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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Aplesnin S. S.
Заглавие : Dimer state in the two-dimensional anisotropic alternated-exchange Heisenberg model
Место публикации : Phys. Solid State: AMER INST PHYSICS, 1998. - Vol. 40, Is. 6. - P986-990. - ISSN 1063-7834, DOI 10.1134/1.1130463
Примечания : Cited References: 14
Предметные рубрики: SPIN-PEIERLS
HUBBARD-MODEL
SUPERCONDUCTIVITY
ANTIFERROMAGNETS
Аннотация: An analysis is made of the two-dimensional Heisenberg model with S = 1/2, anisotropic exchange interaction between nearest neighbors, and alternating exchange in two directions, [100] and [010] (corresponding to condensation of the (pi,pi) mode) and in one direction [100] (corresponding to condensation of the (pi,0) mode), The quantum Monte Carlo method is used to calculate the thermodynamic characteristics and the spin correlation functions which are used as the basis to determine the boundary of stability of an anisotropic antiferromagnetic with respect to alternation of exchange delta = (1 - J(x,y) / J(z))(0.4) in the (pi,pi) model and delta = (1 - J(x,y) / J(z))(0.31) in the (pi,0) model. In the (pi,0) model a disordered quantum state exists in the range (1 - J(x,y) / J(z))(0.31) delta (0.3-0.35). The energy (E - 0.68)
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Korshunov M. M., Gavrichkov V. A., Ovchinnikov S. G., Nekrasov I. A., Kokorina E. E., Pchelkina Z. V.
Заглавие : Dominance of many-body effects over the one-electron mechanism for band structure doping dependence in Nd2-xCexCuO4: the LDA + GTB approach
Разночтения заглавия :авие SCOPUS: Dominance of many-body effects over the one-electron mechanism for band structure doping dependence in Nd2-xCexCuO4: The LDA+GTB approach
Место публикации : J. Phys.: Condens. Matter: IOP PUBLISHING LTD, 2007. - Vol. 19, Is. 48. - Ст.486203. - ISSN 0953-8984, DOI 10.1088/0953-8984/19/48/486203
Примечания : Cited References: 36
Предметные рубрики: NARROW ENERGY BANDS
HUBBARD-MODEL
SUPERCONDUCTORS
DENSITY
TEMPERATURE
ORBITALS
WAVE
Ключевые слова (''Своб.индексиров.''): antiferromagnetism--band structure--correlation methods--crystal structure--local density approximation--superconducting materials--electronic correlations--fermionic quasiparticles--neodymium compounds
Аннотация: In the present work we report band structure calculations for the high-temperature superconductor Nd2-xCexCuO4 in the regime of strong electronic correlations within an LDA + GTB method, which combines the local density approximation (LDA) and the generalized tight-binding method (GTB). The two mechanisms of band structure doping dependence were taken into account. Namely, the one-electron mechanism provided by the doping dependence of the crystal structure, and the many-body mechanism provided by the strong renormalization of the fermionic quasiparticles due to the large on-site Coulomb repulsion. We have shown that, in the antiferromagnetic and in the strongly correlated paramagnetic phases of the underdoped cuprates, the main contribution to the doping evolution of the band structure and Fermi surface comes from the many-body mechanism.
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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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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Korshunov M. M., Eremin I., Shorikov A., Anisimov V. I., Renner M., Brenig W.
