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1.


    Gavrichkov, V. A.
    Low-energy electron spectrum in copper oxides in the multiband p-d model / V. A. Gavrichkov, S. G. Ovchinnikov // Phys. Solid State. - 1998. - Vol. 40, Is. 2. - P. 163-168, DOI 10.1134/1.1130262. - Cited References: 31 . - ISSN 1063-7834
РУБ Physics, Condensed Matter
Рубрики:
HIGH-TC SUPERCONDUCTORS
   SR2CUO2CL2

   STATES

   PLANES

Аннотация: An exact diagonalization of the Hamiltonian in the p-d model of a CuO6 cluster was used to obtain dependences on the model parameters of the lowest-energy two-hole terms: the energy difference between the 2p orbitals of planar and apical oxygen Delta(apex) = epsilon(2p) - epsilon[2p(apex)], the crystal field parameter Delta(d) = epsilon(3z2-r2)-epsilon(x2-y2), and the ratio of the distances between the copper atom and the apical and planar oxygen atoms d(apex)/d(pl). In the limit of large d(apex)/d(pl) and Delta(d), OUT model is equivalent to the three-band p-d model and, in this case, large singlet-triplet splitting Delta epsilon greater than or equal to 1 eV is also observed. As the parameters decrease, a singlet-triplet crossover is observed. Two mechanisms are identified for stabilization of the tripler term B-3(1g)(0) as the ground state. It is shown that for realistic values of the parameters, reduction of the p-d model to the three-band model is limited by the low energies of the current excitations because of the presence of the lower excited B-3(1g), and (1)A(1g) cluster states. Intercluster hopping causes strong mixing of singlet and triplet states far from the Gamma point. The results of the calculations are compared with data obtained by angle-resolved photoelectron emission in Sr2CuO2Cl2. (C) 1998 American Institute of Physics.

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Держатели документа:
LV Kirensky Phys Inst, Krasnoyarsk 660036, Russia
ИФ СО РАН

Доп.точки доступа:
Ovchinnikov, S. G.; Овчинников, Сергей Геннадьевич; Гавричков, Владимир Александрович
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2.


    Ovchinnikov, S. G.
    Spin excitons - A new mechanism of superconducting pairing in copper oxides / S. G. Ovchinnikov // JETP Letters. - 1996. - Vol. 64, Is. 1. - P. 25-31, DOI 10.1134/1.567153. - Cited References: 22 . - ISSN 0021-3640
РУБ Physics, Multidisciplinary
Рубрики:
HIGH-TC SUPERCONDUCTORS
   SINGLET-TRIPLET MODEL

   LA2-XSRXCUO4

   SR2CUO2CL2

   PLANE

Аннотация: The Fermi and Bose quasiparticle spectrum in copper oxides is studied in a many-band p-d model taking account of the strong electronic correlations. It is shown that hole-doped systems possess a Bose mode - a spin exciton - which is associated with the singlet-triplet excitation of the two-hole ground-state term of CuO4 clusters. Intercluster hopping leads to fermion-boson interaction with a spin exciton as the intermediate boson. Such a mechanism does not exist for n-type systems. (C) 1996 American Institute of Physics.

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Держатели документа:
L. V. Kirenskii Institute of Physics, Russian Academy of Sciences, 660036 Krasnoyarsk, Russian Federation
ИФ СО РАН

Доп.точки доступа:
Овчинников, Сергей Геннадьевич
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3.


    Ovchinnikov, S. G.
    Generalized tight binding method for SCES as a perturbative realization of the exact Lehmann representation / S. G. Ovchinnikov // Acta Phys. Pol. B. - 2003. - Vol. 34, Is. 2. - P. 431-434. - Cited References: 12 . - ISSN 0587-4254
РУБ Physics, Multidisciplinary
Рубрики:
BAND-STRUCTURE
   MODEL

   SR2CUO2CL2

Аннотация: Both perturbation approach in the Hubbard operator representation and the exact Lehmann representation proves that the electron quasiparticle in SCES has spin S = 1/2, electric charge e, QP energy and QP spectral weight split over various QP bands. General theory and its application to the hole doped CuO2 layer are considered.

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Доп.точки доступа:
Овчинников, Сергей Геннадьевич; International Conference on Strongly Correlated Electron Systems(Jul. 10-13, 2002 ; Krakow, Poland)
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4.


