). Finally it is shown, that the single-electron spectral-weight redistribution between different Hubbard fermion quasiparticles results in a suppression of electron-phonon interaction which is strongest for the triplet Hubbard band with z oriented copper and oxygen electrons. © 2015 Elsevier B.V. All rights reserved.
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10.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Bulgakov E. N., Sadreev A. F.
Заглавие : Current-voltage characteristics of the resonant tunnelling double-barrier structure under time-periodical perturbation
Место публикации : J. Phys.: Condens. Matter: IOP PUBLISHING LTD, 1996. - Vol. 8, Is. 45. - P.8869-8887. - ISSN 0953-8984, DOI 10.1088/0953-8984/8/45/020
Примечания : Cited References: 38
Предметные рубрики: SEMICONDUCTOR DOUBLE-BARRIER
OSCILLATING QUANTUM-WELL
DEPENDENT TRANSPORT
INFRARED-RADIATION
TUNNELING TIMES
HETEROSTRUCTURES
TRANSMISSION
MODEL
FREQUENCIES
COHERENT
Аннотация: We consider a typical semiconductor resonant tunnelling GaAs/AlGaAs/GaAs nanostructure which forms a double-barrier potential with quasienergy levels corresponding to transition frequencies in the infrared and microwave regions. Two types of dynamical perturbation of the heterostructure in the form V-1(x, t) = V(1)x cos Omega t and V-2(t) = V-2 cos Omega t are considered. We analyse numerically a reconstruction of the electron transmission through the heterostructure and the current-voltage characteristics (IVC) under the influence of these dynamical perturbations. Both weak and strong perturbations are considered. We investigate the dependences of the transmission on the electron energy and the frequency of the external field with the main accent on the case where a frequency of the perturbation is tuned to a transition between quasienergies of the double-barrier structure. it is found that these resonant phenomena give rise to new peaks and dips in the IVC. In particular, it is shown that the dipole type of perturbation V-1(x, t) gives rise to a Rabi splitting of the transmission peaks and under certain conditions to a Rabi splining of the IVC peaks and dips. We demonstrate that dynamical perturbation may induce a direct current opposite to the direction of the applied voltage, and that this phenomenon takes the form of a sharp dip which has a resonant origin. It is observed that the dipole type of perturbation V-1(x, t) of laser radiation is more effective for tuning the IVC than the first perturbation V-2(t). Also absorption and emission of energy by an electron transmitted through the DBRTS are considered.
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