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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Zhou, Guojun, Guo, Shaoqiang, Zhao, Jing, Molokeev M. S., Liu, Quanlin, Zhang, Junying, Xia, Zhiguo
Заглавие : Unraveling the mechanochemical synthesis and luminescence in MnII-based two-dimensional hybrid perovskite (C4H9NH3)2PbCl4
Место публикации : Sci. China Mater. - 2019. - Vol. 62, Is. 7. - P.1013-1022. - ISSN 2095-8226, DOI 10.1007/s40843-018-9404-4. - ISSN 2199-4501(eISSN)
Примечания : Cited References: 40. - The present work was supported by the National Natural Science Foundation of China (91622125, 51722202 and 51572023) and the Natural Science Foundation of Beijing (2172036), and Molokeev M acknowledges the support of the Russian Foundation for Basic Research (17-52-53031). The DFT calculation was carried out at the National Supercomputer Center in Tianjin, and the calculations were performed on TianHe-1(A).
Предметные рубрики: DOPANT ENERGY-TRANSFER
EMISSION
EXCITON
MODEL
Аннотация: The mechanochemical route is a facile and fast way and has received much attention for developing versatile advanced functional materials. Herein, we reported a mechanochemical synthesis for incorporating divalent manganese ions (MnII) into a two-dimensional (2D) hybrid perovskite (C4H9NH3)2PbCl4. The mild external stimuli originating from the grinding at room temperature enabled the formation of MnII-doped 2D hybrid perovskites, and rapidly changed the luminescence characteristics. The photoluminescence analyses show that the violet and orange emissions are attributed to (C4H9NH3)2Pb1–xMnxCl4 band-edge emission and the T1→6A1 transition of Mn2+ resulting from an efficient energy transfer process, respectively. Site preference and distribution of the doped Mn2+ cations on the locations of Pb2+ were analyzed. The formation energy calculated by the density functional theory (DFT) indicates that the Mn2+ ions can rapidly enter the crystal lattice due to the unique 2D crystal structure of the hybrid perovskite. Such a case of mechanochemical synthesis for the 2D hybrid perovskite motivates many novel emerging materials and the related applications.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Kolovsky A. R.
Заглавие : Topological phase transitions in tilted optical lattices
Место публикации : Phys. Rev. A. - 2018. - Vol. 98, Is. 1. - Ст.013603. - ISSN 2469-9926, DOI 10.1103/PhysRevA.98.013603. - ISSN 2469-9934(eISSN)
Примечания : Cited References: 17
Предметные рубрики: BLOCH OSCILLATIONS
REALIZATION
BANDS
MODEL
Аннотация: We analyze the energy spectrum and eigenstates of cold atoms in a tilted brick-wall optical lattice. When the tilt is applied, the system exhibits a sequence of topological phase transitions reflected in an abrupt change of the eigenstates. It is demonstrated that these topological phase transitions can be easily detected in a laboratory experiment by observing Bloch oscillations of cold atoms.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Korshunov M. M., Eremin I.
Заглавие : Theory of magnetic excitations in iron-based layered superconductors
Место публикации : Phys. Rev. B: AMER PHYSICAL SOC, 2008. - Vol. 78, Is. 14. - Ст.140509. - ISSN 1098-0121, DOI 10.1103/PhysRevB.78.140509
Примечания : Cited References: 31
Предметные рубрики: NEUTRON-SCATTERING
INSTABILITY
STATE
ORDER
MODEL
Аннотация: Based on the effective four-band model we analyze the spin response in the normal and superconducting states of the Fe-pnictide superconductors. While the normal-state spin excitations are dominated by the continuum of the interorbital antiferromagnetic fluctuations and the intraband spin-density wave fluctuations, the unconventional superconductivity yields different feedback. The resonance peak in the form of the well-defined spin exciton occurs only for the interband scattering at the antiferromagnetic momentum Q(AFM) for the s(+/-) (extended s wave) superconducting order parameter and it disappears rapidly for q Q(AFM). The resonance feature is extremely weak for the d(x)(2)-y(2)-wave order parameter due to the specific Fermi-surface topology of these compounds. The essential difference between s(+/-)-wave and d(x)(2)-y(2)-wave symmetries for the magnetic excitations can be used for experimental determination of the superconducting wave-function symmetry.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Vasiliev, Alexander D., Cherepakhin, Alexander V., Zaitsev, Alexander I.
