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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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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Hoffman A. E.J., Senkovska I., Wieme J., Krylov A. S., Kaskel S., Van Speybroeck V.
Заглавие : Unfolding the terahertz spectrum of soft porous crystals: rigid unit modes and their impact on phase transitions
Место публикации : J. Mater. Chem. A. - 2022. - Vol. 10, Is. 33. - P.17254-17266. - ISSN 20507488 (ISSN), DOI 10.1039/d2ta01678h
Примечания : Cited References: 80. - This work was financially supported by the Fund for Scientific Research Flanders (FWO), the Research Board of the Ghent University (BOF), the Deutsche Forschungsgemeinschaft (DFG, project number 448809307), and the Russian Foundation for Basic Research (RFBR, project number 21-52-12018). The authors thank Kerstin Zechel for sample synthesis. The computational resources and services used in this work were provided by the Flemish Supercomputer Center (VSC), funded by FWO and the Flemish Government
Аннотация: Phase transitions in flexible metal-organic frameworks or soft porous crystals are mediated by low-frequency phonons or rigid-unit modes. The alteration of specific building blocks may change the lattice dynamics of these frameworks, which can influence the phase transition mechanism. In this work, the impact of building block substitution on the rigid-unit modes in flexible MIL-53 analogs with a winerack topology will be investigated via ab initio lattice dynamics calculations. First, the accuracy of the theoretical simulations is verified via experimental Raman measurements, which provide unique fingerprint vibrations in the terahertz range to characterize the phase transition. Following analysis of the low-frequency vibrations shows that there exists a set of universal rigid-unit modes inducing translations and/or rotations of the building blocks. The theoretical results demonstrate that linker substitutions have a large effect on the rigid-unit mode frequencies, whereas this is less so for inorganic chain substitutions. These findings may help to rationally tune the phonon frequencies in soft porous crystals.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Bikbaev R. G., Vetrov S. Ya., Timofeev I. V., Shabanov V. F.
Заглавие : Photosensitivity and reflectivity of the active layer in a Tamm-plasmon-polariton-based organic solar cell
Место публикации : Appl. Opt. - 2021. - Vol. 60, Is. 12. - P.3338-3343. - ISSN 1559128X (ISSN), DOI 10.1364/AO.421374
Примечания : Cited References: 49. - The reported study was funded by the grant of the President of Russian Federation No. MK-46.2021.1.2 and by Russian Foundation for Basic Research, Government of Krasnoyarsk Territory, Krasnoyarsk Region Science and Technology Support Fund to the research project No. 19-42-240004
Аннотация: We report on a model of an organic solar cell in which a photosensitive layer doped with plasmon nanoparticles acts as not only an absorbing element but also a mirror involved in the formation of the Tamm plasmon polariton. It is shown that such solar cells can be fabricated without metal contacts, thus avoiding undesired losses in the system. Methods for an additional increase in the integral absorption by applying metal or dielectric mirrors to the lower boundary of the photonic crystal are proposed. It has been found that the integral absorption in the active layer can be increased by15%compared to classical optimized planar solar cells.
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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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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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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Shneyder E. I., Nikolaev S. V., Zotova M. V., Kaldin R. A., Ovchinnikov S. G.
Заглавие : Polaron transformations in the realistic model of the strongly correlated electron system
Коллективы : Russian Foundation for Basic Research, Government of Krasnoyarsk Territory; Krasnoyarsk Regional Fund of Science [18-42-240017, 19-42240007]
Место публикации : Phys. Rev. B. - 2020. - Vol. 101, Is. 23. - Ст.235114. - ISSN 2469-9950, DOI 10.1103/PhysRevB.101.235114. - ISSN 2469-9969(eISSN)
Примечания : Cited References: 69. - We acknowledge the stimulating discussions with V. A. Gavrichkov, G. Seibold, and K. I. Kugel. The reported study was funded by Russian Foundation for Basic Research, Government of Krasnoyarsk Territory and Krasnoyarsk Regional Fund of Science according to the research project "Features of electron-phonon coupling in high-temperature superconductors with strong electronic correlations" No. 18-42-240017 and project "Electronic correlation effects and multiorbital physics in iron-based materials and cuprates" No. 19-42240007.
Предметные рубрики: ANOMALOUS-DISPERSION
PHONON INTERACTION
PHASE-TRANSITIONS
LO PHONONS
Аннотация: Electron-phonon coupling, diagonal in a real space formulation, leads to a polaron paradigm of smoothly varying properties. However, fundamental changes, namely the singular behavior of polarons, occur if off-diagonal pairing is involved into consideration. The study of polaron transformations and related properties of matter is of particular interest for realistic models, since competition between diagonal and off-diagonal electron-phonon contributions in the presence of other strong interactions can result in unconventional behavior of the system. Here we consider a two-dimensional multiband pd model of cuprate superconductors with electron-phonon interaction and analyze the features of the systems that are caused by the competition of diagonal and off-diagonal electron-phonon contributions in the limit of strong electron correlations. Using the polaronic version of the generalized tight-binding method, we describe the evolution of the band structure, Fermi surface, density of states at Fermi level, and phonon spectral function in the space of electron-phonon parameters ranging from weak to strong coupling strength of the adiabatic limit. On the phase diagram of polaron properties we reveal two quantum phase transitions and show how electron-phonon interaction gives rise to Fermi surface transformation (i) from hole pockets to true Fermi arcs and (ii) from hole to electron type of conductivity. We also demonstrate the emergence of new states in the phonon spectral function of the polaron and discuss their origin.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Bikbaev R. G., Vetrov S. Ya., Timofeev I. V.
Заглавие : Transparent conductive oxides for the epsilon-near-zero Tamm plasmon polaritons
Место публикации : J. Opt. Soc. Am. B. - 2019. - Vol. 36, Is. 10. - P.2817-2823. - ISSN 07403224 (ISSN), DOI 10.1364/JOSAB.36.002817
Примечания : Cited References: 44. - The reported study was funded by RFBR according to the research project No 18-32-00053 and financial support RFBR and MOST according to the research project No 19-52-52006.
Аннотация: We demonstrate the possibility of using transparent conducting oxides [aluminum-doped zinc oxide (AZO), gallium-doped zinc oxide (GZO), indium tin oxide (ITO)] to form Tamm plasmon polaritons in the near-infrared spectral range where the permittivity of oxides is near zero. The spectral properties of the structures are investigated in the framework of the temporal coupled-mode theory and confirmed by the transfer matrix method. It is found that in the critical coupling conditions, the maximal Q-factor of a Tamm plasmon polariton is achieved when a photonic crystal is conjugated with the AZO film, while at the conjugation with the ITO films, the broadest spectral line is obtained. The sensitivity of the wavelength and spectral width of the Tamm plasmon polariton to changes in the oxide film thickness, bulk concentration of a dopant, and angle of incidence is demonstrated.
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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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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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10.

