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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Boldyrev K. N., Stanislavchuk T. N., Sirenko A. A., Kamenskyi D., Bezmaternykh L. N., Popova M. N.
Заглавие : Bifurcations of coupled electron-phonon modes in an antiferromagnet subjected to a magnetic field
Место публикации : Phys. Rev. Lett.: American Physical Society, 2017. - Vol. 118, Is. 16. - Ст.167203. - ISSN 00319007 (ISSN), DOI 10.1103/PhysRevLett.118.167203
Примечания : Cited References: 26. - This research was supported by the Russian Scientific Foundation under Grant No. 14-12-01033, the President of Russian Federation (MK-3577.2017.2, K. N. B.), and the U.S. Department of Energy under Grant No. DE-FG02-07ER46382 (experiments at U4-IR beam line NSLS-BNL, T. N. S. and A. A. S.). The National Synchrotron Light Source is operated as a user facility for the U.S. Department of Energy under Contract No. DE-AC02-98CH10886. Part of this work was supported by EMFL (Contract No. 26211). M. N. P. thanks B. Z. Malkin and A. V. Popov for helpful discussions.
Ключевые слова (''Своб.индексиров.''): antiferromagnetic materials--bifurcation (mathematics)--electron-phonon interactions--electrons--magnetic fields--magnetism--temperature--antiferromagnetic crystals--bifurcation points--electron phonon couplings--electronic excitation--external magnetic field--field independents--low temperatures--reflection spectra--phonons
Аннотация: We report on a new effect caused by the electron-phonon coupling in a stoichiometric rare-earth antiferromagnetic crystal subjected to an external magnetic field, namely, the appearance of a nonzero gap in the spectrum of electronic excitations in an arbitrarily small field. The effect was registered in the low-temperature far-infrared (terahertz) reflection spectra of an easy-axis antiferromagnet PrFe3(BO3)4 in magnetic fields Bext-c. Both paramagnetic and magnetically ordered phases (including a spin-flop one) were studied in magnetic fields up to 30 T, and two bifurcation points were observed. We show that the field behavior of the coupled modes can be successfully explained and modeled on the basis of the equation derived in the framework of the theory of coupled electron-phonon modes, with the same field-independent electron-phonon interaction constant |W|=14.8 cm-1. © 2017 American Physical Society.
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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 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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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Donkov A., Eremin I., Knolle J., Korshunov M. M.
Заглавие : Electron-Phonon Interaction and Phonon Renormalization in the Lamellar Cobaltate NaxCoO2
Разночтения заглавия :авие SCOPUS: Electron-phonon interaction and phonon renormalization in the lamellar cobaltate Na x CoO 2
Место публикации : J. Supercond. Nov. Magn.: SPRINGER, 2009. - Vol. 22: International Conference on Quantum Phenomena in Complex Matters (JUL 26-AUG 01, 2008, Erice, ITALY), Is. 1. - P37-40. - ISSN 1557-1939, DOI 10.1007/s10948-008-0372-6
Примечания : Cited References: 16
Предметные рубрики: SUPERCONDUCTIVITY
Ключевые слова (''Своб.индексиров.''): electron-phonon interaction--superconductivity--sodium cobaltate--electron-phonon interaction--sodium cobaltate--superconductivity--brillouin zones--cobaltate--conducting electrons--conduction electrons--doping dependences--feedback effects--matrix elements--phonon frequencies--phonon modes--raman experiments--renormalization--sodium cobaltate--sodium cobaltates--atoms--cobalt compounds--critical current density (superconductivity)--electric conductivity--electron-phonon interactions--electrons--flow interactions--penetration depth (superconductivity)--sodium--superconductivity--phonons
Аннотация: We study theoretically the electron-phonon interaction in NaxCoO2. For the A(1g) and E-1g phonon modes found in Raman experiments, we calculate the matrix elements of the electron-phonon interaction. Analyzing the feedback effect of the conduction electrons on the phonon frequency., we investigate the doping dependence of these two phonon modes. Due to the momentum dependence of the electron-phonon interaction, we find the strongest renormalization of the E-1g mode around the Brillouin zone boundary which should be observed in the neutron scattering. At the same time, the A(1g) mode shows the strongest coupling to the conducting electrons around the G point and reveals its doping dependence in the Raman experiments. Our results shed light on the possible importance of the electron-phonon interaction in the lamellar sodium cobaltates.
