Model of electronic subsystem of Fabre salts (TMTTF)₂X and Bechgaard salts (TMTSF)₂X has been studied theoretically within Green function equation of motion approach with special attention to microscopical mechanism for antiferromagnetic order stabilization and pseudogap formation in the electronic spectrum. Conditions for pseudogap opening in the spectrum and anomalies in dispersion of current carriers are determined. Next-nearest-neighbor hopping is shown to break the perfect nesting property and destabilize antiferromagnetic state. On the basis of these results, experimental phase diagrams for quasi-one-dimensional organic superconductors (TMTSF)₂X and (TMTTF)₂X are interpreted.

A model for organic quasi-one-dimensional conductors (TMTTF)₂X and (TMTSF)₂X is considered. The anisotropic\ud character of these compounds is modelled by two different hopping parameters: t between nearest\ud neighbors (NN) in a chain of tetramethyl-tetrathiafulvalene (TMTTF) or tetramethyl-tetraselenfulvalene\ud (TMTSF) molecules and t' between the chains (NNN - between next nearest neighbors). Taking into account\ud the correlated hopping of electrons allows us to describe the effect of site occupancy on hopping processes.\ud In a regime of strong intraatomic correlation, high energy processes are cut off by applying two successive\ud canonical transformations. An effective model is obtained for concentration of electrons n < 1 which contains\ud kinetic exchange terms of antiferromagnetic (AF) nature. Oppositely, NNN hopping and correlated hopping\ud disfavor the AF order. The energy spectrum of the effective model is calculated. Application of the obtained\ud results to quasi-one-dimensional conductors is discussed

In this paper we study the ground state ferromagnetism in a doubly orbitally degenerate Hubbard model generalized by taking into account correlated hopping and inter-atomic exchange interaction. We find that an important role in the stabilization of ferromagnetism is played by the intra- and inter-atomic exchange interactions as well as correlated hopping, which allows us to describe the metallic paramagnetic-ferromagnetic transition with a realistic relationship between the above-mentioned exchange interactions. The expression for magnetization and the criterion of ferromagnetic ground state stability are derived. The obtained results are compared with some experimental data for magnetic materials.

The effect of external magnetic field h on a static conductivity of MottHubbardud material which is described by the model with correlated hoppingud of electrons has been investigated. By means of canonical transformation,ud the effective Hamiltonian is obtained which takes into account strongud intra-site Coulomb repulsion and correlated hopping. Using a variant ofud generalized Hartree-Fock approximation the single-electron Green functionud and quasiparticle energy spectrum of the model have been calculated.ud The static conductivity σ has been calculated as a function of h, electronud concentration n and temperature T . The correlated hopping is shown toud cause the electron-hole asymmetry of transport properties of narrow bandud materialsВ статтi досліджено вплив зовнішнього магнiтного поля на статичнуud провідність Мотт-Габбардiвського матеріалу в моделi з корельованим переносом електронів. Ефективний гамiльтонiан отримано iзud застосуванням канонічного перетворення та з використанням узагальненого наближення Гартрi-Фока знайдено функцію Грiна i енергетичний спектр. Провідність розрахована як функція магнiтного поля, концентрації електронів та температури