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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Shaykhutdinov K. A., Balaev D. A., Gokhfeld D. M., Kuzmin Y. I., Popkov S. I., Petrov M. I.
Заглавие : Study of current-voltage characteristics of Bi-based high-temperature superconductors with fractal cluster structure
Коллективы : International Workshop on Weak Superconductivity
Место публикации : Physica C. - 2006. - Vol. 435, Is. 1-2. - P.19-22. - ISSN 0921-4534, DOI 10.1016/j.physc.2006.01.010
Примечания : Cited References: 18
Предметные рубрики: NORMAL-PHASE
VORTEX MOTION
TRANSPORT
Ключевые слова (''Своб.индексиров.''): superconducting foam--pinning--critical current density--fractal--percolation--cluster--cluster--critical current density--fractal--percolation--pinning--superconducting foam--bismuth--critical current density (superconductivity)--electric currents--electric potential--foams--percolation (solid state)--polycrystalline materials--cluster--fractal--pinning--superconducting foam--superconducting materials
Аннотация: We study the effect of the structure on critical currents and current-voltage characteristics (CVC's) of foamed bismuth-based polycrystalline high-temperature superconductors (HTSC). The fractal cluster structure of superconducting foams has been observed and the fractal dimension of boundaries between superconducting and normal clusters has been determined. Based on the magnetic and transport properties of the foamed polycrystalline superconductors, we have shown that the initial parts of CVC's of the superconducting foams are described well by the model that accounts the magnetic flux trapping in fractal clusters of a normal phase. (c) 2006 Elsevier B.V. All rights reserved.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Karpov S. V., Gerasimov V. S., Isaev I. L., Markel V. A.
Заглавие : Spectroscopic studies of fractal aggregates of silver nanospheres undergoing local restructuring
Место публикации : J. Chem. Phys.: AMER INST PHYSICS, 2006. - Vol. 125, Is. 11. - Ст.111101. - ISSN 0021-9606, DOI 10.1063/1.2229202
Примечания : Cited References: 30
Предметные рубрики: ENHANCED RAMAN-SCATTERING
SMALL-PARTICLE COMPOSITES
OPTICAL-PROPERTIES
DISORDERED CLUSTERS
NONLINEAR OPTICS
LOCALIZATION
NANOPARTICLES
EIGENMODES
BOUNDS
Ключевые слова (''Своб.индексиров.''): large-scale fractal geometry--nonlinear optical responses--restructuring--silver nanospheres--aggregates--colloids--electromagnetic fields--fractals--nonlinear optics--sampling--spectroscopic analysis--silver
Аннотация: We present an experimental spectroscopic study of large random colloidal aggregates of silver nanoparticles undergoing local restructuring. We argue that such well-known phenomena as strong fluctuation of local electromagnetic fields, appearance of "hot spots" and enhancement of nonlinear optical responses depend on the local structure on the scales of several nanosphere diameters, rather than the large-scale fractal geometry of the sample. (c) 2006 American Institute of Physics.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Shalaev V. M., Poliakov E. Y., Markel V. A.
Заглавие : Small-particle composites .2. Nonlinear optical properties
Место публикации : Phys. Rev. B: AMERICAN PHYSICAL SOC, 1996. - Vol. 53, Is. 5. - P2437-2449. - ISSN 0163-1829, DOI 10.1103/PhysRevB.53.2437
Примечания : Cited References: 45
Предметные рубрики: FRACTAL CLUSTERS
RAMAN-SCATTERING
SUSCEPTIBILITY
CONDUCTIVITY
EXCITATIONS
COLLOIDS
LIGHT
Аннотация: Strong fluctuations of local fields may result in very large optical nonlinearities in small-particle composites. Enhancement associated with particle clustering is found for a number of optical processes, including four-wave mixing (FWM), third-harmonic generation (THG), Raman scattering, and nonlinear refraction and absorption in Kerr media. Field fluctuations and optical nonlinear susceptibilities are especially large in fractal clusters. The enhancement of optical processes is expressed in terms of the resonant linear absorption by collective dipolar eigenmodes in a cluster, and quality factors, q, of the modes (q much greater than 1). It is shown that the susceptibility of a composite material consisting of random small-particle clusters is proportional to q(3) for Raman scattering and the Kerr optical nonlinearity, and to q(4) and q(6) for THG and FWM, respectively. For all of these processes, a spectral dependence of the effective susceptibility is found. Broad-scale numerical simulations of the optical response in small-particle composites are performed to complement the theory. The simulations are in reasonable agreement with available experimental data.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Sshalaev V. M., Botet R., Jullien R.
