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Вид документа : Статья из сборника (однотомник)
Шифр издания :
Автор(ы) : Popov A. K., Myslivets S. A., Shalaev M. I., Slabko V. V.
Заглавие : Photonic amplification and switching through nonlinear coupling with negative phonons
Коллективы : International Conference on Photonics in Switching (6; 2012 ; Sept ; 11-14; Ajaccio, France)
Место публикации : Int. Conf. Phot. Switch., PS 2012. - 2012. - Ст.6608287. - P. - ISBN 9782912328618 (ISBN)
Ключевые слова (''Своб.индексиров.''): extraordinary stimulated raman scattering--negative group velocity--nonlinear optical wave mixing--optical phonos--photonic components and devices
Аннотация: A family of switching photonic devices and amplifiers are proposed which mimic and utilize extraordinary coherent nonlinear-optical frequency conversion processes commonly attributed to plasmonic metamaterials. В© 2012 SEE.
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Вид документа : Статья из сборника (однотомник)
Шифр издания :
Автор(ы) : Popov A. K., Shalaev M. I., Myslivets S. A., Slabko V. V.
Заглавие : Photonic devices with negative phonons: a concept, extraordinary properties and materials
Коллективы : Национальный исследовательский университет ИТМО, Оптическое общество им. Д.С. Рождественского, Optics Design Group of Optical Society of Japan, JSAP, International Conference on Optics-Photonics Design and Fabrication (ODF12) (8; 2012 ; July ; 2-5; S.-Petersburg)
Место публикации : 8th International Conference on Optics-Photonics Design and Fabrication (ODF12): Book of abstracts. - 2012. - P.4S4-02
Аннотация: A family of readily available optical materials and photonic devices are proposed which mimic extraordinary coherent nonlinear-optical frequency conversion processes commonly attributed to plasmonic metamaterials that are very challenging to make.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Popov A. K., Shalaev M. I., Myslivets S. A., Slabko V. V.
Заглавие : Unidirectional amplification and shaping of optical pulses by three-wave mixing with negative phonons
Коллективы : US Air Force Office of Scientific Research [FA950-12-1-298]; US National Science Foundation [ECCS-1028353]; Presidium of the Russian Academy of Sciences [24-31]; Russian Federal Program on Science, Education and Innovation [14.A18.21.1942]
Место публикации : Appl. Phys. A: Springer, 2013. - Vol. 115, Is. 2. - P.523-529. - ISSN 0947-8396, DOI 10.1007/s00339-013-8078-4. - ISSN 1432-0630
Примечания : Cited References: 32. - This work was supported in parts by the US Air Force Office of Scientific Research under Grant No. FA950-12-1-298, by the US National Science Foundation under Grant No. ECCS-1028353, by the Presidium of the Russian Academy of Sciences under Grant No. 24-31 and by the Russian Federal Program on Science, Education and Innovation under Grant No. 14.A18.21.1942.
Предметные рубрики: LEFT-HANDED METAMATERIALS
2ND-HARMONIC GENERATION
INDEX METAMATERIALS
NONLINEAR OPTICS
PARAMETRIC AMPLIFICATION
COMPENSATING LOSSES
BACKWARD WAVES
OSCILLATOR
CRYSTALS
Аннотация: A possibility to greatly enhance frequency-conversion efficiency of stimulated Raman scattering is shown by making use of extraordinary properties of three-wave mixing of ordinary and backward waves. Such processes are commonly attributed to negative-index plasmonic metamaterials. This work demonstrates the possibility to replace such metamaterials that are very challenging to engineer by readily available crystals which support elastic waves with contra-directed phase and group velocities. The main goal of this work was to investigate specific properties of indicated nonlinear optical process in short-pulse regime and to show that it enables elimination of fundamental detrimental effect of fast damping of optical phonons on the process concerned. Among the applications is the possibility of creation of a family of unique photonic devices such as unidirectional Raman amplifiers and femtosecond pulse shapers with greatly improved operational properties.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Popov A. K., Slabko V. V., Shalaev M. I., Nefedov I. S., Myslivets S. A.
