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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Huang L., Jia B., Pilipchuk A. S., Chiang Y., Huang S., Li J., Shen C., Bulgakov E. N., Deng F., Powell D. A., Cummer S. A., Li Y., Sadreev A. F., Miroshnichenko A. E.
Заглавие : General framework of bound states in the continuum in an open acoustic resonator
Место публикации : Phys. Rev. Appl. - 2022. - Vol. 18, Is. 5. - Ст.054021. - ISSN 23317019 (eISSN), DOI 10.1103/PhysRevApplied.18.054021
Примечания : Cited References: 47. - L.H. and A.E.M. are supported by the Australian Research Council Discovery Project (Grant No. DP200101353) and the UNSW Scientia Fellowship program. Y.K.C. and D.A.P. are supported by the Australian Research Council Discovery Project (Grant No. DP200101708). B.J., S.H., and Y.L. are supported by the National Natural Science Foundation of China (Grant No. 12074286) and the Shanghai Science and Technology Committee (Grant No. 21JC1405600). A.P., E.B., and A.S. are supported by the Russian Science Foundation (Grant No. 22-12-00070)
Аннотация: Bound states in the continuum (BICs) provide a viable way of achieving high-Q resonances in both photonics and acoustics. In this work, we propose a general method of constructing Friedrich-Wintgen (FW) BICs and accidental BICs in a coupled acoustic waveguide-resonator system. We demonstrate that FW BICs can be achieved with arbitrary two degenerate resonances in a closed resonator, regardless of whether they have the same or opposite parity. Moreover, their eigenmode profiles can be arbitrarily engineered by adjusting the position of the attached waveguide. This suggests an effective way of continuously switching the nature of the BICs from FW BICs to symmetry-protected BICs or accidental BICs. Also, such BICs are sustained in the coupled waveguide-resonator system with shapes such as rectangles, ellipses, and rhomboids. These interesting phenomena are well explained by the two-level effective non-Hermitian Hamiltonian, where two strongly coupled degenerate modes play a major role in forming such FW BICs. Additionally, we find that such an open system also supports accidental BICs in geometry space instead of momentum space via tuning the position of the attached waveguide, which is attributed to the quenched coupling between the waveguide and eigenmodes of the closed cavity. Finally, we fabricate a series of three-dimensional coupled resonator waveguides and experimentally verify the existence of FW BICs and accidental BICs by measuring the transmission spectra. Our results complement the current BIC library in acoustics and provide nice routes for designing acoustic devices, such as acoustic absorbers, filters, and sensors.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Orlov Yu. S., Nikolaev S. V., Dudnikov V. A., Ovchinnikov S. G.
Заглавие : Forming a dielectric exciton phase in strongly correlated systems with spin crossover
Место публикации : Phys. Rev. B. - 2021. - Vol. 104, Is. 19. - Ст.195103. - ISSN 24699950 (ISSN), DOI 10.1103/PhysRevB.104.195103
Примечания : Cited References: 46. - The authors thank the Russian Scientific Foundation for financial support under Grant No. 18-12-00022
Аннотация: Formation of the magnetic structure and exciton condensate of local magnetic excitons in strongly correlated systems near the spin crossover under high pressure is considered in terms of the effective Hamiltonian obtained from a two-band Hubbard model in the regime of strong electron correlations. The coexistence of the long-range antiferromagnetic order and exciton condensate and the occurrence of the magnetization caused by the condensation of local magnetic excitons are demonstrated. Transformation of the electronic structure of the antiferromagnetic high-spin insulator into the paramagnetic two-band correlated metal via a narrow-gap antiferromagnetic excitonic semiconductor is obtained.
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Вид документа : Статья из сборника (однотомник)
Шифр издания :
Автор(ы) : Zobov V. E., Lundin A. A.
