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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Korshunov M. M., Gavrichkov V. A., Ovchinnikov S. G., Manske D., Eremin I.
Заглавие : Effective parameters of the band dispersion in n-type high-T-c superconductors
Разночтения заглавия :авие SCOPUS: Effective parameters of the band dispersion in n-type high-Tc superconductors
Место публикации : Physica C: ELSEVIER SCIENCE BV, 2004. - Vol. 402, Is. 4. - P365-370. - ISSN 0921-4534, DOI 10.1016/j.physc.2003.10.017
Примечания : Cited References: 32
Предметные рубрики: DOPED CUPRATE SUPERCONDUCTORS
TIGHT-BINDING METHOD
QUASI-PARTICLES
COPPER OXIDES
LA2-XSRXCUO4
SYMMETRY
MODEL
EVOLUTION
ORDER
Ключевые слова (''Своб.индексиров.''): high-t-c superconductivity--electronic correlations--electron-doped cuprates--electron-doped cuprates--electronic correlations--high-tc superconductivity--approximation theory--atomic physics--band structure--binding energy--charge transfer--correlation methods--doping (additives)--electronic structure--hamiltonians--mathematical models--mathematical operators--oxide superconductors--perturbation techniques--photoelectron spectroscopy--atomic orbitals--conduction band--electron doped cuprates--electron spins--valence band--high temperature superconductors
Аннотация: The electronic structure of electron-doped cuprates is discussed in the regions of small and optimal doping. For optimal doping we obtain the parameters from a simple tight-binding analysis by fitting ARPES data, and for small doping we study the band structure by the generalized tight-binding method that takes strong electronic correlations into account explicitly. This method has also reproduced well the ARPES data for small doping. The effective low-energy Hamiltonian is the t-t'-J model with hopping parameters t and t'. We compare both methods and find very good agreement for the value of t while t' is different because it is caused by the different contribution of the short-range spin correlations. (C) 2003 Elsevier B.V. All rights reserved.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Korshunov M. M., Ovchinnikov S. G., Sherman A. V.
Заглавие : Effective hamiltonian and properties of the normal and superconducting phases of n-type cuprates
Разночтения заглавия :авие SCOPUS: Effective Hamiltonian and properties of the normal and superconducting phases of n-type cuprates
Место публикации : JETP Letters. - 2004. - Vol. 80, Is. 1. - P.39-43. - ISSN 0021-3640, DOI 10.1134/1.1800212
Примечания : Cited References: 32
Предметные рубрики: T-J MODEL
ORDER-PARAMETER
QUASI-PARTICLES
COPPER OXIDES
FERMI-SURFACE
ELECTRON
SYMMETRY
RANGE
ND1.85CE0.15CUO4
TRANSITIONS
Аннотация: An effective low-energy Hamiltonian is derived from a microscopic multiband p-d model in the regime of strong electron correlations. The parameters of the p-d model are determined by comparison with the ARPES data for undoped Nd2CuO4. The Hamiltonian is the t-J* model in which hopping and exchange slowly decay with distance and are taken into account up to the fifth coordination sphere. The quasiparticle band structure is calculated as a function of the doping concentration with regard to short-range magnetic order, and the superconductivity theory with the spin-fluctuation pairing mechanism is constructed. Assuming that the parameters of the model do not depend on the doping level, we obtained quantitative agreement with the properties observed experimentally for the normal and superconducting phases without introducing fitting parameters. (C) 2004 MAIK "Nauka / Interperiodica".
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Komogortsev S. V., Iskhakov R. S.
Заглавие : Magnetization curve and magnetic correlations in a nanochain of ferromagnetic grains with random anisotropy
Место публикации : Phys. Solid State: AMER INST PHYSICS, 2005. - Vol. 47, Is. 3. - P495-501. - ISSN 1063-7834, DOI 10.1134/1.1884711
Примечания : Cited References: 31
Предметные рубрики: NANOCRYSTALLINE FERROMAGNETS
AMORPHOUS FERROMAGNETS
FIELD
MODEL
MICROSTRUCTURE
SIMULATIONS
DEPENDENCE
SYMMETRY
SYSTEM
MEDIA
Аннотация: The magnetization curve and magnetization correlation function are calculated for a ferromagnetic chain of single-domain nanoparticles with a randomly oriented anisotropy axis for different ratios between the exchange correlation and anisotropy energies. It is shown that the coercive force decreases as the exchange correlations increase. For strong exchange correlations, the magnetization curve is described by the following three successive magnetization processes as the applied field is increased: (i) nonuniform rotation of the magnetization of stochastic domains, (ii) collapse of the magnetic solitons, and (iii) nonuniform rotation of exchange-correlated magnetization vectors of the nanoparticles. For high fields, the calculated correlation function of the transverse magnetization components coincides with that predicted from linear theory. At low and zero fields, the main parameters of the correlation function (the variance and correlation radius) tend to certain finite values rather than diverge (as is the case in linear theory). The irreversible variation in the magnetization at low fields (the hysteresis loop) and the hysteresis of the main parameters of the correlation function are calculated. (c) 2005 Pleiades Publishing, Inc.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Gavrichkov V. A., Korshunov M. M., Ovchinnikov S. G.
