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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Goryachev E. G., Kuzmin E. V., Ovchinnikov S. G.
Заглавие : The electronic-spectrum and the metal-insulator-transition in the hubbard-model
Место публикации : Phys. Lett. A. - 1981. - Vol. 85, Is. 4. - P.236-238. - ISSN 0375-9601, DOI 10.1016/0375-9601(81)90025-6
Примечания : Cited References: 4
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Goryachev E. G., Kuzmin E. V., Ovchinnikov S. G.
Заглавие : Metal-insulator-transition in the hubbard-model by the irreducible green-functions method
Разночтения заглавия :авие SCOPUS: Metal-insulator transition in the Hubbard model by the irreducible Green functions method
Место публикации : Journal of Physics C - Solid State Physics. - 1982. - Vol. 15, Is. 7. - P1481-1493. - ISSN 0022-3719, DOI 10.1088/0022-3719/15/7/015
Примечания : Cited References: 18
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : VALKOV V. V., OVCHINNIKOV S. G.
Заглавие : HUBBARD OPERATORS AND SPIN-WAVE THEORY OF HEISENBERG MAGNETS WITH ARBITRARY SPIN
Место публикации : Theor. Math. Phys.: PLENUM PUBL CORP, 1982. - Vol. 50, Is. 3. - P306-313. - ISSN 0040-5779, DOI 10.1007/BF01016463
Примечания : Cited References: 32
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Goryachev E. G., Kuzmin E. V.
Заглавие : Short-range effects in the hubbard-model
Место публикации : Zhurnal Eksperimentalnoi Teor. Fiz. - 1986. - Vol. 91, Is. 3. - P.902-912. - ISSN 0044-4510
Примечания : Cited References: 15
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Goryachev E. G., Kuzmin E. V.
Заглавие : Effects of a nonlocal correlation in the hubbard-model
Место публикации : Phys. Lett. A. - 1986. - Vol. 119, Is. 1. - P.33-36. - ISSN 0375-9601, DOI 10.1016/0375-9601(86)90640-7
Примечания : Cited References: 11
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Goryachev E. G., Kuzmin E. V.
Заглавие : Ferromagnetic paramagnetic state transition in the ground-state of the hubbard-model
Место публикации : Phys. Lett. A. - 1988. - Vol. 131, Is. 7-8. - P.481-485. - ISSN 0375-9601, DOI 10.1016/0375-9601(88)90306-4
Примечания : Cited References: 9
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Ovchinnikov S. G., Sandalov I. S.
Заглавие : On nonhomogeneous states in a 2-dimensional hubbard-model
Место публикации : Physica C. - 1990. - Vol. 166, Is. 1-2. - P.197-199. - ISSN 0921-4534, DOI 10.1016/0921-4534(90)90573-W
Примечания : Cited References: 12
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : GORYACHEV E. G.
Заглавие : VARIATIONAL APPROACH TO THE 3-PARTICLE PROBLEM IN THE HUBBARD-MODEL - THE EXACT RESULT
Место публикации : Zhurnal Eksperimentalnoi Teor. Fiz.: MEZHDUNARODNAYA KNIGA, 1992. - Vol. 102, Is. 4. - P1280-1285. - ISSN 0044-4510
Примечания : Cited References: 7
Аннотация: A well-defined procedure for the linearization of the equations of motions, which is based on the stationary principle, is proposed. In the special case of a flopped spin in the saturated ferromagnetic state (three-particle problem) the single-particle Green function is found. It is proved that regardless whether the initial (unperturbed) state is a strong coupling band (Bloch representation) or two-level atom system (Hubbard representation) the results for the single-particle Green function coincide for arbitrary values of the hamiltonian constants and electron concentration b up. In the non-trivial limit case U = infinity such a Green function coincides with the exact result of Igarashi - Ruckenstein - Schmitt - Rink [2,3] based on solving the Faddeev equations.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : GORYACHEV E. G.