Заглавие : Itinerant in-plane magnetic fluctuations and many-body correlations in NaxCoO2
Разночтения заглавия :авие SCOPUS: Itinerant in-plane magnetic fluctuations and many-body correlations in Nax Co O2
Место публикации : Phys. Rev. B: AMERICAN PHYSICAL SOC, 2007. - Vol. 75, Is. 9. - Ст.94511. - ISSN 1098-0121, DOI 10.1103/PhysRevB.75.094511
Примечания : Cited References: 47
Предметные рубрики: TRANSITION-METALS
WAVE-FUNCTIONS
HUBBARD-MODEL
FERMI-SURFACE
ENERGY-BANDS
FERROMAGNETISM
APPROXIMATION
DIMENSIONS
SYSTEMS
FIELD
Аннотация: Based on the ab initio band structure for NaxCoO2, we derive the single-electron energies and the effective tight-binding description for the t(2g) bands using projection procedure. Due to the presence of the next-nearest-neighbor hoppings, a local minimum in the electronic dispersion close to the Gamma point of the first Brillouin zone forms. Correspondingly, in addition to a large Fermi surface, an electron pocket close to the Gamma point emerges at high doping concentrations. The latter yields a scattering channel, resulting in a peak structure of the itinerant magnetic susceptibility at small momenta. This indicates dominant itinerant in-plane ferromagnetic fluctuations above a certain critical concentration x(m), in agreement with neutron scattering data. Below x(m), the magnetic susceptibility shows a tendency toward the antiferromagnetic fluctuations. We further analyze the many-body effects on the electronic and magnetic excitations using various approximations applicable for different U/t ratios.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Kagan M. Y., Mitskan V. A., Korovushkin M. M.
Заглавие : High-Tc and Low-Tc superconductivity in electron systems with repulsion
Коллективы : Russian Foundation for Basic Research [14-02-00058, 14-02-31237]; Basic Research Program of the National Research University Higher School of Economics; Dynasty foundation; [SP-1361.2015.1]
Место публикации : J. Supercond. Nov. Magn.: Springer, 2016. - Vol. 29, Is. 4. - P.1043-1048. - ISSN 1557-1939, DOI 10.1007/s10948-016-3384-7. - ISSN 1557-1947(eISSN)
Примечания : Cited References:31. - The authors are grateful to V. V. Val'kov, I. S. Burmistrov, M. V. Feigel'man, and A. Ya. Tzalenchuk for valuable remarks. This work is supported by the Russian Foundation for Basic Research (nos. 14-02-00058 and 14-02-31237). One of the authors (M. Yu. K.) gratefully acknowledges support from the Basic Research Program of the National Research University Higher School of Economics. Another one (M. M. K.) thanks the scholarship SP-1361.2015.1 of the President of Russia and the Dynasty foundation.
Предметные рубрики: Fermion systems
Doped graphene
Hubbard-model
Phase-diagram
Superfluidity
Density
Ключевые слова (''Своб.индексиров.''): unconventional superconductivity--kohn-luttinger mechanism--graphene
Аннотация: We demonstrate the instability of the normal state of purely repulsive fermionic systems towards the transition to the Kohn-Luttinger superconducting state. We construct the superconducting phase diagrams of these systems in the framework of the Hubbard and Shubin-Vonsovsky models on the square and hexagonal lattices. We show that an account for the long-range Coulomb interactions, as well as the Kohn- Luttinger renormalizations, lead to an increase in the critical superconducting temperatures in various materials, such as high-temperature superconductors, idealized monolayer, and bilayer of doped graphene. Additionally, we discuss the role of the structural disorder and the nonmagnetic impurities in superconducting properties of real graphene systems.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Kagan M. Y., Mitskan V. A., Korovushkin M. M.
Заглавие : Kohn-Luttinger superconductivity in monolayer and bilayer semimetals with the Dirac spectrum
Коллективы : RAS Division of Physical Sciences [II.3.1], Russian Foundation for BasicResearch [14-02-00058, 14-02-31237], Russian Federation [MK-526.2013.2], "Dynasty" foundation
Место публикации : J. Exp. Theor. Phys.: MAIK Nauka-Interperiodica / Springer, 2014. - Vol. 119, Is. 6. - P.1140-1149. - ISSN 1063, DOI 10.1134/S1063776114120048. - ISSN 10906509(eISSN)
Примечания : Cited References:70. - This work was performed under the Program of the RAS Division ofPhysical Sciences (project no. II.3.1) and was supported financially bythe Russian Foundation for Basic Research (project nos. 14-02-00058 and14-02-31237) and by the President of the Russian Federation (grant no.MK-526.2013.2). One of the authors (M.M.K.) thanks the "Dynasty"foundation for financial support.