Заглавие : The trigonal polymorph of strontium tetraborate, beta-SrB4O7
Место публикации : Acta Crystallogr. Sect. E.-Struct Rep. Online. - MALDEN: WILEY-BLACKWELL, 2010. - Vol. 66, Part 6. - С. I48-U132. - JUN. - ISSN 1600-5368, DOI 10.1107/S1600536810019069
Примечания : Cited Reference Count: 22. - Гранты: We thank the State Program for Support of Leading Scientific Schools (grant LS-4645.2010.2.)Финансирующая организация: Leading Scientific Schools [LS-4645.2010.2]
Предметные рубрики: CRYSTAL-STRUCTURE
SRB4O7
LUMINESCENCE
MODEL
Ключевые слова (''Своб.индексиров.''): tetra
Аннотация: The asymmetric unit of the title compound, beta-SrB4O7, contains five Sr atoms (three located on a threefold rotation axis), twelve B and 21 O atoms. The structure is made up from BO3 triangles and BO4 tetrahedra in a 1:1 ratio. Pairs of BO3 triangles are linked to BO4 tetrahedra via common corners, forming chains. These chains are further linked to adjacent chains through corner-sharing, leading to a three-dimensional framework with channels running parallel to [001]. The Sr2+ ions reside in the channels and exhibit strongly distorted polyhedra The density of the beta-polymorph is considerably lower than that of beta-SrB4O7, which is constructed solely from BO4 tetrahedra.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Gavrichkov V. A., Ovchinnikov S. G., Yakimov L. E.
Заглавие : The role of orbital ordering in the formation of electron structure in undoped LaMnO3 manganites in the regime of strong electron correlations
Место публикации : J. Exp. Theor. Phys.: MAIK NAUKA/INTERPERIODICA/SPRINGER, 2006. - Vol. 102, Is. 6. - P972-985. - ISSN 1063-7761, DOI 10.1134/S1063776106060112
Примечания : Cited References: 25
Предметные рубрики: COLOSSAL MAGNETORESISTIVE OXIDES
DOUBLE EXCHANGE
BAND
MODEL
Ключевые слова (''Своб.индексиров.''): computational methods--correlation methods--doping (additives)--electrons--ferromagnetic materials--lanthanum compounds--paramagnetic materials--intraatomic electron correlations--mott hubbard correlation gap--orbital ordering--paramagnetic phases--electronic structure
Аннотация: The electron structure of undoped LaMnO3 and slightly doped La1-xSrxMnO3 manganites has been calculated within the framework of a generalized tight binding method with explicit allowance for strong intra-atomic electron correlations. According to the results of these calculations, the ground state in orbitally disordered undoped LaMnO3 ferromagnets would be metallic despite the Mott-Hubbard correlation gap in the spectrum of quasiparticles. Owing to the orbital ordering, the insulating state is stabilized in both antiferromagnetic and paramagnetic phases. In-gap states of a polaron nature with a spectral weight proportional to the dopant concentration have been found near the top of the valence band in La1-xSrxMnO3. As the doping level increases, a metal state appears in the ferromagnetic phase, which has a metallic character for one spin subband and an insulating character for the other subband (representing the so-called half-metallic state).
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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.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Balaev D. A., Popkov S. I., Shaihutdinov K. A., Petrov M. I.
