1,721,154 research outputs found
Electron-phonon interaction in proximity of a Mott transition
No full textThe effects of electron-phonon interaction on the electronic properties of a strongly correlated metal on the verge of a Mott metal-insulator transition are studied by means of dynamical mean-field theory. We show that electron-phonon interactions induce a phase separation instability close to the density driven Mott transition, and give rise to significant renormalization of electronic properties like charge susceptibility. Nonetheless, the strong correlation reduces the effectiveness of the electron-phonon coupling in driving a polaronic crossover. (c) 2005 Elsevier B.V. All rights reserved. RI Grilli, Marco/C-6309-2009; Capone, Massimo/A-7762-200
Small polaron formation in strongly correlated electron systems
No full textWe study the crossover to small polarons in the Holstein model for finite densities in presence of strong electronic correlations. The small polaron formation condition lambda>1, which holds for a single particle in the adiabatic regime omega(0)/t much less than 1 is generalized to the many particle case by means of simple physical arguments. It is shown that a general criterion can be formulated for polaron formation, provided that incoherent 1/lambda corrections are taken into account. RI Grilli, Marco/C-6309-2009; Capone, Massimo/A-7762-200
First-Order Pairing Transition and Phase Separation in the Attractive Hubbard model
No full textThe normal state properties of the Hubbard model are studied by means of the Dynamical Mean-Field Theory. Even in the gauge-symmetric subspace, a first-order transition occurs between a Fermi-liquid phase and a strong-coupling bound-pairs phase, which can be thought as a "disordered" superconductor. The transition is of first order for all densities different from n = 1, and it is accompanied by a region of phase separation between the two phases at different densities. RI Grilli, Marco/C-6309-2009; Capone, Massimo/A-7762-200
Alberto Grilli, Marco Tullio Cicerone, Tuscolane. Libro II. Testo, introduzione, versione e commento
No full textKnecht Daniel. Alberto Grilli, Marco Tullio Cicerone, Tuscolane. Libro II. Testo, introduzione, versione e commento. In: L'antiquité classique, Tome 57, 1988. pp. 391-392
Polaron formation and optical absorption in Su-Schrieffer-Heeger and Holstein models
No full textThe conditions leading to small-polaron formation for a single charge carrier in the Su-Schrieffer-Heeger (SSH) model are compared with the Holstein model. From analytic perturbation theory and exact numerical diagonalization of small clusters different criteria are established, which however have a common physical origin: Polaron formation requires a sizable mass enhancement and a lattice deformation energy gain larger than the loss in the bare electron kinetic energy in both models. The optical absorption of the Su-Schrieffer-Heeger model in the polaronic regime is also shown to exhibit an additional feature not present in the Holstein model. This additional feature arises due to the bond nature of small polarons in the SSH model, and is determined by transitions from the ground state of the bonding character on a shortened bond to excited states of the antibonding character on the same shortened bond. RI Grilli, Marco/C-6309-2009; Capone, Massimo/A-7762-200
First-order pairing transition and single-particle spectral function in the attractive Hubbard model
No full textA dynamical mean-field theory analysis of the attractive Hubbard model in the normal phase is carried out upon restricting to solutions where superconducting order is not allowed. A clear first-order pairing transition as a function of the coupling takes place at all the electron densities out of half filling between a Fermi liquid, stable for U < U-c, and an insulating bound pairs phase for U > Uc, and it is accompanied by phase separation. The spectral function in the metallic phase is constituted by a low-energy structure around the Fermi level, which disappears discontinuously at U = U-c, and two high-energy features (Hubbard bands), which persist in the insulating phase. RI Grilli, Marco/C-6309-2009; Capone, Massimo/A-7762-200
Disorder and correlations in quantum systems
No full textThe conference aims at bringing together experienced researchers from different areas to favor exchange of ideas on the most recent advances in condensed matter physics.
The topics covered by the conference include: low-dimensional superconductors, strongly correlated electronic systems, classical and quantum glassy behavior, cold atoms, spintronics, quantum information and others
Role of electron-lattice interactions in determining the magnetic structure of insulating manganites
No full textTogether with the strong electron-electron interactions, the role of the lattice distorsions turns out to be relevant in determining the specific magnetic structure of some insulating manganites. In particular, while a substantial Jahn-Teller distorsion is needed to account for the layered antiferromagnetic structure of LaMnO3, the observed collective shear of alternate ions in La0.5Ca0.5MnO3 is required to stabilize the CE magnetic structure of this compounds. The specific action of the lattice in stabilizing these peculiar magnetic orderings is thus clarified. RI Grilli, Marco/C-6309-2009; Capone, Massimo/A-7762-200
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