Заглавие : Resonant light-scattering by fractal clusters
Место публикации : Phys. Rev. B. - 1991. - Vol. 44, Is. 22. - P.12216-12225. - ISSN 0163-1829, DOI 10.1103/PhysRevB.44.12216
Примечания : Cited References: 19
Предметные рубрики: AEROGELS
OPTICS
Аннотация: A scale-invariant theory of resonant Rayleigh scattering by fractal clusters is developed. Our main result is that the scattering cross section is greatly enhanced, because of the presence of very high local fields, which are correlated and strongly fluctuating. Simulations dealing with two examples of fractal structures, namely, random walk and cluster-cluster aggregates, are presented. The numerical results confirm the theoretical predictions of the scaling behavior for both absorption and scattering, and allow us to obtain the corresponding exponents. In addition to the results for scattering, the large scale of the simulations of the present work provides a comprehensive confirmation and a substantial extension of a recent study by Markel, Muratov, Stockman, and George [Phys. Rev. B 43, 8183 (1991)].
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Gavrilyuk A. P., Karpov S. V.
Заглавие : Processes in resonant domains of metal nanoparticle aggregates and optical nonlinearity of aggregates in pulsed laser fields
Место публикации : Appl. Phys. B-Lasers Opt. - NEW YORK: SPRINGER, 2009. - Vol. 97, Is. 1. - С. 163-173. - SEP. - ISSN 0946-2171, DOI 10.1007/s00340-009-3592-y
Примечания : Cited Reference Count: 43. - Гранты: Authors are thankful to Prof. V. A. Markel ( University of Pennsylvania) for computation of multipole polarizability of silver nanoparticle bispheres, for the attention to this paper, fruitful discussions and great support. This research was supported by grants: 27.1 of the Presidium of RAS, 9.1 DPS RAS, 5 SB RAS, 3818.2008.3 and 6612.2006.3 of the President of RF ( SS RAS), DSP 2.1.1.1814, 05- 03- 32642 RFBR.Финансирующая организация: [27.1 of the Presidium of RAS]; [9.1 DPS RAS]; [5 SB RAS]; [3818.2008.3]; [6612.2006.3]
Предметные рубрики: SMALL-PARTICLE COMPOSITES
FRACTAL CLUSTERS
SELECTIVE PHOTOMODIFICATION
ABSORPTION-COEFFICIENTS
REFRACTIVE-INDEXES
SILVER
ENHANCEMENT
RESPONSES
GOLD
Ключевые слова (''Своб.индексиров.''): metal nanoparticles--nanosecond pulsed laser--nonlinear refractive index--optical nonlinearity--physical effects--pulsed-laser field--resonant domain--silver nanoparticles--simple physical models--aggregates--laser excitation--nanoparticles--nonlinear optics--organic polymers--pulsed laser applications--refractive index--silver
Аннотация: Optical nonlinearities in aggregates of nanoparticles formed in silver hydrosols (SHs) are studied under pico- and nanosecond pulsed laser excitation. The dependence of the nonlinear refractive index n (2) on the degree of hydrosol aggregation is studied experimentally at the wavelength lambda=1.064 mu m. It is found that n (2) changes sign when the degree of hydrosol aggregation is increased. Various physical effects occurring in resonant domains of the aggregates are analyzed using a simple physical model of two bound silver nanoparticles. The theory takes into account thermal, elastic, electrostatic, and light-induced effects. Experimental results are discussed in the context of this theory.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Karpov S. V., Popov A. K., Slabko V. V.
Заглавие : Photochromic reactions in silver nanocomposites with a fractal structure and their comparative characteristics
Место публикации : Tech. Phys.: MAIK NAUKA/INTERPERIODICA/SPRINGER, 2003. - Vol. 48, Is. 6. - P749-756. - ISSN 1063-7842, DOI 10.1134/1.1583830
Примечания : Cited References: 24
Предметные рубрики: SMALL-PARTICLE COMPOSITES
OPTICAL-PROPERTIES
COLLOIDAL SILVER
SELECTIVE PHOTOMODIFICATION
CLUSTERS
LIGHT
Аннотация: Conditions for a change in the polarization selectivity of dips in the plasmon absorption spectra of fractal silver nanocomposites irradiated by pulsed laser radiation are studied. The energy thresholds of the polarization selectivity are evaluated, and the polarization and spectral threshold characteristics are compared. Mechanisms behind the correlation between the fractal structure of the nanocomposites, on the one hand, and their optical and photochromic properties, on the other hand, are discussed. (C) 2003 MAIK "Nauka / Interperiodica".
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Markel V. A., Shalaev V. M., Poliakov E. Y., George T. F.