Заглавие : Nonlinear optics with backward waves: Extraordinary features, materials and applications
Коллективы : Asian School-Conference on Physics and Technology of Nanostructured Materials, Азиатская школа-конференция по физике и технологии наноструктурированных материалов
Место публикации : Solid State Phenom.: Selected, peer reviewed papers/ ed. N. Galkin. - 2014. - Vol. 213: Physics and Technology of Nanostructured Materials II. - P.222-225. - ISSN 1662-9779, DOI 10.4028/www.scientific.net/SSP.213.222. - ISSN 9783037859704
Ключевые слова (''Своб.индексиров.''): backward waves--negative group velocity--negative-index metamaterials--nonlinear optical frequency mixing--optical phonons--spatial dispersion
Аннотация: Extraordinary properties of nonlinear-optical propagation processes are investigated that involve electromagnetic or elastic waves with negative group velocity. Nanostructured materials that support such waves and prospective unique photonic devices are described. В© (2014) Trans Tech Publications, Switzerland.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Prokert F., Aleksandrov K. S.
Заглавие : Neutron scattering studies on phase transition and phonon dispersion in Cs//2NaBiCl//6
Место публикации : Phys Status Solidi B. - 1984. - Vol. 124, Is. 2. - P.503-513. - ISSN 0370-1972, DOI 10.1002/pssb.2221240208
Примечания : Cited References: 24
Ключевые слова (''Своб.индексиров.''): neutrons - scattering--phonons--phase transition--phonon dispersion--cesium compounds
Аннотация: The structural phase transition (PT) of elpasolite-type crystal Cs//2NaBiCl//6 is investigated by neutron scattering. At first the acoustic phonon dispersion is measured at room temperature for the high-symmetric directions DELTA , SIGMA , and LAMBDA of the Brillouin zone. The transverse rotary mode is studied for phonon wave vectors q parallel as well as perpendicular to DELTA and the dispersion shows a quasi-two-dimensional behavior of the Cl-octahedra rotation. At cooling down to the PT, this branch shows a softening along DELTA , reaching the lowest energies at the zone center. The PT, which is found to be of weakly first order, seems to be driven and triggered by the ferrorotative octahedra mode.
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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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Вид документа : Статья из сборника (однотомник)
Шифр издания :
Автор(ы) : Popov A. K., Shalaev M. I., Myslivets S. A., Slabko, V. V.
Заглавие : Unidirectional Amplification and Shaping of Optical Pulses by Three-Wave Mixing with Negative Phonons
Коллективы : International Conference on Metamaterials, Photonic Crystals and Plasmonics
Место публикации : The 4th International Conference on Metamaterials, Photonic Crystals and Plasmonics (META’13): Proceedings. - 2013. - P.35-40
Примечания : Библиогр.: 30 назв.
Аннотация: A possibility to greatly enhance frequency-conversion efficiency of stimulated Raman scattering is shown by making use of extraordinary properties of three-wave mixing of ordinary and backward waves. Such processes are commonly attributed to negative-index plasmonic metamaterials. This work demonstrates the possibility to replace such metamaterials that are very challenging to engineer by readily available crystals which support elastic waves with contradirected phase and group velocities. The main goal of this work is to investigate specific properties of indicated nonlinear optical process in short pulse regime and to show that it enables elimination of fundamental detrimental effect of fast damping of optical phonons on the process concerned. Among the applications is the possibility of creation of a family of unique photonic devices such as unidirectional Raman amplifiers and femtosecond pulse shapers with greatly improved operational properties.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Krylov A. S., Krylova S. N., Vtyurin A. N., Voronov V. N., Oreshonkov A. S.
Заглавие : Raman Scattering Study Temperature Phase Transitions of Rb2KInF6 Crystal
Место публикации : Ferroelectrics: TAYLOR & FRANCIS LTD, 2011. - Vol. 416. - P95-100. - ISSN 0015-0193, DOI 10.1080/00150193.2011.577713
Примечания : Cited References: 9. - Authors wish to thank prof. K. S. Aleksandrov and prof. I. N. Flerov for their valuable support and useful discussions. This work has been financially supported by grants RFFBR 08-02-00066, 09-02-00062, SS-1011.2008.2.
