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Wyszukujesz frazę "Mn" wg kryterium: Temat


Tytuł:
Indirect RKKY-Type Interaction by Direct Oxygen Hopping
Autorzy:
Rodriguez-Nuńez, J.
Coqblin, B.
Beck, H.
Konior, J.
Powiązania:
https://bibliotekanauki.pl/articles/1930566.pdf
Data publikacji:
1994-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
74.20.Mn
74.25.Jb
Opis:
The three-band Emery model, describing the holes in the CuO$\text{}_{2}$ planes of the high-temperature superconducting oxides, is considered. The model includes the direct oxygen-oxygen hopping integral t$\text{}_{pp}$. The exact Bogolyubov transformation is used to exclude one oxygen band and obtain a two-dimensional Anderson model. Afterward, the effective Hamiltonian is obtained by eliminating the second oxygen band with the use of two approximate canonical transformations. The effective Hamiltonian describes the spins residing on the copper sites and interacting through an indirect interaction J$\text{}_{SX}$(R), where R is the distance between two copper ions. J$\text{}_{SX}$(R) depends on the doping rate δ and is a decaying function of R. Numerical results for J$\text{}_{SX}$(R) are given for different doping rates δ for the case of parabolic bands. The obtained interaction J$\text{}_{SX}$(R), when added to the original antiferromagnetic interaction (present in oxides at δ = 0), might lead to a frustration of the long-range antiferromagnetic ordering upon doping.
Źródło:
Acta Physica Polonica A; 1994, 85, 2; 317-322
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Spin Polaron-Bipolaron Scenario of Three Gap-Like Energy Scales in Superconducting Cuprates
Autorzy:
Wróbel, P.
Maciąg, A.
Suleja, W.
Eder, R.
Micnas, R.
Powiązania:
https://bibliotekanauki.pl/articles/1536806.pdf
Data publikacji:
2010-08
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
74.20.Mn
74.72.Kf
Opis:
We argue that three gaps observed in underdoped cuprates can be attributed to the formation of antiferromagnetic spin polarons and bipolarons. Within the spin polaron scenario the antinodal pseudogap at he high energy scale originates from the change of the Fermi surface topology, induced by antiferromagnetic correlations. That change gives rise to the diminishing of the spectral weight at the antinodal region near the Brillouin zone boundary. We demonstrate that effect by analyzing effective models of doped antiferromagnets. The second type of pseudogap appearing at the intermediate energy scale originates from the phenomena which are precursory to superconductivity and predominantly concern the portion of the Fermi surface near the nodal region. In order to analyze the latter phenomenon we use the negative U Hubbard model, in which many details typical to spin polaron physics are neglected, but which contains the essential ingredient of it, that is the strong short range attraction. The lowest energy scale is related to the true superconducting gap which develops with doping, although both types of pseudogap diminish with doping. This behavior can be explained by the fact that the spin polaron band is empty in the undoped system and therefore the formation of the superconducting state in the system is forbidden. Due to a pedagogical character of this report, we present in the introduction a short overview of mostly recent experimental results which are related to the gap-pseudogap physics.
Źródło:
Acta Physica Polonica A; 2010, 118, 2; 292-298
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Checkerboard-Like Charge Ordering in Underdoped Cuprates
Autorzy:
Wróbel, P.
Powiązania:
https://bibliotekanauki.pl/articles/2046738.pdf
Data publikacji:
2006-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
74.20.Mn
71.10.Fd
Opis:
Recent scanning tunneling microscopy measurements which indicate the formation of two-dimensional density modulations at some doping levels in cuprates were reviewed. A model of hard-core bosons which represent bound hole pairs in the two-dimensional doped antiferromagnet was discussed in the context of these experimental results. By means of an exact numerical diagonalization it was shown that the Coulomb repulsion between bosons brings about the formation of charge modulations.