Заглавие : Effect of intramolecular interaction on time growth of second moment of multiple quantum NMR in solids
Место публикации : INTERNATIONAL CONFERENCE ON RESONANCES IN CONDENSED MATTER: ALTSHULER100. Ser. Journal of Physics Conference Series: IOP PUBLISHING LTD, 2011. - Vol. 324: International Conference on Resonances in Condensed Matter (JUN 21-25, 2011, Kazan, RUSSIA). - Ст.12010. - ISBN 1742-6588, DOI 10.1088/1742-6596/324/1/012010
Примечания : Cited References: 12
Предметные рубрики: COHERENCES
DYNAMICS
Ключевые слова (''Своб.индексиров.''): dipole dipole interactions--double-quantum--intramolecular interactions--multiple quantum nmr--nuclear spin system--quantum spectrum--rate increase--second moments--solids containing methyl groups--time dependence--functional groups--quantum optics--solids--spin dynamics--hamiltonians
Аннотация: The time dependence of the NMR multiple quantum spectrum in solids containing methyl groups is investigated. We studied both of types of the nuclear spin systems: namely linking by secular part of the mutual dipole-dipole interaction and linking by effective double quantum Hamiltonian. It is revealed for the first type of systems the rate with the time of the growing up of the second moment when intramolecular interaction is present becomes less in compare with situation when a strong intramolecular interaction is absent. On the contrary for the second type of Hamiltonian the above rate increases.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Ignatchenko V. A., Polukhin D. S.
Заглавие : Effects of cross correlations between inhomogeneities of the parameters of an isotropic medium on the spectrum and damping of elastic waves
Место публикации : J. Exp. Theor. Phys. - NEW YORK: MAIK NAUKA/INTERPERIODICA/SPRINGER, 2010. - Vol. 110, Is. 2. - С. 345-359. - FEB. - ISSN 1063-7761, DOI 10.1134/S1063776110020184
Примечания : Cited Reference Count: 17. - Гранты: This study was supported in part by the Council on Grants from the President of the Russian Federation for the Support of Leading Scientific Schools (grant no. 3818.2008.3) and the Presidium of the Russian Academy of Sciences (program no. 27.1) and performed within the framework of the Federal Target Program (State Contract no. 02.740.11.0220).Финансирующая организация: Council on Grants from the President of the Russian Federation for the Support of Leading Scientific Schools [3818.2008.3]; Presidium of the Russian Academy of Sciences [27.1]; Federal Target Program [02.740.11.0220]
Ключевые слова (''Своб.индексиров.''): cross correlations--dispersion law--elastic force--inhomogeneities--isotropic medium--negative cross-correlation--physical nature--two parameter--wave spectra--damping--dispersions--elastic waves--hamiltonians--dispersion (waves)
Аннотация: The dispersion and damping laws have been investigated for elastic waves in an isotropic medium with one- and three-dimensional inhomogeneities of the density p(x) of the material and the elastic force constants mu(x) and lambda(x) with allowance for the cross correlations between these inhomogeneities. It has been demonstrated that the positive cross correlations between mu(x) and lambda(x), as well as the negative cross correlations between p(x) and mu(x) or p(x) and lambda(x), lead to an enhancement of the modification of the dispersion law and an increase in the damping of waves. The positive cross correlations between p(x) and mu(x) or p(x) and lambda(x), as well as the negative cross correlations between mu(x) and lambda(x), result in the opposite effects: a weakening of the modification of the dispersion law and a decrease in the damping. An analysis of the results obtained in this paper and in our recent work [15] has made it possible to formulate the general regularity of the effects of cross correlations, irrespective of the physical nature of the waves: the effects of cross correlations between inhomogeneities of any two parameters of the material on the wave spectrum depend on whether both parameters related by the cross correlations belong to the same part of the Hamiltonian (i.e., if they both belong to either the kinetic part or the potential part of the Hamiltonian) or they belong to different parts of the Hamiltonian. The positive cross correlations lead to a greater modification of the dispersion law and to an increase in the damping of waves in the former case and to a decrease in these characteristics in the latter case. Correspondingly, the negative cross correlations in each of these cases result in the opposite effects. This regularity has been explained qualitatively.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Ignatchenko V. A., Polukhin D. S.
