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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Avramov P. V., Ovchinnikov S. G.
Заглавие : Underestimating the width of the bandgap in the electronic spectra of La2CuO4
Место публикации : Phys. Solid State: AMER INST PHYSICS, 1997. - Vol. 39, Is. 3. - P389-391. - ISSN 1063-7834, DOI 10.1134/1.1129865
Примечания : Cited References: 9
Предметные рубрики: SUPERCONDUCTIVITY
Аннотация: It is shown that the width of the bandgap determined by the simultaneous analysis of the experimental photoelectron and inverse photoemission spectra of the surface of La2CuO4 using a common energy scale is underestimated by 1 eV. The electronic and satellite structures of the spectra of La2CuO4 are calculated on the basis of the multiband p-d model and the sudden perturbation approximation. It is shown that shakedown processes shift the one-electron contour of the final two-hole configuration of the photoelectron spectrum 1 eV down the energy scale and shift the contour of the final d(10) configuration of the inverse photoemission spectrum downward by 2 eV; these shifts cause the energy splitting between the filled and empty bands to be underestimated. (C) 1997 American Institute of Physics.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Makarov I. A., Shneyder E. I., Kozlov P. A., Ovchinnikov S. G.
Заглавие : Transition between large and small polaron states in the electronic structure of HTSC cuprates
Коллективы : RFBR [13-02-01395 a, 14-02-31677 mol_a]
Место публикации : J. Supercond. Nov. Magn.: Springer, 2016. - Vol. 29, Is. 4. - P.1063-1068. - ISSN 1557-1939, DOI 10.1007/s10948-016-3375-8. - ISSN 1557-1947(eISSN)
Примечания : Cited References:10. - This work was funded by RFBR according to the research projects No. 13-02-01395 a and No. 14-02-31677 mol_a.
Предметные рубрики: SUPERCONDUCTIVITY
Ключевые слова (''Своб.индексиров.''): cuprates--strong electron correlations--electron-phonon interaction--polaron--franck-condon process--hubbard fermions--band structure
Аннотация: The effect of strong electron correlations (SEC) and strong electron-phonon interaction (EPI) on the electronic structure of cuprates is studied within the polaronic version of the generalized tight binding method. Both diagonal and off-diagonal EPI in terms of ionic coordinates are considered.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Makarov I. A., Ovchinnikov S. G.
Заглавие : Temperature dependence of the electronic structure of La2CuO4 in the multielectron LDA+GTB approach
Место публикации : J. Exp. Theor. Phys.: MAIK Nauka-Interperiodica / Springer, 2015. - Vol. 121, Is. 3. - P.457-464. - ISSN 1063-7761, DOI 10.1134/S1063776115090174
Примечания : Cited References: 38. - The work was supported by the Russian Science Foundation (project no. 14-12-00061)
Предметные рубрики: Copper oxides
Model
Superconductivity
Excitations
Instability
Spectrum
States
Order
Аннотация: The band structure of La2CuO4 in antiferromagnetic and paramagnetic phases is calculated at finite temperatures by the multielectron LDA+GTB method. The temperature dependence of the band spectrum and the spectral weight of Hubbard fermions is caused by a change in the occupation numbers of local multielectron spin-split terms in the antiferromagnetic phase. A decrease in the magnetization of the sublattice with temperature gives rise to new bands near the bottom of the conduction band and the top of the valence band. It is shown that the band gap decreases with increasing temperature, but La2CuO4 remains an insulator in the paramagnetic phase as well. These results are consistent with measurements of the red shift of the absorption edge in La2CuO4 with increasing temperature. © 2015, Pleiades Publishing, Inc.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Li, Oksana A., Lin, Chun-Rong, Chen, Hung-Yi, Hsu, Hua-Shu, Wu, Kai-Wun, Tseng, Yaw-Teng, Bayukov O. A., Edelman I. S., Ovchinnikov S. G., Shih, Kun-Yauh
Заглавие : Structural and magnetic properties of Fe1−xCoxSe1.09 nanoparticles obtained by thermal decomposition
Место публикации : Mater. Res. Express: IOP Publishing, 2015. - Vol. 2, No. 12. - Ст.126501. - ISSN 2053-1591, DOI 10.1088/2053-1591/2/12/126501
Примечания : Cited References: 30. - This work is supported by the Ministry of Science and Technology of Taiwan (MOST103-2811-M-153 -001 and MOST102-2112-M-153 -002 -MY3).
