We report on a Raman scattering investigation of the charge-density-wave (CDW), quasi two-dimensional rare-earth tri-tellurides RTe3 (R= La, Ce, Pr, Nd, Sm, Gd and Dy) at ambient pressure, and of LaTe3 and CeTe3 under externally applied pressure. The observed phonon peaks can be ascribed to the Raman active modes for both the undistorted as well as the distorted lattice in the CDW state by means of a first principles calculation. The latter also predicts the Kohn anomaly in the phonon dispersion, driving the CDW transition. The integrated intensity of the two most prominent modes scales as a characteristic power of the CDW-gap amplitude upon compressing the lattice, which provides clear evidence for the tight coupling between the CDW condensate and the vibrational modes.
@article{arxiv.0806.1455,
title = {Evidence for coupling between collective state and phonons in two-dimensional charge-density-wave systems},
author = {M. Lavagnini and M. Baldini and A. Sacchetti and D. Di Castro and B. Delley and R. Monnier and J. -H. Chu and N. Ru and I. R. Fisher and P. Postorino and L. Degiorgi},
journal= {arXiv preprint arXiv:0806.1455},
year = {2015}
}