Jahn-Teller coupling and double exchange in the two-site Van Vleck-Kanamori model

Abstract

The effect of the dynamical Jahn-Teller coupling on the Anderson-Hasegawa double exchange (DE) in the manganites is studied in a two-site model taking into account the double degeneracy of the eg orbitals and their coupling to the three MnO6 vibrational modes (Q1 , Q2 , and Q3). Both exact diagonalization and the Lang-Firsov approach are used. We find that coupling to the Q2 and Q3 modes reduces the DE, while the Q1 mode is ineffective. The isotope dependence of the DE interaction is consistent with recent experiments.