Related papers: Band antiferromagnetism in a two-band model for ir…
We investigate multi-band Hubbard models for the three iron 3$d$-$t_{2g}$ bands and the two iron 3$d$-$e_g$ bands in ${\rm La O Fe As}$ by means of the Gutzwiller variational theory. Our analysis of the paramagnetic ground state shows that…
The Mott-Hubbard metal-insulator transition is investigated in a two-band Hubbard model within dynamical mean-field theory. To this end, we use a suitable extension of Wilson's numerical renormalization group for the solution of the…
We introduce Gutzwiller wave functions for multi-band models with general on-site Coulomb interactions. As these wave functions employ correlators for the exact atomic eigenstates they are exact both in the non-interacting and in the atomic…
We examine the orbital and magnetic order of the two orbital Hubbard model within dynamical mean field theory. The model describes the low energy physics of a partially filled $e_g$-band as can be found in some transition metal compounds.…
Using a slave boson representation of multi-band Hubbard models, we investigate a two-band model relevant to layered perovskites in the vicinity of half-filling. Beside the strong influence of the Hund's rule coupling, we obtain that the…
We have generalized the Gutzwiller method to the cases of n=>2 correlated bands and report studies on a degenerate two-band model with Hund's rule type on-site interactions. At half band filling the metal-insulator transitions are usually…
The importance of Hund's rule coupling for the stabilization of itinerant ferromagnetism is investigated within a two-band Hubbard model. The magnetic phase diagram is calculated by finite-temperature quantum Monte Carlo simulations within…
We study a two-orbital spin model to describe (pi,0) stripe antiferromagnetism in the iron pnictides. The "double-spin" model has an on-site Hunds's coupling and inter-site interactions extending to second neighbors (inter- and…
Electron correlations in the two-orbital Hubbard model at half-filling are investigated by combining dynamical mean field theory with the exact diagonalization method. We systematically study how the interplay of the intra- and inter-band…
To understand effects of orbital degeneracy on magnetism, in particular effects of Hund's rule coupling, we study the two-orbital Hubbard model on a square lattice by a variational Monte Carlo method. As a variational wave function, we…
We use the Gutzwiller variational theory to calculate the ground-state phase diagram and quasi-particle bands of LaOFeAs. The Fe3d--As4p Wannier-orbital basis obtained from density-functional theory defines the band part of our eight-band…
Strongly correlated materials feature multiple electronic orbitals which are crucial to accurately understand their many-body properties, from cuprate materials to twisted bilayer graphene. In such multi-band models, quantum interference…
Multi-band Gutzwiller-correlated wave functions reconcile the contrasting concepts of itinerant band electrons versus electrons localized in partially filled atomic shells. The approximate evaluation of these variational ground states…
We study the correlation effects on the electronic structure and spin density wave order in Fe-pnictides. Using the multiorbital Hubbard model and Gutzwiller projection, we show that nonperturbative correlation effects are essential to…
Spin wave excitations and stability of the (0,pi) ordered SDW state are investigated within the minimal two-band model for iron pnictides including a Hund's coupling term. The SDW state is shown to be stable in two distinct doping regimes…
We investigate a possibility of Hund's metal behavior in the Hubbard model with asymmetric density of states having peak(s). Specifically, we consider the degenerate two-band model and compare its results to the five-band model with…
Keeping nickel, cobalt and iron in mind, we investigate the origin of the itinerant ferromagnetism. In so doing, we generalize the Gutzwiller approximation. In that,we take account of the effect of the band degeneracy and the Hund's-rule…
This paper is a brief review of our recent studies concerning on magnetism and electronic states of lattice systems with Hund coupling. First we examined the effectiveness of the Hund coupling in realizing ferromagnetism in the doubly…
We use the Gutzwiller Density Functional Theory to calculate ground-state properties and bandstructures of iron in its body-centered-cubic (bcc) and hexagonal-close-packed (hcp) phases. For a Hubbard interaction $U=9\, {\rm eV}$ and…
We explore the ground-state properties of the two-band Hubbard model with degenerate electronic bands, parametrized by nearest-neighbor hopping $t$, intra- and inter-orbital on-site Coulomb repulsions $U$ and $U^\prime$, and Hund coupling…