Заглавие : A VARIATIONAL APPROACH TO THE 3-BODY PROBLEM IN THE HUBBARD-MODEL - EXACT RESULT
Место публикации : Phys. Lett. A: ELSEVIER SCIENCE BV, 1992. - Vol. 166, Is. 2. - P148-152. - ISSN 0375-9601, DOI 10.1016/0375-9601(92)90551-V
Примечания : Cited References: 7
Аннотация: A well-defined method for linearizing the many-body equation of motion in statistical mechanics is proposed. The one-particle retarded Green function for the special case of a single reversed spin in an otherwise fully aligned band is obtained. We prove that the results for the Green function coincide independently of the initial (unperturbed) state we have started with, that is, the band energy limit E(k) = SIGMA(h)b(h)e(ikh) or the two-level atomic limit (E0, E0 + U). This strong result is valid for any parameters of the Hamiltonian and electron concentration of [F\n up\F]. In the nontrivial limited case (U=infinity) the obtained Green function coincides with the exact result of Igarashi, Ruckenstein and Schmitt-Rink based on the solution of the Faddeev equations.
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10.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : SANDALOV I. S., RICHTER M.
Заглавие : FLUX PHASE, NEEL ANTIFERROMAGNETISM, AND SUPERCONDUCTIVITY IN THE T-J MODEL
Разночтения заглавия :авие SCOPUS: Flux phase, Neel antiferromagnetism, and superconductivity in the t-J model
Место публикации : Phys. Rev. B: AMERICAN PHYSICAL SOC, 1994. - Vol. 50, Is. 17. - P12855-12865. - ISSN 0163-1829, DOI 10.1103/PhysRevB.50.12855
Примечания : Cited References: 27
Предметные рубрики: HUBBARD-MODEL
INSTABILITY
ELECTRONS
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11.

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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12.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Kuzmin E. V.
Заглавие : The ground state problem in the infinite-U Hubbard model
Место публикации : Phys. Solid State: AMER INST PHYSICS, 1997. - Vol. 39, Is. 2. - P169-178. - ISSN 1063-7834, DOI 10.1134/1.1130126
Примечания : Cited References: 36
Предметные рубрики: NAGAOKA FERROMAGNETIC STATE
INSTABILITY
HOLES
BAND
Аннотация: The problem of the ground state of the electronic system in the Hubbard model for U=infinity is discussed. The author investigates the normal (singlet or nonmagnetic) N state of the electronic system over the entire range of electron densities n less than or equal to 1. It is shown that the energy of the N state epsilon(0)((1))(n) in a one-particle approximation, such as (e.g.) the extended Hartree-Fock approximation, is lower than the energy of the saturated ferromagnetic FM state epsilon(FM)(n) for all n. The dynamic magnetic susceptibility is calculated in the random phase approximation, and it is shown that the N state is stable over the entire range of electron densities: The static susceptibility (omega=0) does not have a band singularity in the zero-wave vector limit q--0. A formally exact representation is obtained for the mass operator of the one-particle Green's function, and an approximation of this operator is proposed: M-k(E)similar or equal to lambda F(E), where lambda=n(1-n)/(1-n/2)z is the kinematic interaction parameter, z is the number of nearest neighbors, and F(E) is the total single-site Green's function. For an elliptical density of states the integral equation for F(E) is solved exactly, ad it is shown that the spectral intensity rigorously satisfies the sum rule. The calculated energy of the strongly correlated N state epsilon(0)(n)epsilon(FM)(n) for all n, and in light of this relationship the author discusses the hypothesis that the ground state of the system is the normal (singlet) state in the thermodynamic limit. The electron distribution function at T
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13.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Ovchinnikov S. G.
Заглавие : Quasiparticles in strongly correlated electronic systems in cuprate oxides
Место публикации : Uspekhi Fiz. Nauk: MEZHDUNARODNAYA KNIGA, 1997. - Vol. 167, Is. 10. - P.1043-1068. - ISSN 0042-1294
Примечания : Cited References: 227
Предметные рубрики: T-J-MODEL
HIGH-TEMPERATURE SUPERCONDUCTORS
DIMENSIONAL HUBBARD-MODEL
QUASI-PARTICLE DISPERSION
HEISENBERG-ANTIFERROMAGNET SR2CUO2CL2
ANGLE-RESOLVED PHOTOEMISSION
CHARGE FLUCTUATION REGIME
SADDLE-POINT SINGULARITY
SINGLET-TRIPLET MODEL
LA-SR-CU
Аннотация: New experimental and theoretical results on the electronic structure and spectral properties of quasiparticles in cuprate oxides are reviewed. It is shown that the electronic structure transforms from antiferromagnetic insulators to optimally doped high-temperature superconductors as the doping level is varied. The experimental methods considered are primarily angular resolved photoelectron spectroscopy (ARPES), neutron scattering, and NMR. Two types of electronic structure calculations for data interpretation purposes are considered, namely, exact numerical methods for finite clusters (exact diagonalisation and the quantum Monte Carlo method) and approximate schemes for the infinite lattice. As a result, a coherent unified picture emerges, in which the magnetic polaron of a weakly doped antiferromagnetic lattice transforms into a system of Fermi particles dressed by short-range antiferromagnetic type spin fluctuations. In the region of weakly doped metal compositions, deviations from Fermi-liquid properties are seen, such as the failure of Luttinger's theorem, shadowy photoemission bands, and the spin pseudogap effect in spectral and thermodynamic measurements. The situation in the neighbourhood of the insulator-metal concentration transition is described as least understood.
