NONPOLYNOMIAL PHONON ACTION FOR A DIMER WITH ONE-ELECTRON

The partition function of a dimer with one electron, interacting with two local Einstein phonons, is reduced to the pure phonon partition fu nction. It is investigated analytically in the coherent-state path-int egral representation in order to recognize the competition between ele ctron hopping and electron-phonon interaction. The non-polynomial term in the phonon action, promoted by electron hopping, is deduced. The l ow-temperature resonance decoupling between electron and phonon system s destroys the low-temperature tendency of electron localization in th e case of small hopping and large electron-phonon coupling. The compar ison with polaronic theory is completed.