Overscreened single-channel Kondo problem

We consider the single-channel Kondo problem with the Kondo coupling between a spin (Formula presented) impurity and conduction electrons with spin (Formula presented). These problems arise as multicritical points in the parameter spaces of two-and higher-level tunneling systems and some impurity models of heavy fermion compounds. In contrast to the previous Bethe-ansatz conjectures, it turns out that the dynamics of the spin sector is the same as that of a spin-(Formula presented) impurity coupled to (Formula presented) channels of spin-½ electrons with (Formula presented). As a result, for (Formula presented), the system shows non-Fermi-liquid behavior with the same exponents for the thermodynamic quantities as those of the (Formula presented)-channel Kondo problem. However, both the finite-size spectrum and the operator content are different due to the presence of the other sectors and can be obtained by conformal field theory techniques.