Anomalous Raman shift in the ternary fullerides with t1g states

Abstract

Raman shift dependence of charge transfer is studied in the two fulleride families of AxBa3C60 (x=0,3; A=K,Rb) and KxSm2.75C60 (x=0,3.25). It is found that the Raman spectra are essentially identical to each other for all ternary fullerides, The results show a crossover point at the boundary of t1u and t1g bands for the Raman shift dependence of charge transfer. For the t1u fullerides, the Ag(2) pinch mode follows the characteristic shift of ~6.3cm-1 per elementary charge widely observed in KxC60. The two Ag modes in t1g fullerides show a complicated behavior. An anomalous Raman shift is observed in the t1g fullerides. This anomalous Raman shift of the two Ag modes could not be explained only by charge transfer.