Заглавие : Effects of cross correlations between inhomogeneities of the parameters of an isotropic medium on the spectrum and damping of elastic waves
Коллективы :
Место публикации : J. Exp. Theor. Phys.: MAIK NAUKA/INTERPERIODICA/SPRINGER, 2010. - Vol. 110, Is. 2. - P345-359. - ISSN 1063-7761, DOI 10.1134/S1063776110020184
Примечания : Cited References: 17. - This study was supported in part by the Council on Grants from the President of the Russian Federation for the Support of Leading Scientific Schools (grant no. 3818.2008.3) and the Presidium of the Russian Academy of Sciences (program no. 27.1) and performed within the framework of the Federal Target Program (State Contract no. 02.740.11.0220).
Ключевые слова (''Своб.индексиров.''): cross correlations--dispersion law--elastic force--inhomogeneities--isotropic medium--negative cross-correlation--physical nature--two parameter--wave spectra--damping--dispersions--elastic waves--hamiltonians--dispersion (waves)
Аннотация: The dispersion and damping laws have been investigated for elastic waves in an isotropic medium with one- and three-dimensional inhomogeneities of the density p(x) of the material and the elastic force constants mu(x) and lambda(x) with allowance for the cross correlations between these inhomogeneities. It has been demonstrated that the positive cross correlations between mu(x) and lambda(x), as well as the negative cross correlations between p(x) and mu(x) or p(x) and lambda(x), lead to an enhancement of the modification of the dispersion law and an increase in the damping of waves. The positive cross correlations between p(x) and mu(x) or p(x) and lambda(x), as well as the negative cross correlations between mu(x) and lambda(x), result in the opposite effects: a weakening of the modification of the dispersion law and a decrease in the damping. An analysis of the results obtained in this paper and in our recent work [15] has made it possible to formulate the general regularity of the effects of cross correlations, irrespective of the physical nature of the waves: the effects of cross correlations between inhomogeneities of any two parameters of the material on the wave spectrum depend on whether both parameters related by the cross correlations belong to the same part of the Hamiltonian (i.e., if they both belong to either the kinetic part or the potential part of the Hamiltonian) or they belong to different parts of the Hamiltonian. The positive cross correlations lead to a greater modification of the dispersion law and to an increase in the damping of waves in the former case and to a decrease in these characteristics in the latter case. Correspondingly, the negative cross correlations in each of these cases result in the opposite effects. This regularity has been explained qualitatively.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Kolovsky A. R., Korsch H. J., Graefe E. M.
Заглавие : Bloch oscillations of Bose-Einstein condensates: Quantum counterpart of dynamical instability
Место публикации : Phys. Rev. A. - 2009. - Vol. 80, Is. 2. - ISSN 1050-2947, DOI 10.1103/PhysRevA.80.023617
Примечания : Cited Reference Count: 35. - Гранты: We thank D. Witthaut and F. Trimborn for valuable comments. Support from the Deutsche Forschungsgemeinschaft via the Graduiertenkolleg "Nichtlineare Optik und Ultrakurzzeitphysik" is gratefully acknowledged.Финансирующая организация: Deutsche Forschungsgemeinschaft
Предметные рубрики: OPTICAL LATTICE
ATOMS
Ключевые слова (''Своб.индексиров.''): bloch dynamics--bloch oscillations--bogoliubov--bose-einstein condensates--chaotic dynamics--cold atoms--decoherence--dinger equation--dynamical instabilities--equipartition--hubbard--mean-field--optical lattices--quantum counterpart--quasi-one-dimensional--quasimomentum--bose-einstein condensation--hamiltonians--nonlinear equations--steam condensers--stability
Аннотация: We study the Bloch dynamics of a quasi-one-dimensional Bose-Einstein condensate of cold atoms in a tilted optical lattice modeled by a Hamiltonian of Bose-Hubbard type. The corresponding mean-field system described by a discrete nonlinear Schrodinger equation can exhibit dynamical (or modulation) instability due to chaotic dynamics and equipartition over the quasimomentum modes. It is shown that these phenomena are related to Bogoliubov's depletion of the Bose-Einstein condensate and a decoherence of the condensate in the many-particle description. Three types of dynamics are distinguished: (i) decaying oscillations in the region of dynamical instability and (ii) persisting Bloch oscillations or (iii) periodic decay and revivals in the region of stability.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Popova M. N., Stanislavchuk T. N., Malkin B. Z., Bezmaternykh L. N.