Предметные рубрики: X-RAY-DIFFRACTION
MOSSBAUER-SPECTROSCOPY
CRYSTAL-STRUCTURES
IRON SELENIDES
SUPERCONDUCTIVITY
FeSe
MARCASITE
PYRITE
Ключевые слова (''Своб.индексиров.''): nanoparticles--chalcogenide--iron-cobalt selenide--ferrimagnetism--paramagnetism--mossbauer spectroscopy
Аннотация: A series of Fe1−xCoxSe1.09 (x = 0 to ) nanoparticles were synthesized by thermal decomposition method. Particles in composition range Fe0.5Co0.5Se1.09 to CoSe1.09 crystallized in monoclinic structure of Co6.8Se8 , while FeSe1.09 crystallized in hexagonal structure of FeSe achavalite. Magnetization dependences on temperature and external magnetic field reveal complicated magnetic behavior and correspond to the sum of paramagnetic and superparamagnetic response. Mössbauer spectra contain several paramagnetic doublets with parameters corresponding to nonequivalent positions of divalent and trivalent iron cations with low spin. The nonequivalent positions appeared due to inhomogeneous distribution of Co ions or metal vacancies in iron surrounding.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Janowitz C., Seidel U., Unger RST, Krapf A., Manzke R., Gavrichkov V. A., Ovchinnikov S. G.
Заглавие : Strong spin triplet contribution of the first removal state in the insulating regime of Bi2Sr2Ca1-xYxCu2O8+delta
Разночтения заглавия :авие SCOPUS: Strong spin triplet contribution of the first removal state in the insulating regime of Bi2Sr2Ca1-xY xCu2O8+δ
Место публикации : JETP Letters. - 2004. - Vol. 80, Is. 11. - P.692-696. - ISSN 0021-3640, DOI 10.1134/1.1862796
Примечания : Cited References: 18
Предметные рубрики: ELECTRONIC-STRUCTURE
APICAL OXYGEN
MODEL
SUPERCONDUCTIVITY
ONSET
Аннотация: The experimental dispersion of the first removal state in the insulating Bi2Sr2Ca1 - xYxCu2O8 + delta regime is found to differ significantly from that of other parent materials: oxyclorides and La2CuO4. For Y contents of 0.92 greater than or equal to x greater than or equal to 0.55 due to nonstoichiometric effects in the Bi-O layers, the hole concentration in the CuO2 layers is almost constant and, on the contrary, the crystal lattice parameters a, b, c change very strongly. This (a, b) parameter increase and c parameter decrease results in an unconventional three peak structure at (0, 0), (pi/2, pi/2), (pi, pi) for x = 0.92. We can describe the experimental data only beyond the framework of the three-band p-d-model involving the representations of a new triplet counterpart for the Zhang-Rice singlet state. (C) 2004 MAIK "Nauka/Interperiodica".