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14.

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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15.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Kuz'min E. V., Baklanov I. O.
Заглавие : The singlet state in the Hubbard model with U=infinity
Место публикации : J. Exp. Theor. Phys.: AMER INST PHYSICS, 1998. - Vol. 87, Is. 6. - P1159-1166. - ISSN 1063-7761, DOI 10.1134/1.558607
Примечания : Cited References: 16
Предметные рубрики: HOLES
Аннотация: We discuss, in connection with the problem of the ground state in the Hubbard model with U = infinity, the normal (nonmagnetic) N-state of a system over the entire range of electron concentrations n less than or equal to 1. It is found that in a one-particle approximation, e. g., in the generalized Hartree-Fock approximation, the energy epsilon(0)(n) of the N-state is lower than the energy epsilon(FM)(n) of a saturated ferromagnetic state for all values of n. Using the random phase approximation we calculate the dynamical magnetic susceptibility and show that the N-state is stable for all values of n. A formally exact representation is derived for the mass operator of the one-particle electron Green's function, and its expression in the self-consistent Born approximation is obtained. We discuss the first Born approximation and show that when correlations are taken into account, the attenuation vanishes on the Fermi surface and the electron distribution function at T = 0 acquires a Migdal discontinuity, whose magnitude depends on n. The energy of the N-state in this approximation is still lower than epsilon(FM)(n) for n 1.We show that the spin correlation functions are isotropic, which is a characteristic feature of the singlet states of the system. We calculate the spin correlation function for the nearest neighbors in the zeroth approximation as a function of n. Finally, we conclude that the singlet state of the system in the thermodynamic limit is the ground state. (C) 1998 American Institute of Physics. [S1063-7761(98)01712-0].
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16.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Lundin U., Sandalov I., Eriksson O., Johansson B.
Заглавие : Are there two types of f-electrons in Pr-metal?
Коллективы : International Conference on Strongly Correlated Electron Systems
Место публикации : Physica B. - 1999. - Vol. 259-61. - P.231-232. - ISSN 0921-4526, DOI 10.1016/S0921-4526(98)00790-X
Примечания : Cited References: 1
Предметные рубрики:
Ключевые слова (''Своб.индексиров.''): band calculations--hubbard model--f-electrons
Аннотация: We show that in order to properly describe the bonding properties of strongly correlated systems, here demonstrated for praseodymium metal, it is necessary to split the f-electron system into two parts. Using perturbation theory from the atomic limit we show that LDA-based calculations with f-electrons in the core can be considered as the limit of an infinite Hubbard U. Then, the correction to the total energy proportional to 1/U makes the upper f(2)--f(3) intra-atomic transitions (IT) important. Mixing interaction and f-f-hopping delocalize these IT and some of them become populated. These IT give an additional contribution to the cohesive energy. This gain in energy is the reason for the separation of the f-electron system into localized (with reduced spectral weight) and delocalized ones. (C) 1999 Elsevier Science B.V. All rights reserved.
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17.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Fransson J., Eriksson O., Johansson B., Sandalov I. S.
