Competition between Coqblin-Schrieffer and local exchange interactions in Kondo systems by the perturbative renormalization group

A model which accounts for the competition between hybridization and local exchange (LE) interactions in anomalous Ce systems is proposed. In this model a localized magnetic moment j(f)=5/2 has an antiferromagnetic Coqblin-Schrieffer (CS) coupling with l=3 conduction electrons partial waves, due to hybridization, and a contact coupling with l=0 partial waves due to the LE interaction. The last term breaks the SU(N) symmetry of the CS model. Using the perturbative renormalization group, we show that the SU(N) ground state of the CS model remains the ground state even in the presence of a LE interaction stronger than the CS coupling. We discuss the effect of the LE on the Kondo temperature. Moreover, when the LE coupling reaches a critical value the system has a non-Fermi-liquid non-SU(N) ground state, and when it is stronger than the critical value the system falls into an undercompensated Kondo state. [S0163-1829(99)00210-6].