   
    Evolution of the band structure of quasiparticles with doping in copper oxides on the basis of a generalized tight-binding method / V. A. Gavrichkov [et al.] // J. Exp. Theor. Phys. - 2000. - Vol. 91, Is. 2. - P. 369-383, DOI 10.1134/1.1311997. - Cited References: 45 . - ISSN 1063-7761
РУБ Physics, Multidisciplinary
Рубрики:
T-J MODEL
   CUPRATE SUPERCONDUCTORS

   ELECTRONIC-STRUCTURE

   EXCITATIONS

   DEPENDENCE

   TEMPERATURE

   DERIVATION

   SR2CUO2CL2

   SPECTRUM

   DENSITY

Аннотация: Two methods for stabilizing the two-hole B-3(1g) state as the ground state instead of the Zhang-Rice singlet are determined on the basis of an orthogonal cellular basis for a realistic multiband pd model of a CuO2 layer and the dispersion relations for the valence band top in undoped and doped cases are calculated. In the undoped case, aside from the valence band, qualitatively corresponding to the experimental ARPES data for Sr2CuO2Cl2 and the results obtained on the basis of the t-t'-J model, the calculations give a zero-dispersion virtual level at the valence band top itself. Because of the zero amplitude of transitions forming the virtual level the response corresponding to it is absent in the spectral density function. In consequence, the experimental ARPES data do not reproduce its presence in this antiferromagnetic undoped dielectric. A calculation of the doped case showed that the virtual level transforms into an impurity-type band and acquires dispersion on account of the nonzero occupation number of the two-hole states and therefore should be detected in ARPES experiments as a high-energy peak in the spectral density. The computed dispersion dependence for the valence band top is identical to the dispersion obtained by the Monte Carlo method, and the ARPES data for optimally doped Bi2Sr2CaCu2O8 + delta samples. The data obtained also make it possible to explain the presence of an energy pseudogap at the symmetric X point of the Brillouin band of HTSC compounds. (C) 2000 MAIK "Nauka/Interperiodica".

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Публикация на русском языке Эволюция зонной структуры квазичастиц с допированием в оксидах меди в рамках обобщенного метода сильной связи [Текст] / В. А. Гавричков [и др.] // Журн. эксперим. и теор. физ. - 2000. - Т. 118 Вып. 2. - С. 422-437

Держатели документа:
Russian Acad Sci, LV Kirensky Phys Inst, Siberian Div, Krasnoyarsk 660036, Russia
ИФ СО РАН

Доп.точки доступа:
Gavrichkov, V. A.; Гавричков, Владимир Александрович; Ovchinnikov, S. G.; Овчинников, Сергей Геннадьевич; Borisov, A. A.; Goryachev, E. G.
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5.


   
    Electronic transitions and genuine crystal-field parameters in copper metaborate CuB2O4 / R. V. Pisarev [et al.] // Phys. Rev. B. - 2011. - Vol. 84, Is. 7. - Ст. 75160, DOI 10.1103/PhysRevB.84.075160. - Cited References: 65. - Useful discussions with W. Weber on crystal-field splitting of 3d states in cuprates are appreciated. We thank H.-J. Weber for the help in using Cary 2300 spectrophotometer. This work is supported by the Russian Foundation for Basic Research (project No. 09-02-00070) and Federal Agency for Science and Innovations (Grant No. 02.740.11.0384). A. M. K. acknowledges the financial support from the Committee for Science and Higher Education of the Government of Saint Petersburg. . - ISSN 1098-0121
РУБ Physics, Condensed Matter
Рубрики:
OPTICAL-ABSORPTION
   PHASE-DIAGRAM

   CUGEO3

   SPECTRUM

   SUPERCONDUCTORS

   EXCITATIONS

   SR2CUO2CL2

   SCATTERING

   LA2CUO4

   CUPRATE

Аннотация: We present and analyze high-resolution alpha-, sigma-, and pi-polarized absorption spectra related to d-d electronic transitions in tetragonal metaborate CuB2O4 where copper Cu2+ ions occupy two crystallographically distinct 4b and 8d positions. The spectra are characterized by exceptionally rich fine structure in the spectral range of 1.4-2.4 eV. Six zero-phonon (ZP) lines originating from the electronic transitions within the Cu2+ ions in both positions are distinguished and identified. Symmetry analysis explains polarization properties of the ZP lines in the 8d positions but only partially explains them in the 4b positions. Reliable assignment of all six ZP lines to specific transitions allowed us to calculate genuine cubic Dq and tetragonal Ds and Dt crystal-field parameters for both positions. We show that the (3r(2) - z(2)) state, the energy of which is the measure of the Jahn-Teller splitting, is the highest 3d state for both types of Cu2+ ion positions. Using the obtained crystal-field parameters as the reference values, we estimated Dq, Ds, and Dt for several other cuprates with different Cu-O bond lengths. In particular, the 3d level splitting in La2CuO4, Nd2CuO4, CuGeO3, Sr2CuO2Cl2, and Cu3B7O13Cl was analyzed. Our estimates suggest that the Jahn-Teller splitting in some of these cuprates is larger than it was assumed previously.

