Effect of the peierls transition on the phonon spectrum in TTF-TCNQ crystals

Abstract

It was demontrated theoretically that organic crystals of TTF-TCNQ are good candidates for thermoelectric materials. Because not all parameters of these materials are known, it is necessary to determine some of them. We’ll use the Peierls transition phenomenon for this aim. In this work we study how the photon spectrum varies in quasi-one-dimensional organic crystal TTF-TCNQ close to Peierls transition. In the frame of the model, there are considered two the most important electron-phonon interactions. The equation for phonon Green function is deduced in the random phase approximation as a sum of diagrammatic ladder series of close loops of electronic Green functions. The renormalized phonon spectrum is presented for the Peierls model (with one molecule in an unit cell), and for the real model of the crystal (with two molecules in an unit cell).