Berry-phase and Symmetry of the Ground State in Dynamical Jahn-teller Systems

We show through selected examples, relevant to the physics of fullerene ions, that the presence of a Berry phase in dynamical Jahn-Teller systems does not guarantee the degeneracy of the ground state, contrary to what previously believed. Moreover, we introduce a new class of JahnTeller systems with no Berry phase, as a generalization of the basic icosahedral H ⊗ h case.