Предметные рубрики: FERMI-SURFACE
REPULSIVE INTERACTIONS
DOPED GRAPHENE
HUBBARD-MODEL
Аннотация: The effect of Coulomb interaction in an ensemble of Dirac fermions on the formation of superconducting pairing in monolayer and bilayer doped graphene is studied using the Kohn-Luttinger mechanism disregarding the Van der Waals potential of the substrate and impurities. The electronic structure of graphene is described using the Shubin-Vonsovsky model taking into account the intratomic, interatomic, and interlayer (in the case of bilayer graphene) Coulomb interactions between electrons. The Cooper instability is determined by solving the Bethe-Saltpeter integral equation. The renormalized scattering amplitude is obtained with allowance for the Kohn-Luttinger polarization contributions up to the second order of perturbation theory in the Coulomb interaction. It plays the role of effective interaction in the Bethe-Salpeter integral equation. It is shown that the allowance for the Kohn-Luttinger renormalizations as well as intersite Coulomb interaction noticeably affects the competition between the superconducting phases with the f-wave and d + id-wave symmetries of the order parameter. It is demonstrated that the superconducting transition temperature for an idealized graphene bilayer with significant interlayer Coulomb interaction between electrons is noticeably higher than in the monolayer case.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Kagan M. Y., Mitskan V. A., Korovushkin M. M.
Заглавие : Phase diagram of the Kohn-Luttinger superconducting state for bilayer graphene
Место публикации : Eur. Phys. J. B: Springer, 2015. - Vol. 88, Is. 6. - Ст.157. - ISSN 1434, DOI 10.1140/epjb/e2015-60198-x. - ISSN 14346036(eISSN)
Примечания : Cited References:60. - The authors are grateful to V.V. Val'kov for valuable remarks. This work is supported by the Russian Foundation for Basic Research (Projects Nos. 14-02-00058 and 14-02-31237). One of the authors (M.Yu.K.) gratefully acknowledges support from the Basic Research Program of the National Research University Higher School of Economics. Another one (M.M.K.) thanks the scholarship SP-1361.2015.1 of the President of the Russian Federation and the Dynasty foundation.
Предметные рубрики: REPULSIVE INTERACTIONS
DOPED GRAPHENE
HUBBARD-MODEL
FERMI-SURFACE
Аннотация: The effect of Coulomb interaction between Dirac fermions on the formation of the Kohn-Luttinger superconducting state in bilayer doped graphene is studied disregarding of the effect of the van der Waals potential of the substrate and impurities. The phase diagram determining the boundaries of superconductive domains with different types of symmetry of the order parameter is built using the extended Hubbard model in the Born weak-coupling approximation with allowance for the intratomic, interatomic, and interlayer Coulomb interactions between electrons. It is shown that the Kohn-Luttinger polarization contributions up to the second order of perturbation theory in the Coulomb interaction inclusively and an account for the long-range intraplane Coulomb interactions significantly affect the competition between the superconducting phases with the f-, p + ip-, and d + id-wave symmetries of the order parameter. It is demonstrated that the account for the interlayer Coulomb interaction enhances the critical temperature of the transition to the superconducting phase.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Korshunov M. M., Ovchinnikov S. G.
