Slave-Boson Functional-Integral Approach to the Hubbard Model with Orbital Degeneracy

Abstract

A slave-boson functional-integral method has been developed forthe Hubbard model with arbitrary, orbital degeneracy D.Its saddle-point mean-field theory is equivalent to the Gutzwiller approximation, as in the case of single-band Hubbard model.Our theory is applied to the doubly degenerate (D=2) model, whose paramagnetic state has been studied by numerical calculations.The effect of the exchange interaction on the metal-insulator (MI)transition is discussed.The critical interaction for the MI transition is analytically calculated as functions of orbital degeneracy and electron occupancy.