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1.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Korshunov M. M., Gavrichkov V. A., Ovchinnikov S. G., Nekrasov I. A., Pchelkina Z. V., Anisimov V. I.
Заглавие : Hybrid LDA and generalized tight-binding method for electronic structure calculations of strongly correlated electron systems
Место публикации : Phys. Rev. B: AMERICAN PHYSICAL SOC, 2005. - Vol. 72, Is. 16. - Ст.165104. - ISSN 1098-0121, DOI 10.1103/PhysRevB.72.165104
Примечания : Cited References: 82
Предметные рубрики: T-J MODEL
DENSITY-FUNCTIONAL CALCULATION
NARROW ENERGY BANDS
MEAN-FIELD THEORY
COULOMB INTERACTIONS
FERMION SYSTEMS
COPPER OXIDES
SUPERCONDUCTORS
LA2-XSRXCUO4
OXYGEN
Аннотация: A hybrid scheme for the electronic structure calculations of strongly correlated electron systems is proposed. The ab initio local density approximation calculation is used to construct the Wannier functions and obtain single electron and Coulomb parameters of the multiband Hubbard-type model. In strong correlation regime the electronic structure within multiband Hubbard model is calculated by the generalized tight-binding method, which combines the exact diagonalization of the model Hamiltonian for a small cluster (unit cell) with perturbation treatment of the intercluster hopping and interactions. For undoped La2CuO4 and Nd2CuO4 this scheme results in charge transfer insulators with correct values of gaps and dispersions of bands in agreement with the angle-resolved photoemission data.
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2.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Korshunov M. M., Gavrichkov V. A., Ovchinnikov S. G., Pchelkina Z. V., Nekrasov I. A., Korotin M. A., Anisimov V. I.
Заглавие : Parameters of the effective singlet-triplet model for band structure of high-T-c cuprates by alternative approaches
Разночтения заглавия :авие SCOPUS: Parameters of the effective singlet-triplet model for band structure of high-Tc cuprates by alternative approaches
Место публикации : J. Exp. Theor. Phys.: AMER INST PHYSICS, 2004. - Vol. 99, Is. 3. - P559-565. - ISSN 1063-7761, DOI 10.1134/1.1809685
Примечания : Cited References: 48
Предметные рубрики: DENSITY-FUNCTIONAL CALCULATION
TIGHT-BINDING METHOD
COPPER OXIDES
ENERGY-BANDS
SUPERCONDUCTORS
HOLE
LA2-XSRXCUO4
PLANE
SR2CUO2CL2
INSULATORS
Ключевые слова (''Своб.индексиров.''): 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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3.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Balaev D. A., Gokhfeld D. M., Popkov S. I., Shaykhutdinov K. A., Petrov M. I.
Заглавие : Hysteretic behavior of the magnetoresistance and the critical current of bulk Y3/4Lu1/4Ba2CU3O7+CuOcomposites in a magnetic field
Разночтения заглавия :авие SCOPUS: Hysteretic behavior of the magnetoresistance and the critical current of bulk Y3/4Lu1/4Ba2Cu3O7 + CuO composites in a magnetic field
Место публикации : Physica C: ELSEVIER SCIENCE BV, 2007. - Vol. 460: 8th International Conference on Materials and Mechanisms of Superconductivity and High Temperature Superconductors (JUL 09-14, 2006, Dresden, GERMANY). - P1307-1308. - ISSN 0921-4534, DOI 10.1016/j.physc.2007.03.346
Примечания : Cited References: 7
Предметные рубрики: SUPERCONDUCTORS
Ключевые слова (''Своб.индексиров.''): htsc--resistivity--magnetic field--relaxation--htsc--magnetic field--relaxation--resistivity--crystallites--magnetic fields--magnetic hysteresis--magnetoresistance--yttrium barium copper oxides--superconducting crystallites--superconducting systems--tunnel-type josephson junctions--josephson junction devices
Аннотация: The hysteretic behavior of critical current j(C)(H) and magneto-resistance R(H) of composites Y-Ba-Cu-O + CuO have been studied and presented. The composites represent the network of tunnel-type Josephson junctions where copper oxide acts as a material forming barriers between superconducting (YBCO) crystallites. The characteristic features of R(H) and j(C)(H) dependences are discussed in the frames of the conception of "two level superconducting system" (the Josephson media and HTSC crystallites) which is realized in the composites under study. (c) 2007 Elsevier B.V. All rights reserved.
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4.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Balaev D. A., Dubrovskiy A. A., Shaykhutdinov K. A., Popkov S. I., Petrov M. I.