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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11.

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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12.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Peschanskii A. V., Fomin V. I., Gudim I. A.
Заглавие : Raman scattering in multiferroic SmFe3(BO3)4
Место публикации : Low Temp. Phys.: American Institute of Physics, 2016. - Vol. 42, Is. 6. - P.475-483. - ISSN 1063-777X, DOI 10.1063/1.4954783. - ISSN 1090-6517(eISSN)
Примечания : Cited References:21
Предметные рубрики: SINGLE-CRYSTALS
MAGNETOELASTIC PROPERTIES
PHASE-TRANSITIONS
FERROBORATE
PHONONS
Аннотация: Raman spectrum of single-crystal SmFe3(BO3)4 was studied in the frequency range from 3 to 1500 cm−1 at temperatures 10–300 K. All the A 1 and E phonon modes predicted by the group theory for a given symmetry of the crystal were observed. The magnitudes of splitting between the LO and TO components of polar E phonons were determined. It was found that under the transition to a magnetically ordered phase, the behavior of the intensity of the line corresponding to the A 1 vibrational mode is anomalous. It was shown that at low temperatures the spectrum of two-magnon excitations has a complex shape and is observed with both nondiagonal and diagonal components of the scattering tensor. This complex shape reflects the features in the density of states of the magnetic branches. An estimate of the magnon energy Em at the Brillouin zone boundary gave ∼47 cm−1. The structure of the ground multiplet 6 H 5/2 of a Sm+3 ion in paramagnetic and antiferromagnetic states as well as the effect of the magnetic phase transition on it were studied. Electron-phonon interaction for the electronic excitation at 225 cm−1 was revealed.
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13.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Klimin S. A., Kashchenko M. A., Bezmaternykh L. N.
Заглавие : Spin-phonon and electron-phonon interactions in multiferroic GdFe3(BO3)4 and TbFe3(BO3)4 evidenced by IR reflection spectroscopy
Коллективы : Russian Science Foundation [14-12-01033]; Swiss National Science Foundation (SNSF); Science and Technology cooperation program "Switzerland-Russia" of the University of Geneva
Место публикации : J. Low Temp. Phys.: Springer/Plenum Publishers, 2016. - Vol. 185, Is. 5-6. - P.538-543. - ISSN 0022-2291, DOI 10.1007/s10909-016-1597-6. - ISSN 1573-7357(eISSN)
Примечания : Cited References:19. - The authors thank Alexey Kuzmenko and Marina Popova for fruitful discussions. This paper was supported by the Russian Science Foundation under Grant No. 14-12-01033, by the Swiss National Science Foundation (SNSF), and by the Science and Technology cooperation program "Switzerland-Russia" of the University of Geneva.
Предметные рубрики: PHASE-TRANSITIONS
GdFe3(BO3)4
CRYSTALS
SPECTRUM
Ключевые слова (''Своб.индексиров.''): multiferroics--ir-active phonons--spin-phonon interaction--coupled--electron-phonon mode
Аннотация: We study temperature-dependent polarized reflection spectra of multiferroic GdFe3(BO3)4 and TbFe3(BO3)4 single crystals. Signatures of spin–lattice interactions in both compounds and of a formation of the electron–phonon coupled mode in TbFe3(BO3)4 are discussed.
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14.

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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15.

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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16.

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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17.

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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18.

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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19.

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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20.

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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