We present a combined ultrafast optical pump-probe and ultrafast x-ray diffraction measurement of the CDW dynamics in SmTe3 at 300 K. The ultrafast x-ray diffraction measurements, taken at the Linac Coherent Light Source reveal a ∼1.55 THz mode that becomes overdamped with increasing fluence. We identify this oscillation with the lattice component of the amplitude mode. Furthermore, these data allow for a more clear identification of the frequencies present in the optical pump-probe data. In both, reflectivity and diffraction, we observe a crossover of the response from linear (for small displacements) to quadratic in the amplitude of the order parameter displacement. Finally, a time-dependent Ginzburg-Landau model captures the essential features of the experimental observations.
@article{arxiv.1809.09799,
title = {Coherent order parameter dynamics in SmTe$_3$},
author = {M. Trigo and P. Giraldo-Gallo and M. E. Kozina and T. Henighan and M. P. Jiang and H. Liu and J. N. Clark and M. Chollet and J. M. Glownia and D. Zhu and T. Katayama and D. Leuenberger and P. S. Kirchmann and I. R. Fisher and Z. X. Shen and D. A. Reis},
journal= {arXiv preprint arXiv:1809.09799},
year = {2019}
}