THE INFLUENCE OF THE PEIERLS PHASE TRANSITION UPON THE SPECTRUM OF PHONONS IN THE QUASI-ONE-DIMENSIONAL ORGANIC CRISTAL TTF-TCNQ

Anatolie CASIAN*, Silvia ANDRONIC, Viorel DUŞCIAC *Universitatea Tehnică din Moldova Universitatea de Stat din Moldova

Abstract

This paper has studied the variation of the phonon spectrum in the quasi-one-dimensional organic crystal TTF-TCNQ in the vicinity of the Peierls transition. The Peierls critical temperature has been determined as well. For this purpose the model of the quasi-one-dimensional crystal that takes into account two mechanisms of electron-phonon interaction has been used. To determine the renormalized spectrum of acoustic phonons the retarded Green function of the phonons has been calculated and the technique of Feynman diagrams for the Green function dependent on temperature has been applied. The numerical calculations and the dependences of the renormalized spectrum of phonons for various parameters of the crystal at various temperatures have been presented. Keywords: Peierls transition, quasi-one-dimensional crystal, organic crystal, phonon spectrum, crystal TTF-TCNQ.