On the low temperature dependence of the threshold field of CDW in NbSe3: effect of uniaxial stress

We investigated the effect of uniaxial stress on the threshold field in NbSe3. For the upper CDW, we show a clear separation of the threshold field into two additive components, ET'(t) and ET''(t, ε) where t = T/TP. The impurity dependence of ET''(t, ε) indicates that this term is the impurity or bulk pinning term. ET''(t, ε) shows strong temperature dependence near Tp but saturates to a t independent minimum below t ∼ .85. On the other hand, the term ET'(t) takes nearly all the temperature dependence of the ET below tmin; it varies as Eo exp[-t/to]. Comparison with contact effect and size effect data by other researchers indicates that Eo is very sensitive to size effects while to is independent of sample size and of impurity content as well. We argue that the temperature dependence of ET is well described by the equation ET(T) = EFLR + Eoexp(T/To) with To = 16 K for the upper CDW. (orig.)