Now showing items 1-20 of 21

    • Application of the underscreened Kondo lattice model to neptunium compounds 

      Thomas, Christopher; Simoes, Acirete Souza da Rosa; Iglesias, Jose Roberto; Lacroix, Claudine; Coqblin, Bernard (2012) [Journal article]
      The coexistence of Kondo e®ect and ferromagnetic order has been observed in many uranium and neptunium compounds such as UTe or Np2PdGa3. This coexistence can be described within the underscreened Anderson lattice model ...
    • Approximate Treatment of a Two-Dimensional Anisotropic Peierls-Hubbard Model 

      Bernhard, Ben Hur; Iglesias, Jose Roberto (1993) [Journal article]
      A Green-function formalism is presented to study a Peierls-Hubbard Hamiltonian in two dimensions. The 1attice consists of parallel dimerized chains with alternating nearest-neighbor hoppings t and t 11 and another hopping ...
    • Band-filling effects on Kondo-lattice properties 

      Coqblin, Bernard; Lacroix, Claudine; Gusmao, Miguel Angelo Cavalheiro; Iglesias, Jose Roberto (2003) [Journal article]
      We present theoretical results for a Kondo-lattice model with spin-1/2 localized moments, including both the intrasite Kondo coupling and an intersite antiferromagnetic exchange interaction, treated within an extended ...
    • Bohm-Aharonov and Kondo effects on tunneling currents in a mesoscopic ring 

      Davidovich, Maria Augusta; Anda, Enrique V.; Iglesias, Jose Roberto; Chiappe, Giuseppe (1997) [Journal article]
      We present an analysis of the Kondo effect on the Bohm-Aharonov oscillations of the tunneling currents in a mesoscopic ring with a quantum dot inserted in one of its arms. The system is described by an Andersonimpurity ...
    • Doping dependence of the electronic structure and magnetic order in high-tc superconductors 

      Bernhard, Ben Hur; Iglesias, Jose Roberto (1994) [Journal article]
      The local densities of states of an extended Hubbard model describing the Cu02 planes of superconducting cuprates are calculated by means of an approximate treatment that divides the lattice into Cu02 clusters. The exact ...
    • Dynamic modular networks model mediated by confinement 

      Schneider, Éder Mílton; Goncalves, Sebastian; Iglesias, Jose Roberto; Cunha, Bruno Requião da (2019) [Journal article]
      We present a model for network transformation mediated by confinement, as a demonstration of a simple network dynamics that has a direct connection with real world quantities. The model has the capacity of generating complex ...
    • Effect of band filling in the Kondo lattice : a mean-field approach 

      Ruppenthal, Alaor Ricardo; Iglesias, Jose Roberto; Gusmao, Miguel Angelo Cavalheiro (1999) [Journal article]
      The usual Kondo lattice, including an antiferromagnetic exchange interaction between nearest-neighboring localized spins, is treated here in a mean-field scheme that introduces two mean-field parameters: one associated ...
    • Eletronic and phonomic states of the Holstein-Hubbard dimer of variable length 

      Acquarone, C.; Iglesias, Jose Roberto; Gusmao, Miguel Angelo Cavalheiro; Noce, A.; Romano, Alfonso (1998) [Journal article]
      We consider a model Hamiltonian for a dimer of length a including all the electronic one- and two-body terms consistent with a single orbital per site, a free Einstein phonon term for a frequency V, and an electronphonon ...
    • Green-Function Method for a Mixed-Valence Hamiltonian 

      Simoes, Acirete Souza da Rosa; Iglesias, Jose Roberto; Anda, Enrique V. (1984) [Journal article]
      A Green-function diagrammatic method is utilized to calculate the occupation number of a narrow (j) band in a mixed-valence system. The method is a generalization of the Hubbard-1 approximation for a two-band Hamiltonian. ...
    • Growth and form of two-dimensional rotating aggregates 

      Lemke, Ney; Malcum, Marines Grande; Almeida, Rita Maria Cunha de; Mors, Paulo Machado; Iglesias, Jose Roberto (1993) [Journal article]
      We propose a two-dimensional particle-cluster aggregation model which considers explicitly linear and angular momentum conservation. Each aggregate is grown from a seed of given mass and given initial angular velocity, to ...
    • Magnetic susceptibility and specific heat of the anderson lattice : perturbative expansion around the atomic limit 

