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    Wyświetlanie 1-6 z 6
    Tytuł:
    In the Search of Electron Correlation Effects in DNA
    Autorzy:
    Wróbel, A.
    Wróbel, P.
    Powiązania:
    https://bibliotekanauki.pl/articles/1537235.pdf
    Data publikacji:
    2010-08
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    87.14.gk
    75.20.-g
    71.10.Fd
    Opis:
    We discuss the energy scale separation induced in DNA by gaps between molecular orbital states of individual bases and by electron correlations. We also demonstrate how this separation gives rise to effective low energy models of electron transport in DNA.
    Źródło:
    Acta Physica Polonica A; 2010, 118, 2; 409-412
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Theoretical Analysis of the Short Coherence Length Superconductors
    Autorzy:
    Wysokiński, K.
    Ciechan, A.
    Krzyszczak, J.
    Powiązania:
    https://bibliotekanauki.pl/articles/1536554.pdf
    Data publikacji:
    2010-08
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    71.10.Fd
    74.20.-z
    74.81.-g
    Opis:
    Properties of the short coherence length ξ superconductors are markedly different from those with long ξ. The main difference is connected with their response to impurities. Even the s-wave superconductors have been predicted not to obey the so-called Anderson theorem and to show appreciable fluctuations of order parameter. This observation has been recently confirmed in a number of beautiful scanning tunnelling experiments on high temperature cuprate and pnictide superconductors. In this work we study clean two-band systems within BCS-type approach and impure superconductors within mean field Bogolubov-de Gennes approach. In the weak disorder limit both s-wave and d-wave superconductors only weakly react to impurities. Presence of the Van Hove singularities in the density of states of the two-band clean systems strongly increases their superconducting transition temperature if the intra-band pair scattering is the only pairing interaction. The effect of impurities on such superconductors does depend on the sign of the inter-orbital interaction.
    Źródło:
    Acta Physica Polonica A; 2010, 118, 2; 232-237
    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:
    Inhomogeneities in Superconductors Described by the Two-Component Model
    Autorzy:
    Krzyszczak, J.
    Domański, T.
    Wysokiński, K.
    Powiązania:
    https://bibliotekanauki.pl/articles/1537060.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 fluctuations of the superconducting order parameter of s-wave symmetry caused by nonmagnetic disorder present both in the boson and fermion subsystems using the Bogoliubov-de Gennes equations. In particular, we are interested if some features of the d-wave model persist for s-wave symmetry as well. These are: positive correlations between positions of impurities and the magnitude of energy gap, the homogeneity of the local density of states at low energies, nanoscale inhomogeneity of the coherence peak positions and their non-uniform height. We have found that spatial variations of s-wave order parameter are positively correlated with the positions of impurities. Such behavior has been observed in scanning tunneling measurements on d-wave symmetry BSCCO-2122 superconductors.
    Źródło:
    Acta Physica Polonica A; 2010, 118, 2; 360-363
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Real Space Bogoliubov-de Gennes Equations Study of the Boson-Fermion Model
    Autorzy:
    Krzyszczak, J.
    Domański, T.
    Wysokiński, K.
    Powiązania:
    https://bibliotekanauki.pl/articles/1812295.pdf
    Data publikacji:
    2008-07
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    71.10.Fd
    74.20.-z
    74.81.-g
    Opis:
    The boson-fermion model was proposed to describe superconductivity in short coherence length superconductors. In this work we use it to study impurity induced inhomogeneities in high temperature superconductors as found in numerous scanning tunnelling measurements. The model was formulated in real space and solved with help of Bogoliubov-de Gennes approach. Disorder in the boson or fermion subsystem is directly coupled to the superconducting order parameter and leads to severe changes of superconducting properties like local order parameter and density of states. We present the results for many impurities randomly distributed over otherwise clean and periodic two-dimensional square lattice.
    Źródło:
    Acta Physica Polonica A; 2008, 114, 1; 165-169
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Some Properties of the Model of a~Superconductor with Pair Hopping and Magnetic Interactions at Half-Filling
    Autorzy:
    Kapcia, K.
    Powiązania:
    https://bibliotekanauki.pl/articles/1431185.pdf
    Data publikacji:
    2012-04
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    71.10.Fd
    71.10.-w
    74.20.-z
    74.81.-g
    75.30.Fv
    Opis:
    We present our preliminary studies of an effective model of a superconductor with short coherence length involving magnetic interactions. The Hamiltonian considered consists of (i) the effective on-site interaction U, (ii) the intersite magnetic exchange interactions ($J^z,$ $J^{xy}$) between nearest-neighbors and (iii) the intersite charge exchange term I, determining the hopping of electron pairs between nearest-neighbor sites. In the analysis of the phase diagrams and thermodynamic properties of this model for half-filling (n=1) we have adopted the variational approach, which treats the on-site interaction term exactly and the intersite interactions within the mean-field approximation. One finds that the system considered can exhibit very interesting multicritical behaviors (including tricritical, critical-end and bicritical points) caused by the competition between magnetism and superconductivity, even for n=1. Our investigations show that, depending on the values of interaction parameters, the system at half-filling can exhibit three homogeneous phases: superconducting (SS), (anti-)ferromagnetic (F) and nonordered (NO). The transitions between ordered phases (SS, F) and the NO phase can be first order as well as second order ones, whereas SS-F transition is first order one. Temperature dependencies of the order parameters and thermodynamic properties of the system at the sequence of transitions: SS→F→NO with increasing temperature for J/I=0.3, U/I_0 = 0.69 and n=1 are also presented.
    Źródło:
    Acta Physica Polonica A; 2012, 121, 4; 733-737
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-6 z 6

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