Заглавие : The mechanisms responsible for broadening of the resistive transition under magnetic field in the Josephson junction network realized in bulk YBCO+CuO composites
Коллективы : International Workshop on Weak Superconductivity
Разночтения заглавия :авие SCOPUS: The mechanisms responsible for broadening of the resistive transition under magnetic field in the Josephson junction network realized in bulk YBCO + CuO composites
Место публикации : Physica C. - 2006. - Vol. 435, Is. 1-2. - P.12-15. - ISSN 0921-4534, DOI 10.1016/j.physc.2006.01.008
Примечания : Cited References: 15
Предметные рубрики: SUPERCONDUCTORS
MODEL
Ключевые слова (''Своб.индексиров.''): josephson network--ybco plus cuo composites--dissipation--magnetic field--dissipation--josephson network--magnetic field--ybco + cuo composites--composite materials--copper compounds--mathematical models--phase transitions--semiconductor junctions--yttrium compounds--creep model--josephson network--ybco + cuo composites--magnetic field effects
Аннотация: The experimental results of the effect of the magnetic field (up to 60 kOe) on the broadening of the resistive transition of bulk composites Y3/4Lu1/4Ba2CU3O7 (YBCO) + CuO are presented. These composites represent the network of the tunnel-type Josephson junctions where the copper oxide acts as a material forming barriers between YBCO crystallites. The mechanisms responsible for broadening of the resistive transition under magnetic field are discussed. The analysis of experimental R(7) dependences have shown that in the low field range 0-10(2) Oe, the R(7) dependences are described well by the Ambegaokar-Halperin (AH) model. In the range 10(3)-6 x 10(4) Oe, the dissipation follows Arrhenius law R similar to exp(-U(H)/k(B)T) characteristic for thermally activated flux creep model. In the range H similar to 10(2)-10(3), the crossover from AH to flux creep dissipation mechanisms occurs. (c) 2006 Elsevier B.V. All rights reserved.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Ovchinnikov S. G.
Заглавие : The mechanism of the electronic transition in ferroborates under high pressure
Место публикации : J. Phys.: Condens. Matter: IOP PUBLISHING LTD, 2005. - Vol. 17: 2nd International Symposium on Physics of Solids Under High Pressure Using Nuclear Probes (JUL 20-24, 2004, Cologne, GERMANY), Is. 11. - P.S743-S751. - ISSN 0953-8984, DOI 10.1088/0953-8984/17/11/003
Примечания : Cited References: 20
Предметные рубрики: STRUCTURAL PHASE-TRANSITION
MAGNETIC COLLAPSE
OPTICAL-SPECTRA
BAND-STRUCTURE
FEBO3
MODEL
Ключевые слова (''Своб.индексиров.''): carrier concentration--correlation methods--electron transitions--high pressure effects--magnetic moments--mathematical models--metal insulator transition--crystal field--electron correlations--electronic transition--ferroborates--ferromagnetic materials
Аннотация: A novel mechanism for the insulator-semiconductor transition and magnetic collapse in FeBO3 is proposed in the framework of the multielectron model with account taken of strong electron correlations. The electronic transition results from the crossover of the high spin and low spin Fe3+ states induced by the crystal field increasing with pressure. In the high pressure phase a semiconductor-metal transition is expected.
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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.
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10.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Ovchinnikov S. G., Shneyder E. I.
Заглавие : The Interplay of Phonon and Magnetic Mechanism of Pairing in Strongly Correlated Electron System of High-T-c Cuprates
Коллективы :
Разночтения заглавия :авие SCOPUS: The interplay of phonon and magnetic mechanism of pairing in strongly correlated electron system of high-T c cuprates
Место публикации : J. Supercond. Nov. Magn.: SPRINGER, 2010. - Vol. 23, Is. 5. - P733-736. - ISSN 1557-1939, DOI 10.1007/s10948-009-0633-z
Примечания : Cited References: 26. - This work is supported by the Presidium RAS program N 7 "Quantum physics of condensed matter," the integration project SORAN-UrORAN N 40, and the RFFI Grant 09-02-00127.
