VIBRATIONAL PROPERTIES OF THE CDW CONDENSATE IN THE QUASI-ONE-DIMENSIONAL CONDUCTOR (TASE4)(2)I - NUMERICAL AND EXPERIMENTAL-STUDY

We report on the numerical and experimental study of the vibrational s pectrum of the charge-density-wave (CDW) conductor (TaSe4)(2)I. The mi croscopic mechanism accounting for the giant IR peak at frequencies ab out similar to 40 cm(-1) in the (TaSe4)(2)I is proposed. The mechanism is based on an assumption about dynamical charge transfer between adj acent CDW periods accompanying their vibration in corresponding normal mode with wave vector equal to that of superstructure. The mechanism is consistent also with the increase in the IR intensity of the peak o bserved experimentally when heating the (TaSe4)(2)I crystal above the Peierls transition temperature T-p = 261 K. Critical index of the Peie rls transition order parameter determined from the temperature depende nce of the phase phonons intensity is found to be about 0.17, consiste nt with the results of X-ray experiments. (C) 1998 Elsevier Science B. V. All rights reserved.