engleski

Charge density wave – glass in the superstructure

Low frequency relaxation dynamics of charge density wave (CDW) superstructure in several quasi one-dimensional systems bears striking resemblance with canonical glass forming systems. Wide temperature and frequency range dielectric spectroscopy of semiconducting CDW systems o-TaS3 and K0.3MoO3 demonstrates the splitting of the relaxation spectrum in two processes, slower alpha and faster beta, on decreasing the temperature and subsequent freezing of alpha process at finite, glass transition temperature Tg. Maximum observed in thermally stimulated discharge current at Tg corroborates the freezing of alpha process. Our results are explained in the model of cooperatively relaxing CDW domains of coherent phase coupled through electrostatic interaction. At lower temperatures, in the absence of free carrier screening, this leads to the freezing of the elastic degrees of freedom, i.e. alpha process. The remaining beta process represents the dynamics of topological defects developed on the domain boundaries. We draw the parallels between this microscopic model and the phenomenological model of supercooled liquids, bearing in mind micrometer-size characteristic length scales of CDW domain.

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