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Shtarev, Dmitry S., Shtareva, Anna, V, Kevorkyants, Ruslan, Molokeev M. S., Serpone, Nick
Заглавие : Revisiting the BaBiO3 semiconductor photocatalyst: synthesis, characterization, electronic structure, and photocatalytic activity
Коллективы : Russian Science FoundationRussian Science Foundation (RSF) [19-73-10013]
Место публикации : Photochem. Photobiol. Sci. - 2021. - Vol. 20, Is. 9. - P.1147-1160. - ISSN 1474-905X, DOI 10.1007/s43630-021-00086-y. - ISSN 1474-9092(eISSN)
Примечания : Cited References: 48. - We wish to thank the Russian Science Foundation for a Grant (Project No. 19-73-10013) in support of our study. The authors are also grateful to the staff of the following Institutes/Centers for their valuable technical assistance and in providing the needed equipment: (i) the Khabarovsk Innovation and Analytical Center of the Yu. A. Kosygin Institute of Tectonics and Geophysics FEB RAS; and (ii) the Resource Centers of the Research Park at Saint-Petersburg State University, especially the Center for Physical Methods of Surface Investigation and the Nanophotonics Center. One of us (NS) is grateful to the staff of the PhotoGreen Laboratory of the University of Pavia, Italy, for their continued hospitality
Предметные рубрики: RHODAMINE-B
OXIDE
DRIVEN
SUPERCONDUCTIVITY
PSEUDOPOTENTIALS
Аннотация: This article revisits the properties of BaBiO3 examined extensively in the last two decades because of its electronic properties as a superconductor and as a semiconductor photocatalyst. Solid-state syntheses of this bismuthate have often involved BaCO3 as the barium source, which may lead to the formation of BaBiO3/BaCO3 heterostructures that could have an impact on the electronic properties and, more importantly, on the photocatalytic activity of this bismuthate. Accordingly, we synthesized BaBiO3 by a solid-state route to avoid the use of a carbonate; it was characterized by XRD, SEM, and EDX, while elemental mapping characterized the composition and the morphology of the crystalline BaBiO3 and its thin films with respect to structure, optoelectronic, and photocatalytic properties. XPS, periodic DFT calculations, and electrochemical impedance spectroscopy ascertained the electronic and electrical properties, while Raman and DRS spectroscopies assessed the relevant optical properties. The photocatalytic activity was determined via the degradation of phenol in aqueous media. Although some results accorded with earlier studies, the newer electronic structural data on this bismuthate, together with the photocatalytic experiments carried out in the presence of selective radical trapping agents, led to elucidating some of the mechanistic details of the photocatalytic processes that previous views of the BaBiO3 band structure failed to address or clarify. Analytical refinement of the XRD data inferred the as-synthesized BaBiO3 adopted the C2/m symmetry rather than the I2/m structure reported earlier, while Tauc plots from DRS spectra yielded a bandgap of 2.05 eV versus the range of 1.1–2.25 eV reported by others; the corresponding flatband potentials were 1.61 eV (EVB) and − 0.44 eV (ECB). The photocatalytic activity of BaBiO3 was somewhat greater than that of the well-known Evonik P25 TiO2 photocatalyst under comparable experimental conditions.
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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) : Kagan M. Y., Val'kov V. V., Woelfle P.
Заглавие : Manifestation of the upper Hubbard band in the 2D Hubbard model at low electron density
Место публикации : Low Temp. Phys. - 2011. - Vol. 37, Is. 9-10. - P.834-839. - ISSN 1063-777X, DOI 10.1063/1.3670026; \b Физика низких температур
Примечания : Cited References: 31. - This work was supported by RFBR Grants No. 11-0200798 and 11-02-00741.
Предметные рубрики: 2-DIMENSIONAL FERMI GAS
LIQUID BEHAVIOR
SPECTRAL FUNCTIONS
TRANSITION METALS
SUPERCONDUCTIVITY
FERROMAGNETISM
DIMENSIONS
SCATTERING
STATE
Ключевые слова (''Своб.индексиров.''): electron density--electronic density of states--fermi liquid--green's function methods--hubbard model
Аннотация: We consider the 2D Hubbard model in the strong-coupling case (U W) and at low electron density (nd(2) ≪1). We find an antibound state as a pole in the two-particle T-matrix. The contribution of this pole in the self-energy reproduces a two-pole structure in the dressed one-particle Green-function similar to the Hubbard-I approximation. We also discuss briefly the Engelbrecht-Randeria mode which corresponds to the pairing of two holes below the bottom of the band for U W and low electron density. Both poles produce nontrivial corrections to Landau Fermi-liquid picture already at low electron density but do not destroy it in 2D.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Val'kov V. V., Zlotnikov A. O.
