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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Korshunov M. M., Zakharova E. V., Nekrasov I. A., Pchelkina Z. V., Ovchinnikov S. G.
Заглавие : The Fermi surface and the role of electronic correlations in Sm2-xCexCuO4
Коллективы :
Разночтения заглавия :авие SCOPUS: The Fermi surface and the role of electronic correlations in Sm 2-xCexCuO4
Место публикации : J. Phys.: Condens. Matter: IOP PUBLISHING LTD, 2010. - Vol. 22, Is. 1. - Ст.15701. - ISSN 0953-8984, DOI 10.1088/0953-8984/22/1/015701
Примечания : Cited References: 35. - We would like to thank A A Kordyuk and I Eremin for useful discussions. The authors acknowledge support from RFBR (grants 08-02-00021, 10-02-00662, 08-02-91200 and 07-02-00226), the RAS programs on 'Low temperature quantum phenomena', 'Quantum physics of condensed matter' and 'Strongly correlated electrons solids', President of Russia (grants MK-614.2009.2 (IN) and MK-3227.2008.2 (ZP)), Scientific School (grant SS-1929.2008.2), Interdisciplinary UB-SB RAS project, Dynasty Foundation (ZP) and Russian Science Support Foundation (IN).
Предметные рубрики: T-C SUPERCONDUCTOR
IN-GAP STATES
SPIN CORRELATIONS
BAND
LA2-XSRXCUO4
EXCITATIONS
TRANSITION
EVOLUTION
SM2CUO4
OXIDES
Ключевые слова (''Своб.индексиров.''): antiferromagnetics--doping evolution--electron-doped--electronic correlation--emery model--experimental data--generalized tight bindings--high-t--hybrid scheme--magnetic orders--spin-liquid--tight binding model--two-regime--antiferromagnetism--cerium--cerium compounds--copper oxides--corundum--doping (additives)--fermi surface--fermions--tin--surfaces
Аннотация: Using a LDA + GTB (local density approximation + generalized tight-binding) hybrid scheme we investigate the band structure of the electron-doped high-T-c material Sm2-xCexCuO4. Parameters of the minimal tight-binding model for this system (the so-called three-band Emery model) were obtained within the NMTO (Nth-order muffin-tin orbital) method. The doping evolution of the dispersion and the Fermi surface in the presence of electronic correlations was investigated in two regimes of magnetic order: short-range (spin-liquid) and long-range (antiferromagnetic metal). Each regime is characterized by the specific topologies of the Fermi surfaces and we discuss their relation to recent experimental data.
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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) : Ovchinnikov S. G., Borisov A. A., Gavrichkov V. A., Korshunov M. M.
Заглавие : Prediction of the in-gap states above the top of the valence band in undoped insulating cuprates due to the spin-polaron effect
Место публикации : J. Phys.: Condens. Matter: IOP PUBLISHING LTD, 2004. - Vol. 16, Is. 8. - PL93-L100. - ISSN 0953-8984, DOI 10.1088/0953-8984/16/8/L04
Примечания : Cited References: 25
Предметные рубрики: ELECTRONIC-STRUCTURE
LA2-XSRXCUO4
MODEL
ANTIFERROMAGNETISM
SPECTRA
OXIDES
Ключевые слова (''Своб.индексиров.''): quasiparticle band structure--spin-polaron effect--antiferromagnetic materials--approximation theory--doping (additives)--electronic structure--hamiltonians--insulation--magnetic fields--strontium compounds--thermal effects--lanthanum compounds
Аннотация: In the framework of the generalized tight binding method we have calculated the quasiparticle band structure and the spectral functions of the undoped cuprates such as La2CuO4, Sr2CUO2Cl2 etc. Due to spin fluctuations the in-gap state appears above the top of the valence band in the undoped antiferromagnetic insulator similar to in-gap states induced by hole doping. In the ARPES experiments the in-gap states can be detected as weak low energy satellites.
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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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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Ovchinnikov S. G., Shneyder E. I.
Заглавие : The Interplay of Phonon and Magnetic Mechanism of Pairing in Strongly Correlated Electron System of High-T-c Cuprates
Коллективы :
Разночтения заглавия :авие SCOPUS: The interplay of phonon and magnetic mechanism of pairing in strongly correlated electron system of high-T c cuprates
Место публикации : J. Supercond. Nov. Magn.: SPRINGER, 2010. - Vol. 23, Is. 5. - P733-736. - ISSN 1557-1939, DOI 10.1007/s10948-009-0633-z
Примечания : Cited References: 26. - This work is supported by the Presidium RAS program N 7 "Quantum physics of condensed matter," the integration project SORAN-UrORAN N 40, and the RFFI Grant 09-02-00127.
