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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Gluck M., Kolovsky A. R., Korsch H. J.
Заглавие : Fractal stabilization of Wannier-Stark resonances
Место публикации : Europhys. Lett. - 2000. - Vol. 51, Is. 3. - P.255-260. - ISSN 0295-5075, DOI 10.1209/epl/i2000-00345-2
Примечания : Cited References: 17
Предметные рубрики: BLOCH PARTICLE
FIELDS
STATISTICS
QUANTUM
SYSTEMS
AC
DC
ELECTRONS
Аннотация: The quasienergy spectrum of a Bloch electron affected by dc-ac fields is known to have a fractal structure as a function of the so-called electric matching ratio, which is the ratio of the ac field frequency and the Bloch frequency. This paper studies a manifestation of the fractal nature of the spectrum in the system "atom in a standing laser wave", which is a quantum-optical realization of a Bloch electron. It is shown that for an appropriate choice of the system parameters the atomic survival probability (a quantity measured in laboratory experiments) also develops a fractal structure as a function of the electric matching ratio. Numerical simulations under classically chaotic scattering conditions show good agreement with theoretical predictions based on random matrix theory.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Aplesnin S. S.
Заглавие : Quantum Monte Carlo investigation of the magnetic properties of weakly interacting antiferromagnetic chains with an alternating exchange interaction with spin S=1/2
Место публикации : J. Exp. Theor. Phys.: MAIK NAUKA/INTERPERIODICA/SPRINGER, 2000. - Vol. 90, Is. 1. - P194-201. - ISSN 1063-7761, DOI 10.1134/1.559075
Примечания : Cited References: 35
Предметные рубрики: PEIERLS COMPOUND CUGEO3
MAGNON DISPERSION
BI2CUO4
EXCITATIONS
RESONANCE
SYSTEMS
SCATTERING
DYNAMICS
NEUTRON
PHASE
Аннотация: An approximation dependence of the spontaneous magnetic moment at a site, sigma/sigma(0) - 1 = 0.71(6)delta(2.5(2)), and the antiferromagnet-singlet state phase boundary, J(2)/J(1) = 0.52(3)delta, are determined by the quantum Monte Carlo method in the self-consistent sublattice molecular field approximation for weakly interacting (J(2)) antiferromagnetic chains with spin S = 1/2 and alternating exchange interaction (J(1) +/- delta). The Neel temperature and a number of critical temperatures which could be related with the filling energy of two singlets (Delta S-z = 0) and one triplet (Delta S-z= 1) spin bands, each of which is split by the sublattice field (h(x,y)not equal h(z)) into two subbands, are determined on the basis of the computed correlation radii of the two- and four-spin correlation function, the squared total spin (S-z)(2) with respect to the longitudinal components, the dimerization parameter, and the correlation functions between the nearest neighbors with respect to longitudinal and transverse spin components. On the basis of the Monte Carlo calculations, the critical temperatures and possible energy gaps at the band center are determined for the antiferromagnets CuWO4 and Bi2CuO4 and for the singlet compounds (VO)(2)P2O7 and CuGeO3 , agreeing satisfactorily with existing results, and new effects are also predicted. (C) 2000 MAIK "Nauka / Interperiodica".
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Aplesnin S. S.
