title: Spin-vibronic superexchange in Mott-Hubbard fullerides.
abstract: In the Mott-Hubbard cubic fulleride Li3(NH3)6C60 the superexchange energy is found to be much smaller than the rotational quantum for Jahn-Teller deformations at fullerene sites. This gives rise to a new type of superexchange interaction involving threefold degenerate vibronic ground states of C3-60 ions. In contrast with spin-orbital models, the spin-vibronic superexchange can be only antiferromagnetic and shows a significant vibronic reduction of the superexchange amplitude, in agreement with magnetic susceptibility data. As a function of the transfer parameters, two quadrupolar fully dynamical vibronic orders with quenched vibronic moments on sites develop in the ground state.
authors.affiliation: Department of Chemistry, University of Leuven, Celestijnenlaan 200F, B-3001 Leuven, Belgium.
authors.forename: L F
authors.initials: LF
authors.lastname: Chibotaru