Renormalized phonon spectrum in quasi-onedimensional organic crystals of tetrathiotetraceneiodide

Abstract

The metal-insulator transition in quasi-one-dimensional organic crystals of tetrathiotetraceneiodide, TTT2I3, is studied in the 2D approximation. In the frame of the crystal model two the most important hole-phonon interaction mechanisms are considered. One is similar to that of deformation potential and the other is of polaron type. The scattering on defects is also considered and it is crucial for the explanation of the transition. The renormalized phonon spectrum is calculated in the random phase approximation for different temperatures applying the method of Green functions. We show that the transition is of Peierls type. The effect of lattice distortion on the dispersion of renormalized acoustic phonons is analyzed.