      Brunnet, Leonardo Gregory; Gusmao, Miguel Angelo Cavalheiro; Iglesias, Jose Roberto (1992) [Journal article]
      The Green's functions relevant to the periodic Anderson Hamiltonian are calculated via perturbation theory around the atomic limit. The approximation reproduces exact results in three different limits: zero bandwidth, zero ...
    • Mesoscopic magnetic states in metallic alloys with strong electronic correlations : a percolative scenario for CeNi/sub 1-x/Cu/sub x/ 

      Marcano, N.; Gómez Sal, J.C.; Espeso, José Ignacio; De Teresa, J.M.; Algarabel, P.A.; Paulsen, C.; Iglesias, Jose Roberto (2007) [Journal article]
      We present evidence for the existence of magnetic clusters of approximately 20 Å in the strongly correlated alloy system CeNi1-xCux (0.7 ≤ x ≤ 0.2) based on small angle neutron scattering experiments as well as the occurrence ...
    • Mitosis and growth in biological tissues 

      Mombach, Jose Carlos Merino; Almeida, Rita Maria Cunha de; Iglesias, Jose Roberto (1993) [Journal article]
      We present a simulation of the growth of a two-dimensional biological cellular system in which the cells experience mitosis whenever the (area)/(perimeter) ratio reaches a critical value. The model also includes the effect ...
    • Modeling two-dimensional magnetic domain patterns 

      Iglesias, Jose Roberto; Goncalves, Sebastian; Nagel, Oscar Amadeo; Kiwi, Miguel (2002) [Journal article]
      Two-dimensional magnetic garnets exhibit complex and fascinating magnetic domain structures, like stripes, labyrinths, cells, and mixed states of stripes and cells. These patterns do change in a reversible way when the ...
    • Phase diagram for the Anderson lattice model 

      Bernhard, Ben Hur; Lacroix, Claudine; Iglesias, Jose Roberto; Coqblin, Bernard (2000) [Journal article]
      We study the competition between the Kondo effect and the Ruderman-Kittel-Kasuya-Yosida interaction in the framework of the Anderson lattice model with an extra intersite exchange term. By using an approximation based on ...
    • Revisited doniach diagram : influence of short-range antiferromagnetic correlations in the Kondo lattice 

      Iglesias, Jose Roberto; Lacroix, Claudine; Coqblin, Bernard (1997) [Journal article]
      The Kondo lattice model including nearest-neighbor magnetic exchange interactions is studied here in a mean-field approximation describing both the Kondo state and the intersite magnetic correlations. In the case of ...
    • Statistical thermodinamics of a two-dimensional cellular system 

      Iglesias, Jose Roberto; Almeida, Rita Maria Cunha de (1991) [Journal article]
      The principies of statistical physics are applied to the study of cellular systems. Cells that fill a flat surface are characterized by area, perimeter, and number of sides. A set of constraints is established, taking into ...
    • Temperature dependence of the electric field gradient generated by nearest-neighbor impurity atoms in cubic Ag metal 

      Baumvol, Israel Jacob Rabin; Behar, Moni; Iglesias, Jose Roberto; Livi, Rogerio Pohlmann; Zawislak, Fernando Claudio (1978) [Journal article]
      The electric quadrupole interactions produced by near-neighbor (nn) and distant-neighbor impurity atoms of Cu, Au, Zn, In, Ga, Al, Sn, and Sb in a cubic Ag lattice are measured as a function of the temperature by the time ...
    • The S=1 underscreened anderson lattice model for uranium compounds 

      Thomas, Christopher; Simoes, Acirete Souza da Rosa; Iglesias, Jose Roberto; Lacroix, Claudine; Perkins, Natalia B.; Coqblin, Bernard (2011) [Journal article]
      Magnetic properties of uranium and neptunium compounds showing coexistence of the Kondo e®ect and ferromagnetic order are investigated within the degenerate Anderson Lattice Hamiltonian, describing a 5f2 electronic ...
    • Two-cell correlations in biological tissues 

      Mombach, Jose Carlos Merino; Almeida, Rita Maria Cunha de; Iglesias, Jose Roberto (1993) [Journal article]
      We present two-cell correlation functions ml(n), which give the average number of t-sided cells adjacent to n-sided ones, obtained experimentally from vegetable tissues and through a numerical simulation that includes ...