Functional-integral approach for the doubly degenerate two-impurity problem

Abstract

The study of the nondegenerate two-impurity problem by Evenson et al. has been extended to the case of degenerate impurities using the functional-integral approach. We have used the two-orbital Hubbard model with Coulomb and exchange interactions only on the two sites-or the so-called doubly degenerate two-impurity Wolff model. It is found that for the case of two nearest-neighbor impurities with half-filled shells, the antiferromagnetic state is more favorable than the ferro- or nonmagnetic states-a result which is in agreement with the recent findings of Inagaki and Kubo for metals.