Repulsion between Conduction Electrons as a Relevant Perturbation against the Stability of Non-Fermi-Liquid Fixed Point of Multichannel Kondo Problem

It is shown that a non-Fermi-liquid fixed point of the multichannel Kondo problem is unstable for repulsive interaction at the impurity site between conduction electrons with different flavors and the same pseudospin. The anomalous fixed point is shown, by the perturbative renormalization group argument, to move into the strong coupling region with increasing repulsion. The low-temperature properties at the so-called “Toulouse limit, are calculated by the bosonization method to show that the Fermi-liquid like behavior is recovered quickly as soon as repulsion is switched on. This result poses a question as to the reality of the non-Fermi-liquid state for the multichannel Kondo model which has been examined extensively so far.