Предметные рубрики: PHASE-TRANSITIONS
OXIDE SUPERCONDUCTORS
SYMMETRY
COPPER
MODEL
BAND
BI2SR2CACU2O8+DELTA
LA2-XSRXCUO4
PB
Ключевые слова (''Своб.индексиров.''): high-t-c superconductivity--strong correlated electron systems--mechanisms of superconducting pairing--high-t c superconductivity--mechanisms of superconducting pairing--strong correlated electron systems--ab initio--buckling mode--correlated electron systems--critical temperatures--cuprates--fitting parameters--high-t--isotope effect--low energies--magnetic mechanisms--order of magnitude--phonon mode--strongly correlated electron system--strongly correlated electrons--superconducting pairing--superconductivity mechanism--type theory--buckling--copper compounds--electrons--isotopes--magnetic materials--phonons--superconductivity--superconducting magnets
Аннотация: We consider magnetic mechanism of superconducting pairing in the effective low energy t - t' - t '' - J* model with all parameters calculated ab initio. Interaction of strongly correlated electrons with different phonon modes is also incorporated. In a BCS type theory, the d(x2-y2) gap is given by a sum of magnetic and phonon contributions. The main contribution to the only fitting parameter G is determined by a competition of the breathing and buckling modes. Fitting the parameter G from the isotope effect, we obtain that magnetic and phonon contributions to the critical temperature T-c work together and are of the same order of magnitude.
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11.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : OVCHINNIKOV S.G.
Заглавие : THE INFLUENCE OF THE ANTIFERROMAGNETISM ON THE ELECTRONIC-STRUCTURE OF LA2CUO4
Разночтения заглавия :авие SCOPUS: The influence of the antiferromagnetism on the electronic structure of La2CuO4
Место публикации : J. Supercond.: PLENUM PUBL CORP, 1995. - Vol. 8: University-of-Miami Workshop on High-Temperature Superconductivity - Physical Properties and Mechanisms (JAN 05-11, 1995, CORAL GABLES, FL), Is. 5. - P675-676. - ISSN 0896-1107, DOI 10.1007/BF00727473
Примечания : Cited References: 15
Предметные рубрики: OXIDES
MODEL
Ключевые слова (''Своб.индексиров.''): electron correlations--electron structure--spin fluctuations--electron correlations--electron structure--spin fluctuations--antiferromagnetism--band structure--calculations--correlation theory--electrons--lanthanum compounds--paramagnetism--perturbation techniques--antiferromagnetic phase--electron correlations--intercluster interactions--spin fluctuations--electronic structure
Аннотация: The quasiparticle approach for electronic structure calculations considering strong electron correlations is given. The exact diagonalization of a multiband Hubbard Hamiltonian for a small cluster is combined with perturbation theory for intercluster hopping. The band structure of paramagnetic and antiferromagnetic La2CuO4 are discussed.
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12.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Ovchinnikov S. G., Zabluda V. N.
Заглавие : The energy band structure and optical spectra of FeBO3 calculated with allowance for strong electron correlations
Место публикации : J. Exp. Theor. Phys.: AMER INST PHYSICS, 2004. - Vol. 98, Is. 1. - P135-143. - ISSN 1063-7761, DOI 10.1134/1.1648107
Примечания : Cited References: 32. - This study was supported by the Russian Foundation for Basic Research (project no. 03-02-16286) and by the “Strongly Correlated Electrons” Program of the Department of Physical Sciences of the Russian Academy of Sciences
Предметные рубрики: PHASE-TRANSITION
HIGH-PRESSURE
FERROMAGNETISM
MODEL
Ключевые слова (''Своб.индексиров.''): atomic physics--band structure--charge transfer--excitons--green's function--light absorption--dielectric gap--energy band structure--lehmann spectral representation--optical spectra--iron compounds
Аннотация: A model of the energy band structure of iron borate (FeBO3) is proposed that combines a one-electron description of the sp states of boron and oxygen with a many-electron description of the d states of iron. The Green functions of d electrons are calculated using the exact Lehmann spectral representation. The energies of the d-type quasiparticles are calculated using terms of the d(4) , d(5) , and d(6) electron configurations. The optical absorption spectrum of FeBO3 is determined by local excitons and by the electron excitations with charge transfer. The latter excitations control the nature of the dielectric gap in FeBO3 crystals. The model parameters are determined from a comparison to the exciton energies. The density of single-particle states in FeBO3 is calculated. The main bands in the calculated optical absorption spectrum agree well with experimental data for energies up to 3 eV. (C) 2004 MAIK "Nauka/Interperiodica".
