Frequency domain simulations of charge-density-wave strains: Comparison with electro-optic measurements

We have studied changes in charge-density-wave strain under application of square-wave currents of variable amplitude and frequency by numerically solving the phase-slip augmented diffusion model introduced by Adelman et al. [T.L. Adelman, M.C. de Lind van Wijngaarden, S.V. Zaitsev-Zotov, D. DiCarlo, R.E. Thorne, Phys. Rev. B 53 (1996) 1833]. The frequency dependence of the strain, at each position and amplitude, was fitted to a modified harmonic oscillator expression, and the position and current dependence of the fitting parameters determined. In particular, the delay time (1 /resonant frequency) vanishes adjacent to the contact and grows with distance from the contact, and both the delay time and relaxation time decrease rapidly with increasing current (and phase-slip rate), as experimentally observed in the electro-optic response of blue bronze. We have also found that pinning the phase at the contacts causes more rapid changes in strain between the contacts than allowing the phase to flow outside the contacts.