Interactions of sliding charge-density waves with phonons

While it is well known that the depinning of a charge-density wave (CDW) in a quasi-one-dimensional conductor causes unusual electron transport proper ties, it also affects the lattice phonons in surprising ways. In this paper , we discuss two such effects. In orthorhombic TaS3, depinning causes low-f requency acoustic velocities to decrease, presumably because the local phas e of the CDW can relax in an oscillating strain when it is depinned. We hav e used torsional oscillator measurements to determine the voltage dependenc e of the average relaxation time. In monoclinic K0.3MoO3, we have measured changes in the frequencies, oscillator strengths, and bandwidths of optic p honons near current contacts. The sign of these changes depends on the pola rity of the current, indicating that they are due to polarization of the CD W which accompanies depinning. (C) 2000 Academic Press.