Role of the superexchange interaction in magnetic transition and polaron crossover

摘要

0The Hubbard-Holstein model is studied including double-exchange interaction and superexchange interaction using a variational phonon basis obtained through the modified Lang-Firsov transformation followed by the squeezing transformation. The kinetic energy, polaron crossover and magnetic transition are investigated as a function of electron-phonon (e-ph) coupling and electron concentration for different values of antiferromagnetic superexchange interaction (J) between the core spins. The polaron crossover, magnetic transition and the suppression of ferromagnetic transition with J are discussed for the model. (C) 2003 Elsevier B.V. All rights reserved.