材料期刊网

Influences of the squeezing-antisqueezed effect of phonons arising from polaron motion on the ground state in strongly coupled electron-phonon systems with high and low electron-densities were studied by a new state ansatz including the correlated effects among displacement and squeezing of phonons and polarons in the Holstein model. The squeezing-antisqueezed effect caused significant decrease of the ground state energy of the systems and increase of the binding energy of the polarons appeared in the systems. Therefore the stabilities of the polaron and of the systems are enhanced simultaneously. The results obtained show that the new state ansatz is very relevant and accurate for the nonadiabatically coupled electron-phonon systems, especially in strongly coupling and large squeezing cases. (C) 2000 Elsevier Science Ltd. All rights reserved.