Заглавие : Manifestation of spin-charge fluctuations in the spectral and thermodynamic properties of quasi-two-dimensional rare-earth intermetallic compounds
Коллективы : RFBR [16-02-00073-a, 15-42-04372-r-Siberia-a]; Government of the Krasnoyarsk Region; Regional Science Foundation [07/16]; Integrated program II.2P of SB RAS [0358-2015-0002]; Presidential scholarships for young PhDs [SP-1370.2015.5]
Место публикации : Low Temp. Phys.: American Institute of Physics, 2017. - Vol. 43, Is. 2. - P.191-199. - ISSN 1063-777X, DOI 10.1063/1.4977211. - ISSN 1090-6517(eISSN)
Примечания : Cited References:35. - This work was supported by RFBR (Grants Nos. 16-02-00073-a and 15-42-04372-r-Siberia-a), the Government of the Krasnoyarsk Region and the Regional Science Foundation (Ext. Agreement No. 07/16), as well as the Integrated program II.2P of SB RAS (Project No. 0358-2015-0002). One of the authors (A.O.Z.) acknowledges the support by the Presidential scholarships for young PhDs (SP-1370.2015.5).
Предметные рубрики: PERIODIC ANDERSON MODEL
INTERMEDIATE-VALENCE COMPOUNDS
MAGNETIC PHASE-DIAGRAM
HEAVY
SUSCEPTIBILITY
APPROXIMATION
ANTIFERROMAGNETISM
SUPERCONDUCTIVITY
LATTICE
METALS
Аннотация: In the framework of the modified periodic Anderson model with exchange interaction in the subsystem of localized states, it is shown that spin-charge fluctuations in quasi-two-dimensional intermetallic compounds with rare-earth ions in the mixed valence state significantly affect both the spectrum of magnetic excitations and the conditions at which the antiferromagnetic phase is realized. The spectral characteristics of the phase were obtained by the method of the diagram technique for Hubbard operators in the one-loop approximation, which allows to account for the spincharge fluctuation contributions to the components of the mass and the force operators. The developed theory allowed to quantitatively describe the pressure dependence of the Neel temperature observed in a quasi-two-dimensional antiferromagnetic heavy-fermion intermetallic compound CeRhIn5. Published by AIP Publishing.
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10.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Aksenov S. V., Zlotnikov A. O., Shustin M. S.
Заглавие : Majorana modes in BDI-class wire with strong Coulomb correlations [Electronic resource]
Место публикации : ArXiv. - 2019. - Ст.1911.01035
Вид и объем ресурса: Electronic text data
Примечания : Cited References: 55. - We acknowledge fruitful discussions with V.V. Valkov and V.A. Mitskan. The reported study was funded by the RAS Presidium programs for fundamental research Nos. 12 and 32, Russian Foundation for Basic Research (projects Nos. 18-32-00443, 19-02-00348), Government of Krasnoyarsk Territory, Krasnoyarsk Regional Fund of Science to the research projects: ”The manifestation of Coulomb interactions and effects of bounded geometry in the properties of topological edge states of nanostructures with spin-orbit interaction” (No. 18-42-243017), ”Coulomb interactions in the problem of Majorana modes in low-dimensional systems with nontrivial topology” (No. 19-42-240011). S.A. and A.Z. are grateful to the Council of the President of the Russian Federation for Support of Young Scientists and Leading Scientific Schools, projects Nos. MK-3722.2018.2, MK-3594.2018.2.
Предметные рубрики: Mesoscale and Nanoscale Physics
Strongly Correlated Electrons
Superconductivity
Аннотация: In this study the problem of strong Coulomb interactions in topological superconducting wire is analyzed by means of the density-matrix-renormalization-group (DMRG) approach. To obtain the topological phase diagrams and analyze properties of edge states in the BDI-class structure the quantity called Majorana polarization is used. Its behavior agrees with the entanglement-spectrum degeneracy which has topological nature. The DMRG calculations for the Shubin-Vonsovsky-type model of the wire show the transformation of phases with Majorana single and double modes (MSMs and MDMs, respectively) under the increase of on- and inter-site correlations. In particular, the effects of MSM and MDM robustness as well as their induction are observed. It is shown that in the strongly correlated regime the contributions of single-particle excitations to the Majorana-type states significantly decrease if averaged on-site spin-dependent concentrations have comparable values. Moreover, the t−J∗−V-model is derived allowing to study the effective interactions and improve the DMRG numerics. In order to demonstrate the key role of spin and charge fluctuations in the revealed effects we analytically consider the limiting case of the effective Hamiltonian with infinitely strong on-site repulsion using the Hubbard-I approximation. Finally, the ways to probe the MSMs and MDMs via the features of caloric functions are discussed.