Предметные рубрики: LIGHT-SCATTERING
LATTICE-DYNAMICS
OPTICAL PHONONS
ELPASOLITE
RB2KSCF6
Ключевые слова (''Своб.индексиров.''): rb2kinf6--temperature phase transitions--raman scattering--lattice dynamics
Аннотация: Raman scattering spectra of Rb2KInF6 crystal have been studied in a wide temperature range, including two phase transitions: from cubic to tetragonal, and then - to the monoclinic phase. Hardening of soft phonon modes was observed that attributes them to the transitions of displacive type. Parameters of Raman lines have been quantitatively analyzed and found in good agreement with known thermodynamic characteristics of these transitions. No evidences of order - disorder processes were observed in the Raman spectra of the high-symmetry phase.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Krylov A. S., Vtyurin A. N., Bulou A., Voronov V. N.
Заглавие : Raman spectra and phase transitions in the Rb2KScF6 elpasolite
Коллективы : Russian-CIS-Baltic-Japanese symposium on ferroelectricity
Место публикации : Ferroelectrics: Taylor & Francis LTD, 2003. - Vol. 284. - P221-238. - ISSN 0015-0193, DOI 10.1080/00150190390204709
Примечания : Cited References: 13
Предметные рубрики: LIGHT-SCATTERING
OPTICAL PHONONS
MODE
Ключевые слова (''Своб.индексиров.''): rb2kscf6--phase transitions--raman scattering--soft modes
Аннотация: Raman spectra of Rb2KScF6 elpasolite crystal have been studied in a wide temperature range, including two transition points: from cubic to tetragonal, and then-to the monoclinic phase. For the first time both for this crystal and for fluoride elpasolites in general soft modes restoration has been found below transition points; in agreement with selection rules a splitting of degenerate modes has been observed as well both for lattice vibrations and internal modes of ScF6 octahedrons. Parameters of Raman lines have been quantitatively analyzed and found in good agreement with known thermodynamic characteristics of these transitions; in particular, lines widths are shown to be determined by tree-phonons anharmonic interactions. A wide region of pretransitional fluctuations was found above the upper transition point.
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10.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Рогинский Е. М., Крылов, Александр Сергеевич, Марков Ю. Ф.
Заглавие : Неэмпирические подходы при изучении фазовых переходов и барическое поведение фононов в молекулярных кристаллах
Место публикации : Наноматер. и нанострукт. - XXI век: Радиотехника, 2015. - Т. 6, № 2. - С. 21-27. - ISSN 2225-0999
Примечания : Библиогр.: 12
Ключевые слова (''Своб.индексиров.''): ab initio--фононы--сегнетоэластики--фазовые переходы--раман-спектроскопия--динамика решетки--phonon--ferroelastics--phase transition--raman spectra--lattice dynamics
Аннотация: При изучении барического поведения фононного спектра кристаллов Hg2Cl2 были предсказаны теоретически и обнаружены экспериментально в низкосимметричной, ромбической фазе мягкие моды из различных высокосимметричных точек зоны Бриллюэна (ЗБ), частоты которых уменьшается при повышении давления. В раман спектрах наблюдается мягкий фонон, который смягчается вплоть до критического давления c = 9,2 ГПа, выше которого полностью исчезает, что свидетельствует в пользу второго структурного фазового перехода, обнаруженного в настоящей работе, в кристаллах Hg2Cl2. Показано, что в случае молекулярных или квазимолекулярных кристаллов для корректного описания электронной структуры важно учитывать дисперсионные дальнодействующие поправки функционала зарядовой плотности.Under the study of phonon spectra pressure behaviour of Hg2Cl2 crystals the soft modes at the set of high-symmetry Brillouin zone(BZ) points was predicted theoretically and observed experimentally. The frequency of soft modes reduces under pressure. In the raman spectra soft mode at the center of BZ was observed and studied. The frequency of soft mode decrease at the hydrostatic pressure up to P c = 9.2 GPa and disappears at higher pressure in spectra. Such changes in spectra points to the existence of the second phase transition observed in the present work. It was shown that in the case of molecular crystals the long-range dispersion corrections of the electron density functional is required for a proper electronic structure description.
