Temperature-Induced Metal-Insulator Transition in a Narrow-Band Model   with Non-Equivalent Hubbard Subbands at Half-Filling
  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. 
Leonid Didukh, Vasyl Hankevych (Ternopil State Technical University,   Ukraine)