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13.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Makarov I. A., Ovchinnikov S. G.
Заглавие : Temperature dependence of the electronic structure of La2CuO4 in the multielectron LDA+GTB approach
Место публикации : J. Exp. Theor. Phys.: MAIK Nauka-Interperiodica / Springer, 2015. - Vol. 121, Is. 3. - P.457-464. - ISSN 1063-7761, DOI 10.1134/S1063776115090174
Примечания : Cited References: 38. - The work was supported by the Russian Science Foundation (project no. 14-12-00061)
Предметные рубрики: Copper oxides
Model
Superconductivity
Excitations
Instability
Spectrum
States
Order
Аннотация: The band structure of La2CuO4 in antiferromagnetic and paramagnetic phases is calculated at finite temperatures by the multielectron LDA+GTB method. The temperature dependence of the band spectrum and the spectral weight of Hubbard fermions is caused by a change in the occupation numbers of local multielectron spin-split terms in the antiferromagnetic phase. A decrease in the magnetization of the sublattice with temperature gives rise to new bands near the bottom of the conduction band and the top of the valence band. It is shown that the band gap decreases with increasing temperature, but La2CuO4 remains an insulator in the paramagnetic phase as well. These results are consistent with measurements of the red shift of the absorption edge in La2CuO4 with increasing temperature. © 2015, Pleiades Publishing, Inc.
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14.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Patrin G. S., Shiyan Ya. G., Patrin K. G., Yurkin G. Yu.
Заглавие : Synthesis and magnetic properties of [(CoP)soft/NiP/(CoP)hard/NiP]n films
Место публикации : J. Low Temp. Phys.: Springer, 2016. - Vol. 182, Is. 3-4. - P.73-81. - ISSN 00222291 (ISSN), DOI 10.1007/s10909-015-1363-1
Примечания : Cited References: 25. - This study was supported by the Ministry of Education and Science of the Russian Federation for the Siberian Federal University, state Order No. 3.2534.2014/K and the Russian Foundation for Basic Research, Project No. 14-02-00238-a.
Предметные рубрики: Exchange
Phase
Model
Ключевые слова (''Своб.индексиров.''): interlayer coupling--magnetic heterostructure--hysteresis loop--interlayer coupling--magnetic spring
Аннотация: Magnetic interactions in Co–Ni–P multilayers consisting of alternating magnetically soft and magnetically hard layers are experimentally investigated. The variation in the shape of magnetization loops at the conjugation of magnetically soft and magnetically hard layers and the saturation field oscillations with varying number of layer pairs are established. It is demonstrated that insertion of a nonmagnetic spacer significantly affects the magnetization reversal in the structure. It is concluded that in studying the interlayer coupling it is necessary to take into account the biquadratic interaction.
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15.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Janowitz C., Seidel U., Unger RST, Krapf A., Manzke R., Gavrichkov V. A., Ovchinnikov S. G.