Предметные рубрики: PHASE-TRANSITIONS
OXIDE SUPERCONDUCTORS
SYMMETRY
COPPER
MODEL
BAND
BI2SR2CACU2O8+DELTA
LA2-XSRXCUO4
PB
Ключевые слова (''Своб.индексиров.''): high-t-c superconductivity--strong correlated electron systems--mechanisms of superconducting pairing--high-t c superconductivity--mechanisms of superconducting pairing--strong correlated electron systems--ab initio--buckling mode--correlated electron systems--critical temperatures--cuprates--fitting parameters--high-t--isotope effect--low energies--magnetic mechanisms--order of magnitude--phonon mode--strongly correlated electron system--strongly correlated electrons--superconducting pairing--superconductivity mechanism--type theory--buckling--copper compounds--electrons--isotopes--magnetic materials--phonons--superconductivity--superconducting magnets
Аннотация: We consider magnetic mechanism of superconducting pairing in the effective low energy t - t' - t '' - J* model with all parameters calculated ab initio. Interaction of strongly correlated electrons with different phonon modes is also incorporated. In a BCS type theory, the d(x2-y2) gap is given by a sum of magnetic and phonon contributions. The main contribution to the only fitting parameter G is determined by a competition of the breathing and buckling modes. Fitting the parameter G from the isotope effect, we obtain that magnetic and phonon contributions to the critical temperature T-c work together and are of the same order of magnitude.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Ovchinnikov S. G., Korshunov M. M., Zakharova E. V.
Заглавие : Temperature evolution of spin-polaron in-gap states in undoped antiferromagnetic cuprates
Коллективы :
Место публикации : Phys. Solid State: MAIK NAUKA/INTERPERIODICA/SPRINGER, 2008. - Vol. 50, Is. 8. - P1401-1406. - ISSN 1063-7834, DOI 10.1134/S1063783408080027
Примечания : Cited References: 26. - This work was supported by the Russian Foundation for Basic Research (project nos. 06-02-16100 and 0602- 90537-BNTS), the Presidium of the Russian Academy of Sciences (program "Quantum Macrophysics"), and INTAS (YS grant no. 05-109-4891).
Предметные рубрики: J MODEL
LA2-XSRXCUO4
SUPERCONDUCTORS
BAND
Аннотация: The temperature evolution of in-gap states created by the spin polaron effect and located within the gap with charge transfer between the valence and conduction bands is studied for the case of strong electron correlations using the t-t'-t ''-J model of antiferromagnetic undoped cuprates. The effect of temperature is taken into account by temperature renormalization of the magnon concentration, which is calculated using the Heisenberg model with inclusion of weak interlayer exchange and weak in-plane spin anisotropy, and by introducing a Lorentzian with a temperature-dependent half-width in the form corresponding to the marginal Fermi liquid model. With increasing temperature, the spectral weight of the in-gap state, which is proportional to the magnon concentration, grows leading to an increased intensity of the corresponding peak of the spectral function in all points of the Brillouin zone. At points (pi/2, pi/2) and (pi, 0), the main peak is approached by the satellite peak related to the in-gap band and, at points (0, 0) and (pi, pi), the peaks move away from each other.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Ovchinnikov S. G.
Заглавие : Spin excitons - A new mechanism of superconducting pairing in copper oxides
Место публикации : JETP Letters. - 1996. - Vol. 64, Is. 1. - P.25-31. - ISSN 0021-3640, DOI 10.1134/1.567153
Примечания : Cited References: 22
Предметные 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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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Ovchinnikov S. G.
Заглавие : Modification of magnetic and superconducting properties of layered cuprates due to copper substitution for zinc and nickel
Место публикации : Fiz. Tverd. Tela: MEZHDUNARODNAYA KNIGA, 1995. - Vol. 37, Is. 12. - P3645-3654. - ISSN 0367-3294
Примечания : Cited References: 28
Предметные рубрики: ELECTRONIC-STRUCTURE
LA2CUO4
LA2-XSRXCUO4
EXCITATIONS
DENSITY
PLANE
NI
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Nikolaev S. V., Ovchinnikov S. G.
