Single-band Hubbard model at criticality of the metal-insulator transition is studied using approximations derived from parquet theory. It is argued that only the electron-hole and interaction two-particle channels in the parquet algebra are relevant. A scheme is proposed how to reduce the parquet equations to a manageable form the complexity of which is comparable with single-channel approxima...

Within the time-dependent Gutzwiller approximation for the Hubbard model we compute the magnetic fluctuations of vertical metallic stripes with parameters appropriate for La(1.875)Ba(0.125)CuO(4) (LBCO). For bond- and site-centered stripes the excitation spectra are similar, consisting of a low-energy incommensurate acoustic branch which merges into a "resonance peak" at the antiferromagnetic w...

We have used an exact diagonalization technique to study the stability of the t − J-Holstein and Hubbard-Holstein models under the influence of the electron-phonon interaction. Previous results have been obtained using frozen-phonon technique or introducing only a few dynamical phonon modes due to the large Hilbert space. To check these results we have done exact diagonalization in a small clus...

With an increasing complexity of nanoscopic systems and the modeling thereof, new theoretical tools are needed for a reliable calculation of complex systems with strong electronic correlations. To this end, we propose a new approach based on the recently introduced dynamical vertex approximation. We demonstrate its reliability already on the one-particle vertex (i.e., dynamical mean field theor...

In order to investigate charge ordering phenomena under electric field, static nonequilibrium Hartree approximation (SNHA) method is formulated on the basis of the nonequilibrium Green’s functions introduced by Keldysh. By applying the SNHA to the 3/4-filling extended Hubbard model on anisotropic triangular lattice, we study the stabilities and amplitudes of 3-fold and horizontal charge orders ...

Using the dynamical mean-field approximation we investigate the formation of excitonic condensate in the two-band Hubbard model in the vicinity of the spin-state transition. With temperature and band filling as the control parameters we realize all symmetry allowed spin-triplet excitonic phases, some exhibiting a ferromagnetic polarization. While the transitions are first order at low temperatu...

The spectral functions of the one-band half-filled 1D Hubbard chain are calculated using exchange-correlation potential formalism developed recently. is adopted from exact derived dimer. Within an approximation in which full Green function replaced by a non-interacting one, can be analytically. Despite simplicity approximation, resulting spectra favorable agreement with more accurate results ob...

We present a theoretical study on the response properties to an external electric field of strongly correlated one-dimensional metals. Our investigation is based on the recently developed Bethe ansatz local-density approximation BALDA to the density functional theory formulation of the Hubbard model. This is capable of describing both Luttinger liquid and Mott-insulator correlations. The BALDA ...

We examine the effects of a van Hove singularity (vHs) in the density of states (DOS) of a two dimensional, t− t−U Hubbard model within the local approximation. Within our approximation the non-interacting Fermi surface is always retained away from half-filling; and we find that the vHs in the DOS survives, and for hole doping is nearly ”pinned” to the Fermi level due to the enhancement of the ...