Заглавие : Numerical studies of second- and fourth-order correlation functions in cluster-cluster aggregates in application to optical scattering
Место публикации : Phys. Rev. E: AMERICAN PHYSICAL SOC, 1997. - Vol. 55, Is. 6. - P7313-7333. - ISSN 1063-651X, DOI 10.1103/PhysRevE.55.7313
Примечания : Cited References: 21
Предметные рубрики: DIFFUSION-LIMITED AGGREGATION
COLLOIDAL AGGREGATION
FRACTAL CLUSTERS
ANTICORRELATION
SIMULATIONS
Аннотация: Two- and four-point density correlation functions p(2)(r) and p(4)(r) are studied numerically and theoretically in computer-generated three-dimensional lattice cluster-cluster aggregates (CCA) with the number of particles N up to 20 000 in application to the light scattering problem. The ''pure'' aggregation algorithm is used, where subclusters of all possible sizes are allowed to collide. We find that large CCA clusters demonstrate pronounced multiscaling. In particular, the fractal dimension determined from the slope of p(2)(r) at small distances differs from that found from the dependence of the radius of gyration on the number of monomers (according to our data, 1.80 and 1.94, respectively). We also consider different functional forms for p(2) and their general properties and applicability. We find that the best fit to the numerical data is provided by the generalized exponential cutoff function with coefficients depending on N. The latter dependence is a manifestation of multiscaling. We propose some theoretical approaches for calculating p(4)(r), assuming p(2)(r) is known. In particular, we find the small-r asymptote for the p(4)(r) and verify it numerically. In addition, we find that p(4)(r) cannot be represented by a scaling dependence with a cutoff function, like p(2)(r) Instead, p(4)(r) is given by an expansion in terms of integer powers of r(2D-3), where D is the fractal dimension (approximate to 1.8 for CCA clusters).
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Butenko A. V., Danilova Y. E., Ishikaev S. M., Karpov S. V., Popov A. K., Rautian S. G., Safonov V. P., Slabko V. V., Crubakov P. A., Shalaev V. M., Shtokman M. I.
Заглавие : Nonlinear optics of metallic fractal clusters
Место публикации : Izvestiya Akademii Nauk SSSR Seriya Fizicheskaya. - 1989. - Vol. 53, Is. 6. - P.1195-1201. - ISSN 0367-6765
Примечания : Cited References: 13
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Karpov S. V., Gerasimov V. S., Isaev I. L., Markel V. A.
Заглавие : Local anisotropy and giant enhancement of local electromagnetic fields in fractal aggregates of metal nanoparticles
Место публикации : Phys. Rev. B: AMER PHYSICAL SOC, 2005. - Vol. 72, Is. 20. - Ст.205425. - ISSN 1098-0121, DOI 10.1103/PhysRevB.72.205425
Примечания : Cited References: 56
Предметные рубрики: SMALL-PARTICLE COMPOSITES
DIFFUSION-LIMITED AGGREGATION
OPTICAL-PROPERTIES
SELECTIVE PHOTOMODIFICATION
NUMERICAL-SIMULATION
DISORDERED CLUSTERS
ABSORPTION-SPECTRUM
PARTICULATE MATTER
NONLINEAR OPTICS
LIGHT-SCATTERING
Аннотация: We have shown within quasistatic approximation that the giant fluctuations of a local electromagnetic field in random fractal aggregates of silver nanospheres are strongly correlated with a local anisotropy factor S which is defined in this paper. The latter is a purely geometrical parameter which characterizes the deviation of local environment of a given nanosphere in an aggregate from spherical symmetry. Therefore, it is possible to predict the sites with anomalously large local fields in an aggregate without explicitly solving the electromagnetic problem. We have also demonstrated that the average (over nanospheres) value of S does not depend noticeably on the fractal dimension D, except when D approaches the trivial limit D=3. In this case, as one can expect, the average local environment becomes spherically symmetrical and S approaches zero. This corresponds to the well-known fact that in trivial aggregates, fluctuations of local electromagnetic fields are much weaker than in fractal aggregates. Thus, we find that, within the quasistatics, the large-scale geometry does not have a significant impact on local electromagnetic responses in nanoaggregates in a wide range of fractal dimensions. However, this prediction is expected not to be correct in aggregates which are sufficiently large for the intermediate- and radiation-zone interaction of individual nanospheres to become important.
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10.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Butenko A. V., Shalayev V. M., Stockman M. I.
Заглавие : Giant impurity nonlinearities in optics of fractal clusters
Место публикации : Zhurnal |Eksperim. Teor. Fiz.: MEZHDUNARODNAYA KNIGA, 1988. - Vol. 94, Is. 1. - P107-124. - ISSN 0044-4510
Примечания : Cited References: 12
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