Заглавие : Static and dynamic magnetic properties of coupled spin-1/2 antiferromagnetic chains
Место публикации : J. Phys.: Condens. Matter: IOP PUBLISHING LTD, 2000. - Vol. 12, Is. 37. - P.8191-8207. - ISSN 0953-8984, DOI 10.1088/0953-8984/12/37/316
Примечания : Cited References: 21
Предметные рубрики: ONE-DIMENSIONAL ANTIFERROMAGNETS
SYSTEMS
SUSCEPTIBILITY
EXCITATIONS
SR2CUO3
CA2CUO3
KCUF3
Ключевые слова (''Своб.индексиров.''): computational methods--copper compounds--correlation methods--functions--magnetic field effects--magnetic properties--magnetization--monte carlo methods--quantum theory--specific heat--thermal effects--excitation spectroscopy--interchain coupling--intrachain couplings--mean-field approximation--spin-spin correlation function--spinons--antiferromagnetic materials
Аннотация: Calculations of the thermodynamic quantities, and the spectra of spinons, triplet excitations, and two-particle spin-singlet (Delta S-z = 0, +/- 1) excitations for a weakly coupled antiferromagnetic S = 1/2 spin chain are made using a mean-field approximation for the interchain couplings (J(2)) by the quantum Monte Carlo method. The mass gaps in these excitation spectra are estimated as functions of the interchain coupling. The critical held H-c, and the temperatures at which the spinon and singlet gaps close (T-1 and T-2, respectively) are obtained. Some peculiarities of the staggered magnetization, the specific heat, and the spin-spin correlation function are found at T-1 = 0.9J(2), T-2 = 1.5J(2), H-c = 3.8J(2), as determined by linear function fitting for J(2)/J(1) 0.15 The intrachain and interchain couplings, and the staggered magnetization for KCuF3, Sr2CuO3, and Ca2CuO3 are estimated, and mass gaps are predicted to exist in the spectra of the spinons and the singlet two-particle excitations.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Pichugin K., Schanz H., Seba P.
Заглавие : Effective coupling for open billiards
Место публикации : Phys. Rev. E: AMERICAN PHYSICAL SOC, 2001. - Vol. 64, Is. 5. - Ст.56227. - ISSN 1063-651X, DOI 10.1103/PhysRevE.64.056227
Примечания : Cited References: 30
Предметные рубрики: QUANTUM CHAOTIC SCATTERING
MICROWAVE CAVITY
RESONANCE POLES
QUANTIZATION
STATISTICS
DYNAMICS
FORMULA
SYSTEMS
STATES
Аннотация: We derive an explicit expression for the coupling constants of individual eigenstates of a closed billiard that is opened by attaching a waveguide. The Wigner time delay and the resonance positions resulting from the coupling constants are compared to an exact numerical calculation. Deviations can be attributed to evanescent modes in the waveguide and to the finite number of eigenstates taken into account. The influence of the shape of the billiard and of the boundary conditions at the mouth of the waveguide are also discussed. Finally we show that the mean value of the dimensionless coupling constants tends to the critical value when the eigenstates of the billiard follow random-matrix theory.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Myagkov V. G., Bykova L. E., Bondarenko G. N., Bondarenko G. V., Myagkov F. V.
Заглавие : Solid-phase reactions and the order-disorder phase transition in thin films
Место публикации : Tech. Phys.: MAIK NAUKA/INTERPERIODICA/SPRINGER, 2001. - Vol. 46, Is. 6. - P743-748. - ISSN 1063-7842, DOI 10.1134/1.1379645
Примечания : Cited References: 28
Предметные рубрики: HIGH-TEMPERATURE SYNTHESIS
ALLOY-FILMS
KINETICS
MULTILAYERS
SYSTEMS
GROWTH
Аннотация: A comparative analysis was carried out of the initiation temperatures of solid-phase reactions in bilayer solid films and the Kurnakov temperatures of the phases forming in the reaction products. It has been shown that in superstructures where ordering is usually observed, the Kurnakov temperature coincides with the initiation temperature of the solid-phase reactions if no other solid-phase structural transformation precedes the order-disorder phase transition in the state diagram. A rule was proposed by which pairs of films capable of entering into solid-phase reactions and their initiation temperatures can be determined. (C) 2001 MAIK "Nauka/Interperiodica".
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Ignatchenko V. A., Mankov Y. I., Maradudin A. A.