Заглавие : On the non-orthogonality problem in the description of quantum devices
Коллективы : International Conference on Nonequilibrium Carrier Dynamics in Semiconductors
Место публикации : Physica B/ International Conference on Nonequilibrium Carrier Dynamics in Semiconductors (11 ; 1999 ; July ; 19-23 ; Kyoto, Japan). - 1999. - Vol. 272, Is. 1-4. - P.28-30. - ISSN 0921-4526, DOI 10.1016/S0921-4526(99)00343-9
Примечания : Cited References: 8
Предметные рубрики:
Ключевые слова (''Своб.индексиров.''): non-orthogonality--current--tunneling--correlation methods--electric contacts--electric currents--electron energy levels--electron tunneling--equations of motion--green's function--mathematical operators--matrix algebra--hubbard operators--potential barriers--tunneling currents--semiconductor quantum dots
Аннотация: An approach which allows to include the corrections from non-orthogonality of electron states in contacts and quantum dots is developed. Comparison of the energy levels and charge distributions of electrons in 1D quantum dot (QD) in equilibrium, obtained within orthogonal (OR) and non-orthogonal representations (NOR), with the exact ones shows that the NOR provides a considerable improvement, for levels below the top of barrier. The approach is extended to non-equilibrium states. A derivation of the tunneling current through a single potential barrier is performed using equations of motion for correlation functions. A formula for transient current derived by means of the diagram technique for Hubbard operators is given for the problem of QD with strongly correlated electrons interacting with electrons in contacts. The non-orthogonality renormalizes the tunneling matrix elements and spectral weights of Green functions. (C) 1999 Elsevier Science B.V. All rights reserved.
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18.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Lundin U., Sandalov I., Johansson B.
Заглавие : Mott-Hubbard transition in the N-orbital Hubbard model
Коллективы : Yamada Conference on Strongly Correlated Electon Systems
Место публикации : Physica B. - 2000. - Vol. 281. - P.836-837. - ISSN 0921-4526, DOI 10.1016/S0921-4526(99)00980-1
Примечания : Cited References: 5
Ключевые слова (''Своб.индексиров.''): hubbard model--mott-hubbard transition--d(1) systems
Аннотация: The Mort-Hubbard insulator-metal transition (MHT) is studied for the N-orbital symmetrical Hubbard model with diagonal (t(1)) and non-diagonal(t(2)) hopping matrix elements. In the paramagnetic state (PM) For an n = 1 filling the non-diagonal hopping gives rise to two wide Hubbard sub-bands with small spectral weight of the order of similar to 1/N and 2N - 2 narrow sub-bands with a large weight similar to (1 - 1/N). No orbital polarization arises in this solution. In some directions in the (t(1), t(2))-plane the insulating energy gap in the density of stares is closed in the vicinity of a critical Hubbard repulsion of U-c similar to z(t(1) + (N - 1)t(2)) (z-coordination number), whereas the narrow bands in this region of parameters still correspond to a deeply correlated phase (with bandwidth z(t(1) - t(2))). (C) 2000 Elsevier Science B.V. All rights reserved.
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19.

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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20.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Kuz'min E. V., Ovchinnikov S. G., Baklanov I. O., Goryachev E. G.
Заглавие : Microscopic model of the coexistence of superconductivity and ferromagnetism in the hybrid ruthenate-cuprate oxide RuSr2GdCu2O8
Место публикации : J. Exp. Theor. Phys.: AMER INST PHYSICS, 2000. - Vol. 91, Is. 2. - P353-360. - ISSN 1063-7761, DOI 10.1134/1.1311995
Примечания : Cited References: 37
Предметные рубрики: T-J MODEL
HUBBARD-MODEL
LAYERED PEROVSKITE
SR2RUO4
ELECTRONS
COPPER
SPECTRUM
Аннотация: A microscopic t-J-I model with competing antiferromagnetic (J) and ferromagnetic (I) exchange interactions is proposed for strongly correlated electrons in RuSr2GdCu2O8 . It is assumed that J much greater than I for CuO2 layers and J much less than I for RuO2 layers. A superconducting solution of d(x2-y2) symmetry was obtained for the CuO2 layers while competition between ferromagnetism and p-type triplet superconducting pairing is obtained for RuO2 layers. It is shown that the RuO2 layers have a lower carrier concentration in the Hubbard subband formed by coupled ((d(xy)-p)-pi) orbitals compared with a bulk Sr2RuO4 crystal, which leads to stabilization of the ferromagnetic state in the RuO2 layer. (C) 2000 MAIK "Nauka/Interperiodica".
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