NbSe3:: Effect of uniaxial stress on the threshold field and fermiology

We have measured the effect of elastic strain epsilon On the threshold field ET for the motion of the higher-temperature charge density wave (CDW) in NbSe3. We find that E-T exhibits acritical behavior, E-T similar to (1 -epsilon/epsilon(gamma)) where epsilon(c) is about 2.6%, gamma similar to 1.2. This expression remains valid over more than two decades of E-T, up to the highest fields of about 1.5 kV/m measured using pulse techniques. Neither gamma nor epsilon(c) is very sensitive to the impurity content of the sample. The transition temperature is linear with epsilon, and dT(p)/d epsilon = 10 K/% shows no anomaly near E,. The slope of the narrow band noise frequency versus the CDW current does not change appreciably with epsilon. Shubnikov-de Haas measurements show that the extremal area of the Fermi surface decreases with increasing E. We conclude that there is a very intimate relationship between pinning and the ferminology in NbSe3.