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Вид документа : Статья из сборника (однотомник)
Шифр издания :
Автор(ы) : Popov A.K., Slabko V.V., Shalaev M.I., Myslivets S. A.
Заглавие : Engineering localized nonlinear - optical transport with optical phonons
Коллективы : International Conference on Transparent Optical Networks
Место публикации : 13th International Conference on TransparenT Optical Network. - 2011. - Ст.5971107
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Imasaka, Kotaro, Pisarev, Roman, V, Bezmaternykh L. N., Shimura, Tsutomu, Kalashnikova, Alexandra M., Satoh, Takuya
Заглавие : Excitation of multiple phonon modes in copper metaborate CuB2O4 via nonresonant impulsive stimulated Raman scattering
Коллективы : Japanese Society for Promotion of Sciences (JSPS) via the Short-Term Fellowship Program; JSPS KAKENHI [JP15H05454, JP26103004]; JSPS Core-to-Core Program (A. Advanced Research Networks); Russian Science Foundation [16-12-10456]
Место публикации : Phys. Rev. B. - 2018. - Vol. 98, Is. 5. - Ст.054303. - ISSN 2469-9950, DOI 10.1103/PhysRevB.98.054303. - ISSN 2469-9969(eISSN)
Примечания : Cited References: 64. - We thank V. Yu. Davydov for help with the spontaneous Raman scattering experiments. A.M.K. acknowledges support from the Japanese Society for Promotion of Sciences (JSPS) via the Short-Term Fellowship Program for European and North-Americanyoung researchers during her stay at the University of Tokyo. T.S. was supported by JSPS KAKENHI (No. JP15H05454 and No. JP26103004) and JSPS Core-to-Core Program (A. Advanced Research Networks). R.V.P. acknowledges the support from the Russian Science Foundation (Grant No. 16-12-10456).
Предметные рубрики: SPIN-WAVE SPECTRUM
COHERENT PHONONS
OPTICAL MANIPULATION
Аннотация: The excitation of four coherent phonon modes of different symmetries is realized in copper metaborate CuB2O4 via impulsive stimulated Raman scattering (ISRS). The phonons are detected by monitoring changes in the linear optical birefringence using the polarimetric detection (PD) technique. We compare the results of the ISRS-PD experiment to the polarized spontaneous Raman scattering spectra. We show that agreement between the two sets of data obtained by these allied techniques in a wide phonon frequency range of 4-14 THz can be achieved by taking into account the symmetry of the phonon modes and corresponding excitation and detection selection rules. It is also important to account for the difference between incoherent and coherent phonons in terms of their contributions to the Raman scattering process. This comparative analysis highlights the importance of the ratio between the frequency of a particular mode, and the pump and probe spectral widths. We analytically demonstrate that the pump and probe pulse durations of 90 and 50 fs, respectively, used in our experiments limit the highest frequency of the excited and detected coherent phonon modes to 12 THz, and define their relative amplitudes.
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Вид документа : Статья из сборника (выпуск продолж. издания)
Шифр издания :
Автор(ы) : Ignatchenko V. A., Polukhin D. S.
Заглавие : Green's functions of polaritons in a medium with zero-mean inhomogeneous coupling parameter
Коллективы : International Conference on Photonics of Nano- and Bio-Structures, International Conference on Photonics of Nano- and Bio-Structures
Место публикации : Physics Procedia: Elsevier, 2017. - Vol. 86. - P.117-121. - , DOI 10.1016/j.phpro.2017.01.031
Примечания : Cited References: 10
Ключевые слова (''Своб.индексиров.''): electromagnetic waves--optical phonons--crossing resonance--polaritons--green's functions--self-consistent approximation
Аннотация: Dynamic susceptibilities (Green's functions) of the interacting electromagnetic waves G”e(ω) and optical phonons G”u(ω) in a medium with zero-mean inhomogeneous coupling parameter have been considered. The calculation was performed using a self-consistent approximation for the two stochastically interacting wave fields. It is shown that on the tops of the resonance maxima of the imaginary parts of the Green functions the fine structure is formed: a minimum (dip) on the top of G”e(ω) and narrow maximum (peak) on the top of G”u(ω). With increasing the correlation wavenumber of inhomogeneities kc (i.e., with decreasing the size of inhomogeneities), the width of the peak on G”u(ω) decreases, and two resonance maxima in the function G”e(ω) are formed. Because of the large difference in the speeds of light and optical phonons, the fine structure of the polaritons is manifested itself more clearly and saved to a much larger values of kc, than for the studied earlier crossing resonance of spin and elastic waves.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Gorev M. V., Flerov I. N., Bondarev V. S., Sciau P.