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11.

Вид документа : Однотомное издание
Шифр издания :
Автор(ы) : Ovchinnikov S. G., Makarov I. A., Shneyder E. I., Togushova Yu.N., Gavrichkov V. A., Korshunov M. M.
Заглавие : Magnetic mechanisms of pairing in strongly correlated electron system of copper oxides [Electronic resource]
Место публикации : arXiv. - 2015. - Ст.eprint arXiv:1510.08640
Примечания : Cited References: 214. - The authors acknowledge support from FCP Scientific and Research-and-Educational Personnel of Innovative Russia for 2009-2013 (GK 16.740.12.0731 and GK 16.740.11.0740), RFBR (Grants 12-02-31534 and 12-02-31597), Siberian Federal University (Theme #F-11), Governmental support of leading scientific schools of Russia (NSh-1044.2012.2), Program of SB RAS #44, Presidium of RAS program #20.7. EIS, IAM, and MMK are grateful to The Dynasty Foundation and ICFPM forthe financial supportIn book.: Recent advances in superconductivity research", ed. by C.B. Taylor, 321 p., Nova Science Publishers Inc. New York, 2013 ISBN: 978-1-62618-406-0, Chapter 6
Предметные рубрики: Condensed matter-- Strongly correlated electrons
Superconductivity
Ключевые слова (''Своб.индексиров.''): strong electronic correlations--cuprates--hubbard operators--electronic structure--quantum phase transitions--magnetic mechanism of pairing
Аннотация: The multielectron LDA+GTB approach has been developed to calculate electronic structure of strongly correlated cuprates. At low energies the effective Hamiltonian of the t−t′−t"−t⊥−J∗−J⊥-model has been derived with parameters coming from the ab initio calculation for LSCO. The electronic structure of LSCO has been calculated self-consistently with the short-range antiferromagnetic order for various doping level. Two Lifshitz-type quantum phase transitions with Fermi surface topology changes have been found at dopings xc1=0.15 and xc2=0.24. Its effect on normal and superconducting properties has been calculated. The interatomic exchange parameter and its pressure dependence has been calculated within LDA+GTB scheme. The magnetic mechanisms of d-wave pairing induced by static and dynamical spin correlations are discussed. Simultaneous treatment of magnetic and phonon pairing results in the conclusion that both contributions are of the same order. For two layer cuprates like YBCO the interlayer hopping and exchange effects on the electronic structure and doping dependence of Tc is discussed as well as the Coulomb interaction induced mechanism of pairing.
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12.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Sandalov I. S., Richter M.
Заглавие : Local gauge invariance versus slave boson-like representations in systems with strongly correlated electrons
Место публикации : Phys. Scr.: ROYAL SWEDISH ACAD SCIENCES, 1996. - Vol. 54, Is. 4. - P410-416. - ISSN 0281-1847, DOI 10.1088/0031-8949/54/4/020
Примечания : Cited References: 38
Предметные рубрики: T-J MODEL
VALENCE-BOND STATE
DIAGRAM TECHNIQUE
ANDERSON MODEL
HUBBARD MODEL
SUPERCONDUCTIVITY
LIMIT
PHASE
Аннотация: The flux phase solutions in the t-J model the gauge theories with Chern-Simons term, promising new exciting physics, are so far obtained only within slave-boson (or fermion) approaches, where local gauge invariance is not taken into account exactly. We inspect the possibility to do this, mainly, in the example of the t-J model The analysis of different parametrizations in the functional representation shows that (i) calculations which take into account constraints for the number of on-site-available states are describing quasiparticles in terms of the wrong local statistics, and contain gauge non-invariant objects; (ii) application of the projection technique in the slave-boson(fermion) representation reproduces the correct statistics, and is exactly equivalent to the conventional diagram technique for Hubbard operators. In the language of slave bosons this means that the Fourier transformation leading to Bloch states should be made only after accounting constraints in the measure of functional integral.
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13.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Kagan M. Y., Efremov D. V., Mar'enko M. S., Val'kov V. V.