Заглавие : Optical spectroscopy of PrFe3(BO3)(4): Crystal-field and anisotropic Pr-Fe exchange interactions
Коллективы : Russian Foundation for Basic Research [07-02-01185, 09-02-00930]; Russian Academy of Sciences under the Programs for Basic Research
Разночтения заглавия :авие SCOPUS: Optical spectroscopy of PrFe3 (BO3) 4: Crystal-field and anisotropic Pr-Fe exchange interactions
Место публикации : Phys. Rev. B. - 2009. - Vol. 80, Is. 19. - Ст.195101. - ISSN 1098-0121, DOI 10.1103/PhysRevB.80.195101
Примечания : Cited References: 36. - We thank S. Klimin for useful information concerning the structure of PrFeINF3/INF(BOINF3/INF)INF4/INF and E. Chukalina for participating in some measurements. This work was supported in part by the Russian Foundation for Basic Research (Grants No. 07-02-01185 and No. 09-02-00930) and by the Russian Academy of Sciences under the Programs for Basic Research.
Предметные рубрики: TRIGONAL GDFE3(BO3)(4)
NDFE3(BO3)(4)
DYFE3(BO3)(4)
TRANSITIONS
BORATE
ION
ND
Ключевые слова (''Своб.индексиров.''): antiferromagnetic materials--crystal field interactions--exchange interactions (electron)--infrared spectra--iron compounds--magnetic susceptibility--magneto-optical effects--paramagnetic materials--praseodymium compounds--spin hamiltonians--visible spectra
Аннотация: High-resolution polarized optical absorption spectra of PrFe3(BO3)(4) in the paramagnetic and antiferromagnetic phases are reported. The measured energies of the crystal-field (CF) levels within the 4f(2) configuration of Pr3+ in the paramagnetic PrFe3(BO3)(4) are described by the CF model that involves the 4f(2)/4f5d and 4f(2)/4f6p configuration interactions. Ordering of Fe spins along the crystalline c axis below T-N=32 K is confirmed by the analysis of the spectra of Er3+ introduced as a probe into PrFe3(BO3)(4). To account for the observed changes in the optical spectra of Pr3+ at temperatures below T-N, in particular, for the shift of the CF levels, splitting of the CF doublets, and the appearance of forbidden lines, the Pr-Fe exchange Hamiltonian defined by seven parameters is considered. The theoretical approach has been tested by calculating the temperature dependence of the magnetic susceptibility. A good agreement between theory and optical and magnetic experimental data is found demonstrating the validity of the model used. The obtained results confirm that the model of the iron dimers inside the spiral chains of Fe3+(O2-)(6) octahedrons introduced by us earlier for NdFe3(BO3)(4) and modified in the present work may serve as a basis for analyzing the low-temperature properties of other rare-earth iron borates.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Zinenko V. I., Zamkova N. G.
Заглавие : Ab initio calculation of the ferroelectric phase transition in disordered and ordered PbSc0.5Ta0.5O3 and PbSc0.5Nd0.5O3 solid solutions with the use of a model Hamiltonian
Разночтения заглавия :авие SCOPUS: Ab initio calculation of the ferroelectric phase transition in disordered and ordered PbSc0.5Ta0.5O3 and PbSc 0.5Nd0.5O3 solid solutions with the use of a model Hamiltonian
Место публикации : J. Exp. Theor. Phys.: MAIK NAUKA/INTERPERIODICA/SPRINGER, 2008. - Vol. 106, Is. 3. - P542-549. - ISSN 1063-7761, DOI 10.1134/S1063776108030138
Примечания : Cited References: 17
Предметные рубрики: RELAXOR FERROELECTRICS
PEROVSKITES
BATIO3
PBTIO3
Ключевые слова (''Своб.индексиров.''): approximation theory--ferroelectric materials--hamiltonians--mathematical models--monte carlo methods--phase transitions--ferroelectric phase transition--gordon-kim model--local-mode approximation--solid solutions
Аннотация: To describe the ferroelectric phase transition in ordered and disordered PbSc0.5Ta0.5O3 (PST) and PbSc0.5Nd0.5O3 (PSN) solid solutions, a model Hamiltonian is written in the local-mode approximation, in which long-range dipole-dipole and short-range interactions of local modes are taken into account. The Hamiltonian parameters are determined from the set of energies of a series of distorted structures, calculated within the nonempirical generalized Gordon-Kim model. The statistical mechanics of the systems with a model Hamiltonian is investigated by the Monte Carlo method. It is revealed that PSN solid solutions undergo a transition to the ferroelectric rhombohedral phase through an intermediate phase, existing in a narrow temperature range. PST solid solutions undergo a ferroelectric phase transition directly from the paraelectric cubic to the ferroelectric rhombohedral phase.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Ovchinnikov S. G., Orlov Yu. S.