Źródło:
Acta Physica Polonica A; 2006, 109, 4-5; 533-539
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Application of Statistical Spin Liquid Concept to High-Temperature Superconductivity
Autorzy:
Byczuk, K.
Spałek, J.
Powiązania:
https://bibliotekanauki.pl/articles/1930571.pdf
Data publikacji:
1994-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.27.+a
74.20.Mn
Opis:
We apply the concept of statistical spin liquid, in which the doubly occupied quasimomentum configurations {|k⇅⟩} for quasiparticles are excluded from the Fock space, to a planar superconductor with real space pairing. The results compare very well with experimental data for the cuprates, namely (i) the condensed state appears only for the number of holes 0 < δ < 0.15-0.25; (ii) the temperature dependence of the gap is close to the BCS result, but the gap has systematically lower value and is of an extended s-wave form.
Źródło:
Acta Physica Polonica A; 1994, 85, 2; 337-340
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Electron Spectrum and Dieleclric Susceptibility of the Hubbard Model with Local Lattice Anharmonicity
Autorzy:
Stasyuk, I. V.
Shvaika, A. M.
Powiązania:
https://bibliotekanauki.pl/articles/1930577.pdf
Data publikacji:
1994-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
74.20.Mn
71.45.Gm
Opis:
The investigation of single-electron spectrum of the Hubbard model with local lattice anharmonicity is performed. The influence of the interaction with the vibrational subsystem on the effective exchange constant is considered. The static transverse dielectric susceptibility of the model is calculated. Analysis of the possible dielectric anomalies is performed on this basis.
Źródło:
Acta Physica Polonica A; 1994, 85, 2; 363-366
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Unconventional Superconductivity, Spontaneous Time-Reversal Symmetry Breaking and Lowering of Kinetic Energy in Doped, Short-Range Antiferromagnets
Autorzy:
Wróbel, P.
Maciąg, A.
Eder, R.
Fulde, P.
Micnas, R.
Powiązania:
https://bibliotekanauki.pl/articles/2038385.pdf
Data publikacji:
2004-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
74.20.Mn
71.10.Fd
Opis:
In this paper we focus on the anomalous temperature dependence of the in-plane conductivity and symmetry mixing of the superconducting order parameter observed in various experiments on cuprates. We show that the one-band Hubbard model is not capable of describing the physics of cuprates because the kinetic energy is lowered in this model in the superconducting state, which contradicts experimental observations. The proper model to investigate doped, short-range antiferromagnets is the t-J model, for which our results agree with experiments. We analyze a spin polaron model, that is an effective model for a doped antiferromagnet. In the framework of this model we also study the superconducting order-parameter symmetry-mixing phenomenon. We show that the expected mixing of d-wave symmetry with p-wave symmetry takes place in the superconducting order-parameter at a finite value of the doping parameter. This symmetry mixing brakes the time-reversal symmetry.
Źródło:
Acta Physica Polonica A; 2004, 106, 5; 575-581
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Spin Polarons in Two-Dimensional Systems
Autorzy:
Morkowski, J. A.
Powiązania:
https://bibliotekanauki.pl/articles/2011229.pdf
Data publikacji:
2000-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.27.+a
72.10.Di
74.20.Mn
Opis:
The problem of motion of holes on a square lattice of antiferromagnetically ordered spins is considered. An overview of the theory of hole dynamics in the antiferromagnetic background is presented. Motion of a single hole is rather well understood both by numerical and analytical methods. For small but finite concentration of holes a treatment analogous to the standard polaron theory is discussed starting with an exact mapping of the t-J Hamiltonian into holon and pseudospin variables.
Źródło:
Acta Physica Polonica A; 2000, 97, 1; 101-110
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Destruction of Antiferromagnetic Order by Localized Polarons
Autorzy:
Wilamowski, Z.
Hankiewicz, E. M.
