ELASTIC ANOMALIES AT CHARGE DENSITY WAVE TRANSITIONS IN TaS₃ AND NbSe₃.

The temperature dependence of the Young's modulus and internal friction of TaS//3 (orthorhombic) and NbSe//3 were measured by the vibrating reed technique. The very small anomalies observed in the Young's modulus of NbSe//3 imply very anisotropic stress dependence of temperatures and the overwhelming influence of interchain bonds on the Fermi surface. In TaS//3, a much larger anomaly was observed, consistent with the one-dimensional character of the material. The increase in internal friction below the transition may be due to the hysteretic motion of domain walls.