Simple formulation of the two-channel Kondo model

We reformulate the two-channel Kondo model to explicitly remove the unscattered charge degrees of freedom. This procedure permits us to move the non-Fermi-liquid fixed point to infinite coupling where we can apply a perturbative strong-coupling expansion. The fixed-point Hamiltonian involves a three-body Majorana zero mode whose scattering effects give rise to marginal self-energies. The compactified model is the N=3 member of a family of O(N) Kondo models that can be solved by semiclassical methods in the large N limit. For odd N, fermionic ``kink'' fluctuations about the N={∞} mean-field theory generate a fermionic N-body bound state which asymptotically decouples at low energies. For N=3, our semiclassical methods fully recover the non-Fermi-liquid physics of the original two-channel model. Using the same methods, we find that the corresponding O(3) Kondo lattice model develops a spin-gap and a gapless band of coherently propagating three-body bound states. Its strong-coupling limit offers a rather interesting realization of a marginal Fermi liquid.