Powiązania:
https://bibliotekanauki.pl/articles/2013011.pdf
Data publikacji:
2000-03
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
74.20.-z
75.10.-b
74.20.Mn
Opis:
Analysis of a finite spin cluster indicates a possibility of the formation of purely magnetic polarons in low-dimensional antiferromagnets. It is shown that for parameters characteristic of CuO$\text{}_{2}$ based superconductors a strong antiferromagnetic polaron can occur. The destruction of antiferromagnetic order by the presence of a magnetic polaron is discussed.
Źródło:
Acta Physica Polonica A; 2000, 97, 3; 403-406
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Superconductivity and Charge-Density Wave Phase in the Holstein Model: a Weak Coupling Limit
Autorzy:
Grzybowski, P.
Micnas, R.
Powiązania:
https://bibliotekanauki.pl/articles/2047304.pdf
Data publikacji:
2007-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.38.-k
71.45.Lr
74.20.Mn
Opis:
The variational canonical transformation method has been applied to the Holstein model to obtain an effective polaronic Hamiltonian, which is subsequently analyzed in the limit of a weak effective electron-electron interaction. A competition between the superconducting and charge-density wave phases has been studied in the light of strong polaronic effects. The phase diagrams illustrating the system evolution from adiabatic to anti-adiabatic limit are presented.
Źródło:
Acta Physica Polonica A; 2007, 111, 4; 453-463
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Electromagnetic Response in Kinetic Energy Driven Superconductivity: the Meissner Effect
Autorzy:
Krzyzosiak, M.
Lan, Y.
Feng, S.
Jacak, L.
Gonczarek, R.
Powiązania:
https://bibliotekanauki.pl/articles/1536649.pdf
Data publikacji:
2010-08
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
74.25.Ha
74.25.N-
74.20.Mn
Opis:
Electromagnetic response of cuprate superconductors is studied within the model of kinetic energy driven d-wave superconductivity by analyzing the Meissner effect. The kernel of the linear response function is found and employed to calculate the magnetic field penetration depth and the superfluid density of cuprate superconductors within the specular reflection model for a purely transverse vector potential. It is shown that the magnetic field penetration depth and the superfluid density depend linearly on temperature, except for a strong deviation from the linear characteristics at extremely low temperatures, which is attributed to nonlocal effects. The zero-temperature superfluid density is found to decrease linearly with decreasing doping concentration in the underdoped regime. The problem of gauge invariance in the theoretical description of the electromagnetic response is addressed, and an approximation which does not violate local charge conservation is proposed.
Źródło:
Acta Physica Polonica A; 2010, 118, 2; 283-288
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Influence of Electronic Structure on the Phase Diagram of Weakly Doped Superconducting Cuprates
Autorzy:
Maciąg, A. M.
Wróbel, P.
Powiązania:
https://bibliotekanauki.pl/articles/2047334.pdf
Data publikacji:
2007-05
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.10.Fd
74.20.Mn
74.25.Dw
Opis:
Motivated by the difference between the experimental phase diagram of cuprates and expectations of the t-J model, we analyze the influence of the electronic structure on superconducting state generation for small levels of doping. Following some theoretical studies of the Fermi surface for hole doped superconducting cuprates we base our calculations on the t-t'-t''-J model. We construct the spin polaron model, which is an effective model for the t-J model, and we expand it by adding the new terms related to the next neighbor hopping integrals t' and t''. In the framework of this model we study evolutions of superconducting correlation functions with doping. As a result of numerical calculations we find out that superconducting state vanishes for small levels of doping and finite values of t' and t''. This is in qualitative agreement with experimental results.
Źródło:
Acta Physica Polonica A; 2007, 111, 5; 721-725
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Asymmetric Tunneling Conductance in Doped Antiferromagnets
Autorzy:
Maciąg, A.
Wróbel, P.
