相关论文: From the double-exchange Hamiltonian to the $t-J$ …
We propose a scheme for constructing classical spin Hamiltonians from Hunds coupled spin-fermion models in the limit J_H/t \to \infinity. The strong coupling between fermions and the core spins requires self-consistent calculation of the…
The t-J model with constant t and J between any pair of sites is studied by exploiting the symmetry of the Hamiltonian with respect to site permutations. For a given number of electrons and a given total spin the exchange term simply yields…
We present a theoretical framework for evaluating effective interactions between localized spins mediated by itinerant electrons in double-exchange models. Performing the expansion with respect to the spin-dependent part of the electron…
A simple derivation of the effective spin-wave Hamiltonian for a double-exchange system with infinitely large Hund's-rule coupling is demonstrated. The formalism can be applied to models with arbitrary range of hopping as well as those with…
The effects of the charge/spin currents of conduction electrons on the dynamics of the localized spins are studied in terms of the perturbation in the exchange coupling $J_{K}$ between them. The equations of motion for the localized spins…
We report on {\it ab initio} time-dependent spin dynamics simulations for a two-center magnetic molecular complex based on time-dependent non-collinear spin density functional theory. In particular, we discuss how the dynamical behavior of…
The generalized t-J model conserving the number of double occupancies is constructed from the Hubbard model at and in the vicinity of half-filling at strong coupling. The construction is realized by a self-similar continuous unitary…
A new strongly correlated electron model is presented. This is formed by two types of sites: one where double occupancy is forbidden, as in the t-J model, and the other where double occupancy is allowed but vacancy is not allowed, as an…
A derivation of the t-J model of a highly-correlated solid is given starting from the general many-electron Hamiltonian with account of the non-orthogonality of atomic wave functions. Asymmetry of the Hubbard subbands (i.e. of ``electron''…
The t-J model is regarded as a canonical model of spin-singlet pairing induced by the {\em kinetic exchange interaction} responsible also for an antiferromagnetic ordering in the strongly correlated narrow-band systems. In the orbitally…
The t-J model in the spinless-fermion representation is studied. An effective Hamiltonian for the quasiparticles is derived using canonical transformation approach. It is shown that the rather simple form of the transformation generator…
Different scenarios of the implementation of the two-band model in strongly correlated electrons systems, including frustrated magnets, high-temperature superconductors, and Kondo lattices, are considered. The interaction of current…
The Hubbard model and the lattice Kondo model are shown to become identical in the strong-coupling limit. A departure from the strong-coupling regime produces distinct theories, however: the relevant perturbation terms give rise to either…
A new generalization of the t-J model with a nearest-neigbor hopping is formulated and solved exactly by the Bethe-ansatz method. The model describes the dynamics of spin-S fermions with isotropic or anisotropic interactions. In the case…
We present a systematic derivation of effective lattice spin Hamiltonians derived from a rotationally invariant multi-orbital Hubbard model including a term ensuring Hund's rule coupling. The Hamiltonians are derived down-folding the…
We have investigated the formation of bound state of two electrons in different kind of lattices using a t-J-U model.
The direct exchange integral and the transfer integral are calculated for the anti-bonding wave-function of the HTSC cuprates. The direct exchange integral yields a value three times larger than the indirect exchange of the t-J Hamiltonian.…
An anisotropic t-J-U model Hamiltonian is used to model electron behaviour in quasi-2d materials in the dilute limit, and as a highly simplified representation of the weakly coupled CuO2 planes of the high-Tc cuprates we model the very poor…
Several series of shallow large-size ($l \gg lattice~ spacing$) two-hole bound states are found in the two-dimensional t-J model. Their binding energies depend exponentially on the inverse value of the hole-spin-wave coupling constant.…
In this work, we study the t-J model using a two-pole approximation within the composite operator method. We choose a basis of two composite operators -- the constrained electrons and their spin-fluctuation dressing -- and approximate their…