Заглавие : Doping dependent electronic structure of cuprates and the effective low energy Hamiltonian for the magnetic pairing
Коллективы : International Conference on New Theories, Discoveries and Applications of Superconductors and Related Materials
Место публикации : Int. J. Mod. Phys. B/ International Conference on New Theories, Discoveries and Applications of Superconductors and Related Materials (5 ; 2004 ; June ; 11-16 ; Chongqing, China). - 2005. - Vol. 19, Is. 1-3. - P.247-249. - ISSN 0217-9792, DOI 10.1142/S0217979205028335
Примечания : Cited References: 14
Предметные рубрики: COPPER OXIDES
SYMMETRY
MODEL
Ключевые слова (''Своб.индексиров.''): electronic structure--strong electron correlations--magnetic mechanism of pairing--electronic structure--magnetic mechanism of pairing--strong electron correlations--copper derivative--calculation--chemical reaction--chemical structure--conference paper--correlation analysis--electron--electronics--energy--hybridization--intermethod comparison--magnetism--mathematical analysis--mathematical model
Аннотация: The properties of the normal and superconducting phases of p- and n-type cuprates are investigated in the appropriate low-energy models in the approximation beyond Hubbard I considering spin fluctuations. Calculated chemical potential dependence on doping, Fermi surface and T,(x) phase diagram for n-type cuprates are in remarkably good agreement with the experimental ones. Comparison of the singlet-triplet t-J model with simple t-J model shows that the spin-exciton mechanism originated from singlet-triplet hybridization leads to small contribution to the T-c(x) - optimal doping value becomes slightly lower and the maximum value of T-c become slightly higher.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Aplesnin S. S.
Заглавие : Quantum spin liquid in the 2D anisotropic Heisenberg model with frustrated next nearest neighbor exchange
Место публикации : Low Temp. Phys. - 1998. - Vol. 24, Is. 8. - P.572-577. - ISSN 1063-777X, DOI 10.1063/1.593639; \b Физика низких температур
Примечания : Cited References: 25
Предметные рубрики: SQUARE-LATTICE ANTIFERROMAGNETS
VALENCE BOND STATES
SYSTEMS
SUPERCONDUCTIVITY
SYMMETRY
Аннотация: The two-dimensional (2D) Heisenberg model with anisotropic exchange (Delta = 1 - J(x)/J(z)) and with negative next nearest neighbor exchange (J(2)) with S = 1/2 is investigated by using the quantum-mechanical Monte-Carlo method. The energy, magnetic moment at a site, heat capacity, and spin-spin correlation functions are calculated. The stability regions for Neel ordering of spins as well as the strip-phase and gapless quantum spin liquid are determined in the interval Delta/2 less than or equal to J(2)/ J(1)less than or equal to 1/(2 Delta). (C) 1998 American Institute of Physics. [S1063-777X(98)00808-1].
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Shneyder E. I., Ovchinnikov S. G.
Заглавие : Isotope effect in the model of strongly correlated electrons with the magnetic and phonon superconducting pairing mechanisms
Коллективы : Presidium of the Russian Academy of Sciences [40]; Russian Academy of Sciences; Russian Foundation for Basic Research [09-02-00127]
Место публикации : J. Exp. Theor. Phys. - 2009. - Vol. 109, Is. 6. - P.1017-1021. - ISSN 1063-7761, DOI 10.1134/S1063776109120139
Примечания : Cited References: 42. - This study was financed under programs 5.7 and "Quantum Physics of Condensed Matter" of the Presidium of the Russian Academy of Sciences, integration project no. 40 of the Siberian Branch and Ural Division of the Russian Academy of Sciences, and the Russian Foundation for Basic Research (project no. 09-02-00127).
Предметные рубрики: CUPRATE SUPERCONDUCTORS
PHASE-TRANSITIONS
3-CENTER INTERACTIONS
HUBBARD-MODEL
TEMPERATURE
LA2-XSRXCUO4
SYMMETRY
EXCHANGE
COPPER
BI2SR2CACU2O8+DELTA
Ключевые слова (''Своб.индексиров.''): ab initio calculations--calculated values--cooper pairing--isotope effect--magnetic mechanisms--order of magnitude--pairing mechanism--phonon mechanism--strongly correlated electrons--superconducting pairing mechanism--superconducting state--type theory--carrier mobility--electron-phonon interactions--isotopes--superconductivity--superconducting magnets
Аннотация: Peculiarities of the temperature isotope effect in a BCS-type theory describing the exchange and phonon mechanisms of Cooper pairing in a system of strongly correlated electrons are considered. The electron-phonon interaction constant is determined from the fitting of the calculated value of the isotope-effect index to the observed value with the parameters of La(2 - x) Sr (x) CuO(4) obtained from ab initio calculations. The value of this constant indicates that the contribution from the traditional pairing mechanism to the superconducting state is of the same order of magnitude as the contribution from the magnetic mechanism.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Flerov I. N., Burriel R., Gorev M. V., Isla P., Voronov V. N.