Заглавие : The spectrum and damping of waves in partially randomized multilayers
Место публикации : J. Phys.: Condens. Matter: IOP PUBLISHING LTD, 1999. - Vol. 11, Is. 13. - P.2773-2790. - ISSN 0953-8984, DOI 10.1088/0953-8984/11/13/013
Примечания : Cited References: 24
Предметные рубрики: SPIN-WAVES
SEMICONDUCTOR SUPERLATTICES
LOCALIZATION
SYSTEMS
Аннотация: The spectrum and damping of waves in partially randomized multilayer structures are calculated. A method of calculation that was proposed and demonstrated earlier, for the model of a superlattice with a harmonic dependence of its material parameters along its axis in the initial state, is extended to the case of a multilayer structure (i.e., a superlattice with sharp interfaces). One- and three-dimensional random modulations of the period are considered, and the correlation function of the superlattice is derived as a series in which each term is a product of a harmonic and a monotonically decaying function. The law of decay of the correlation function is Gaussian for smooth inhomogeneities, and has different forms for one- and three-dimensional short-wavelength inhomogeneities. The spectrum and damping of waves in the superlattice described by this correlation function are found in the weak-coupling approximation in the vicinities of all of the odd Brillouin zone boundaries. Analytical dependences of the main characteristics of the spectrum and damping on the zone number n are obtained. The conditions for the closing of the gaps at the Brillouin zone boundaries are derived, and depend on the dimensionality of the inhomogeneities and the degree of their smoothness.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Ignatchenko V. A., Mankov Y. I., Maradudin A. A.
Заглавие : Spectrum of waves in randomly modulated multilayers
Место публикации : Phys. Rev. B: AMERICAN PHYSICAL SOC, 1999. - Vol. 59, Is. 1. - P42-45. - ISSN 0163-1829, DOI 10.1103/PhysRevB.59.42
Примечания : Cited References: 14
Предметные рубрики: SEMICONDUCTOR SUPERLATTICES
LOCALIZATION
SYSTEMS
Аннотация: The spectrum and damping of waves in partially randomized multilayer structures are calculated. A method of calculation which was proposed and demonstrated earlier for the model of a superlattice with a harmonic dependence of its material parameters along its axis in the initial state, is extended here to the case of a multilayer structure (i.e., a superlattice with sharp interfaces). One- and three-dimensional inhomogeneities are considered, and the correlation function of the superlattice is derived. The spectrum and damping of waves in the superlattice described by this correlation function are found in the weak-coupling approximation in the vicinities of all the odd Brillouin zone boundaries. [S0163-1829(99)14501-6].
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Gluck M., Kolovsky A. R., Korsch H. J.
Заглавие : Lifetime statistics for a Bloch particle in ac and dc fields
Место публикации : Phys. Rev. E: AMERICAN PHYSICAL SOC, 1999. - Vol. 60, Is. 1. - P247-258. - ISSN 1063-651X, DOI 10.1103/PhysRevE.60.247
Примечания : Cited References: 27
Предметные рубрики: DYNAMIC LOCALIZATION
QUANTUM
TRANSITION
SCATTERING
MATRICES
SYSTEMS
LADDER
STATES
ATOMS
LIGHT
Аннотация: We study the statistics of the Wigner delay time and resonance width for a Bloch particle in ac and de fields in the regime of quantum chaos. It is shown that after appropriate rescaling the distributions of these quantities have a universal character predicted by the random matrix theory of chaotic scattering. [s1063-651X(99)09907-9].
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Alekseev K. N., Perina J.
Заглавие : The 1/N-expansion, quantum-classical correspondence and nonclassical states generation in dissipative higher-order anharmonic oscillators
Место публикации : Phys. Scr.: ROYAL SWEDISH ACAD SCIENCES, 2000. - Vol. 61, Is. 1. - P7-16. - ISSN 0281-1847, DOI 10.1238/Physica.Regular.061a00007
Примечания : Cited References: 38
Предметные рубрики: 2ND-HARMONIC GENERATION
HARMONIC-GENERATION
SQUEEZED STATES
CHAOS
LIGHT
MECHANICS
DYNAMICS
STATISTICS
SYSTEMS
OPTICS
Аннотация: We develop a method for the determination of the dynamics of dissipative quantum systems in the limit of large number of quanta N, based on the 1/N-expansion of Heidmann et al. [Opt. Commun. 54, 189 (1985)] and the quantum-classical correspondence. Using this method, we End analytically the dynamics of nonclassical states generation in the higher-order anharmonic dissipative oscillators for an arbitrary temperature of a reservoir. We show that the quantum correction to the classical motion increases with time quadratically up to some maximal value, which is dependent on the degree of nonlinearity and a damping constant, and then it decreases. Similarities and differences with the corresponding behavior of the quantum corrections to the classical motion in the Hamiltonian chaotic systems are discussed. We also compare our results obtained for some limiting cases with the results obtained by using other semiclassical tools and discuss the conditions for validity of our approach.
