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

Due to the frequent presence of a Berry phase, in most cases of dynamical JahnTeller systems the symmetry of the ground state is the same as that of the electronic state. However, the H ⊗ h icosahedral case, relevant for the physics of fullerene ions, provides a first example of linear coupling leading, at strong coupling, to a change in symmetry of the ground state to a totally symmetric nondegenerate state. We generalize this observation and show through detailed examples that the absence of a Berry phase can, but does not necessarily, lead to a nondegenerate ground state.