Заглавие : Heat capacity study of relaxor PbMg1/3Nb2/3O3 in a wide temperature range
Разночтения заглавия :авие SCOPUS: Heat capacity study of relaxor PbMg1/3Nb2/3O 3 in a wide temperature range
Место публикации : J. Exp. Theor. Phys.: MAIK NAUKA/INTERPERIODICA/SPRINGER, 2003. - Vol. 96, Is. 3. - P531-537. - ISSN 1063-7761, DOI 10.1134/1.1567427
Примечания : Cited References: 21
Предметные рубрики: DIFFUSE PHASE-TRANSITION
FERROELECTRICS
Ключевые слова (''Своб.индексиров.''): differential scanning calorimetry--mathematical models--phonons--random processes--specific heat--spectrum analysis--thermal effects--bond-random field models--wide temperature intervals--lead compounds
Аннотация: Heat capacity of the PbMg1/3Nb2/3O3 compound is measured using the methods of adiabatic and differential scanning calorimetry in the temperature range 80-750 K. Two blurred anomalies on the C-p(T) dependence are observed in wide temperature intervals of 200- 400 K and 500-700 K. The results of studies are discussed together with data on the structure and phonon spectrum in the framework of spherical random bond-random field model. (C) 2003 MAIK "Nauka/Interperiodica".
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Handunkanda, Sahan U., Curry, Erin B., Voronov V. N., Hancock, Jason N.
Заглавие : Infrared lattice dynamics in negative thermal expansion material in single-crystal ScF3
Место публикации : J. Phys.: Condens. Matter. - 2020. - Vol. 32, Is. 3. - Ст.035403. - ISSN 0953-8984, DOI 10.1088/1361-648X/ab4955. - ISSN 1361-648X(eISSN)
Примечания : Cited References: 49. - Work at the University of Connecticut is supported by National Science Foundation Award No. DMR-1506825
Предметные рубрики: LONGITUDINAL-OPTIC MODES
TEMPERATURE-DEPENDENCE
ABSORPTION
Аннотация: Simple cubic 'open' perovskite ScF3 stands out among trifluoride materials in its large, isotropic negative thermal expansion (NTE), but also its proximity of its zero-temperature state to a structural phase transition. Here we report a temperature- and frequency-dependent lattice dynamical study of Brillouin zone center lattice excitations of single crystals of ScF3 using infrared reflectivity measurements. In addition to quantifying the mode strengths and energies in single crystals of this interesting material, we also find strong evidence for multiphonon absorption processes which excite the zone-edge incipient soft modes associated with NTE and the structural quantum phase transition. In this way, we identify an optically-allowed pathway to excite soft modes provides a means to athermally populate modes associated with NTE in ScF3.
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10.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Roginskii E. M., Krylov A. S., Markov Y. F., Smirnov M. B.
Заглавие : Lattice dynamics and baric behavior of phonons in Hg2Cl2 crystals at high hydrostatic pressures
Место публикации : Bull. Russ. Acad. Sci. Phys.: Allerton Press, 2016. - Vol. 80, Is. 9. - P.1033-1037. - ISSN 10628738 (ISSN), DOI 10.3103/S1062873816090409
Примечания : Cited References: 12
Ключевые слова (''Своб.индексиров.''): chlorine compounds--crystal lattices--density functional theory--hydraulics--hydrostatic pressure--inorganic compounds--density functionals--high hydrostatic pressure--intermolecular interactions--orthorhombic phase--phonon spectrum--range dispersion--structural phase transition--theoretical modeling--phonons
Аннотация: A theoretical model based on long-range dispersion corrections of the charge density functional is proposed for model Hg2Cl2 calomel crystals, typical representatives of molecular inorganic compounds where the intermolecular interaction is found to play an important role. This model successfully describes the electronic state and the phonon spectrum of the above crystal, predicts the earlier unstudied phase transition at high hydrostatic pressure. Study of the baric behavior of the phonon spectrum with Raman spectroscopy observes the soft mode in the low-symmetry orthorhombic phase with the frequency softening as the pressure rises. Pressures above 9 GPa considerably transform the Raman spectra, indicating a structural phase transition. © 2016, Allerton Press, Inc.
