High-Temperature Superconductivity

Аксенов, В. Л.; Bogolubov, N.M.; Плакида, Н. М.

doi:10.1007/978-3-642-78406-4

Cited by 291 publications

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“…In this sense, the operator projection theory belongs to a family of equation-of-motion approaches. 3,4,5,13,79,80,82,83,84) Operator projection theories are, however, more sophisticated in that it produces a systematic way of performing a continued-fraction expansion in energy. The OPM opens a possibility to systematically extract the lower-energy spectral properties projecting out higher-energy degrees of freedom in a self-consistent fashion.…”

Section: )mentioning

confidence: 99%

Filling-Control Metal-Insulator Transition in the Hubbard Model Studied by the Operator Projection Method

Onoda

Imada

2001

J. Phys. Soc. Jpn.

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Thermodynamic and dynamical properties of filling-control metal-insulator transition (MIT) in the Hubbard model are studied by the operator projection method, especially in two dimensions. This is a non-perturbative analytic approach to many-body systems. The present theory incorporates the Mott-Hubbard, Brinkman-Rice and Slater pictures of the MIT into a unified framework, together with reproducing low-energy narrow band arising from spin-charge fluctuations. At half filling, single-particle spectra A(ω, k) show formation of two Hubbard bands and their antiferromagnetic shadows separated by a Mott gap in the plane of energy ω and momentum k with lowering temperatures. These four bands produce splitting to two low-energy narrow bands and two SDW-like bands in the dispersion. Near half filling, the low-energy narrow band persists at low temperatures. This narrow band has a particularly weak dispersion and large weights around (π, 0) and (0, π) momenta. The velocity of these low-energy excitations is shown to vanish towards the MIT, indicating the mass divergence as in the Brinkman-Rice picture, but most prominently around (π, 0) and (0, π) with strong momentum dependence. This reflects the suppression of the coherence near the MIT. Main structures in A(ω, k) show remarkable similarities to quantum Monte-Carlo results in two dimensions as well as in the one-dimensional Hubbard model. The charge compressibility appears to diverge with decreasing doping concentration in both one and two dimensions in agreement with the exact and quantum Monte-Carlo results. We also discuss implications of the flat dispersion formed near the Fermi level to the observations in high-Tc cuprate superconductors.KEYWORDS: metal-insulator transition, Hubbard model, projection operator §1. IntroductionThe issue of the metal-insulator transitions (MIT) postulated by Mott 1) has opened extensive studies on the subject from both theoretical and experimental aspects.2) Pioneering works by Hubbard 3, 4, 5) and Kanamori 6) played an active part in theoretical studies on strong electron correlations in narrow-band electron systems.7) In spite of a long history of studies on strongly correlated electrons, 7, 2) an appropriate and satisfactory theoretical description of the MIT remains controversial, even for the simple Hubbard model. Particularly, in one and two dimensions, fluctuations become significant near the MIT. This makes it difficult to reliably describe physical properties related to the MIT. This paper aims at developing a formalism of operator projection 8,9,10) to construct a new non-perturbative analytic theory of many-body correlated electrons.11) This method allows us to systematically improve the Hartree-Fock theory, perturbation theories, Hubbard approximations 3, 5) and two-pole approximations. 12, 13) Using this new method, we give static and dynamical properties of the Hubbard model in one and two dimensions at and near half filling.Early theories on transitions from metals to insulators in clean systems are divided into three ...

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Section: )mentioning

confidence: 99%

Filling-Control Metal-Insulator Transition in the Hubbard Model Studied by the Operator Projection Method

Onoda

Imada

2001

J. Phys. Soc. Jpn.

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“…The Hamiltonian of the t − J * model differs from the Hamiltonian of t − J model in that it consist the three-center term H (3) (6). In the representation of the Hubbard operators [13,14], the Hamiltonians take the form where…”

Section: Formulation Of Modelsmentioning

confidence: 99%

“…In the regime U |t| (U is the Hubbard repulsion of electrons at one site, t is the hopping integral) it is advisable to pass to the effective Hamiltonian. As an efficient models are the t−J [6] and t−J * models [7] obtained with accuracy up to terms of the second order in the parameter |t|/U. The superconducting phase with a complex order parameter within the t − J model on a triangular lattice was considered in [8,9,10].…”

Section: Introductionmentioning

confidence: 99%

Effect of the three-center terms on the chiral superconducting d-wave pairing of the Hubbard fermions on the triangular lattice

Вальков

Valkova

Mitskan

2017

Journal of Magnetism and Magnetic Materials

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This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting galley proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. AbstractUsing the diagram technique for the Hubbard operators an integral equation that determines the order parameter of the superconducting phase Δ(p) was obtained in the framework of t − J − V and t − J * − V models on triangular lattice. It is shown that there are two scenarios of formation of superconducting phase with gapless spectrum at the critical concentration of carriers x c . The effect of three-center terms on implementation of this phase was also considered.

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“…The AFM spin fluctuations can also be responsible for anomalous normal state properties of cuprates (see, e.g. [1]) and for the superconducting pairing as proposed by Anderson [2]. In in a number of studies of the reduced one-band t-J model (see, e.g.…”

Section: Introductionmentioning

confidence: 99%

A theory of superconductivity in cuprates

Plakida¹

2005

Condens. Matter Phys.

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A microscopic theory of superconducting pairing mediated by antiferromagnetic (AFM) exchange and spin-fluctuations is developed within the effective p − d Hubbard model for the CuO 2 plane. It is proved that retardation effects for AFM exchange interaction are unimportant and result in pairing of all electrons in the conduction band and high T c proportional to the Fermi energy. The spin-fluctuations caused by the kinematic interaction give an additional contribution to the d-wave pairing. T c dependence on the hole concentration and lattice constants (or pressure) is studied. Small oxygen isotope shift of T c is explained. The data are compared with the results for the t − J model.

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High-Temperature Superconductivity

Cited by 291 publications

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Filling-Control Metal-Insulator Transition in the Hubbard Model Studied by the Operator Projection Method

Filling-Control Metal-Insulator Transition in the Hubbard Model Studied by the Operator Projection Method

Effect of the three-center terms on the chiral superconducting d-wave pairing of the Hubbard fermions on the triangular lattice

A theory of superconductivity in cuprates

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