Related papers: Dispersion-driven ferromagnetism in a flat-band Hu…
Ground state properties of the repulsive Hubbard model on a cubic lattice are investigated by means of the auxiliary-field quantum Monte Carlo method. We focus on low-density systems with varying on-site interaction $U/t$, as a model…
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 investigate the location and nature of the para-ferro transition of interacting electrons in dispersionless bands using the example of the Hubbard model on the Tasaki lattice. This case can be analyzed as a geometric site-percolation…
We construct a set of exact ground states with a localized ferromagnetic domain wall and an extended spiral structure in a deformed flat-band Hubbard model. In the case of quarter filling, we show the uniqueness of the ground state with a…
In order to study conditions for the appearance of ferromagnetism in a wide filling region, we investigate numerically three types of one-dimensional Lieb-ferrimagnetic Hubbard models: a periodic diamond (PD) chain, a periodic…
The Random-Field Ising Model (RFIM) has been extensively studied as a model system for understanding the effects of disorder in magnets. Since the late 1970s, there has been a particular focus on realizations of the RFIM in site-diluted…
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 study the ground-state properties of the double-chain Hubbard model coupled with ferromagnetic exchange interaction by using the weak-coupling theory, density-matrix renormalization group technique, and Lanczos exact-diagonalization…
We study a ferromagnetic instability in a single-band Hubbard model on the hypercubic lattice away from half filling. Using dynamical mean-field theory with the continuous-time quantum Monte Carlo simulations based on the segment algorithm,…
We present a certain class of two-dimensional frustrated quantum Heisenberg spin systems with multiple ring exchange interactions which are rigorously demonstrated to have quantum disordered ground states without magnetic long-range order.…
We study the influence of on-site disorder on the magnetic properties of the ground state of the infinite U 1D Hubbard model. We find that the ground state is not ferromagnetic. This is analyzed in terms of the algebraic structure of the…
This paper presents a theory of interaction-induced band-flattening in strongly correlated electron systems. We begin by illustrating an inherent connection between flat bands and index theorems, and presenting a generic prescription for…
We study the influence of on-site disorder on the magnetic properties of the ground state of the infinite $U$ Hubbard model. We find that for one dimensional systems disorder has no influence, while for two dimensional systems disorder…
Thirty years ago the Hubbard model was introduced by Gutzwiller, Hubbard and Kanamori with the main purpose of mimicking the ferromagnetism of transition metals. Soon after, Nagaoka and Thouless pointed out a basic mechanism for…
In a Hartree-Fock picture, itinerant ferromagnetism results from a competition between kinetic and exchange energy, with the magnetized state being favored at large interaction strength. In a recent paper \cite{spings} we showed that in…
Electrons in condensed matter may transition into a variety of broken-symmetry phase states due to electron-electron interactions. Applying diverse mean-field approximations to the interaction term is arguably the simplest way to identify…
As a prototype model of antiferromagnetism, we propose a repulsive Hubbard Hamiltonian defined on a graph $\L={\cal A}\cup{\cal B}$ with ${\cal A}\cap {\cal B}=\emptyset$ and bonds connecting any element of ${\cal A}$ with all the elements…
An unusual metallic phase is proven to develop in the one dimensional ionic Hubbard model, at half-filling and zero magnetization, at intermediate electron-electron repulsion $U$ when second neighbors hopping is allowed and tuned close to a…
Using a positive semidefinite operator technique one deduces exact ground states for a zig-zag hexagon chain described by a non-integrable Hubbard model with on-site repulsion. Flat bands are not present in the bare band structure, and the…
In a lattice model subject to a perpendicular magnetic field, when the lattice constant is comparable to the magnetic length, one enters the "Hofstadter regime," where continuum Landau levels become fractal magnetic Bloch bands. Strong…