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11.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Roginskii E. M., Krylov A. S., Markov Y. F.
Заглавие : Lattice Dynamics and Baric Behavior of Phonons in the Hg2Br2 Model Ferroelastics
Место публикации : Phys. Solid State. - 2019. - Vol. 61, Is. 2. - P.187-191. - ISSN 10637834 (ISSN), DOI 10.1134/S1063783419020227
Примечания : Cited References: 13. - This study was supported by the Presidium of the Russian Academy of Sciences, Programs no. 1.4 “Urgent Problems of Low-Temperature Physics” and no. 1.7 “Physics of Condensed Matter and New-Generation Materials.” The authors are grateful to Yu.E. Kitaev for fruitful discussions.
Аннотация: Raman spectra of Hg2Br2 model improper ferroelastic crystals have been investigated in a wide range of high hydrostatic pressures. Baric dependences of the phonon frequencies have been obtained; of greatest interest are the observed soft mode originating from the slowest TA1 acoustic branch at the Brillouin zone boundary (X point) of the tetragonal phase and the anomalous behavior of this mode. In the ferroelastic phase spectra, the ignition of the second acoustic TA2 from the same point has also been detected and its baric behavior has been studied. Under sufficiently high pressures, splitting of doubly degenerate phonons with the Eg symmetry has been observed and explained. The parameters of the Grüneisen constants have been determined from the baric dependences of the phonon frequencies and discussed.
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12.

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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13.

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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14.

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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15.

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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16.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Sukhanov A. S., Nikitin S. E., Pavlovskii M. S., Sterling T. C., Andryushin N. D., Cameron A. S., Tymoshenko Y. V., Walker H. C., Morozov I. V., Chernyavskii I. O., Aswartham S., Reznik D., Inosov D. S.
Заглавие : Lattice dynamics in the double-helix antiferromagnet FeP
Место публикации : Phys. Rev. Research. - 2020. - Vol. 2, Is. 4. - Ст.043405. - ISSN 2643-1564 (eISSN), DOI 10.1103/PhysRevResearch.2.043405
Примечания : Cited References: 57. - A.S.S. thanks D. A. Maksimov for fruitful discussions. I.V.M. thanks RSF 19-43-04129 for financial support in the frame of the joint DFG-RSF project, I.O.C. thanks the RFBR fund (grant 18-33-01282 [58]). D.S.I. acknowledges support from the German Research Foundation (DFG) under Grant No. IN 209/9-1, via the project C03 of the Collaborative Research Center SFB 1143 (project-id 247310070) at the TU Dresden and the Würzburg-Dresden Cluster of Excellence on Complexity and Topology in Quantum Matterials — ct.qmat (EXC 2147, project-id 390858490). S.A. acknowledges DFG funding No. AS 523∖4-1. This work used phonon explorer software for data analysis. Work at the University of Colorado-Boulder was supported by the U.S. Department of Energy, Office of Basic Energy Sciences, Office of Science, under Contract No. DE-SC0006939
Предметные рубрики: Lattice dynamics
Phonons
Аннотация: We present a comprehensive investigation of lattice dynamics in the double-helix antiferromagnet FeP by means of high-resolution time-of-flight neutron spectroscopy and ab initio calculations. Phonons can hybridize with the magnetic excitations in noncollinear magnets to significantly influence their properties. We observed a rich spectrum of phonon excitations, which extends up to ∼50 meV. We performed detailed analysis of the observed and calculated spectra for all high-symmetry points and high-symmetry directions of the Brillouin zone. We show that the DFT calculations quantitatively capture the essential features of the observed phonons, including both dispersions and scattering intensities. By making use of the detailed intensity comparison between the theory and the data, we were able to identify displacement vectors for the majority of the observed modes. The overall excellent agreement between the DFT predictions and the experimental results breaks down for the lowest mode at the Y point, whose energy is lower than calculated by ∼13%. The present study provides vital information on the lattice dynamics in FeP and demonstrates applicability of the DFT to novel pressure-induced phenomena in related materials, such as MnP and CrAs.