Заглавие : Strong spin triplet contribution of the first removal state in the insulating regime of Bi2Sr2Ca1-xYxCu2O8+delta
Разночтения заглавия :авие SCOPUS: Strong spin triplet contribution of the first removal state in the insulating regime of Bi2Sr2Ca1-xY xCu2O8+δ
Место публикации : JETP Letters. - 2004. - Vol. 80, Is. 11. - P.692-696. - ISSN 0021-3640, DOI 10.1134/1.1862796
Примечания : Cited References: 18
Предметные рубрики: ELECTRONIC-STRUCTURE
APICAL OXYGEN
MODEL
SUPERCONDUCTIVITY
ONSET
Аннотация: The experimental dispersion of the first removal state in the insulating Bi2Sr2Ca1 - xYxCu2O8 + delta regime is found to differ significantly from that of other parent materials: oxyclorides and La2CuO4. For Y contents of 0.92 greater than or equal to x greater than or equal to 0.55 due to nonstoichiometric effects in the Bi-O layers, the hole concentration in the CuO2 layers is almost constant and, on the contrary, the crystal lattice parameters a, b, c change very strongly. This (a, b) parameter increase and c parameter decrease results in an unconventional three peak structure at (0, 0), (pi/2, pi/2), (pi, pi) for x = 0.92. We can describe the experimental data only beyond the framework of the three-band p-d-model involving the representations of a new triplet counterpart for the Zhang-Rice singlet state. (C) 2004 MAIK "Nauka/Interperiodica".
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16.

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.
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17.

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".
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18.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Aplesnin S. S., Petrakovskii G. A., Miroshnichenko N. I.
Заглавие : Simulation of magnetic properties of the two-dimensional magnetic with anisotropic antiferromagnetic interactions and cluster ordering by quantum Monte Carlo
Место публикации : Phys. Lett. A: ELSEVIER SCIENCE BV, 2008. - Vol. 372, Is. 26. - P4722-4725. - ISSN 0375-9601, DOI 10.1016/j.physleta.2008.05.010
Примечания : Cited References: 12
Предметные рубрики: SPIN SYSTEM
EXCITATIONS
CU3B2O6
MODEL
Ключевые слова (''Своб.индексиров.''): anisotropic antiferromagnetic--cluster ordering--plateau of magnetization--modulated structure--exchange in cu3b2o6--anisotropic antiferromagnetic--cluster ordering--exchange in cu3b2o6--modulated structure--plateau of magnetization
Аннотация: Magnetic with anisotropic anti ferromagnetic exchange interactions and special topology of coupling in the square lattice with spins pairs ordering is studied by quantum Monte Carlo method. The antiferromagnetic order is found to be more stable as compared to spin liquid state. Exchange interactions and wave vector of structure modulation for Cu3B2O6 is estimated. Neel temperature versus strength of exchange in spin pair is calculated. Plateau and modulation of magnetic structure in field magnetization dependence is revealed. (C) 2008 Elsevier B.V. All rights reserved.
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19.

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.
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20.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Ovchinnikov S. G.
Заглавие : Role of zinc and nickel impurities in high-temperature superconductors
Место публикации : Phys. Solid State: AMER INST PHYSICS, 1999. - Vol. 41, Is. 4. - P534-538. - ISSN 1063-7834, DOI 10.1134/1.1130819
Примечания : Cited References: 32
Предметные рубрики: PR2-XCEXCUO4+DELTA SINGLE-CRYSTALS
SR-CU-O
COPPER OXIDES
MAGNETIC-PROPERTIES
NI
MODEL
ZN
SUBSTITUTION
SCATTERING
SPECTRUM
Аннотация: The local changes produced in the electronic structure and their effect on the physical properties of the superconducting and normal phases when zinc and nickel are substituted for copper are examined on the basis of a multiband p-d model. It is shown that strong electronic correlations suppress the S = 1 configuration of Ni2+ and cause the superposition of the S = 1/2 and S = 0 states of nickel. The change in the density of states in p- and n-type systems is studied, and the peculiarity of Zn impurity for p- type systems and Ni impurity for n-type systems is shown. The universal dependence of the T-c on the residual resistance in lightly doped superconductors and deviations from it in optimally doped systems are discussed. (C) 1999 American Institute of Physics. [S1063-7834(99)00704-2].
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