Библиотека института физики им. Л.В. Киренского СО РАН

Главная

Базы данных

Труды сотрудников ИФ СО РАН - результаты поиска

Вид поиска

Каталог книг и брошюр библиотеки ИФ СО РАН

Каталог журналов библиотеки ИФ СО РАН

Труды сотрудников ИФ СО РАН

Область поиска

в найденном

Формат представления найденных документов:
полный	информационный	краткий

Отсортировать найденные документы по:
автору	заглавию	году издания	типу документа

Поисковый запрос: (<.>S=Model<.>)

Общее количество найденных документов : 83
Показаны документы с 1 по 10

1-10 11-20 21-30 31-40 41-50 51-60

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Zobov V. E., Lundin A. A.
Заглавие : Second moment of multiple-quantum NMR and a time-dependent growth of the number of multispin correlations in solids
Место публикации : J. Exp. Theor. Phys.: MAIK NAUKA/INTERPERIODICA/SPRINGER, 2006. - Vol. 103, Is. 6. - P904-916. - ISSN 1063-7761, DOI 10.1134/S1063776106120089
Примечания : Cited References: 39
Предметные рубрики: NUCLEAR-MAGNETIC-RESONANCE
LINE-SHAPE
SPIN SYSTEMS
DYNAMICS
SPECTRA
COHERENCES
STATE
BEHAVIOR
CRYSTAL
MODEL
Ключевые слова (''Своб.индексиров.''): correlation methods--mathematical models--nuclear magnetic resonance spectroscopy--spectrum analysis--time series analysis--four-spin time correlation--multispin correlations--second moment--time power series--quantum theory
Аннотация: The time evolution of multispin correlations (the growth of the number of correlated spins as a function of time) can be observed directly using the multiple-quantum nuclear magnetic resonance spectroscopy of solids. A quantity related to this number, namely, the second moment n(2)(t) of the intensity distribution of coherences of different orders in the multiple-quantum spectrum can be calculated using the theory proposed in this work. An approach to the calculation of the four-spin time correlation function through which this moment is expressed is developed. The main sequences of contributions in the expansion of this function into a time power series are summed using the approximation of a large number of neighbors both for systems with a secular dipole-dipole interaction and for systems with a nonsecular effective interaction. An exponential dependence of n(2)(t) is obtained. The value of n(2)(t) is additionally calculated using an expansion in terms of orthogonal operators for three model examples corresponding to different limiting realizations of spin systems. It is shown that the results of the microscopic theory at least qualitatively agree with both the results obtained for model examples and experimental results obtained recently for adamantane.
WOS,
Scopus,
Читать в сети ИФ
Найти похожие

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Zobov V. E., Popov M. A.
Заглавие : On the radius of convergence of series in powers of time for spin correlation functions of the Heisenberg magnet at high temperature
Место публикации : Theor. Math. Phys.: PLENUM PUBL CORP, 1997. - Vol. 112, Is. 3. - P1182-1191. - ISSN 0040-5779, DOI 10.1007/BF02583049
Примечания : Cited References: 22
Предметные рубрики: AUTO-CORRELATION FUNCTION
INFINITE-TEMPERATURE
PARAMAGNET
DYNAMICS
MODEL
Аннотация: The convergence of series in powers of time for spin autocorrelation functions of the Heisenberg magnet are investigated at infinite temperatures on lattices of different dimensions d. The calculation data available at the present time for the coefficients of these series are used to estimate the corresponding radii of convergence, whose growth with decreasing d is revealed and explained in a self-consistent approximation. To this end, a simplified nonlinear equation corresponding to this approximation is suggested and solved for the autocorrelation function of a system with an arbitrary number Z of nearest neighbors. The coefficients of the expansion in powers of time for the solution are represented in the form of trees on the Bethe lattice with the coordination number Z. A computer simulation method is applied to calculate the expansion coefficients for trees embedded in square, triangular, and simple cubic lattices under the condition that the intersection of tree branches is forbidden. It is found that the excluded volume effect that manifests itself in a decrease in these coefficients and in an increase in the coordinate and exponent of the singularity of the autocorrelation function on the imaginary time axis is intensified with decreasing lattice dimensions.
WOS,
Scopus
Найти похожие

