Related papers: Ferromagnetism in an itinerant electron system: Hu…
Using a straightforward extension of the analysis of Lieb and Wu, we derive a simple analytic form for the ground state energy of a one-dimensional Hubbard ring in the atomic limit. This result is valid for an \textit{arbitrary} number of…
The Hubbard model with strong correlations is treated in the many-electron representation of Hubbard's operators. The regions of stability of saturated and non-saturated ferromagnetism in the n-U plane for the square and simple cubic…
The influence of disorder and interaction on the ground state polarization of the two-dimensional (2D) correlated electron gas is studied by numerical investigations of unrestricted Hartree-Fock equations. The ferromagnetic ground state is…
We consider a modified version of the one-dimensional Hubbard model, the t1-t2 Hubbard chain, which includes an additional next-nearest-neighbor hopping. It has been shown that at weak coupling this model has a Luttinger liquid phase or a…
We study the mean-field phase diagram of the repulsive Hubbard model in the Lieb lattice. Far from half-filling, the most stable phases are paramagnetism for low on-site interaction $U/t$ and ferromagnetism for high $U/t$, as in the case of…
We have found the exact (factorized) ground state of a general class of ferrimagnets in the presence of a magnetic field which covers the frustrated, anisotropic and long range interactions for arbitrary dimensional space. In particular…
The Hubbard model on fcc-type lattices is studied in the dynamical mean-field theory of infinite spatial dimensions. At intermediate interaction strength finite temperature Quantum Monte Carlo calculations yield a second order phase…
We investigate the instability of the saturated ferromagnetic ground state (Nagaoka state) in the Hubbard model on various lattices in dimensions d=2 and d=3. A variational resolvent approach is developed for the Nagaoka instability both…
We study tight-binding models of itinerant electrons in two different bands, with effective on-site interactions expressing Coulomb repulsion and Hund's rule. We prove that, for sufficiently large on-site exchange anisotropy, all ground…
We construct exact ground states of interacting electrons on triangle and diamond Hubbard chains. The construction requires (i) a rewriting of the Hamiltonian into positive semidefinite form, (ii) the construction of a many-electron ground…
A novel magnetic ground state is reported for the Hubbard Hamiltonian in strained graphene. When the chemical potential lies close to the Dirac point, the ground state exhibits locally both the N\'{e}el and ferromagnetic orders, even for…
We present a simple method for the construction of exact ground states of generalized Hubbard models in arbitrary dimensions. This method is used to derive rigorous criteria for the stability of various ground state types, like the…
In this paper the spin configurations of the ground state and one- and two-electron excited states of the Hubbard model on the square lattice are studied. We profit from a general rotated-electron description, which is consistent with the…
We study the strong coupling limit of a two-band Hubbard Hamiltonian that also includes an inter-orbital on-site repulsive interaction $U_{ab}$. When the two bands have opposite parity and are quarter filled, we prove that the ground state…
We construct exact non-trivial ground states of spin-2 quantum antiferromagnets on the hexagonal lattice. Using the optimum ground state approach we determine the ground state in different subspaces of a general spin-2 Hamiltonian…
The paper presents a computational study of the ground-state properties of a quantum nanomagnet possessing the shape of a finite two-legged ladder composed of 12 spins $S=1/2$. The system is described with isotropic quantum Heisenberg model…
We study strongly correlated electrons on a kagome lattice at 1/6 and 1/3 filling. They are described by an extended Hubbard Hamiltonian. We are concerned with the limit |t|<<V<<U with hopping amplitude t, nearest-neighbor repulsion V and…
The microscopic basis for the stability of itinerant ferromagnetism in correlated electron systems is examined. To this end several routes to ferromagnetism are explored, using both rigorous methods valid in arbitrary spatial dimensions, as…
We carry out \textit{ab initio} study of ground state phase diagram of spin-1/2 cold fermionic atoms within two-fold degenerate $p$-band of an anisotropic optical lattice. Using the Gutzwiller variational approach, we show that a robust…
The properties of the ground state and excitations of a four-component Hubbard-like model are studied by the Lieb-Schultz-Mattis approach. It is proven rigorously that the ground state of the model is nondegenerate and excitations are…