Influence of irradiation-induced defects on the properties of charge density wave system TaS3

In charge density wave (CDW) systems the interaction of CDW superstructure with the random defects introduces the localized low energy states which are responsible for various glass-like phenomena. In particular, the cooperative dynamics of phase coherent domains leads to the glass transition [1] on the level of the CDW superstructure. The domain size, which depends on the amount of disorder, is supposed to play an important role in determination of the glass transition. In order to test this assumption we have investigated the dielectric response and the nonlinear conductivity of a number of o-TaS3 samples irradiated with protons in a wide range of irradiation doses. Our results demonstrate that the increase of disorder with irradiation leads to the strong decrease of the low frequency dielectric response corresponding to the high temperature relaxation process ( process of [1]), but does not affect substantially the low temperature, or  process. Moreover, the relaxation time of  process increases faster at low temperatures, indicating the increase of the glass transition temperature. At sufficiently high irradiation doses  process in not detectable any more, consistent with prior results for Nb doped samples [2]. The threshold field ET, on the other hand, increases with irradiation. This increase is non-uniform and it is the most pronounced in the temperature region where the  process dominates. This leads to the quantitative changes in the temperature dependence of ET, where a characteristic minimum disappears at high irradiation doses. Nevertheless, the inverse proportionality of ET and the dielectric constant still remains. [1] D. Starešinić, K. Biljaković, W. Brütting, K. Hosseini, P. Monceau, H. Berger, F. Levy, Phys. Rev. B 65, 165109 (2002) [2] D. Starešinić, K. Biljaković, P. Lunkenheimer, A. Loidl, J. C. Lasjaunias, J. Phys. IV France 131, 191 (2005)