Torsional Strain of TaS$_3$ Whiskers on the Charge-Density Waves Depinning

TL;DR

This study demonstrates that electric current exceeding a threshold induces significant torsional deformation in TaS$_3$ whiskers due to charge-density wave surface shear, suggesting potential for torsional actuation.

Contribution

It reveals a novel current-induced torsional strain in TaS$_3$ caused by CDW surface shear, highlighting its potential as a torsional actuator.

Findings

Electric current causes torsion in TaS$_3$ with hysteresis.

The effect depends on current polarity and surface shear.

Estimated piezoelectric coefficients exceed 10^{-4} cm/V.

Abstract

We find that electric current $I$ exceeding the threshold value results in torsion deformation of o-TaS$_3$ samples with one contact freely suspended. The rotation angle, $\delta \phi$, of the free end achieves several degrees and exhibits hysteresis as a function of $I$. The sign of $\delta \phi$ depends on the $I$ polarity; a polar axis along the conducting chains (the {\it c}-axis) is pointed out. We associate the effect with surface shear of the charge-density waves (CDW) coupled to the crystal shear. The current-induced torsional strain could be treated in terms of enormous piezoelectric coefficients ($>10^{-4}$ cm/V) corresponding to shear. In essence, TaS$_3$ appears to be a ready torsional actuator based on the unique intrinsic property of the CDW.