Related papers: The two-dimensional t-t'-U model as a minimal mode…
The Roth's two-pole approximation has been used by the present authors to study the effects of the hybridization in the superconducting properties of a strongly correlated electron system. The model used is the extended Hubbard model which…
We consider an extended Hubbard model with nearest-neighbor correlated hopping and next nearest-neighbor hopping t' obtained as an effective model for cuprate superconductors. Using a generalized Hartree-Fock BCS approximation, we find that…
The half-filled extended Hubbard model, in one and two dimensions, is studied by means of the 2-pole approximation within the Composite Operator Method with the aim at improving the possibilities to describe some of the experimental…
The Hubbard model, which augments independent-electron band theory with a single parameter to describe electron-electron correlations, is widely regarded to be the `standard model' of condensed matter physics. The model has been remarkably…
The electronic states of the two-dimensional Hubbard model are investigated by means of a 4-pole approximation within the Composite Operator Method. In addition to the conventional Hubbard operators, we consider other two operators, which…
We present a numerical study of the doping dependence of the spectral function of the n-type cuprates. Using a variational cluster-perturbation theory approach based upon the self-energy-functional theory, the spectral function of the…
We study the strong coupling regime of the $t-t'$ Hubbard model,filled up to the level of the van Hove singularities, by means of an exact diagonalization approach. We characterize the different phases of the model by the different sectors…
A Hamiltonian H(\Gamma) applicable to cuprate HTS, with a doping dependent pairing interaction \Gamma(x) = V(x) + U(x), is linked to a Cu3d-O2p state probability model(SPM). A consequence of doping induced electron hopping, the SPM mandates…
The one-dimensional Hubbard model at half-filling is studied in the framework of the Composite Operator Method using a static approximation. A solution characterized by strong antiferromagnetic correlations and a gap for any nonzero on-site…
We study the superconducting instabilities of singlet and triplet pairing in a two-dimensional Hubbard model on the basis of the third-order perturbation theory (TOPT). We investigate the effect of the vertex correction that is given by…
We apply a renormalization group approach to the determination of the phase diagram of the t-t' Hubbard model at the Van Hove filling, as function of t'/t, for small values of U/t. The model presents ferromagnetic, antiferromagnetic and…
By using variational Monte Carlo and auxiliary-field quantum Monte Carlo methods, we perform an accurate finite-size scaling of the $s$-wave superconducting order parameter and the pairing correlations for the negative-$U$ Hubbard model at…
We present a stability analysis of the 2D t-t' Hubbard model on a square lattice for various values of the next-nearest-neighbor hopping t' and electron concentration. Using the free energy expression, derived by means of the flow equations…
An essential ingredient in many model Hamiltonians, such as the Hubbard model, is the effective electron-electron interaction $U$, which enters as matrix elements in some localized basis. These matrix elements provide the necessary…
Although the mechanism of superconductivity in the cuprates remains elusive, it is generally agreed that at the heart of the problem is the physics of doped Mott insulators. The cuprate parent compound has one unpaired electron per Cu site,…
Using computational techniques, it is shown that pairing is a robust property of hole doped antiferromagnetic (AF) insulators. In one dimension (1D) and for two-leg ladder systems, a BCS-like variational wave function with long-bond…
The variety of the normal-state magnetic properties of cuprate high-Tc superconductors is interpreted based on the self-consistent solution of the self-energy equations for the two-dimensional t-J model. The observed variations of the spin…
A Hubbard model at half-filling on an anisotropic triangular lattice has been proposed as the minimal model to describe conducting layers of $\kappa-(BEDT-TTF)_2X$ organic materials. The model interpolates between the square lattice and…
Understanding physics of high-$T_c$ cuprate superconductors remains one of the important problems in materials science. Though a number of diverse theories argue about the superconductivity and competing orders, ab initio and quantitative…
Upon doping, Mott insulators often exhibit symmetry breaking where charge carriers and their spins organize into patterns known as stripes. For high-Tc superconducting cuprates, stripes are widely suspected to exist in a fluctuating form.…