Physica Status Solidi B, Basic Research vol:242 issue:2 pages:211-217
The interplay between Jahn-Teller effect and electron correlation in alkali doped fullerides is reviewed for compounds from both sides of Mott-Hubbard transition. In Mott-Hubbard fullerides the nature of low-lying excitations strongly depends on the symmetry of the compounds, corresponding either to spin (Heisenberg) type for low symmetry compounds (K-3(NH3)C-60) or to spin-vibronic superexchange for cubic compounds (Li-3(NH3)(6)C-60). In the band fullerides (A(3)C(60), A(4)C(60), A = K, Rb) the Jahn-Teller effect leads to a splitting of the cubic band structure in three or two unequally populated subbands (orbital disproportionation), which gives rise to a number of features in the spectroscopy of these compounds. (c) 2005 WILEY-VCH Verlag GmbH T Co. KGTA, Weinheim.