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Wyświetlanie 1-15 z 89
Tytuł:
Bound States of Fermions on 2d Lattice in a Dilute Limit
Autorzy:
Bąk, M.
Micnas, R.
Powiązania:
https://bibliotekanauki.pl/articles/2012890.pdf
Data publikacji:
2000-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
74.20.-z
03.65.Ge
71.10.Fd
Opis:
We examine extended bound states in a dilute limit of the extended Hubbard model on the two-dimensional square lattice. By solving exactly the two-body problem we have determined the binding energies, mobilities, and dispersion curves across the Brillouin zone for bound states of various symmetries. It turns out that the d-wave pairing is strongly favored by the nnn hopping and the intersite local pairs can have small effective masses, even in the case of strong binding.We have also found a possibility of extended s-$d_{x^{2}-y^{2}}$ mixing of the bound states.
Źródło:
Acta Physica Polonica A; 2000, 97, 1; 209-212
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Critical Values for Electron Pairing in t-U-J-V and t-J-V Models
Autorzy:
Bak, M.
Powiązania:
https://bibliotekanauki.pl/articles/1812342.pdf
Data publikacji:
2008-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
74.20.-z
74.20.Fg
74.20.Rp
74.25.Dw
71.10.Fd
71.27.+a
Opis:
The critical values for pairing of s*- and d-wave symmetry are calculated within the t-U-J-V and the t-J-V models in renormalized mean field theory. It is shown that the first model yields the proper critical values in the low density limit while the other does not. Renormalized mean field theory strongly decreases the absolute value of (negative) critical values for larger electron densities.
Źródło:
Acta Physica Polonica A; 2008, 114, 1; 275-279
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Evolution from the BCS to the Bose-Einstein Limit in a d-Wave Superconductor at T=0
Autorzy:
Borkowski, L. S.
Sá de Melo, C. A. R.
Powiązania:
https://bibliotekanauki.pl/articles/2027398.pdf
Data publikacji:
2001-06
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
74.20.-z
74.25.Gz
67.40.Db
Opis:
We study the evolution from BCS to Bose limit in a two-dimensional d-wave superconductor at zero temperature and low density of charge carriers within the mean-field theory. We examine single quasiparticle properties when particle density and attraction strength are varied. For sufficiently high interaction strength there is a critical density below which the system has a gap. The spectral and thermodynamic properties of the system do not evolve smoothly from the BCS-like to the Bose-like regime.
Źródło:
Acta Physica Polonica A; 2001, 99, 6; 691-698
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Inter-Orbital Effects in the Impure Pnictide Superconductors
Autorzy:
Ciechan, A.
Wysokiński, K.
Powiązania:
https://bibliotekanauki.pl/articles/1537057.pdf
Data publikacji:
2010-08
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.10.Fd
74.20.-z
74.81.-g
Opis:
We study the local properties of the iron oxypnictides by means of the real space Bogolubov-de Gennes equations. Starting with the realistic energy spectrum and assuming small amount of impurities we calculate the energy dependence of the local density of states and spatial distribution of the local values of the superconducting energy gap. We pay particular attention to the role of the inter-orbital scattering of pairs and the effect of impurity scattering on the superconducting state. The effect of inter-orbital impurities depends on the relative signs of the order parameters related to two orbitals in question. For opposite signs impurities produce bound states inside the gap, while for the same sign of the order parameters they hardly affect the superconductor. The results obtained for impure systems have been shown as maps of the order parameters and local density of states. They well compare with the existing scanning tunnelling microscopy spectra of the iron pnictides.
Źródło:
Acta Physica Polonica A; 2010, 118, 2; 356-359
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Pairing Correlations around Negative-U Centre in the Two-Band Model
Autorzy:
Ciechan, A.
Wysokiński, K.
Powiązania:
https://bibliotekanauki.pl/articles/1812284.pdf
Data publikacji:
2008-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
74.20.-z
74.81.-g
74.90.+n
Opis:
The electron energy spectrum of many superconducting materials is characterised by the presence of few bands at the Fermi level. In some cases the superconducting properties seem to be dominated by single band but in others the many-band approach is essential ingredient of their description. In this paper we shall study the properties of superconducting impurity placed in a non-superconducting medium. We are interested in the evolution of superconducting correlations within non-superconducting 1- or 2-dimensional system, their dependence on the distance from impurity and changes induced by the presence of the second band and interband scattering. We use real space description of the material and Bogolyubov-de Gennes approach to superconductivity.