Заглавие : Kohn-Luttinger effect and anomalous pairing in repulsive Fermi-systems at low density : Review Article
Место публикации : Low Temp. Phys.: American Institute of Physics, 2012. - Vol. 38, Is. 9. - P.874-879. - ISSN 1063-777X, DOI 10.1063/1.4752091
Примечания : Cited References: 59. - We acknowledge helpful discussions with A. V. Chubukov, A. S. Alexandrov, V. V. Kabanov, K. I. Kugel, Yu. V. Kopaev, N. M. Plakida, and N. V. Prokof'ev. M. Yu. K's work was supported by RFBR Grant No 11-02-00741-a.
Предметные рубрики: T-J MODEL
SUPERFLUID TRANSITION-TEMPERATURE
2-BAND HUBBARD-MODEL
LOW ELECTRON-DENSITY
FRACTIONAL-STATISTICS
PHASE-SEPARATION
SUPERCONDUCTIVITY
GAS
ENHANCEMENT
MECHANISM
Ключевые слова (''Своб.индексиров.''): d-wave superconductivity--electron density--electron spin polarisation--high-temperature superconductors--hubbard model--superconducting transition temperature--t-j model--two-dimensional electron gas
Аннотация: We demonstrate the possibility of triplet p-wave pairing at low electron density a large number of models such as 3D and 2D Fermi-gas models with hard-core repulsion, 3D and 2D Hubbard models, and the Shubin-Vonsovsky model. The critical temperature for p-wave pairing can be considerably higher in the spin-polarized case or even in a two-band situation at low density and can reach experimentally observable values of 1–5 K. We also discuss briefly the d-wave pairing and high-Tc superconductivity with Tc ∼ 100 K which arise in the extended Hubbard model and in the generalized t-Jmodel when close to half-filling.
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14.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Val'kov V. V., Shklyaev A. A., Korovushkin M. M., Barabanov A. F.
Заглавие : Influence of triplet states on the spectrum of collective spin-polaron excitations in a 2D kondo lattice
Место публикации : Phys. Solid State: MAIK NAUKA/INTERPERIODICA/SPRINGER, 2011. - Vol. 53, Is. 10. - P1997-2000. - ISSN 1063-7834, DOI 10.1134/S1063783411100337
Примечания : Cited References: 10. - This study was supported by the Presidium of the Russian Academy of Sciences (Program "Quantum Physics of Condensed Matter"), the Siberian Branch of the Russian Academy of Sciences (Interdisciplinary Integration project no. 53), the Ministry of Education and Science of the Russian Federation (Russian Federal Targeted Program "Scientific and Scientific-Pedagogical Personnel of the Innovative Russia" in 2009-2013), and the Russian Foundation for Basic Research (projects nos. 09-02-00127, 10-02-00614).
Предметные рубрики: SUPERCONDUCTIVITY
ANTIFERROMAGNET
Аннотация: The normal and superconducting phases of the ensemble of spin polarons in a two-dimensional Kondo lattice have been considered under the conditions when the hopping integral is comparable to the s-d exchange interaction energy. The polaron excitation spectrum and the superconducting transition temperature have been found taking into account upper triplet states. The change in the concentration dependence of the critical temperature of the transition to the superconducting phase with the relation between the hopping integral and the integral of the s-d exchange coupling has been analyzed.
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15.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Bykov A. A., Gokhfeld D. M., Savitskaya N. E., Terentjev K. Yu., Popkov S. I., Mistonov A. A., Grigoryeva N. A., Zakhidov A., Grigoriev, S., V
Заглавие : Flux pinning mechanisms and a vortex phase diagram of tin-based inverse opals
Коллективы : Russian Foundation for Basic ResearchRussian Foundation for Basic Research (RFBR) [17-72-10067]
Место публикации : Supercond. Sci. Technol. - 2019. - Vol. 32, Is. 11. - Ст.115004. - ISSN 0953-2048, DOI 10.1088/1361-6668/ab3db7. - ISSN 1361-6668(eISSN)
Примечания : Cited References: 31. - The work was supported by the Russian Foundation for Basic Research, project no. 17-72-10067.
