Title: ENERGY SPECTRUM OF A DOUBLY ORBITALLY DEGENERATE MODEL WITH NON-EQUIVALENT SUBBANDS
Author(s): L.Didukh, Yu.Skorenkyy, Yu.Dovhopyaty (Ternopil State Technical University, Department of Physics, 56 Rus'ka Str., 46001 Ternopil, Ukraine, E-mail: didukh@tu.edu.te.ua)

In the present paper we investigate a doubly orbitally degenerate narrow-band model with correlated hopping. The model peculiarity takes into account the matrix element of electron-electron interaction which describes intersite hoppings of electrons. In particular, this leads to the concentration dependence of the effective hopping integral. The cases of the strong and weak Hund's coupling are considered. By means of a generalized mean-field approximation the single-particle Green function and quasiparticle energy spectrum are calculated. Metal-insulator transition is studied in the model at different integer values of the electron concentration. Using the obtained energy spectrum we find criteria of metal-insulator transition.

Key words: narrow energy bands, orbital degeneracy, metal-insulator transition, correlated hopping
PACS: 71.28.+d, 71.27.+a, 71.10.Fd, 71.30.+h