Заглавие : Time relaxation of residual resistance of HTSC-based composites
Место публикации : Physica C: ELSEVIER SCIENCE BV, 2007. - Vol. 460: 8th International Conference on Materials and Mechanisms of Superconductivity and High Temperature Superconductors (JUL 09-14, 2006, Dresden, GERMANY). - P1309-1310. - ISSN 0921-4534, DOI 10.1016/j.physc.2007.03.347
Примечания : Cited References: 5
Предметные рубрики: SUPERCONDUCTORS
Ключевые слова (''Своб.индексиров.''): granular htsc--resistance--relaxation--magnetic flux--granular htsc--magnetic flux--relaxation--resistance--copper oxides--crystallites--magnetic flux--magnetic relaxation--magnetization--yttrium barium copper oxides--anderson-like relaxation processes--flux trapping--residual resistance--time relaxation--josephson junction devices
Аннотация: Magnetoresistance curves R(H) and time relaxation of the residual resistance of bulk YBCO + CuO composites have been studied. These composites represent the network of Josephson junctions, where CuO acts as a barrier between YBCO grains. It has been shown that hysteresis of the R(H) dependences is related to the flux trapping within the YBCO crystallites. This flux induces magnetic field in the intergrain media. Time relaxation of the residual resistance is caused by relaxation of the magnetization of YBCO grains. The time dependence of the residual resistance obeys a logarithmic law, which describes the Anderson-like relaxation processes in the YBCO grains. (c) 2007 Elsevier B.V. All rights reserved.
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5.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Gokhfeld D. M., Semenov S. V., Balaev D. A., Yakimov I. S., Dubrovskiy A. A., Terentyev K. Yu., Freydman A. L., Krasikov A. A., Petrov M. I.
Заглавие : Establishing of peak effect in YBCO by Nd substitution
Коллективы : Euro-Asian Symposium "Trends in MAGnetism", "Trends in MAGnetism", Euro-Asian Symposium, Институт физики им. Л.В. Киренского Сибирского отделения РАН , Russian Foundation for Basic Research [16-38-00400]
Место публикации : J. Magn. Magn. Mater.: Elsevier Science, 2017. - Vol. 440. - P.127-128. - ISSN 0304-8853, DOI 10.1016/j.jmmm.2016.12.089. - ISSN 1873-4766(eISSN)
Примечания : Cited References:10. - The work was supported by Russian Foundation for Basic Research Grant No. 16-38-00400.
Предметные рубрики: SUPERCONDUCTORS
Ключевые слова (''Своб.индексиров.''): peak effect--magnetization--bulk superconductors--critical current--ybco--nd3+
Аннотация: Y0.75Nd0.25Ba2Cu3O7−d superconductor has the peak effect with pronounced fishtail feature on magnetization hysteresis. The magnetic field of the peak effect maximum is in ~4 times higher than one of NdBa2Cu3O7−d. The magnetization hysteresis is tilted anticlockwise due to paramagnetic Nd3+ ions occurred on the surface of grains and in the vortex cores.
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6.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Shestakov V. A., Korshunov M. M., Togushova Yu. N., Dolgov, O., V
Заглавие : Decisive proofs of the s± → s++ transition in the temperature dependence of the magnetic penetration depth
Коллективы : Russian Foundation for Basic Research (RFBR)Russian Foundation for Basic Research (RFBR) [19-32-90109]; RFBRRussian Foundation for Basic Research (RFBR); Government of Krasnoyarsk Territory; Krasnoyarsk Regional Fund of Science to the Research Projects 'Electronic correlation effects and multiorbital physics in iron-based materials and cuprates' [19-42-240007]
Место публикации : Supercond. Sci. Technol. - 2021. - Vol. 34, Is. 7. - Ст.075008. - ISSN 0953-2048, DOI 10.1088/1361-6668/abff6f. - ISSN 1361-6668(eISSN)
Примечания : Cited References: 40. - We are grateful to D V Efremov, A S Fedorov, S G Ovchinnikov, E I Shneyder, D Torsello, and A N Yaresko for useful discussions. This work was supported in part by the Russian Foundation for Basic Research (RFBR) Grant No. 19-32-90109 and by RFBR and Government of Krasnoyarsk Territory and Krasnoyarsk Regional Fund of Science to the Research Projects 'Electronic correlation effects and multiorbital physics in iron-based materials and cuprates' Grant No. 19-42-240007.
Предметные рубрики: ORDER-PARAMETER
IMPURITIES
SUPERCONDUCTORS
STATES
MODEL
Аннотация: One of the features of the unconventional s± state in iron-based superconductors is possibility to transform to the s++ state with the increase of the nonmagnetic disorder. Detection of such a transition would prove the existence of the s± state. Here we study the temperature dependence of the London magnetic penetration depth within the two-band model for the s± and s++ superconductors. By solving Eliashberg equations accounting for the spin-fluctuation mediated pairing and nonmagnetic impurities in the T-matrix approximation, we have derived a set of specific signatures of the s± → s++ transition: (1) sharp change in the behavior of the penetration depth λL as a function of the impurity scattering rate at low temperatures; (2) before the transition, the slope of ΔλL(T) = λL(T) - λL(0) increases as a function of temperature, and after the transition this value decreases; (3) the sharp jump in the inverse square of the penetration depth as a function of the impurity scattering rate, λL-2(Γa), at the transition; (4) change from the single-gap behavior in the vicinity of the transition to the two-gap behavior upon increase of the impurity scattering rate in the superfluid density ρs(T).