Предметные рубрики: SUPERCONDUCTIVITY
Аннотация: Three-dimensional periodic tin structures were synthesized by filling pores in silicon opals with a sphere diameter of 194 nm (Sn190) and 310 nm (Sn300). The samples were examined by the ultra-small-angle x-ray diffraction method, energy dispersive x-ray microanalysis and scanning electron microscopy. It was found that the inverse opal structure consists of tin nanoparticles inscribed in octahedral and tetrahedral pores with diameters of 128 nm and 70 nm for the sample Sn300, and 80 nm and 42 nm for the sample Sn190. The study of the magnetic properties of the samples by SQUID magnetometry showed that magnetization reversal curves exhibit hysteretic behavior. The mechanisms of magnetic flux pinning in the samples depend on the size of the tin nanoparticles. Tin nanoparticles in Sn300 behave like a classical type-I superconductor. The hysteretic behavior of the magnetization reversal curves at low magnetic fields is due to the formation of a network of superconducting contours in Sn300. These superconducting contours effectively trap the magnetic flux. The octahedral tin nanoparticles in Sn190 remain type-I superconductors, but smaller tetrahedral particles behave like type-II superconductors. Type-I and II superconducting particles in Sn190 lead to the coexistence of different mechanisms of flux pinning These are flux trapping by superconducting contours at low magnetic fields and flux pinning by tetrahedral particles due to the surface barrier at high magnetic fields.
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16.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Donkov A., Eremin I., Knolle J., Korshunov M. M.
Заглавие : Electron-Phonon Interaction and Phonon Renormalization in the Lamellar Cobaltate NaxCoO2
Разночтения заглавия :авие SCOPUS: Electron-phonon interaction and phonon renormalization in the lamellar cobaltate Na x CoO 2
Место публикации : J. Supercond. Nov. Magn.: SPRINGER, 2009. - Vol. 22: International Conference on Quantum Phenomena in Complex Matters (JUL 26-AUG 01, 2008, Erice, ITALY), Is. 1. - P37-40. - ISSN 1557-1939, DOI 10.1007/s10948-008-0372-6
Примечания : Cited References: 16
Предметные рубрики: SUPERCONDUCTIVITY
Ключевые слова (''Своб.индексиров.''): electron-phonon interaction--superconductivity--sodium cobaltate--electron-phonon interaction--sodium cobaltate--superconductivity--brillouin zones--cobaltate--conducting electrons--conduction electrons--doping dependences--feedback effects--matrix elements--phonon frequencies--phonon modes--raman experiments--renormalization--sodium cobaltate--sodium cobaltates--atoms--cobalt compounds--critical current density (superconductivity)--electric conductivity--electron-phonon interactions--electrons--flow interactions--penetration depth (superconductivity)--sodium--superconductivity--phonons
Аннотация: We study theoretically the electron-phonon interaction in NaxCoO2. For the A(1g) and E-1g phonon modes found in Raman experiments, we calculate the matrix elements of the electron-phonon interaction. Analyzing the feedback effect of the conduction electrons on the phonon frequency., we investigate the doping dependence of these two phonon modes. Due to the momentum dependence of the electron-phonon interaction, we find the strongest renormalization of the E-1g mode around the Brillouin zone boundary which should be observed in the neutron scattering. At the same time, the A(1g) mode shows the strongest coupling to the conducting electrons around the G point and reveals its doping dependence in the Raman experiments. Our results shed light on the possible importance of the electron-phonon interaction in the lamellar sodium cobaltates.
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17.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Val'kov V. V., Korovushkin M. M., Barabanov A. F.
Заглавие : Effective Interactions and the Nature of Cooper Instability of Spin Polarons in the 2D Kondo Lattice
Коллективы :
Разночтения заглавия :авие SCOPUS: Effective interactions and the nature of Cooper instability of spin polarons in the 2D Kondo lattice
Место публикации : JETP Letters. - 2008. - Vol. 88, Is. 6. - P.370-374. - ISSN 0021-3640, DOI 10.1134/S0021364008180069
Примечания : Cited References: 9. - This work was supported by the Presidium of the Russian Academy of Sciences (program "Quantum Microphysics"), the Russian Foundation for Basic Research (project no. 06-02-16100), and the Siberian Branch, Russian Academy of Sciences (integration project no. 3.4). The work of M. M. Korovushkin was supported by the Krasnoyarsk Regional Science Foundation (project no. 18G).
