Showing papers by "Ternopil Ivan Pul'uj National Technical University published in 1998"
TL;DR: In this paper, the metal-insulator transition in a generalized Hubbard model with correlated hopping at half-filling and zero temperature was studied and the expressions for energy gap width and the concentration of polar states (holes or doublons) were obtained.
Abstract: In the present paper metal-insulator transition is studied in a generalized Hubbard model with correlated hopping at half-filling and zero temperature. Single-particle Green function and energy spectrum of electron system are calculated. The expressions for energy gap width and the concentration of polar states (holes or doublons) are obtained. The conditions for metallic and insulating states are found.
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TL;DR: In this article, a model for description of materials with narrow energy bands is proposed and it is shown that in narrow-band materials electron-hole symmetry is absent in contrast to the Hubbard model.
Abstract: A model for description of materials with narrow energy bands is proposed. It is shown that in narrow-band materials electron-hole symmetry is absent in contrast to the Hubbard model. In this paper metal-insulator transition is studied. The obtained results are compared with experimental data for narrow-band materials. Some specific narrow-band effects are discussed.
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TL;DR: In this paper, the authors studied metal-insulator transition in a generalized Hubbard model with correlated hopping at half-filling and zero temperature and showed that metal-to-insulators can undergo transition from a metallic state to an insulating state with the increase of temperature.
Abstract: In the previous papers (Journ. of Phys. Stud. 2, 362 (1998); cond-mat/9811213) we have studied metal-insulator transition in a generalized Hubbard model with correlated hopping at half-filling and zero temperature. The present paper is devoted to a further study of metal-insulator transition in this model,in particular, an investigation of temperature-induced metal-to-insulator transition. The dependence of energy gap on concentration of doubly occupancy leads to increasing energy gap width with increase of temperature. Thus narrow-band system can undergo transition from a metallic state to an insulating state with the increase of temperature. For some values of intra-atomic Coulomb repulsion $U$ and $w_0$ ($w_0$ is half-bandwidth) we find the values of temperature when narrow-band material undergoes transition from a metallic state to an insulating state. We show that at given $U/w_0$ metal-insulator transition in model with non-equivalent Hubbard sub-bands can occur at smaller temperature than in the Hubbard model. It testifies on the fact that taking into account of correlated hopping is important for a consideration of metal-insulator transition problem.