X-Ray Scattering Measurements of the Transient Structure of a Driven Charge-Density-Wave

TL;DR

This study uses time-resolved x-ray scattering to investigate how a charge-density-wave in NbSe3 responds dynamically to electric field reversal, revealing response times and behavior near depinning threshold.

Contribution

It provides the first detailed measurement of the transient structural response of a CDW to electric field reversal, including a phenomenological model and damping constant estimation.

Findings

Response time varies from 15 ms near threshold to 2 ms above threshold.

Line shape becomes bimodal near depinning threshold.

Damping constant matches transport measurement values.

Abstract

We report time-resolved x-ray scattering measurements of the transient structural response of the sliding {\bf Q}$_{1}$ charge-density-wave (CDW) in NbSe$_{3}$ to a reversal of the driving electric field. The observed time scale characterizing this response at 70K varies from $\sim$ 15 msec for driving fields near threshold to $\sim$ 2 msec for fields well above threshold. The position and time-dependent strain of the CDW is analyzed in terms of a phenomenological equation of motion for the phase of the CDW order parameter. The value of the damping constant, $\gamma = (3.2 \pm 0.7) \times 10^{-19}$ eV $\cdot$ seconds $\cdot$ \AA$^{-3}$, is in excellent agreement with the value determined from transport measurements. As the driving field approaches threshold from above, the line shape becomes bimodal, suggesting that the CDW does not depin throughout the entire sample at one well-defined voltage.