Related papers: Antiferromagnetic long range order in the uniform …
We present a Schwinger-boson approach for the RVB state of the spin-1/2 Heisenberg antiferromagnet on a triangular lattice. It is shown that Gutzwiller projection of the mean-field state that includes both antiferromagnetic and…
We propose that a valence-bond-solid (VBS) order can be stabilized in certain two-dimensional antiferromagnets due to spin-lattice coupling. In contrast to the VBS state of the Affleck-Kennedy-Lieb-Tesaki (AKLT) type in which the spin $2S$…
In this work, a long-range resonating valence bond state is proposed as a variational wave function for the ground state of the $S=1/2$ antiferromagnetic Heisenberg model on the honeycomb lattice. Employing Variational Monte Carlo (VMC)…
We study the S=1 Heisenberg antiferromagnet on a spatially anisotropic triangular lattice by the numerical diagonalization method. We examine the stability of the long-range order of a three-sublattice structure observed in the isotropic…
A linear spin-wave approach, a variational method and exact diagonlization are used to investigate the magnetic long-range order (LRO) of the spin-1/2 Heisenberg antiferromagnet on a two-dimensional 1/7-depleted triangular (maple leaf)…
An investigation of the N\'eel Long Range Order (NLRO) in the ground state of antiferromagnetic Heisenberg spin system on the two-dimensional, uniform, bipartite lattice consisting of squares, hexagons and dodecagons is presented. Basing on…
We study magnetic order in the Heisenberg antiferromagnet on the checkerboard lattice, a two-dimensional version of the pyrochlore network with strong geometric frustration. By employing the semiclassical (1/S) expansion we find that…
We extend the formulation of the spin wave theory for the Kondo lattice model, which was mainly used for the ferromagnetic metallic state, to general magnetic orders including complex noncollinear and noncoplanar orders. The 1/S expansion…
We propose a Real-Space Gutzwiller variational approach and apply it to a system of repulsively interacting ultracold fermions with spin 1/2 trapped in an optical lattice with a harmonic confinement. Using the Real-Space Gutzwiller…
The ground state properties of random-exchange spin-1/2 Heisenberg antiferromagnets on the square lattice are investigated using a combination of quantum Monte Carlo simulations, exact numerical diagonalizations, and spin wave calculations.…
The Resonating Valence Bond (RVB) theory for two-dimensional quantum antiferromagnets is shown to be the correct paradigm for large enough ``quantum frustration''. This scenario, proposed long time ago but never confirmed by microscopic…
We consider a superexchange Hamiltonian, $H=-\sum_{<i,j>}(2{\bf S}_i\cdot {\bf S}_j-\frac 12)(2{\bf T}_i\cdot {\bf T}_j-\frac 12)$, which describes systems with orbital degeneracy and strong electron-phonon coupling in the limit of large…
Based on a Gutzwiller projected BCS wavefunction, it is shown that a local S=1/2 moment is present around a vacancy site (zinc impurity) in a form of staggered magnetic moments, which is a direct consequence of the short-ranged…
We study quantum antiferromagnets on two-dimensional bipartite lattices. We focus on local variations in the properties of the ordered phase which arise due to the presence of inequivalent sites or bonds in the lattice structure, using…
A variational ground state of the repulsive Hubbard model on a square lattice is investigated numerically for an intermediate coupling strength (U = 8t) and for moderate sizes (from 6 x 6 to 10 x 10). Our ansatz is clearly superior to other…
The spin-1 Heisenberg antiferromagnet on a triangular lattice with the nearest- and next-nearest-neighbor couplings, $J_1=(1-p)J$ and $J_2=pJ$, $J>0$, is studied in the entire range of the parameter $p$. Mori's projection operator technique…
We study a lattice fermion model with antiferromagnetic interactions on the three-dimensional cubic lattice. The hopping term of the Hamiltonian has a Weyl-type dispersion. We prove that the model has reflection positivity. Moreover, by…
We investigate spin and orbital states of the two-orbital Hubbard model on a square lattice by using a variational Monte Carlo method at quarter-filling, i.e., the electron number per site is one. As a variational wave function, we consider…
We study an antiferromagnetic order in the ground state of the half-filled Hubbard model on the Penrose lattice and investigate the effects of quasiperiodic lattice structure. In the limit of infinitesimal Coulomb repulsion $U \rightarrow…
The effective Hamiltonian of strongly correlated electrons on a square lattice is replaced by a renormalised Hamiltonian and the factors that renormalise the kinetic energy of holes and the Heisenberg spin-spin coupling are calculated using…