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11.

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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12.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Davydov V. Yu., Klochikhin A. A., Smirnov A. N., Strashkova I. Y., Krylov A. S., Lu H., Schaff W. J., Lee H. M., Hong Y. L., Gwo S.
Заглавие : Resonant Raman Scattering and Dispersion of Polar Optical and Acoustic Phonons in Hexagonal InN
Коллективы :
Разночтения заглавия :авие SCOPUS: Resonant raman scattering and dispersion of polar optical and acoustic phonons in hexagonal inn
Место публикации : Semiconductors: MAIK NAUKA/INTERPERIODICA/SPRINGER, 2010. - Vol. 44, Is. 2. - P161-170. - ISSN 1063-7826, DOI 10.1134/S1063782610020065
Примечания : Cited References: 19. - This study was supported by the Russian Foundation for Basic Research (project nos. 09-02-01280 and 08-02-92003-NNS) and by the program of the Russian Academy of Sciences "New Materials and Structures."
Аннотация: It is shown that a study of the dependence of impurity-related resonant first-order Raman scattering on the frequency of excitation light makes it possible to observe the dispersion of polar optical and acoustic branches of vibrational spectrum in hexagonal InN within a wide range of wave vectors. It is established that the wave vectors of excited phonons are uniquely related to the energy of excitation photon. Frequencies of longitudinal optical phonons E(1)(LO) and A(1)(LO) in hexagonal InN were measured in the range of excitation-photon energies from 2.81 to 1.17 eV and the frequencies of longitudinal acoustic phonons were measured in the range 2.81-1.83 eV of excitation-photon energies. The obtained dependences made it possible to extrapolate the dispersion of phonons A(1)(LO) and E(1)(LO) to as far as the point Gamma in the Brillouin zone and estimate the center-band energies of these phonons (these energies have not been uniquely determined so far).
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13.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Zinenko V. I., Zamkova N. G., Maksimov E. G., Sofronova S. N.
Заглавие : Lattice dynamics and ferroelectric instability in ordered and disordered PbSc1/2Ta1/2O3 and PbSc1/2Nb1/2O3 solid solutions
Разночтения заглавия :авие SCOPUS: Lattice dynamics and ferroelectric instability in ordered and disordered PbSc1/2Ta1/2O3 and PbSc1/2Nb 1/2O3 solid solutions
Место публикации : J. Exp. Theor. Phys.: MAIK NAUKA/INTERPERIODICA/SPRINGER, 2007. - Vol. 105, Is. 3. - P617-625. - ISSN 1063-7761, DOI 10.1134/S1063776107090191
Примечания : Cited References: 23
Предметные рубрики: RELAXOR FERROELECTRICS
PHASE-TRANSITION
LOCAL-STRUCTURE
PB(SC1/2NB1/2)O-3
PEROVSKITE
CRYSTALS
Ключевые слова (''Своб.индексиров.''): dipole moment--lattice vibrations--negative ions--phonons--positive ions--solid solutions--dynamic born charges--ferroelectric instabilities--frequency spectra--gordon-kim models--oxygen anions--phonon spectra--ferroelectricity
Аннотация: The dynamic Born charges and the frequency spectra of lattice oscillations in the crystals of ordered and disordered PbSc1/2Ta1/2O3 (PST) and PbSc1/2Nb1/2O3 (PSN) solid solutions have been calculated within the framework of the generalized Gordon-Kim model with allowance for the dipole and quadrupole polarizabilities. The phonon spectra of both compounds contain ferroelectric soft modes. The influence of various interactions on the magnitude of dynamic charges and ferroelectric instability in PSN and PST solid solutions has been studied and it is shown that both these charges and the ferroelectric instability are determined by the competition between long-range dipole-dipole interactions and short-range dipole-charge interactions, the determining role played by the interaction of Nb (Ta) cations and oxygen anions in the Nb-O (Ta-O) bond direction.