Заглавие : Low-temperature specific heat of the Rb2KScF6 elpasolite
Место публикации : Phys. Solid State: AMER INST PHYSICS, 2003. - Vol. 45, Is. 1. - P167-170. - ISSN 1063-7834, DOI 10.1134/1.1537430
Примечания : Cited References: 9
Предметные рубрики: PHASE-TRANSITIONS
CRYOLITE (NH4)(3)SCF6
DISTORTED PHASES
SYMMETRY
Аннотация: The specific heat of single-crystal Rb2KScF6 is measured using ac calorimetry in the range 4-280 K. The results are discussed in the context of a group-theoretical analysis of possible distortions of the elpasolite structure and of experimental data obtained earlier with an adiabatic calorimeter in a narrower temperature region. (C) 2003 MAIK "Nauka/Interperiodica".
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Korshunov M. M., Ovchinnikov S. G.
Заглавие : The effective Hamiltonian of the singlet-triplet model for copper oxides
Место публикации : Phys. Solid State: AMER INST PHYSICS, 2001. - Vol. 43, Is. 3. - P416-419. - ISSN 1063-7834, DOI 10.1134/1.1356113
Примечания : Cited References: 15
Предметные рубрики: HIGH-TC SUPERCONDUCTORS
BAND-STRUCTURE
LA2-XSRXCUO4
MECHANISM
SYMMETRY
SPECTRUM
Аннотация: The effective Hamiltonian for a realistic multiband p-d model is developed. In the case of electron doping, the Hamiltonian coincides with that for the standard t-J model. For hole doping, the singlet-triplet t-J model takes place. (C) 2001 MAIK "Nauka/Interperiodica".
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Aleksandrov K. S.
Заглавие : Phase-transitions and distortions of the structure in the family of crystals related to alpha-k2so
Место публикации : Kristallografiya. - 1993. - Vol. 38, Is. 1. - P.128-139. - ISSN 0023-4761; Crystallogr. Rep.
Примечания : Cited References: 38
Предметные рубрики: X-RAY
EXPECTED STRUCTURES
A2BX4 COMPOUNDS
TEMPERATURE
(NH4)2BEF4
CHEMISTRY
DISORDER
SYMMETRY
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10.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Zhu J., Xia, Zhiguo, Zhang Y., Molokeev M. S., Liu Q.
Заглавие : Structural phase transitions and photoluminescence properties of Eu3+ doped Ca(2-x)BaxLaNbO6 phosphors
Место публикации : Dalton Trans.: Royal Society of Chemistry, 2015. - Vol. 44, Is. 42. - P.18536-18543. - ISSN 1477-9226, DOI 10.1039/c5dt03430b
Примечания : Cited References: 27. - The present work was supported by the National Natural Science Foundation of China (Grant No. 51272027, 51472028 and 51272242), Natural Science Foundations of Beijing (2132050), the Program for New Century Excellent Talents in the University of the Ministry of Education of China (NCET-12-0950), Beijing Nova Program (Z131103000413047), Beijing Youth Excellent Talent Program (YETP0635), and the Funds of the State Key Laboratory of New Ceramics and Fine Processing, Tsinghua University (KF201306)
Предметные рубрики: Double-perovskite
Luminescence properties
Thermal-stability
Crystal-chemistry
Red phosphors
White LEDs
Symmetry
Band
Ta
Ln
Аннотация: Crystal structures of the series of double perovskites Ca(2-x)BaxLaNbO6:Eu3+ phosphors have been examined by powder X-ray diffraction and Rietveld refinements. Ca2LaNbO6 has a monoclinic (P21/n) and Ba2LaNbO6 has a monoclinic (C2/m) structure. The structural phases of Ca(2-x)BaxLaNbO6:Eu3+ samples are divided into three sections depending on different Ca/Ba ratios: (1) monoclinic phase (P21/n) as Ca2LaNbO6 in the range of x = 0-0.1, (2) mixed phases containing Ca2LaNbO6 and Ba2LaNbO6 between 0.15 and 1.2, and (3) monoclinic phase (C2/m) as Ba2LaNbO6 for x = 1.4-2. Eu3+ ions act as the structural probes to study the structural phase transitions, and the evolution of the photoluminescence properties and thermal stability behaviours has been also comparatively investigated depending on different structural symmetries from Ca2LaNbO6 to Ba2LaNbO6 phase. The strong red emission from 5D0-7F2 peaking at 618 nm can be found in Ca2LaNbO6:Eu3+ phosphors, which is attributed to the low crystal field effect of the activator ions located in the highly distorted [Lao8] polyhedra sites. The composition-optimized phosphors can find applications in white light emitting diodes (LEDs).
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