Заглавие : Effect of hole doping on the electronic structure and the Fermi surface in the Hubbard model within norm-conserving cluster pertubation theory
Место публикации : J. Exp. Theor. Phys.: MAIK Nauka-Interperiodica / Springer, 2012. - Vol. 114, Is. 1. - P.118-131. - ISSN 1063-7761, DOI 10.1134/S1063776111150143
Примечания : Cited References: 51. - This study was supported financially by the Russian Foundation for Basic Research (project nos. 10-02-90725-mob_st and 09-02-00127), Program 18.7 of the Presidium of the Russian Academy of Sciences, the Federal Target Program "Personnel" (state contract no. P891), and the integrated project no. 40 of the Siberian Branch of the Russian Academy of Sciences.
Предметные рубрики: HIGH-TEMPERATURE SUPERCONDUCTORS
NARROW ENERGY-BANDS
CORRELATED ELECTRONS
PSEUDOGAP
EVOLUTION
La2-XSRXCuO4
INSULATOR
Аннотация: The concentration dependences of the band structure, spectral weight, density of states, and Fermi surface in the paramagnetic state are studied in the Hubbard model within cluster pertubation theory with 2 x 2 clusters. Representation of the Hubbard X operators makes it possible to control conservation of the spectral weight in constructing cluster perturbation theory. The calculated value of the ground-state energy is in good agreement with the results obtained using nonperturbative methods such as the quantum Monte Carlo method, exact diagonalization of a 4 x 4 cluster, and the variational Monte Carlo method. It is shown that in the case of hole doping, the states in the band gap (in-gap states) lie near the top of the lower Hubbard band for large values of U and near the bottom of the upper band for small U. The concentration dependence of the Fermi surface strongly depends on hopping to second (t') and third (t '') neighbors. For parameter values typical of HTSC cuprates, the existence of three concentration regions with different Fermi surfaces is demonstrated. It is shown that broadening of the spectral electron density with an energy resolution typical of contemporary ARPES leads to a pattern of arcs with a length depending on the concentration. Only an order-of-magnitude decrease in the linewidth makes it possible to obtain the true Fermi surface from the spectral density. The kinks associated with strong electron correlations are detected in the dispersion relation below the Fermi level.
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10.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Makarov I. A., Ovchinnikov S. G., Shneider E. I.
Заглавие : Dependence of the critical temperature of high-temperature cuprate superconductors on hoppings and spin correlations between CuO2 planes
Место публикации : J. Exp. Theor. Phys.: MAIK Nauka-Interperiodica / Springer, 2012. - Vol. 114, Is. 2. - P.329-342. - ISSN 1063-7761, DOI 10.1134/S1063776112020264
Примечания : Cited References: 73. - This study was supported in part by the Presidium of the Russian Academy of Sciences (program "Quantum Physics of Condensed Media," project no. 18.7), jointly by the Siberian and Ural branches of the Russian Academy of Sciences (integration projects project no. 40), the Russian Foundation for Basic Research (project no. 09-02-00127), the Presidential Program in Support of Young Scientists in Russia (project no. MK-1683.2010.2), and the federal target program "Specialists" (project no. P891). One of the authors (E.I.Sh.) gratefully acknowledges support from the nonprofit Dynasty foundation.
Предметные рубрики: T-J MODEL
BAND HUBBARD-MODEL
SINGLE-CRYSTALS
TRANSITION-TEMPERATURE
FERMI-SURFACE
DOPING DEPENDENCE
THERMAL-EXPANSION
COPPER OXIDES
ANISOTROPY
LA2-XSRXCUO4
Аннотация: The influence of interlayer hoppings on the superconducting transition temperature (T c) in bilayer cuprates has been studied. The parameter of hopping between layers is expressed as t ⊥(k) = t ⊥(cos(k x ) − cos(k y ))2 and treated as a small perturbation for the states of two CuO2 planes described by the t-t′-t″-J* model. In the generalized mean field approximation for dx2−y2{d_{{x. } - {y. }}} symmetry of the superconducting gap, neither the interlayer hopping or exchange interaction, nor the pair hopping between CuO2 layers provides an additional mechanism of Cooper pair formation or an increase in T c. In the concentration dependence of T c, the bilayer splitting of the upper Hubbard band of quasi-holes is manifested as two peaks with temperatures slightly lower than the maximum T c for a single-layer cuprate. Interlayer antiferromagnetic spin correlations suppress bilayer splitting.
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