It has been shown that the static spin susceptibility of the Hubbard model of correlations for a narrow band calculated in the CPA remains finite for any simple-band model and the carrier number, except possibly in the case of a precisely half filled band. We show that this statement is more general and should be true if the Hubbard model could be solved exactly within the alloy analogy approxi...

Threedifferent butrelated problemsam discussed inthiscontribution, allrelated to theso.called Anderson, Hubbard,and t-J Hamiltonians -theprototype Hamiltonians forsystemswithhighlycorrelated lectrons: (1)The relationship -basedon thewell known canonical (Schrieffer-Wolff) transformation --.betweentheAndersonmodel(inthe small.hybridization and large.Coulomb-interaction regime) and the local mome...

We calculate the density of states in the half-filled Hubbard model on a Bethe lattice with infinite connectivity. Based on our analytical results to second order in t/U , we propose a new ‘Fixed-Energy Exact Diagonalization’ scheme for the numerical study of the Dynamical Mean-Field Theory. Corroborated by results from the Random Dispersion Approximation, we find that the gap opens at Uc = 4.4...

Ferromagnetism in the two dimensional t-t ′ Hubbard model at the Van Hove density Abstract Using an improved version of the projection quantum Monte Carlo technique, we study the square-lattice Hubbard model with nearest-neighbor hopping t and next-nearest-neighbor hopping t ′ , by simulation of lattices with up to 20×20 sites. For a given R = 2t ′ /t, we consider that filling which leads to a ...

We study the Hubbard model with bond-charge interaction ~‘‘correlated hopping’’! in terms of the Gutzwiller wave function. We show how to express the Gutzwiller expectation value of the bond-charge interaction in terms of the correlated momentum-space occupation. This relation is valid in all spatial dimensions. We find that in infinite dimensions, where the Gutzwiller approximation becomes exa...

Some technical aspects of Cluster Perturbation Theory (CPT) are presented. CPT is an approximation scheme for calculating the oneparticle Green function of the Hubbard model of interacting electrons on a lattice. It proceeds by (i) dividing the lattice into identical clusters and calculating the Green function by exact diagonalization on a given cluster (ii) extending this Green function to the...

We report spectroscopic ellipsometry measurements of the anisotropy of the interband transitions parallel and perpendicular to the planes of (LaTiO3)n(LaAlO3)5 multilayers with n=1-3. These provide direct information about the electronic structure of the two-dimensional (2D) 3d{1} state of the Ti ions. In combination with local density approximation, including a Hubbard U calculation, we sugges...

A general theory of superconductivity is formulated within the thermodynamic Green function method for various types of pairing mediated by phonons, spin fluctuations, and strong Coulomb correlations in the Hubbard and t-J models. A rigorous Dyson equation for matrix Green functions is derived in terms of a self-energy as a many-particle Green function. By applying the noncrossing approximation...

The Hubbard model with additional intersite interaction ‘V ’ ( the extended Hubbard model) is investigated by the correlator projection method (CPM). CPM is a newly developed numerical method which combines the equation-of-motion approach and the dynamical mean-field theory. Using this method, properties of the extended Hubbard Model at quarter filling are discussed with special emphasis on the...