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14.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Zinenko V. I., Pavlovskii M. S.
Заглавие : Lattice dynamics and the phase transition from the cubic phase to the tetragonal phase in the LaMnO3 crystal within the polarizable-ion model
Место публикации : Phys. Solid State: MAIK NAUKA/INTERPERIODICA/SPRINGER, 2007. - Vol. 49, Is. 9. - P1749-1758. - ISSN 1063-7834, DOI 10.1134/S1063783407090235
Примечания : Cited References: 23
Предметные рубрики: NEUTRON-DIFFRACTION
PEROVSKITES
MANGANITES
PHONONS
Аннотация: The paper reports on the results of ab initio calculations of the static and dynamic properties of the LaMnO3 crystal with a perovskite structure in the cubic, rhombohedral, and orthorhombic phases. The calculations are performed within the ionic crystal model, which takes into account the deformability and polarizability of the ions. It is revealed that the spectrum of lattice vibrations in the cubic phase contains unstable vibrational modes, which occupy the phase space in the entire Brillouin zone. The eigenvectors of the softest mode at the boundary point R of the Brillouin zone are associated with the displacements of the oxygen ions and correspond to the "rotation" of the MnO6 octahedron. The condensation of one, two, and three components of this mode leads to the tetragonal, orthorhombic, and rhombohedral distortions of the structure. The structural phase transition is described in terms of the local mode approximation with the use of the double perovskite unit cell, in which the MnO6 octahedron is explicitly separated. The parameters of the model Hamiltonian are determined. The static properties are investigated by the Monte Carlo method. The calculated temperature of the phase transition from the cubic phase (9800 K) is considerably higher than the melting temperature of the crystal under investigation. The calculated frequencies of long-wavelength lattice vibrations in the experimentally observed orthorhombic and rhombohedral phases are in reasonable agreement with experimental data.
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15.

Вид документа : Статья из сборника (однотомник)
Шифр издания :
Автор(ы) : Vtyurin A. N., Krylov A. S., Gerasimova J. V., Fokina V. D., Kocharova A. G., Laptash N. M., Voyt E. I., Surovtsev N. V.
Заглавие : Raman scattering study of ordering processes and phase transitions in A(2)BWO(3)F(3) oxyfluorides crystals
Разночтения заглавия :авие SCOPUS: Raman scattering study of ordering processes and phase transitions in A2BWO3F3oxyfluorides crystals
Место публикации : 12TH INTERNATIONAL CONFERENCE ON PHONON SCATTERING IN CONDENSED MATTER (PHONONS 2007). Ser. Journal of Physics Conference Series: IOP PUBLISHING LTD, 2007. - Vol. 92: 12th International Conference on Phonon Scattering in Condensed Matter (PHONONS 2004) (JUL 15-20, 2007, Paris, FRANCE). - Ст.12158. - ISBN 1742-6588, DOI 10.1088/1742-6596/92/1/012158
Примечания : Cited References: 6
Предметные рубрики: (NH4)(3)WO3F3
Аннотация: Raman spectra of perovskite-like (NH(4))(3)WO(3)F(3), (NH(4))(2)KWO(3)F(3) and Cs(2)(NH(4))WO(3)F(3) oxyfluorides are obtained in a wide temperature range including transition points. Transition anomalies are found and analyzed. Transformation in (NH(4))(3)WO(3)F(3) is shown to be bound with octahedron groups ordering and strong distortion of ammonium ions due to H-bond formation, that is accompanied by cell volume multiplication, hardening and formation of complex discrete low frequency lattice spectrum. Same cell doubling was found in (NH(4))(2)KWO(3)F(3), but without lattice ordering Cs(2)(NH(4))WO(3)F(3) lattice stays disordered down to 15 K.
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16.

