Glass transition in charge-density-wave systems o-TaS ₃ and K _0.3MoO ₃

Abstract
We present experimental evidence for the glass transition in charge density wave (CDW) superstructure of two quasi one-dimensional systems, o-TaS ₃ and K _0.3MoO ₃. 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 T . Below T secondary, or process becomes dominant. Activation energies obtained from the temperature evolution of the characteristic relaxation times of a and processes correspond to the activation energies of the temperature evolution of the DC conductivity above and below T 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-TaS ₃ and K _0.3MoO ₃ is made.