Заглавие : Covalence-induced stabilization of an intermediate-spin state and the magnetic susceptibility of LaCoO3
Место публикации : J. Exp. Theor. Phys.: MAIK NAUKA/INTERPERIODICA/SPRINGER, 2007. - Vol. 104, Is. 3. - P436-444. - ISSN 1063-7761, DOI 10.1134/S1063776107030090
Примечания : Cited References: 24. - This work was supported by the program of the Division of Physical Sciences of the Russian Academy of Sciences “Strong Electronic Correlations,” the integration project SORAN-URORAN (grant no. 74), and the Krasnoyarsk krai Science Foundation
Предметные рубрики: TRANSITION
Ключевые слова (''Своб.индексиров.''): band structure--electron transitions--ground state--hamiltonians--magnetic susceptibility--magnetic variables measurement--spin dynamics--covalence induced stabilization--diagnoalization--orbital degeneracy--spin states--lanthanum compounds
Аннотация: The energies of terms with spins S = 0, 1, 2 have been found using exact diagonalization of the multielectron Hamlitonian of a multiband pd model for the CoO6 cluster. Co (e(g) orbital)-O hops, which form the covalent sigma bond, are shown to decrease the energy of the state (IS) with an intermediate spin (S = 1) as compared to the energy of the state (LS) with a low spin (S = 0). An analogue of the Tanabe-Sugano diagram that takes into account the covalence of the CoO6 cluster is constructed. The state with S = 1 is shown to be a ground state at certain model parameters. An increase in temperature is established to decrease the crystal field and, thus, favors the transition of the ground state from LS to IS at T = 100 K and the transition of the IS ground state to a state (HS) with a high spin (S = 2) at T = 550 K. The magnetic susceptibility of LaCoO3 is calculated with allowance for the LS, IS, and HS states and for the fact that the HS state exhibits threefold orbital degeneracy of the t(2g) shell, which results in an effective orbital moment L = 1 and the importance of spin-orbit interaction. The behavior of this magnetic susceptibility agrees well with the experimental chi(T) dependence of LaCoO3.
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10.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Bulgakov E. N., Rotter I.
Заглавие : Spectroscopic properties of large open quantum-chaotic cavities with and without separated time scales
Место публикации : Phys. Rev. E: AMER PHYSICAL SOC, 2006. - Vol. 73, Is. 6. - Ст.66222. - ISSN 1539-3755, DOI 10.1103/PhysRevE.73.066222
Примечания : Cited References: 24
Предметные рубрики: HELMHOLTZ EQUATION
SYSTEMS
DYNAMICS
STATES
TRANSMISSION
BILLIARDS
Ключевые слова (''Своб.индексиров.''): hamiltonians--numerical analysis--phase control--quantum theory--spectroscopic analysis--wave transmission--bunimovich cavity--hamiltonian formalism--phase rigidity--quantum-chaotic cavities--cavity resonators
Аннотация: The spectroscopic properties of an open large Bunimovich cavity are studied numerically in the framework of the effective Hamiltonian formalism. The cavity is opened by attaching two leads to it in four different ways. In some cases, the transmission takes place via standing waves with an intensity that closely follows the profile of the resonances. In other cases, short-lived and long-lived resonance states coexist. The short-lived states cause traveling waves in the transmission while the long-lived ones generate superposed fluctuations. The traveling waves oscillate as a function of energy. They are not localized in the interior of the large chaotic cavity. In all considered cases, the phase rigidity fluctuates with energy. It is mostly near to its maximum value and agrees well with the theoretical value for the two-channel case.
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