Вид документа : Статья из сборника (однотомник)
Шифр издания :
Автор(ы) : Zamkova N. G., Zinenko V. I.
Заглавие : Lattice dynamics and ferroelectric phase transitions in solid solutions PbSc(1/2)Nb(1/2)O(3) and PbSc(1/2)Ta(1/2)O(3)
Разночтения заглавия :авие SCOPUS: Lattice dynamics and ferroelectric phase transitions in solid solutions PbSc1/2Nb1/2O3 and PbSc1/2Ta 1/2O3
Место публикации : 12TH INTERNATIONAL CONFERENCE ON PHONON SCATTERING IN CONDENSED MATTER (PHONONS 2007). Ser. Journal of Physics Conference Series: IOP PUBLISHING LTD, 2007. - Vol. 92: 12th International Conference on Phonon Scattering in Condensed Matter (PHONONS 2004) (JUL 15-20, 2007, Paris, FRANCE). - Ст.12162. - ISBN 1742-6588, DOI 10.1088/1742-6596/92/1/012162
Примечания : Cited References: 14
Предметные рубрики: PEROVSKITES
BATIO3
Аннотация: The calculation of the lattice dynamics and ferroelectric phase transitions for disordered and ordered solid solution PbSc(1/2)Nb(1/2)O(3) and PbSC(1/2)Ta(1/2)O(3) in the framework of the Gordon-Kim model are performed. The unstable ferroelectric modes were found in all cases. The model Hamiltonian for the study finite temperature behavior during for the ferroelectric phase transition is used. The transition temperatures, phase sequences and spontaneous polarizations are calculated by Monte-Carlo method.
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17.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Ovchinnikov S. G., Shneider E. I.
Заглавие : Effective Hamiltonian for HTSC cuprates taking into account electron-phonon interaction in the strong-correlation regime
Место публикации : J. Exp. Theor. Phys.: AMER INST PHYSICS, 2005. - Vol. 101, Is. 5. - P844-855. - ISSN 1063-7761, DOI 10.1134/1.2149064
Примечания : Cited References: 38. - This work was supported by the Russian Foundation for Basic Research (project no. 03-02-16124), the program “Quantum Macrophysics” of the Presidium of the Russian Academy of Sciences, the Foundation in Support for Russian Science, the Foundation of Noncommercial
Предметные рубрики: HIGH-TEMPERATURE SUPERCONDUCTORS
D-WAVE SUPERCONDUCTIVITY
T-C
DISPERSION
SCATTERING
OXIDES
STATE
MODEL
Ключевые слова (''Своб.индексиров.''): electron beams--electronic structure--optimization--phonons--electron correlations--hubbard x operators--spin-photon interaction--hamiltonians
Аннотация: Electron-phonon interaction is sequentially derived from a realistic p-d multiband model for the cuprates under conditions of strong electron correlations. The electronic structure is described using the representation of the Hubbard X operators in a generalized tight-binding method. Dependences of the diagonal and off-diagonal (on lattice sites) matrix elements of electron-phonon interaction on the wavevectors are found for three phonon modes, namely, breathing, apical breathing, and bending modes. The interactions of the breathing and bending modes with electrons are shown to contribute to the formation of kinks in the (0; 0)-(pi; pi) and (0; 0)-(pi; 0) directions, respectively. A low-energy t-J* model with phonons is developed; apart from electron-phonon interaction, it also includes spin-phonon interaction. The elimination of phonons gives an effective electron-electron interaction that depends on the occupation number of a multielectron term and on the carrier concentration due to strong electron correlations. (c) 2005 Pleiades Publishing, Inc.
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18.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Aplesnin S. S.
