A new two - pole approximation in the Hubbard model . Metal - insulator transition
نویسنده
چکیده
A new two-pole approximation in the Hubbard model. Two-pole approaches in the Hubbard model [1] and the Hubbard bands conception (being the consequence of a two-pole approximation) have been useful for understanding of the peculiarities of electric and magnetic properties of narrow-band materials [1]-[13]. However within the framework of two-pole approaches there are series of issues, in particular the problem of metal-insulator transition description. In this paper a new two-pole approximation, which allows to describe the transition from an insulating state to a metallic one at increase of bandwidth, and also the observable in some compounds transition from a metalic state to an insulating one with increasing temperature, is presented. Let us take the operators of creation and destruction of an electron with spin σ (σ =↓, ↑) on i-site in the form:
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