Exotic Kondo effects in electron-phonon systems

Hotta, Takashi

We theoretically predict the Kondo effect due to geometrical degree of freedom. In an electron system coupled with dynamical Jahn-Teller impurity, the angular moment of the rotational Jahn-Teller mode with clockwise and anti-clockwise directions are screened by conduction electron orbital moment. We also predict the phonon-associated Kondo effect. It is found that the Kondo effect is significantly enhanced, when Coulomb interaction is canceled by the effective attraction mediated by Holstein phonons. We discuss possible relevance of this phenomenon to the exotic Kondo behavior observed experimentally in molecular quantum dots.