Źródło:
Acta Physica Polonica A; 2008, 114, 1; 123-127
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Relativistic Theory of Superconductivity: BCS vs. Bogolyubov-de Gennes Approaches
Autorzy:
Ciechan, A.
Donabidowicz, A.
Wysokiński, K. I.
Powiązania:
https://bibliotekanauki.pl/articles/2041454.pdf
Data publikacji:
2004-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
74.20.-z
74.20.Fg
74.20.Rp
Opis:
In this paper we shall present the results of numerical calculations of the superconducting characteristics (temperature dependence of the gap function and specific heat) for few different symmetries of the order parameter in relativistic theory of superconductivity. We shall discuss relevance of the results to describe newly discovered superconductors, particularly those containing heavy elements with strong spin-orbit coupling.
Źródło:
Acta Physica Polonica A; 2004, 106, 5; 699-702
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Specific Heat Study of Fulde-Ferrell-Larkin-Ovchinnikov Superconducting States in Multibands Materials - Iron-Based Systems
Autorzy:
Crivelli, D.
Ptok, A.
Powiązania:
https://bibliotekanauki.pl/articles/1398585.pdf
Data publikacji:
2016-08
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
74.20.-z
74.70.Xa
Opis:
The Fulde-Ferrell-Larkin-Ovchinnikov phase is the superconducting state for which the Cooper pairs have non-zero total momentum. From the time of conception of this phase, many groups have been searching for a realization of the state. Here we describe a proposal of experimental verification of this state in the case of multi-bands systems, by carrying out the specific-heat measurement.
Źródło:
Acta Physica Polonica A; 2016, 130, 2; 507-510
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
Tytuł:
Phase Diagrams of the Penson-Kolb-Hubbard Model with Repulsive Pair-Hopping Interaction
Autorzy:
Czart, W.
Robaszkiewicz, S.
Powiązania:
https://bibliotekanauki.pl/articles/1398641.pdf
Data publikacji:
2016-08
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
74.20.-z
71.28.+d
74.20.Mn
Opis:
We study the extended Hubbard model with on-site density-density U and intersite pair hopping J interactions, i.e. the Penson-Kolb-Hubbard model. This report focuses mainly on the properties of the model at T ≥q 0 in the case of repulsive J (J < 0) which may stabilize superconductivity with η-pairing. The analysis is performed within the (broken symmetry) Hartree-Fock approximation for arbitrary interaction parameters (J < 0 and U) and electron concentration (0 < n < 2) on the d = 2 square lattice. The phase diagrams of the model at T=0 and at finite temperatures are examined taking into account magnetic and charge-ordered phases and superconducting states with η- and s-wave pairing.
Źródło:
Acta Physica Polonica A; 2016, 130, 2; 613-616
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Electron Orderings of Half-Filled Extended Hubbard Models with Spin- and Charge-Exchange Interaction
Autorzy:
Czart, W. R.
Robaszkiewicz, S.
Powiązania:
https://bibliotekanauki.pl/articles/2046752.pdf
Data publikacji:
2006-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.10.Fd
75.10.-b
75.30.Gw
71.45.Lr
74.20.-z
Opis:
The electron orderings of the half-filled extended Hubbard models (i) with anisotropic spin-exchange interactions (the t-U-J$\text{}_{ǁ}$-J$\text{}_{⊥}$ model) and (ii) with charge-exchange interaction (the t-U-I model) are discussed. In particular, we present new results concerning the phase diagrams of the model (i) in the case of uniaxial spin exchange (J$\text{}_{ǁ}$≢0) for d-dimensional hypercubic lattices (1≤d≤∞) and conclude about the basic effects of the particular spin- and charge-exchange interaction terms (J$\text{}_{ǁ}$, J$\text{}_{⊥}$, and I) in both models.
Źródło:
Acta Physica Polonica A; 2006, 109, 4-5; 577-582
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Influence of Coulomb Interactions on the Properties of Induced Pairing Model
Autorzy:
Czart, W. R.