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10.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Aplesnin S. S., Petrakovskii G. A.
Заглавие : Investigation of the magnetic properties of chains with alternating ferro- and antiferromagnetic exchange interactions in the Heisenberg model with spin S=1/2
Место публикации : Phys. Solid State: MAIK NAUKA/INTERPERIODICA/SPRINGER, 1999. - Vol. 41, Is. 9. - P1511-1512. - ISSN 1063-7834, DOI 10.1134/1.1131042
Примечания : Cited References: 11
Предметные рубрики: HALDANE-GAP
SYSTEMS
Аннотация: The quantum Monte Carlo method is used to calculate the susceptibility and pairwise spin-spin correlation functions of chains with alternating ferro (K)- and antiferromagnetic (J)-exchange interactions within the Heisenberg model with spin S=1/2. From the susceptibility, the energy gap between the ground state and excited triplet states is determined for arbitrary ratios K/J. The value of the gap coincides with the Haldane gap for spin S=1 when K/J 1.25. (C) 1999 American Institute of Physics. [S1063-7834(99)02409-0].
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11.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Frolov G. I.
Заглавие : Magnetic properties of 3d-metal nanocrystalline films
Место публикации : Tech. Phys.: MAIK NAUKA/INTERPERIODICA/SPRINGER, 2004. - Vol. 49, Is. 7. - P909-915. - ISSN 1063-7842, DOI 10.1134/1.1778867
Примечания : Cited References: 34
Предметные рубрики: ULTRAFINE GRAIN-STRUCTURE
SIZE DEPENDENCE
FERROMAGNETS
COERCIVITY
SYSTEMS
DENSITY
Аннотация: The problem of designing high-resistivity soft magnetic materials based on 3d-metal nanocrystalline films is discussed. To increase the electrical resistivity, nanogranular composites are proposed; they consist of superparamagnetic particles embedded into a dielectric matrix. To obtain the required soft magnetic properties in such composites, it is necessary to realize magnetic ordering due to the effects of magnetic interaction between nanoparticles. As an example, magnetic films that exhibit good high-frequency properties in a range up to several hundreds of megahertz are presented. (C) 2004 MAIK "Nauka / Interperiodica".
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12.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Ignatchenko V. A., Mankov Y. I., Maradudin A. A.
Заглавие : Effects of the dimensionality of inhomogeneities on the wave spectrum of superlattices
Место публикации : Phys. Rev. B: AMERICAN PHYSICAL SOC, 2003. - Vol. 68, Is. 2. - Ст.24209. - ISSN 1098-0121, DOI 10.1103/PhysRevB.68.024209
Примечания : Cited References: 26
Предметные рубрики: ELASTIC MEDIUM THEORY
PERIODIC MULTILAYERS
SPIN-WAVES
LOCALIZATION
SYSTEMS
MEDIA
DISORDER
Аннотация: Dependences of the dispersion laws and damping of waves in an initially sinusoidal superlattice on the dimensionality of inhomogeneities modulating the period of the superlattice are studied. The cases of one- and three-dimensional modulations, as well as modulation by a mixture of inhomogeneities of both of these dimensionalities, are considered. The correlation function of the superlattice K(r) has the form of a product of the same periodic function and a decreasing function that is significantly different for these different cases. For r -- infinity the decreasing function goes to zero for the one-dimensional inhomogeneities and to a nonzero asymptote for the three-dimensional ones. Consequently, the transition from the disordered to ordered states is accompanied in the three-dimensional case not only by an increase of the correlation radius as in the one-dimensional case, but also by a change in the relationship between the volumes of the superlattices with finite and infinite correlation radii. The decreasing part of the correlation function for the mixture of inhomogeneities of different dimensionalities has the form of a product of the decreasing parts of the correlation functions of the components of the mixture. This leads to the nonadditivity of the contributions of the components of different dimensionalities to the resulting modification of the parameters of the wave spectrum that are due to the inhomogeneities (the damping of waves for the mixture of these components is smaller than the sum of the dampings of the components, the maximum gap in the spectrum corresponds to the simultaneous presence of both components, and so on).