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Держатели документа:
[Pisarev, R. V.
Kalashnikova, A. M.] Russian Acad Sci, AF Ioffe Phys Tech Inst, St Petersburg 194021, Russia
[Schoeps, O.] Dortmund Tech Univ, Inst Phys, D-44221 Dortmund, Germany
[Bezmaternykh, L. N.] Russian Acad Sci, Siberian Branch, Inst Phys, Krasnoyarsk 660036, Russia
ИФ СО РАН
Ioffe Physical-Technical Institute, Russian Academy of Sciences, 194021 St. Petersburg, Russian Federation
Institute of Physics, Dortmund Technical University, 44221 Dortmund, Germany
Institute of Physics, Siberian Branch, Russian Academy of Sciences, 660036 Krasnoyarsk, Russian Federation

Доп.точки доступа:
Pisarev, R. V.; Kalashnikova, A. M.; Schops, O.; Bezmaternykh, L. N.; Безматерных, Леонард Николаевич
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6.


   
    Parameters of the effective singlet-triplet model for band structure of high-T-c cuprates by alternative approaches / M. M. Korshunov [et al.] // J. Exp. Theor. Phys. - 2004. - Vol. 99, Is. 3. - P. 559-565, DOI 10.1134/1.1809685. - Cited References: 48 . - ISSN 1063-7761
РУБ Physics, Multidisciplinary
Рубрики:
DENSITY-FUNCTIONAL CALCULATION
   TIGHT-BINDING METHOD

   COPPER OXIDES

   ENERGY-BANDS

   SUPERCONDUCTORS

   HOLE

   LA2-XSRXCUO4

   PLANE

   SR2CUO2CL2

   INSULATORS

Кл.слова (ненормированные):
Band structure -- Carbon dioxide lasers -- Copper oxides -- Doping (additives) -- Parameter estimation -- Electron systems -- Generalized tight binding (GTB) -- Parameters extraction -- Singlet triplet model -- Technetium compounds
Аннотация: We consider the problem of determining the parameters for high-T-c superconducting copper oxides. Alternative approaches, the ab initio LDA and LDA + U calculations and the generalized tight-binding (GTB) method for strongly correlated electron systems, are used to calculate hopping and exchange parameters of the effective singlet-triplet model for the CuO2 layer. The resulting parameters are in remarkably good agreement with each other and with parameters extracted from experiment. This set of parameters is proposed for proper quantitative description of the physics of hole-doped high-T-c cuprates in the framework of effective models. (C) 2004 MAIK "Nauka / Interperiodica".

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Держатели документа:
Russian Acad Sci, Kirensky Inst Phys, Siberian Div, Krasnoyarsk 660036, Russia
Russian Acad Sci, Inst Met Phys, Ural Div, Ekaterinburg 620219, Russia
ИФ СО РАН
Kirensky Institute of Physics, Siberian Division, Russian Academy of Sciences, Krasnoyarsk, 660036, Russian Federation
Institute of Metal Physics, Ural Division, Russian Academy of Sciences, Ekaterinburg, 620219, Russian Federation

Доп.точки доступа:
Korshunov, M. M.; Коршунов, Максим Михайлович; Gavrichkov, V. A.; Гавричков, Владимир Александрович; Ovchinnikov, S. G.; Овчинников, Сергей Геннадьевич; Pchelkina, Z. V.; Nekrasov, I. A.; Korotin, M. A.; Anisimov, V. I.
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7.


    Val'kov, V. V.
    Modification of the superconducting order parameter Delta(k) by long-range interactions / V. V. Val'kov, D. M. Dzebisashvili // JETP Letters. - 2003. - Vol. 77, Is. 7. - P. 381-384, DOI 10.1134/1.1581965. - Cited References: 18 . - ISSN 0021-3640
РУБ Physics, Multidisciplinary
Рубрики:
T-J MODEL
   BAND HUBBARD-MODEL

   SR2CUO2CL2

Аннотация: It is demonstrated that the inclusion of long-range intersite interactions qualitatively modifies the dependence of a superconducting gap on quasimomentum for both s- and d-symmetry types. In particular, the order parameter of a superconducting phase with the symmetry type depends on two amplitudes and has the form Delta(k) = Delta(1)(cosk(x)-cosk(y)) + Delta(2)(cos2k(x)-cos2k(y)). In this case, the theoretical dependence of the critical temperature on the degree of doping agrees with the experimental dependence. (C) 2003 MAIK "Nauka/Interperiodica".

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Держатели документа:
Russian Acad Sci, Kirenskii Inst Phys, Siberian Div, Krasnoyarsk 660036, Russia
Krasnoyarsk State Tech Univ, Krasnoyarsk 660074, Russia
Krasnoyarsk State Univ, Krasnoyarsk 660075, Russia
ИФ СО РАН
Kirenskii Institute of Physics, Siberian Division, Russian Academy of Sciences, Krasnoyarsk, Akademgorodok, 660036, Russian Federation
Krasnoyarsk State Technical University, Krasnoyarsk, 660074, Russian Federation
Krasnoyarsk State University, Krasnoyarsk, 660075, Russian Federation

Доп.точки доступа:
Dzebisashvili, D. M.; Дзебисашвили, Дмитрий Михайлович; Вальков, Валерий Владимирович
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