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17.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Bikbaev R. G., Pykhtin D. A., Vetrov S. Ya., Timofeev I. V., Shabanov V. F.
Заглавие : Nanostructured photosensitive layer for Tamm-plasmon-polariton-based organic solar cells
Место публикации : Appl. Opt. - 2022. - Vol. 61, Is. 17. - P.5049-5054. - ISSN 1559128X (ISSN), DOI 10.1364/AO.456413
Примечания : Cited References: 47. - Council on Grants of the President of the Russian Federation (MK-46.2021.1.2)
Аннотация: The influence of the volume fraction of plasmonic nanoparticles on the efficiency of the Tamm-plasmon-polariton-based organic solar cell is investigated in the framework of temporal coupled mode theory and confirmed by the transfer matrix method. It is shown that, unlike a conventional plasmonic solar cell, in which the efficiency is directly proportional to the volume fraction of nanoparticles in the photosensitive layer, the efficiency of the proposed solar cell reaches the highest value at low volume fractions. This effect is explained by the fact that at these volume fractions, the critical coupling condition of the incident field with the Tamm plasmon polariton is fulfilled. Thus, for the incoming radiation range of 350 to 500 nm, a maximal cell efficiency of 28% is achieved with a volume fraction of nanoparticles equal to 10%. Additionally, the optical properties of the photosensitive layer are compared for the cases of determining its complex refractive index by effective medium theory and the S-parameter retrieval method. A good agreement between the results is demonstrated, which encourages the use of the effective medium theory for preliminary calculations.
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18.

Вид документа : Статья из сборника (однотомник)
Шифр издания :
Автор(ы) : Popov A.K., Shalaev M.I., Myslivets S. A., Slabko V.V.
Заглавие : Negative-index nonlinear optics: phonons vs plasmons
Коллективы : International Conference on Electrodynamics of complex Materials for Advanced Technologies, Самаркандский государственный университет им. А. Навои
Место публикации : Proc. Int. Conf. on Electrodynamics of complex Materials for Advanced Technologies (PLASMETA'11). - 2011. - С. 43-44
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19.

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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20.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Aplesnin S. S.
Заглавие : Nonadiabatic interaction of acoustic phonons with spins S=1/2 in the two-dimensional Heisenberg model
Разночтения заглавия :авие SCOPUS: Nonadiabatic interaction of acoustic phonons with spins S = 1/2 in the two-dimensional heisenberg model
Место публикации : J. Exp. Theor. Phys.: AMER INST PHYSICS, 2003. - Vol. 97, Is. 5. - P969-977. - ISSN 1063-7761, DOI 10.1134/1.1633952
Примечания : Cited References: 18
Предметные рубрики: QUANTUM MONTE-CARLO
EU2CUO4
GD2CUO4
POLARON
Ключевые слова (''Своб.индексиров.''): antiferromagnetic materials--correlation methods--crystal symmetry--magnetic couplings--magnetic moments--magnetization--monte carlo methods--quantum theory--acoustic phonons--nonadiabatic interaction--orthorhombicity--quantum spin liquid transitions--phonons
Аннотация: The ground state of a two-dimensional antiferromagnet having spins S = 1/2 and interacting with acoustic phonons is investigated in the nonadiabatic approximation using the quantum-mechanical Monte Carlo method. The critical parameters of the spin-phonon coupling, corresponding to the formation of bound spin-phonon excitations, crystal symmetry lowering, and the emergence of a gap in the spin excitation spectrum, as well as the antiferromagnet-quantum spin liquid transition, are determined. The orthorhombicity parameter, the sublattice magnetization, the violation of the spherical symmetry of spin-spin correlation functions, and the magnetic moment in Gd2CuO4 and Eu2CuO4 are calculated. (C) 2003 MAIK "Nauka / Interperiodica".
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