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13.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Bulgakov E. N., Sadreev A. F.
Заглавие : Statistics of wave functions and currents induced by spin-orbit interaction in chaotic billiards
Место публикации : Phys. Rev. E: AMER PHYSICAL SOC, 2004. - Vol. 70, Is. 5. - Ст.56211. - ISSN 1539-3755, DOI 10.1103/PhysRevE.70.056211
Примечания : Cited References: 33
Предметные рубрики: HELMHOLTZ-EQUATION
PERSISTENT CURRENTS
ELECTRON-GAS
RINGS
EIGENFUNCTIONS
SYSTEMS
PHASE
Ключевые слова (''Своб.индексиров.''): approximation theory--chaos theory--degrees of freedom (mechanics)--eigenvalues and eigenfunctions--electric field effects--electric potential--electron gas--hamiltonians--heterojunctions--microwaves--statistical methods--chaotic robnik billiards--current distributions--spin-orbit interaction (soi)--wave functions--quantum theory
Аннотация: We show that the wave function and current statistics in chaotic Robnik billiards crucially depend on the constant of the spin-orbit interaction (SOI). For small constant the current statistics is described by universal current distributions derived for slightly opened chaotic billiards [Saichev et al. J. Phys. A. 35, L87 (2002)] although one of the components of the spinor eigenfunctions is not universal. For strong SOI both components of the spinor eigenstate are complex random Gaussian fields. This observation allows us to derive the distributions of spin-orbit persistent cut-rents which well describe numerical statistics. For intermediate values of the statistics of the eigenstates and currents, both are deeply nonuniversal.
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14.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Sadreev A. F., Bulgakov E. N., Rotter I.
Заглавие : Trapping of an electron in the transmission through two quantum dots coupled by a wire
Место публикации : JETP Letters. - 2005. - Vol. 82, Is. 8. - P.498-503. - ISSN 0021-3640, DOI 10.1134/1.2150869
Примечания : Cited References: 32
Предметные рубрики: NUCLEAR REACTIONS
CIRCULAR BENDS
UNIFIED THEORY
WAVE-GUIDES
S-MATRIX
STATES
BILLIARD
SYSTEMS
Аннотация: We consider single-channel transmission through a double quantum dot that consists of two identical single dots coupled by a wire. The numerical solution for the scattering wave function shows that the resonance width of a few of the states may vanish when the width (or length) of the wire and the energy of the incident particle each take a certain value. In such a case, a particle is trapped inside the wire as the numerical visualization of the scattering wave function shows. To understand these numerical results, we explore a simple model with a small number of states, which allows us to consider the problem analytically. If the eigenenergies of the closed system cross the energies of the transmission zeroes, the wire effectively decouples from the rest of the system and traps the particle. (C) 2005 Pleiades Publishing, Inc.
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15.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Val'kov V. V., Dzebisashvili D. M.
Заглавие : The electron energy spectrum and superconducting transition temperature of strongly correlated fermions with three-center interactions
Место публикации : J. Exp. Theor. Phys.: AMER INST PHYSICS, 2005. - Vol. 100, Is. 3. - P608-616. - ISSN 1063-7761, DOI 10.1134/1.1901772
Примечания : Cited References: 29
Предметные рубрики: T-J MODEL
BAND HUBBARD-MODEL
VALENCE BOND STATE
RANGE-ORDER
SYSTEMS
WAVE
Ключевые слова (''Своб.индексиров.''): antiferromagnetic materials--approximation theory--fermions--ground state--hamiltonians--superconductivity--density of states--electron energy spectrum--strongly correlated fermions--superconducting phase--superconducting transition temperature
Аннотация: The renormalizations of the fermionic spectrum are considered within the framework of the t-J* model taking into account three-center interactions (H-(3)) and magnetic fluctuations. Self-consistent spin dynamics equations for strongly correlated fermions with three-center interactions were obtained to calculate quasi-spin correlators. A numerical self-consistent solution to a system of ten equations was obtained to show that, in the nearest-neighbor approximation, simultaneously including H-(3) and magnetic fluctuations at n n(1) (n(1) approximate to 0.72 for 2t/U = 0.25) caused qualitative changes in the structure of the energy spectrum. A new Van Hove singularity is then induced in the density of states, and an additional maximum appears in the T-c(n) concentration dependence of the temperature of the transition to the superconducting phase with order parameter symmetry of the d(x2-y2) type. (C) 2005 Pleiades Publishing, Inc.
