Related papers: Orbital order, stacking defects and spin-fluctuati…
We consider the exchange Hamiltonian H_ST = -J Sum_{<rr'>} (2 S_r S_r' - 1/2) (2 T_r T_r' - 1/2) describing two isotropic spin-1/2 Heisenberg antiferromagnets coupled by a quartic term on equivalent bonds. The model is relevant for systems…
We study the classical version of the 120-degree model. This is an attractive nearest-neighbor system in three dimensions with XY (rotor) spins and interaction such that only a particular projection of the spins gets coupled in each…
Microscopic models of electronic subsystems with orbital degeneracy of energy states and non-diagonal matrix elements of electron interactions (correlated hopping) are considered within the configuration-operator approach. Equations for…
Using the multiband $d-p$ model and unrestricted Hartree-Fock approximation we investigate the electronic structure and spin-orbital order in three-dimensional MnO$_3$ lattice such as realized in LaMnO$_3$. The orbital order is induced and…
In view of recent controversy regarding the orbital order in the frustrated spinel ZnV2O4, we analyze the orbital and magnetic groundstate of this system within an ab initio density functional theory approach. While LDA+U calculations in…
We solve the orbitally degenerate two-band Hubbard model within dynamical mean field theory and map out the instabilities to various symmetry-broken phases based on an analysis of the corresponding lattice susceptibilities. Phase diagrams…
The doping and temperature dependent optical conductivity spectra of the quasi-two-dimensional Ca_{2-x}Sr_xRuO_4 (0.0=<x=<2.0) system were investigated. In the Mott insulating state, two electron correlation-induced peaks were observed…
We report on first principles Self-Interaction Corrected LSD (SIC-LSD) calculations of electronic structure of LaMnO$_{3}$ in the cubic phase. We found a strong tendency to localisation of the Mn $e_{g}$ electron and to orbital ordering. We…
The collective behavior of correlated electrons in the VO$_2-$interface layer of LaVO$_3$/SrTiO$_3$ heterostructure is studied within a quarter-filled $t_{2g}$-orbital Hubbard model on a square lattice. We argue that the ground state is…
Nonequilibrium control of electronically ordered hidden phases may lead to the development of ultrafast switches and memory devices. In this study, we demonstrate tunable hidden orders in the photo-doped two-orbital extended Hubbard model.…
It is shown that in the presence of strong magnetic fields, spin-orbit scattering causes a sharp increase in the effective density of states in the variable-range hopping regime when temperature decreases. This effect leads to an…
We start from an effective Hamiltonian for Ru ions in a square lattice, which includes the on-site interactions between t_2g orbitals derived from Coulomb repulsion, and a tetragonal crystal-field splitting. Using perturbation theory in the…
The electronic properties of excitonic insulators have been examined precisely in recent years. Pictures of exciton condensation may be applied to the spin-state transition observed in perovskite cobalt oxides. We examine the crystal-field…
We investigate the collective behavior of orbital angular momentum in the spin ferromagnetic state of a Mott insulator with $t_{2g}$ orbital degeneracy. The frustrated nature of the interactions leads to an infinite degeneracy of classical…
The nondegenerate two-orbital Hubbard model is studied within the dynamic mean-field theory to reveal the influence of two important factors, i.e. crystal field splitting and interorbital hopping, on orbital selective Mott transition (OSMT)…
We analyze the role of orbital degeneracy in possible magnetic and orbital instabilities by solving exactly a two-site molecule with two orbitals of either $e_g$ or $t_{2g}$ symmetry at quarter-filling. As a generic feature of both models…
Two-magnon Raman scattering intensity is obtained for two-dimensional spin-1/2 antiferromagnets in presence of hopping disorder. A consistent mode assignment scheme is prescribed which essentially establishes a correspondence between the…
We have analyzed the experimental evidence of charge and orbital ordering in La0.5Sr1.5MnO4 using first principles band structure calculations. Our results suggest the presence of two types of Mn sites in the system. One of the Mn sites…
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…
We study the zero-temperature spin fluctuations of a two-dimensional itinerant-electron system with an incommensurate magnetic ground state described by a single-band Hubbard Hamiltonian. We introduce the (broken-symmetry) magnetic phase at…