Existence of a two-channel Kondo regime for tunneling impurities with resonant scattering

Dynamical tunneling systems have been proposed earlier to display a two-channel Kondo effect, the orbital index of the particle playing the role of a pseudospin in the equivalent Kondo problem, and the spin being a silent channel index. However, as shown by Aleiner et al. Phys. Rev. Lett. 86 2629 (2001), the predicted two-channel Kondo behavior can never be observed in the weak coupling regime, where the tunneling induced splitting of the levels of the tunneling system always dominates the physics. Here we show that the above scenario changes completely in the strong coupling regime, where—as a nonperturbative analysis reveals—the two-channel Kondo regime can easily be reached. We show that tunneling systems end up quite naturally in this regime if the conduction electrons are scattered by resonant scattering off the tunneling impurity, and we also speculate about the possible origins of such a resonant scattering.