Reduction Factors for the Jahn-Teller Effect in Solids

Abstract

In the linear Jahn-Teller effect of an electronic $E$ state, we report on the distinction between coupling with one set of doubly degenerate vibrational modes, and coupling with several such sets of different frequencies (the multimode Jahn-Teller effect) as is the case for an impurity in a solid. Whereas the combination of the reduction factors $2q-p$ is exactly unity in the former case, it is shown to be less than unity in the latter. Also, the value of $q$ may decrease below ½.