Заглавие : Two-dimensional quantum spin liquid with S=1/2 spins interacting with acoustic phonons
Разночтения заглавия :авие SCOPUS: Two-dimensional quantum spin liquid with S = 1/2 spins interacting with acoustic phonons
Место публикации : Phys. Lett. A. - 2004. - Vol. 333, Is. 5-6. - P.446-449. - ISSN 0375-9601, DOI 10.1016/j.physleta.2004.10.064
Примечания : Cited References: 11
Предметные рубрики: ANTIFERROMAGNET
Ключевые слова (''Своб.индексиров.''): spin-phonon interactions--spin-liquid--spinon excitations--spin-liquid--spin-phonon interactions--spinon excitations--ferromagnetic material--acceleration--acoustics--article--density--energy--liquid--magnetic field--mathematical analysis--monte carlo method--phonon--quantum mechanics
Аннотация: The spin density of states of a two-dimensional antiferromagnet in magnetic field having spins-1/2 and interacting with acoustic phonons is investigated in the nonadiabatic approximation using the quantum Monte Carlo method. It is found the gap energy A in the single particle spin excitations spectrum closes at magnetic field Delta similar or equal to H-c, W-ph W-s and Delta similar or equal to (1/2)H-c, W-ph W-s, where W-ph and W-s are the bandwidths of phonon and spin excitations in antiferromagnet. (C) 2004 Elsevier B.V All rights reserved.
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19.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Krylova S. N., Vtyurin A. N., Bulou A., Krylov A. S., Zamkova N. G.
Заглавие : Lattice dynamics and raman scattering spectrum of elpasolite Rb2KScF6: Comparative analysis
Разночтения заглавия :авие SCOPUS: Lattice dynamics and Raman scattering spectrum of elpasolite Rb 2KScF6: Comparative analysis
Место публикации : Phys. Solid State: MAIK NAUKA/INTERPERIODICA/SPRINGER, 2004. - Vol. 46, Is. 7. - P1311-1319. - ISSN 1063-7834, DOI 10.1134/1.1778457
Примечания : Cited References: 18
Предметные рубрики: STRUCTURAL PHASE-TRANSITION
LIGHT-SCATTERING
OPTICAL PHONONS
SOFT-MODE
CRYSTAL
Аннотация: Raman scattering spectra of elpasolite Rb2KScF6 are studied in a wide temperature range including two phase transitions: from the cubic to the tetragonal phase and then to the monoclinic phase. The experimental Raman scattering spectrum is compared with the lattice vibration spectra of these phases calculated using an ab initio approach. A number of anomalies (caused by structural rearrangement during the phase transitions) are revealed and quantitatively analyzed in the ranges of both the intramolecular vibrations of the octahedron molecular ScF6 ions and low-frequency intermolecular lattice vibrations. The interaction between low-frequency intramolecular vibrations and the intermolecular modes is found to be significant, and strong resonance interaction of the rotational soft modes (which are recovered below the phase transition points) with hard low-frequency vibrations of the rubidium ion sublattice is detected. These interactions are shown to substantially complicate the spectra. (C) 2004 MAIK "Nauka / Interperiodica".
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20.

Вид документа : Статья из сборника (однотомник)
Шифр издания :
Автор(ы) : Zinenko V. I., Sofronova S. N.
Заглавие : The nonempirical calculation of the cation ordering and lattice dynamics in the solid solutions of PbSc1/2Nb1/2O3 and PbSc1/2Ta1/2O3
Место публикации : 11th International Conference on Phonon Scattering in Condensed Matter (PHONONS 2004) (JUL 25-30, 2004, St Petersburg, RUSSIA): WILEY-V C H VERLAG GMBH, 2004. - P3047-3051. - ISBN 3-527-40588-7, DOI 10.1002/pssc.200405286
Примечания : Cited References: 10
Аннотация: An effective Hamiltonian for the study of Sc-Nb(Ta) cation ordering in PbSc1/2Nb(Ta)(1/2)O-3 solid solutions is written out. To determine the parameters of the effective Hamiltonian, a nonempirical calculation is performed within an ionic-crystal model taking into account the deformation, dipole and quadrupole polarizabilities of ions. The phase transition temperatures are calculated by mean field, cluster approximations and Monte-Carlo method. Within the same ionic-crystal model, we calculated the high-frequency permittivity, Born dynamic charges, and the phonon spectrum for a completely disordered and ordered phases. (C) 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
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