First-order calculation of the phonon propagator of a quasi-one-dimensional electron-phonon system

Abstract

Using Green function technics the phonon propagator is calculated consistently in the first order with respect to both the square of the electron-phonon interaction matrix element and the matrix element of the Coulomb interaction of the electronic subsystem. It is shown that the so-called self-energy and exchange contributions lead to an increase of the Peierls temperatureT p in comparison with the result of the usual random-phase approximation (RPA), whereas the Umklapp processes tend to lowerT p .