Предметные рубрики: SUPERCONDUCTIVITY
ANTIFERROMAGNET
MODEL
Аннотация: It has been shown that two- and three-center interactions arise in the strong-coupling regime for the 2D Kondo lattice; these interactions both induce and suppress the Cooper instability. It is important that, in contrast to the t-J* model, the three- center interactions promote the Cooper pairing and ensure the appearance of the superconducting phase with a high critical temperature T(c). The calculated concentration dependences of T(c) agree well with the experimental data for the cuprate superconductors.
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18.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : OVCHINNIKOV S. G.
Заглавие : EFFECT OF SUBSTITUTIONAL IMPURITY SPECIES ON THE SUPPRESSION OF MAGNETIC-PROPERTIES OF WEAKLY DOPED COPPER OXIDES
Место публикации : Fiz. Tverd. Tela: MEZHDUNARODNAYA KNIGA, 1994. - Vol. 36, Is. 5. - P1307-1310. - ISSN 0367-3294
Примечания : Cited References: 16
Предметные рубрики: ELECTRONIC-STRUCTURE
SUPERCONDUCTIVITY
LA2CUO4
EXCITATIONS
SPECTRA
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19.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Petrov M. I., Balaev D. A., Gokhfel'd Yu. S., Dubrovskii A. A., Shaikhutdinov K. A.
Заглавие : Effect of heterovalent substitution of rare-earth elements on the magnetic and transport properties of YBa2Cu3O7
Место публикации : Phys. Solid State: MAIK NAUKA/INTERPERIODICA/SPRINGER, 2007. - Vol. 49, Is. 11. - P2047-2051. - ISSN 1063-7834, DOI 10.1134/S1063783407110054
Примечания : Cited References: 18
Предметные рубрики: PR
SUPERCONDUCTIVITY
CE
ND
TRANSITION
SYSTEM
LA
Аннотация: The Y(1-x) Ce (x) Ba2Cu3O7 system with low cerium concentrations has been synthesized. The cerium solubility limit measured using x-ray powder diffraction analysis is about 2.4 at. %. The temperature dependences of the magnetization M(T) are measured for samples cooled in a magnetic field (FC) and in a zero field (ZFC). The difference between the magnetizations M-ZFC-M-FC at 77.4 K, which is proportional to the pinning potential, passes through a maximum at x = 0.0156. This concentration corresponds to the average distance (equal to eight lattice constants) between the impurity ions in the plane of the rare-earth elements, which is comparable to the diameter of Abrikosov vortices in YBa2Cu3O7.
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20.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Kuz'min E. V., Ovchinnikov S. G., Singh D. J.
Заглавие : Effect of frustrations on magnetism in the Ru double perovskite Sr2YRuO6
Место публикации : Phys. Rev. B: AMERICAN PHYSICAL SOC, 2003. - Vol. 68, Is. 2. - Ст.24409. - ISSN 1098-0121, DOI 10.1103/PhysRevB.68.024409
Примечания : Cited References: 24
Предметные рубрики: MOTT TRANSITION
LATTICE
SPIN
ANTIFERROMAGNETISM
SUPERCONDUCTIVITY
FERROMAGNETISM
Аннотация: Localized Ru5+ spins in Sr2YRuO6 form a fcc lattice with an antiferromagnetic (AFM) nearest-neighbor (NN) coupling J approximate to 25 meV and rather low Neel temperature T-N= 26 K. Analysis of the electronic structure of Sr2RuO4 results in the effective Heisenberg model. We have studied the effect of frustrations on the AFM type-I structure of Sr2YRuO6 in the spin-wave approximation. In the model with only NN coupling the AFM state is unstable due to frustrations, and T-N = 0. Stabilization of the AFM state occurs due to the next-nearest-neighbor coupling I or due to the magnetic anisotropy D. Very small values D/J similar to I/J less than or equal to 10(-3) are enough to obtain the experimental values of T-N and sublattice magnetization m = 1.85 mu(B) /Ru (62% from the nominal S = 3/2 value).
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