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Band hybridization effect on indirect magnetic coupling of localized moments
No full textWe study the influence of interorbital hybridization γk on the indirect exchange interaction J(k) in a model of two bcc bands of s-type. We report two cases where the stable magnetic structure changes due to γk. However, γk generally leaves unchanged the structure, while reducing greatly its stability vs. temperatur
Distance-depending electron-phonon interactions from one- and two-body electronic terms in a dimer
No full textEffect of intersite band hybridization and on-site correlation on the magnetism of localized-moment systems
No full textWe study the effect of the conduction-electron density of states on magnetic transition temperatures in metallic systems with localized magnetic moments. We assume the indirect-exchange interaction to originate from s-f mixing of the Anderson type and we perform calculations of the coupling parameters, up to fourth-nearest neighbors, in the formalism of da Silva and Falicov. The density-of-states models are obtained from a two-component band in tight-binding scheme and we include on-site Coulomb correlation. We find that the magnetic energy has a modulated Ruderman-Kittel-Kasuya-Yoshida–like behavior as a function of the number of conduction electrons n. This is, however, dominated by two strong maxima when n is such that the Fermi level lies on a peak of the density of states. In this condition the transition temperature is enhanced by at least 1 order of magnitude with respect to the weaker background. This behavior is found for different values of the virtual excitation energy of the s-f mixing mechanis
A non-perturbative treatment of the generalized Su-Schrieffer-Heeger Hamiltonian on a dimer
No full textStarting from the Hamiltonian for a dimer which includes all the electronic and electron-phonon terms consistent with a non-degenerate orbital, by a sequence of displacement and squeezing transformation we obtain an effective polaronic Hamiltonian. The renormalized electronic interactions differ from the results of semiclassical or perturbative treatments. The properties of the variationally determined ground state of two particles in the orbital are discussed for variable dimer length in the adiabatic limit
Model Calculation of Distance-Dependent Electron–Phonon Coupling Parameters Derived from One- and Two-Body Interactions for a Dimer
No full textRelationship between electronic conduction states and indirect magnetic exchange
No full textn attempt to find a quantitative relationship between magnetic transition temperature and conductionstates properties in metallic materials is presented. The exchange interaction among magnetic moments is assumed to be of the Anderson's s-f type and the conductionstates have s-d orbital character. The results are analyzed vs. different amount of s-d hybridization within LCAO schem
Phase Diagrams at Different Fillings of the EffectiveExtended Hubbard–Holstein Hamiltonian for a Four-SiteRing of Variable Length
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