Заглавие : Doping-dependent evolution of low-energy excitations and quantum phase transitions within an effective model for high-T-c copper oxides
Разночтения заглавия :авие SCOPUS: Doping-dependent evolution of low-energy excitations and quantum phase transitions within an effective model for high-T c copper oxides
Место публикации : Eur. Phys. J. B: SPRINGER, 2007. - Vol. 57, Is. 3. - P271-278. - ISSN 1434-6028, DOI 10.1140/epjb/e2007-00179-2
Примечания : Cited References: 49
Предметные рубрики: ELECTRON CORRELATIONS
HUBBARD-MODEL
RANGE-ORDER
DIMENSIONS
WAVE
FERMIONS
SYSTEMS
BANDS
METAL
Ключевые слова (''Своб.индексиров.''): doping dependent evolution--kinematic correlation functions--low energy excitations--quantum phase transitions--doping (additives)--electric excitation--mean field theory--parameter estimation--phase transitions--quantum theory--copper oxides
Аннотация: In this paper a mean-field theory for the spin-liquid paramagnetic non-superconducting phase of the p- and n-type high-T-c cuprates is developed. This theory applied to the effective t-t'-t ''-J* model with the ab initio calculated parameters and with the three-site correlated hoppings. The static spin-spin and kinematic correlation functions beyond Hubbard-I approximation are calculated self-consistently. The evolution of the Fermi surface and band dispersion is obtained for the wide range of doping concentrations x. For p-type systems the three different types of behavior are found and the transitions between these types are accompanied by the changes in the Fermi surface topology. Thus a quantum phase transitions take place at x = 0.15 and at x = 0.23.Due to the different Fermi surface topology we found for n-type cuprates only one quantum critical concentration, x = 0.2. The calculated doping dependence of the nodal Fermi velocity and the effective mass are in good agreement with the experimental data.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Korshunov M. M., Ovchinnikov S. G.
Заглавие : Generalization of Luttinger's theorem for strongly correlated electron systems
Место публикации : Phys. Solid State: AMER INST PHYSICS, 2003. - Vol. 45, Is. 8. - P1415-1422. - ISSN 1063-7834, DOI 10.1134/1.1602872
Примечания : Cited References: 19. - The authors are grateful to V.V. Val’kov for helpful remarks. This work was supported by the INTAS (grant no. INTAS-01-0654), the Russian Foundation for Basic Research and the Krasnoyarsk KraÏ Science Foundation (program “EniseÏ,” project no. 02-02-97705), the program of the Russian Academy of Sciences “Quantum Macrophysics,” and the Russian Academy of Sciences, Siberian Division (Lavrent’yev Contest for Youth Projects)
Предметные рубрики: NARROW ENERGY BANDS
HUBBARD-MODEL
FERMI-SURFACE
LATTICE
Аннотация: By on the analyzing the general structure of the Green function of a strongly correlated electron system, it is shown that, for the regime of strong correlations, Luttinger's theorem should be generalized in the following way: the volume of the Fermi surface of the system of noninteracting particles is equal to that of the quasiparticles in the strongly correlated system with due regard for the spectral weight of the quasiparticles. An investigation of the t-J model and of the Hubbard model, as applied to the paramagnetic nonsuperconducting phase, shows that the generalized Luttinger theorem is valid for these models. (C) 2003 MAIK "Nauka/Interperiodica".
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10.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Kuz'min E. V., Ovchinnikov S. G., Baklanov I. O.
Заглавие : Comparison of superconductivity in Sr2RuO4 and copper oxides
Место публикации : Phys. Rev. B: AMER PHYSICAL SOC, 2000. - Vol. 61, Is. 22. - P15392-15397. - ISSN 1098-0121, DOI 10.1103/PhysRevB.61.15392
Примечания : Cited References: 21
Предметные рубрики: T-J MODEL
HUBBARD-MODEL
LAYERED PEROVSKITE
ELECTRONS
Аннотация: To compare the superconductivity in strongly correlated electron systems with the antiferrornagnetic fluctuations in the copper oxides and with the ferromagnetic fluctuations in Sr2RuO4 a t-J-l model is proposed. The antiferromagnetic coupling J results in the superconducting state of d(x2-y2) symmetry and the ferromagnetic coupling I results in the spin-triplet p-type state. The difference in the gap anisotropies provides the large difference in T-c values, for the typical values of the coupling constants: T-c similar to 1 K for the ruthenste and T-c similar to 100 K for the cuprates.
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