Robaszkiewicz, St.
Powiązania:
https://bibliotekanauki.pl/articles/2027440.pdf
Data publikacji:
2001-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
74.20.-z
74.20.Mn
71.28.+d
74.25.Ha
Opis:
We study the superconducting properties of a model of coexisting itinerant carriers and local pairs with finite binding energy, taking into account the effects of Coulomb (density-density) and direct pair hopping interactions. The evolution of the phase diagrams and superfluid characteristics with electron concentration, interaction parameters and the relative position of the bands is examined. The model is found to exhibit several kinds of superconducting behaviors ranging from the BCS-like to the local-pair-like. The relevance of the obtained results to the interpretation of experimental data for the doped bismuthates (Ba$\text{}_{1-x}$K$\text{}_{x}$BiO$\text{}_{3}$ and BaPb$\text{}_{1-x}$BiO$\text{}_{3}$) is pointed out.
Źródło:
Acta Physica Polonica A; 2001, 100, 1; 75-88
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Superconducting Characteristics of the Penson-Kolb Model
Autorzy:
Czart, W. R.
Robaszkiewicz, S.
Powiązania:
https://bibliotekanauki.pl/articles/2012898.pdf
Data publikacji:
2000-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
74.20.-z
71.28.+d
74.25.Ha
Opis:
We study superconducting properties of the Penson-Kolb model, i.e. the tight-binding model with the pair-hopping (intersite charge exchange) interaction J. The evolution of the critical fields, the coherence length, the Ginzburg ratio, and the London penetration depth with particle concentration n and pairing strength are determined. The results are compared with those found earlier for the attractive Hubbard model.
Źródło:
Acta Physica Polonica A; 2000, 97, 1; 217-220
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Superconducting Properties of theη-Pairing State in the Penson-Kolb-Hubbard Model
Autorzy:
Czart, W. R.
Robaszkiewicz, S.
Powiązania:
https://bibliotekanauki.pl/articles/2041460.pdf
Data publikacji:
2004-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
74.20.-z
71.28.+d
74.25.Ha
Opis:
The Penson-Kolb-Hubbard model, i.e. the Hubbard model with the pair-hopping interaction J is studied. We focus on the properties of the superconducting state with the Cooper-pair center-of-mass momentum q= Q (η-phase). The transition into theη-phase, which is favorized by the repulsive J (J<0) is found to occur only above some critical value |J$\text{}_{c}$|, dependent on band filling, on-site interaction U and band structure, and the system never exhibits standard BCS-like features. This is in obvious contrast with the properties of the isotropic s-wave state, stabilized by the attractive J and attractive U, which exhibit at T=0 a smooth crossover from the BCS-like limit to that of tightly bound pairs with increasing pairing strength.
Źródło:
Acta Physica Polonica A; 2004, 106, 5; 709-713
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Superconductivity of the Two-Dimensional Penson-Kolb Model
Autorzy:
Czart, W. R.
Robaszkiewicz, S.
Powiązania:
https://bibliotekanauki.pl/articles/2029270.pdf
Data publikacji:
2001-12
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
74.20.-z
71.28.+d
74.25.Ha
Opis:
Two-dimensional (d=2) Penson-Kolb model, i.e. the tight-binding model with the pair-hopping (intersite charge exchange) interaction, is considered and the effects of phase fluctuations on the s-wave superconductivity of this system are discussed within the Kosterlitz-Thouless scenario. The London penetration depth λ at T=0, the Kosterlitz-Thouless critical temperature T$\text{}_{c}$, and the Hartree-Fock approximation critical temperature T$\text{}_{p}$ are determined as a function of particle concentration and interaction. The Uemura type plots (T$\text{}_{c}$ vs.λ$\text{}^{-2}$(0)) are derived. Beyond weak coupling and for low concentrations they show the existence of universal scaling: T$\text{}_{c}$ ~1/λ$\text{}^{2}$(0), as it was previously found for the attractive Hubbard model and for the models with intersite electron pairing.
Źródło:
Acta Physica Polonica A; 2001, 100, 6; 885-895
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Wyświetlanie 1-15 z 89

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