Glass transition in charge-density-wave systems o-TaS3 and K0.3MoO3

Abstract

We present experimental evidence for the glass transition in charge density wave (CDW) superstructure of two quasi one-dimensional systems, o-TaS3 and K0.3MoO3. Low frequency dielectric response of both systems exhibits typical glass-like phenomenology, featuring the splitting of the relaxational spectrum into two processes on decreasing the temperature and the subsequent freezing of primary or a process at finite temperature of glass transition Tg. Below Tg secondary, or β process becomes dominant. Activation energies obtained from the temperature evolution of the characteristic relaxation times of a and β processes correspond to the activation energies of the temperature evolution of the DC conductivity above and below Tg respectively. The results are discussed in respect to the relevant theories of low frequency CDW dynamics, with the emphasis on the Coulomb hardening of CDW in absence of screening by free carriers. An attempt to understand observed differences in freezing of CDW in o-TaS3 and K0.3MoO3 is made.