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Zobov V. E., Popov M. A.
Заглавие : On the coordinate of a singular point of the time correlation function for a spin system on a simple hypercubic lattice at high temperatures
Место публикации : Theor. Math. Phys. - 2002. - Vol. 131, Is. 3. - P.862-872. - ISSN 0040-5779, DOI 10.1023/A:1015935809388
Примечания : Cited References: 19
Предметные рубрики: NUCLEAR-DOUBLE-RESONANCE
HEISENBERG MAGNET
DEPENDENCE
MODEL
Ключевые слова (''Своб.индексиров.''): spin dynamics--correlation functions--power series in time--frequency moments--singular points--generated functions--lattice trees--multidimensional expansion--correlation functions--frequency moments--generated functions--lattice trees--multidimensional expansion--power series in time--singular points--spin dynamics
Аннотация: Using the d(-1) expansion method (d is the space dimension), we estimate the coordinate of the time-dependent autocorrelation function singular point on the imaginary time axis for the spin 1/2 Heisenberg model on a simple hypercubic lattice at high temperatures. We represent the coefficients of the time expansion (the spectral moments) for the autocorrelation function as the sums of the weighted lattice figures in which the trees constructed from the double bonds give the leading contributions with respect to d(-1) and the same trees with the built-in squares from six bonds or diagrams with the fourfold bonds give the contribution of the next-to-leading order. We find the corrections to the coordinate of the autocorrelation function singular point that are due to the latter contributions.
WOS,
Scopus,
Читать в сети ИФ
Найти похожие

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Zinenko V. I., Sofronova S. N.
Заглавие : Statistical mechanics of cation ordering in PbSc1/2Ta1/2O3 and PbSc1/2Nb1/2O3 solid solutions
Разночтения заглавия :авие SCOPUS: Statistical mechanics of cation ordering in PbSc1/2Ta 1/2O3 and PbSc1/2Nb1/2O3 solid solutions
Место публикации : Phys. Solid State: AMER INST PHYSICS, 2005. - Vol. 47, Is. 12. - P2309-2314. - ISSN 1063-7834, DOI 10.1134/1.2142896
Примечания : Cited References: 17
Предметные рубрики: PHASE-TRANSITION
PEROVSKITE
DISORDER
FERROELECTRICS
CRYSTALS
MODEL
Аннотация: A model Hamiltonian for B cation ordering (Sc-Nb(Ta)) in PbSc1/2Nb1/2O3 and PbSc1/2Ta1/2O3 solid solutions is constructed. The parameters of the model Hamiltonian are determined from the ab initio calculation within the ionic crystal model with allowance made for the deformability and the dipole and quadrupole polarizabilities of the ions. The temperatures of the phase transition due to the ordering of the B cations are calculated by the Monte Carlo method in the mean-field and cluster approximations. The phase transition temperatures calculated by the Monte Carlo method (1920 K for PbSc1/2Ta1/2O3 and 1810 K for PbSc1/2Nb1/2O3) are consistent with the experimental data (1770 and 1450 K, respectively). The thermodynamic properties of the cation ordering are investigated using the Monte Carlo method. (c) 2005 Pleiades Publishing, Inc.
WOS,
Scopus,
Читать в сети ИФ
Найти похожие

