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1.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Shneyder E. I., Spitaler J., Kokorina E. E., Nekrasov I. A., Gavrichkov V. A., Draxl C., Ovchinnikov S. G.
Заглавие : Coupling of Hubbard fermions with phonons in La2 CuO4: A combined study using density-functional theory and the generalized tight-binding method
Место публикации : J. Alloys Compd.: Elsevier, 2015. - Vol. 648. - P.258-264. - ISSN 0925-8388, DOI 10.1016/j.jallcom.2015.05.150
Примечания : Cited References: 60. - We acknowledge the stimulating discussions with V.V. Val'kov, D.M. Dzebisashvilly, M.M. Korshunov and I.S. Sandalov. E.I.S. and S.G.O. are thankful to the Russian Science Foundation (project No. 14-12-00061) for the support of the research given in Sections 2, 6 and 7. E.E.K. and I.A.N. are thankful to the State Contract No. 0389-2014-0001 and RFBR grant No. 14-02-00065 for the support of the research given in Section 5. Financial support of the research given in Sections 3 and 4 by the Austrian Federal Government (in particular from Bundesministerium fur Verkehr, Innovation und Technologie and Bundesministerium fur Wissenschaft, Forschung und Wirtschaft) represented by Osterreichische Forschungsforderungsgesellschaft mbH and the Styrian and the Tyrolean Provincial Government, represented by Steirische Wirtschaftsforderungsgesellschaft mbH and Standortagentur Tirol, within the framework of the COMET Funding Programme is gratefully acknowledged by C.D. and J.S.
Предметные рубрики: MEAN-FIELD THEORY
LINEAR-RESPONSE THEORY
CUPRATE SUPERCONDUCTORS
ELECTRONIC-STRUCTURE
CORRELATED SYSTEMS
LATTICE-DYNAMICS
BAND-STRUCTURE
LA2CUO4
MODEL
LA2-XSRXCUO4
Ключевые слова (''Своб.индексиров.''): high-temperature superconductivity--electron-phonon coupling--density-functional theory--generalized tight-binding approach
Аннотация: We present results for the electron-phonon interaction of the Γ-point phonons in the tetragonal high-temperature phase of La2 CuO4 obtained from a hybrid scheme, combining density-functional theory (DFT) with the generalized tight-binding approach. As a starting point, eigenfrequencies and eigenvectors for the Γ-point phonons are determined from DFT within the frozen phonon approach utilizing the augmented plane wave + local orbitals method. The so obtained characteristics of electron-phonon coupling are converted into parameters of the generalized tight-binding method. This approach is a version of cluster perturbation theory and takes the strong on-site electron correlations into account. The obtained parameters describe the interaction of phonons with Hubbard fermions which form quasiparticle bands in strongly correlated electron systems. As a result, it is found that the Γ-point phonons with the strongest electron-phonon interaction are the A2u modes (236 cm-1, 131 cm-1 and 476 cm-1). Finally it is shown, that the single-electron spectral-weight redistribution between different Hubbard fermion quasiparticles results in a suppression of electron-phonon interaction which is strongest for the triplet Hubbard band with z oriented copper and oxygen electrons. © 2015 Elsevier B.V. All rights reserved.
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2.

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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3.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Gavrichkov V. A., Kuz'min E. V., Ovchinnikov S. G.
Заглавие : Electronic structure and order parameter symmetry in high-temperature superconductors
Место публикации : Uspekhi Fiz. Nauk: MEZHDUNARODNAYA KNIGA, 2000. - Vol. 170, Is. 2. - P.189-192. - ISSN 0042-1294
Примечания : Cited References: 31
Предметные рубрики: CORRELATED ELECTRONS
HUBBARD-MODEL
OXIDES
LA2-XSRXCUO4
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4.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Gavrichkov V. A., Ovchinnikov S. G.
Заглавие : The band structure of n-type cuprate superconductors with the T '(T) structure taking into account strong electron correlation
Разночтения заглавия :авие SCOPUS: The band structure of n-type cuprate superconductors with the T′(T) structure taking into account strong electron correlation
Место публикации : J. Exp. Theor. Phys.: AMER INST PHYSICS, 2004. - Vol. 98, Is. 3. - P556-564. - ISSN 1063-7761, DOI 10.1134/1.1705708
Примечания : Cited References: 18. - This work was financially supported by the Russian Foundation for Basic Research (project no. 03-02-16124), RFFI-KKFN “Eniseœ” (project no. 02-02-97705), INTAS (project no. 01-0654), integration program of URO and Siberian Division, Russian Academy of Sciences
Предметные рубрики: QUASI-PARTICLES
COPPER OXIDES
TEMPERATURE
LA2-XSRXCUO4
ND2-XCEXCUO4
EVOLUTION
MOMENTS
Ключевые слова (''Своб.индексиров.''): dielectric properties--electric conductance--electron transitions--electronic structure--fermi level--phase diagrams--semiconductor doping--conduction bands--electron correlation--spectral density--superconducting materials
Аннотация: The spectral density, dispersion relations, and the position of the Fermi level for n-doped compositions based on NCO and LCO were calculated within the framework of the generalized tight binding method. As distinguished from LCO, the dielectric gap in NCO is nonlinear in character. We observe a virtual level both at the bottom of the conduction band and at the top of the valence band in both compounds. However, its position corresponds to the extreme bottom of the conduction band in LCO and is 0.1 - 0.2 eV above the bottom in NCO. This explains why we observe Fermi level pinning in n-LCO as the concentration of the doping component grows and reproduce its absence in NCCO at low doping values. We also found both compositions to be unstable in a narrow concentration range with respect to a nonuniform charge density distribution. The relation between the phase diagram for NCCO and the calculated electronic structure is discussed. (C) 2004 MAIK "Nauka/Interperiodica".
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5.

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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6.

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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7.

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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8.

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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9.

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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10.

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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