Fononii оn apropierea tranziţiei de fază peierls оn cristale organice cvasiunidimensionale

Abstract

Many quasi-one-dimensional organic crystals, known as synthetic metals at room temperature, become insulators when the temperature decreases, due to a Peierls transition. In the crystals withhalf filled conduction band the dimerization of lattice takes place at some critical temperature that determines the phase transition. The equation for phonon Green function is deduced in the random phase approximation as a sum of diagrammatic ladder series of close loops of electronicGreen functions. A more complete crystal model is used which takes into account two main electron-phonon interactions. The dispersion equation for renormalized phonons is obtained and the polarization operator is calculated. The phonon spectra in dependence of temperature and crystal parameters are modeled. The critical temperature of transition is calculated.