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Val'kov V. V., Shustin M. S.
Заглавие : The modification of low-temperature magnetic properties of the Fe-based double-zigzag single-chain magnet under irradiation
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. - P.19-22. - ISSN 0304-8853, DOI 10.1016/j.jmmm.2016.12.100
Примечания : Cited References: 14. - This study was supported by the Presidium of the Russian Academy of Sciences, program Actual problems of low temperature physics (project 0358-2015-0005); the Russian Foundation for Basic Research, projects nos. 16-42-243057 (partly with Government of Krasnoyarsk Territory) and 15-42-04372; Technology Support Fund to the research project nos. 14/16. The work of M.S.S. was supported by grant of the President of the Russian Federation (project MK-1398.2017.2).
Предметные рубрики: SPIN-CROSSOVER
MODEL
Ключевые слова (''Своб.индексиров.''): single-chain magnets--light-induced spin crossover--magnetic susceptibility--quantum phase transitions
Аннотация: An exact solution for a generalized Ising model describing single-chain magnet {[FeIII(Tp*)(CN)3]2FeII(bpmh)}·2H2O with alternating high-spin and low-spin iron ions and double-zigzag magnetic topology has been calculated making use of the transfer-matrix technique. The introduction of a statistical ensemble taking into account the presence of iron ions with high-spin (HS) and low-spin (LS) states made it possible to describe the modification of magnetic susceptibility under optical irradiation. It has been shown that joint implementation of iron ions with photoinduced magnetic states and non-magnetic intersite repulsion ions of these states is caused by the difference of the ionic radii of HSFeIIHSFeII and LSFeIILSFeII leads to the quantum phase transitions in the system.
Смотреть статью,
WOS,
Читать в сети ИФ
Найти похожие

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Val'kov V. V., Mitskan V. A., Petrakovskii G. A.
Заглавие : The magnetoelastic mechanism of singlet phase formation in a two-dimensional quantum antiferromagnet
Место публикации : J. Exp. Theor. Phys.: MAIK NAUKA/INTERPERIODICA/SPRINGER, 2006. - Vol. 102, Is. 2. - P234-247. - ISSN 1063-7761, DOI 10.1134/S106377610602004X
Примечания : Cited References: 18
Предметные рубрики: GROUND-STATE
SPIN
TRANSITION
CUGEO3
MODEL
Ключевые слова (''Своб.индексиров.''): crystal lattices--elasticity--mathematical models--oscillations--phase diagrams--phase transitions--quantum theory--two dimensional--atomic representation--magnetoelastic mechanism--quantum antiferromagnets--singlet phase formation--antiferromagnetic materials
Аннотация: A model describing the second-order phase transition with respect to the magnetoelastic coupling parameter from the anti ferromagnetic (AFM) to the singlet state in a two-dimensional quantum magnet on a square lattice is proposed. The spectrum of elementary excitations in the singlet and AFM phases is calculated using an atomic representation, and the evolution of transverse and longitudinal branches of this spectrum is studied in the vicinity of the transition point. It is established that the AFM to singlet phase transition is related to softening of the longitudinal branch of oscillations. In the singlet phase, the gap plays the role of a parameter characterizing the distance to the phase transition point. It is shown that the spectrum of transverse oscillations in the AFM phase corresponds to the Goldstone boson. Based on an analysis of the stability of the spectrum of elementary excitations, a phase diagram is constructed that determines the regions of the existence of phases with plaquette-deformed lattices.
WOS,
Scopus,
Читать в сети ИФ
Найти похожие

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Val'kov V. V., Dzebisashvili D. M., Kravtsov A. S.
Заглавие : Spectral representations and description of a superconducting state with S-type order parameter Delta(k)
Разночтения заглавия :авие SCOPUS: Spectral representations and description of a superconducting state with S-type order parameter Δ(k)
Место публикации : JETP Letters. - 2003. - Vol. 77, Is. 9. - P.505-509. - ISSN 0021-3640, DOI 10.1134/1.1591980
Примечания : Cited References: 11
Предметные рубрики: GREENS FUNCTIONS
MODEL
Аннотация: The inclusion of a singular contribution to the spectral intensity of the anomalous correlation function is shown to regain the sum rule and remove the unjustified forbidding of the S-symmetry order parameter in superconductors with strong correlations. For the order parameter of this symmetry, the solution to the self-consistency equation is analyzed beyond the nearest-neighbor approximation. (C) 2003 MAIK "Nauka / Interperiodica".
WOS,
Scopus,
Читать в сети ИФ
Найти похожие

