A study of the polaronic band width and the small-to-large-polaron transition in a many-polaron system

Abstract

A short-range electron-phonon (e-ph) interaction is considered in a many-electron narrow-band system where electron hopping is comparable with the phonon frequency. The behaviour of the polarons as a function of the e-ph interaction strength and the electron concentration is studied within the framework of the mean-field theory using a modified Lang-Firsov transformation and two-phonon coherent states of the phonon subsystem. The small-to-large-polaron transition and the effect of the two-phonon coherent state are discussed.