Electron-hole asymmetry in electron systems with orbital degeneracy and correlated hopping

Microscopic models of electronic subsystems with orbital degeneracy of energy states and non-diagonal matrix elements of electron interactions (correlated hopping) are considered within the configuration-operator approach. Equations for arbitrary-temperature numerical calculation of the doublon concentration for the integer band filling $n=1$ at different forms of the model density of states are derived. The energy spectra obtained within the Green function method are discussed with special emphasis on the role of correlated hopping in transition from itinerant to localized behavior observed in vanadium Magneli phases V$_n$O$_{2n-1}$, transition-metal dichalcogenides NiS$_{2-x}$Se$_x$, fulleride A$_n$C$_{60}$ systems.