Powiązania:
https://bibliotekanauki.pl/articles/2046776.pdf
Data publikacji:
2006-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.10.Fd
74.20.Mn
74.25.Fy
Opis:
We calculate the tunneling conductance in the framework of the spin polaron model, which is an effective model for the t-J model, in the limit where at least short-range antiferromagnetic correlations exist. We show that both in the normal state and in the superconducting state the asymmetry of tunneling conductance is present. This fact is the implication of the particle-hole asymmetry of the spin polaron Hamiltonian in the limit of low density of spin polarons which are quasiparticles emerging in a hole doped antiferromagnet. Experimental evidence of analogous asymmetric tunneling conductance was found in the tunneling spectroscopy measurements of high T$\text{}_{c}$ superconductors.
Źródło:
Acta Physica Polonica A; 2006, 109, 4-5; 607-610
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Pairing-Symmetry Selection in a Weakly Doped Canted Antiferromagnet on the Triangular Lattice
Autorzy:
Wróbel, P.
Suleja, W.
Powiązania:
https://bibliotekanauki.pl/articles/1812329.pdf
Data publikacji:
2008-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.10.Fd
74.20.Mn
75.50.Ee
Opis:
The mechanism of superconductivity generation by spin fluctuations in the electron doped canted antiferromagnet on the triangular lattice was analyzed. The underlying assumption is that the formation of the bound state is the prerequisite of pairing. The outcome of this analysis is also valid if an additional isotropic attraction is active but the anisotropic spin-fluctuation mediated force decides on the symmetry of the two-particle bound state. When the canted antiferromagnetic state is generated, the symmetry of the point group $C_{6v}$ for the triangular lattice is lowered to the symmetry of $C_{3v}$. It is demonstrated that spin fluctuations definitely favor the p-wave bound state, which transforms according to the E representation of $C_{3v}$. Since the inversion is not an element of $C_{3v}$, the parity is not a good quantum number and thus the predicted paired state will be a mixture of singlet and triplet. Such a scenario may be relevant to physics of superconducting triangular cobaltates or organics.
Źródło:
Acta Physica Polonica A; 2008, 114, 1; 225-228
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Ground State Phase Diagrams of the Extended Hubbard Model with Repulsive Pair-Hopping Interaction for Nonfrustrated 2D Lattice
Autorzy:
Czart, W.
Robaszkiewicz, S.
Powiązania:
https://bibliotekanauki.pl/articles/1385232.pdf
Data publikacji:
2015-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
74.20.-z
71.28.+d
74.20.Mn
Opis:
We analyze the extended Hubbard model with pair-hopping interaction J, i.e. the Penson-Kolb-Hubbard model, in the case of repulsive J (J < 0) within the (broken symmetry) Hartree-Fock approximation. We focus our study on the effects of on-site U interaction on the mutual stability of magnetic, charge-ordered, and superconducting states including the eta-pairing phase, i.e. the state with the Cooper-pair center-of-mass momentum q=Q. The ground state phase diagrams are obtained for arbitrary particle concentration n on nonfrustrated d=2 square lattice.
Źródło:
Acta Physica Polonica A; 2015, 127, 2; 275-277
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Ground State Phase Properties of the Penson-Kolb-Hubbard Model with Attractive Pair-Hopping Interaction
Autorzy:
Czart, W.
Robaszkiewicz, S.
Powiązania:
https://bibliotekanauki.pl/articles/1385235.pdf
Data publikacji:
2015-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
74.20.-z
71.28.+d
74.20.Mn
Opis:
We study the ground state phase diagrams of the extended Hubbard model with the pair-hopping interaction J, i.e. the Penson-Kolb-Hubbard model. We concentrate on the case of attractive J (J > 0) which can stabilise s-wave pairing superconductivity in the system and competes with the on-site repulsive U. The evolution of the phase diagrams and order parameters for arbitrary electron density and representative values of the interaction parameters are analyzed within the (broken symmetry) Hartree-Fock approximation. The calculations are performed for the case of nearest-neighbors electron hopping t on the d=2 square lattice.
Źródło:
Acta Physica Polonica A; 2015, 127, 2; 278-280
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł

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