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16.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Bulgakov E. N., Sadreev A. F.
Заглавие : Rectangular microwave resonators with magnetic anisotropy. Mapping onto pseudointegrable rhombus
Место публикации : Europhys. Lett. - 2002. - Vol. 57, Is. 2. - P.198-204. - ISSN 0295-5075, DOI 10.1209/epl/i2002-00561-8
Примечания : Cited References: 24
Предметные рубрики: TIME-REVERSAL SYMMETRY
SPECTRAL STATISTICS
STADIUM BILLIARD
EIGENFUNCTIONS
SYSTEMS
CHAOS
Аннотация: A rectangular microwave resonator filled with ferrite with uniaxial magnetic anisotropy is considered. It is shown that this task can be reduced to an empty rhombus resonator with the vertex angle defined by an external magnetic field, provided that the magnetic anisotropy of the ferrite is strong. Therefore, the statistics of eigenfrequencies for TM modes is described by the Brody or semi-Poisson distribution with some exceptional cases.
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17.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Ignatchenko V. A., Mankov Y. I., Maradudin A. A.
Заглавие : Effects of one- and three-dimensional inhomogeneities on the wave spectrum of multilayers with finite interface thicknesses
Место публикации : Phys. Rev. B: AMERICAN PHYSICAL SOC, 2002. - Vol. 65, Is. 2. - Ст.24207. - ISSN 1098-0121, DOI 10.1103/PhysRevB.65.024207
Примечания : Cited References: 24
Предметные рубрики: PERIODIC MULTILAYERS
SPIN-WAVES
LOCALIZATION
SUPERLATTICES
SYSTEMS
DISORDER
AVERAGE
MEDIA
Аннотация: To describe a partially randomized multilayer structure with arbitrary thicknesses of the interfaces between layers, we introduce a model in which the dependence of a material parameter along the axis of such a Superlattice is described by a Jacobian elliptic sine function with a random spatial modulation of its period. Both one- and three-dimensional inhomogeneities of the period are considered. We develop the correlation function for this model, and investigate the dispersion law and damping of averaged waves in this superlattice. The dependencies of the widths of the gaps in the spectrum and the damping at the boundaries of all odd Brillouin zones, on the thicknesses of the interfaces, and on the dimensionality, intensity, and correlation wave number of the inhomogeneities are found. It is shown that experimental investigations of the widths of the gaps and damping for several Brillouin zones could permit, in principle, determining all parameters of the superlattice as well as the parameters of the inhomogeneities from these spectral characteristics.
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18.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Zinenko V. I., Zamkova N. G., Sofronova S. N.
Заглавие : The structural properties of RbMnX3 (X=F, Cl, Br) halides
Разночтения заглавия :авие SCOPUS: The structural properties of RbMnX3 (X = F, Cl, Br) halides
Место публикации : J. Exp. Theor. Phys.: AMER INST PHYSICS, 2003. - Vol. 96, Is. 4. - P747-756. - ISSN 1063-7761, DOI 10.1134/1.1574547
Примечания : Cited References: 15
Предметные рубрики: POLARIZATION
SYSTEMS
Ключевые слова (''Своб.индексиров.''): crystals--formability--hydrostatic pressure--ions--phase transitions--polarization--rubidium compounds--cubic structures--hexagonal structures--quadrupole polarizabilities--structural properties--halogen compounds
Аннотация: The results of nonempirical calculation of energies of three polytypes (cubic, two-layer hexagonal, and six-layer hexagonal) are given for RbMnX3 (X=F, Cl, Br) crystals. The calculation is performed using an ionic crystal model with regard for the deformability and the dipole and quadrupole polarizabilities of ions. The behavior of these crystals under the action of hydrostatic pressure is studied. It is demonstrated that, at normal pressure, the RbMnCl3 and RbMnBr3 crystals have a six-layer hexagonal structure. At pressures above 11 kbar, RbMnCl3 passes to a phase with a cubic structure; RbMnBr3 at pressures above 90 kbar passes to a phase with a two-layer hexagonal structure. The RbMnF3 crystal under normal conditions has a cubic structure and experiences no phase transformations under the effect of pressure. The obtained results are in satisfactory agreement with the known experimental data. (C) 2003 MAIK "Nauka/Interperiodica".
