Self-detection of ultrasonic standing waves and anomaly of Young’s modulus at uniaxial extension whiskers of the quasi-one-dimensional conductor TaS$_3$

Mechanical vibrations of whiskers of the quasi-one-dimensional conductor TaS$_3$ that appear at the application of an ac voltage above the threshold value for the sliding of a charge density wave have been studied by the heterodyning method. It has been shown that the highest frequency modes correspond to the excitation of longitudinal ultrasonic standing waves. A sharp minimum of the frequencies of ultrasonic resonances at a critical tension of $\varepsilon_{c}\approx0.7\,\%$ has been detected in the region of transition of the charge density wave to a new state.