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Val'kov V. V., Shustin M. S.
Заглавие : Radiation-induced modification of the temperature dependence of the magnetic susceptibility of a 1D magnet
Коллективы : Russian Foundation for Basic Research [12-02-31130, 13-02-00523, 13-02-98013]
Место публикации : JETP Letters. - 2014. - Vol. 100, Is. 7. - P.455-462. - ISSN 0021-3640, DOI 10.1134/S0021364014190138. - ISSN 1090-6487
Примечания : Cited References: 28. - This work was supported by the Russian Foundation for Basic Research, project nos. 12-02-31130, 13-02-00523, and 13-02-98013.
Предметные рубрики: SINGLE-CHAIN MAGNETS
EASY-PLANE
ARRANGEMENT
MODEL
IONS
Аннотация: TThe excitation spectrum of a catena-[FeII(ClO4)2{FeIII(bpca)2}]ClO4 anisotropic 1D magnet with alternating high-spin and low-spin iron ions has been calculated with the use of the diagrammatic technique for Hubbard operators. This has allowed establishing conformity with the Ising model, for which the magnetic susceptibility has been calculated by the transfer-matrix method. The introduction of a statistical ensemble taking into account the presence of chains with different lengths and iron ions with different spins has allowed describing the modification of the magnetic susceptibility under optical irradiation.
Смотреть статью,
Scopus,
WOS,
Читать в сети ИФ
Найти похожие

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Val'kov V. V., Dzebisashvili D. M., Barabanov A. F.
Заглавие : Origin of the spin polaron quasiparticles and their cooper instability in High-Tc superconductors
Коллективы : Russian Foundation for Basic Research [13-02-00523, 13-02-00909]; Dynasty Foundation
Место публикации : J. Supercond. Nov. Magn.: Springer, 2016. - Vol. 29, Is. 4. - P.1049-1055. - ISSN 1557-1939, DOI 10.1007/s10948-016-3383-8. - ISSN 1557-1947(eISSN)
Примечания : Cited References:15. - This study was supported by the Russian Foundation for Basic Research, projects nos. 13-02-00523, 13-02-00909 and the Dynasty Foundation.
Предметные рубрики: Model
State
Ключевые слова (''Своб.индексиров.''): cuprate high-t-c superconductors--spin polarons--spin-fermion model
Аннотация: IIn the framework of the spin-fermion model, it is shown that accounting for the strong spin-charge fluctuations between holes of copper and oxygen ions in cuprate High-T c superconductors leads to the formation of the Fermi spin-polaron quasiparticles. It is demonstrated that the large value of the binding energy of such quasiparticle is determined by the processes in which hopping intensity of the oxygen holes depends significantly on the spin configuration of holes on the copper and oxygen ions. It was found that the ensemble of such quasiparticles manifests Cooper instability and the concentration dependence of the critical temperature is in good agreement with the experimental data.
Смотреть статью,
WOS,
Читать в сети ИФ
Найти похожие

10.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Val'kov V. V., Dzebisashvili D. M., Barabanov A. F.
Заглавие : Nature of Cooper instability of spin polarons in cuprate high-Tc superconductors
Коллективы : Russian Foundation for Basic Research [13-02-00523, 13-02-00909], Dynasty Foundation
Место публикации : J. Low Temp. Phys.: Springer/Plenum Publishers, 2015. - Vol. 181, Is. 3-4. - P.134-138. - ISSN 0022, DOI 10.1007/s10909-015-1331-9. - ISSN 15737357(eISSN)
Примечания : Cited References:10. - This study was supported by the Russian Foundation for Basic Research, Projects Nos. 13-02-00523, 13-02-00909 and the Dynasty Foundation.
Предметные рубрики: OXIDES
MODEL
Ключевые слова (''Своб.индексиров.''): high-t-c superconductors--spin polarons--spin-fermion model
Аннотация: It is shown that the exchange interaction in the subsystem of localized moments of copper ions can trigger a Cooper instability in the ensemble of spin-polaron quasiparticles in cuprate high-temperature superconductors. It is important that, inherent to cuprates, strong coupling between Fermi and spin degrees of freedom leads on the one hand to formation of spin-polaron quasiparticles and, on the other hand, allows to transfer the interaction between Bose degrees of freedom onto the interaction between Fermi quasiparticles. The solution of the integral equation for the d-wave superconducting order parameter is well consistent with the available experimental data.
Смотреть статью,
Scopus,
WOS,
Читать в сети ИФ
Найти похожие