INTERPLAY OF JAHN-TELLER EFFECT AND KONDO EFFECT FOR ORBITALLY DEGENERATE IMPURITY IONS

Impurity ions with an orbitally degenerate ground-state electronic con figuration embedded in metals are subject to both the Kondo effect and the Jahn-Teller instability. While increasing the Jahn-Teller couplin g one passes from the region of parameters where perturbation theory i s applicable, through a complicated intermediate region, to a region w here phonons, localized electrons, and conduction electrons form a coh erent state.