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19.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Ignatchenko V. A., Maradudin A. A., Poszdnyakov A. V.
Заглавие : Waves in a superlattice with anisotropic inhomogeneities
Место публикации : JETP Letters. - 2003. - Vol. 78, Is. 9. - P.592-596. - ISSN 0021-3640, DOI 10.1134/1.1641491
Примечания : Cited References: 28
Предметные рубрики: PERIODIC MULTILAYERS
SPIN-WAVES
SPECTRUM
LOCALIZATION
SYSTEMS
MEDIA
DISORDER
AVERAGE
Аннотация: Dependences of the dispersion laws and damping of waves in an initially sinusoidal superlattice on inhomogeneities with anisotropic correlation properties are studied for the first time. The period of the superlattice is modulated by the random function described by the anisotropic correlation function K-phi(r) that has different correlation radii, k(parallel toparallel to)(-1) and k(perpendicular to)(-1), along the axis of the superlattice z and in the plane xy, respectively. The anisotropy of the correlation is characterized by the parameter lambda = 1 - k(perpendicular to)/k(parallel toparallel to) that can change from lambda = 0 to lambda = 1 when the correlation wave number k(perpendicular to) changes from k(perpendicular to) = k(parallel toparallel to) (isotropic 3D inhomogeneities) to k(perpendicular to) = 0 (1D inhomogeneities). The correlation function of the superlattice K(r) is developed. Its decreasing part goes to the asymptote L that divides the correlation volume into two parts, characterized by finite and infinite correlation radii. The dependences of the width of the gap in the spectrum at the boundary of the Brillouin zone Deltanu and the damping of waves xi on the value of lambda are studied. It is shown that decreasing L leads to the decrease of Deltanu, and increase of xi, with the increase of lambda. (C) 2003 MAIK "Nauka / Interperiodica".
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20.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Ignatchenko V. A., Mankov Y. I., Maradudin A. A.
Заглавие : Effects of the mixture of one- and three-dimensional inhomogeneities on the wave spectrum of superlattices
Место публикации : JETP Letters. - 2003. - Vol. 77, Is. 6. - P.285-290. - ISSN 0021-3640, DOI 10.1134/1.1577758
Примечания : Cited References: 24
Предметные рубрики: PERIODIC MULTILAYERS
SPIN-WAVES
LOCALIZATION
SYSTEMS
THICKNESSES
DISORDER
AVERAGE
MEDIA
Аннотация: Dependences of the dispersion laws and damping of waves in an initially sinusoidal superlattice on the dimensionality of inhomogeneities modulating the period of the superlattice are studied. The cases of one- and three-dimensional modulations, as well as modulation by a mixture of inhomogeneities of both of these dimensionalities, are considered. The correlation function of the superlattice K(r) has the form of a product of the same periodic function and a decreasing function that is significantly different for these different cases. The decreasing part of the correlation function for the mixture of inhomogeneities of different dimensionalities has the form of a product of the decreasing parts of the correlation functions of the components of the mixture. This leads to the nonadditivity of the contributions of the components of different dimensionalities to the resulting modification of the parameters of the wave spectrum that are due to the inhomogeneities (the damping of waves for the mixture of these components is smaller than the sum of the dampings of the components, the maximum gap in the spectrum corresponds to the simultaneous presence of both components of the mixture, not only of the three-dimensional inhomogeneities). (C) 2003 MAIK "Nauka / Interperiodica".
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