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7.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Balaev D. A., Popkov S. I., Shaihutdinov K. A., Petrov M. I.
Заглавие : The mechanisms responsible for broadening of the resistive transition under magnetic field in the Josephson junction network realized in bulk YBCO+CuO composites
Коллективы : International Workshop on Weak Superconductivity
Разночтения заглавия :авие SCOPUS: The mechanisms responsible for broadening of the resistive transition under magnetic field in the Josephson junction network realized in bulk YBCO + CuO composites
Место публикации : Physica C. - 2006. - Vol. 435, Is. 1-2. - P.12-15. - ISSN 0921-4534, DOI 10.1016/j.physc.2006.01.008
Примечания : Cited References: 15
Предметные рубрики: SUPERCONDUCTORS
MODEL
Ключевые слова (''Своб.индексиров.''): josephson network--ybco plus cuo composites--dissipation--magnetic field--dissipation--josephson network--magnetic field--ybco + cuo composites--composite materials--copper compounds--mathematical models--phase transitions--semiconductor junctions--yttrium compounds--creep model--josephson network--ybco + cuo composites--magnetic field effects
Аннотация: The experimental results of the effect of the magnetic field (up to 60 kOe) on the broadening of the resistive transition of bulk composites Y3/4Lu1/4Ba2CU3O7 (YBCO) + CuO are presented. These composites represent the network of the tunnel-type Josephson junctions where the copper oxide acts as a material forming barriers between YBCO crystallites. The mechanisms responsible for broadening of the resistive transition under magnetic field are discussed. The analysis of experimental R(7) dependences have shown that in the low field range 0-10(2) Oe, the R(7) dependences are described well by the Ambegaokar-Halperin (AH) model. In the range 10(3)-6 x 10(4) Oe, the dissipation follows Arrhenius law R similar to exp(-U(H)/k(B)T) characteristic for thermally activated flux creep model. In the range H similar to 10(2)-10(3), the crossover from AH to flux creep dissipation mechanisms occurs. (c) 2006 Elsevier B.V. All rights reserved.
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8.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Gokhfeld D. M., Balaev D. A., Popkov S. I., Shaykhutdinov K. A., Petrov M. I.
Заглавие : Magnetization loop and critical current of porous Bi-based HTS
Место публикации : Physica C: ELSEVIER SCIENCE BV, 2006. - Vol. 434, Is. 2. - P135-137. - ISSN 0921-4534, DOI 10.1016/j.physc.2005.12.088
Примечания : Cited References: 11
Предметные рубрики: SUPERCONDUCTORS
Ключевые слова (''Своб.индексиров.''): porous superconductor--critical current--bean model--foam--bean model--critical current--foam--porous superconductor--hysteresis--magnetization--mathematical models--porous materials--bean model--critical current--foam--porous superconductor--superconductivity
Аннотация: The magnetization of porous Bi(1.8)Pb(0.3)Sr(2)Ca(2)Cu(3)O(x) has been investigated. The experimental magnetization hysteretic loops of M(H) were described in the frames of Val'kov-Khrustalev model developed for type II granular superconductors. (c) 2005 Elsevier B.V. All rights reserved.
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9.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Pisarev R. V., Kalashnikova A. M., Schops O., Bezmaternykh L. N.
Заглавие : Electronic transitions and genuine crystal-field parameters in copper metaborate CuB2O4
Разночтения заглавия :авие SCOPUS: Electronic transitions and genuine crystal-field parameters in copper metaborate CuB 2O 4
Место публикации : Phys. Rev. B: AMER PHYSICAL SOC, 2011. - Vol. 84, Is. 7. - Ст.75160. - ISSN 1098-0121, DOI 10.1103/PhysRevB.84.075160
Примечания : 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.
Предметные 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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10.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Ovchinnikov S. G., Nikolaev S. V.
Заглавие : Calculation of the Fermi Surface with Complex Topology from Norm-Conserving Cluster Perturbation Theory for Doping Dependent Electronic Structure of the Hubbard Model
Место публикации : JETP Letters. - 2011. - Vol. 93, Is. 9. - P.517-520. - ISSN 0021-3640, DOI 10.1134/S0021364011090116
Примечания : Cited References: 27. - This work was supported by the Presidium of the Russian Academy of Sciences (program no. 18.7); the Russian Foundation for Basic Research (project nos. 09-02-00127, 10-02-90725-mob_st); Siberian Branch, Russian Academy of Sciences (Integration Project no. N40); and the Ministry of Education and Sciences of the Russian Federation (state contract no. P891, Program "Kadry").
Предметные рубрики: QUANTUM OSCILLATIONS
SUPERCONDUCTORS
EVOLUTION
Аннотация: The results of recently developed norm-conserving cluster perturbation theory for doping dependent electronic structure of the Hubbard model are reported. We have found that the momentum distribution of the spectral weight strongly depends on the broadening value delta. At delta = 0.1t, we reproduce the angle-resolved photoemission spectroscopy data, while at delta = 0.01t we obtain two quantum phase transitions. DOI: 10.1134/S0021364011090116
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