We present a high energy-resolution inelastic x-ray scattering investigation of the soft phonon mode in the charge-density-wave system TbTe3. We analyze our data based on lattice dynamical calculations using density-functional-perturbation-theory and find clear evidence that strongly momentum dependent electron-phonon-coupling defines the periodicity of the CDW superstructure: Our experiment reveals strong phonon softening and increased phonon line widths over a large part in reciprocal space adjacent to the CDW ordering vector qCDW=(0,0,0.3). Further, qCDW is clearly offset from the wave vector of (weak) Fermi surface nesting qFS=(0,0,0.25) and our detailed analysis indicates that electron-phonon-coupling is responsible for this shift. Hence, we can add TbTe3, which was previously considered as a canonical CDW compound following the Peierls scenario, to the list of distinct charge-density-wave materials characterized by momentum dependent electron-phonon coupling.
@article{arxiv.1410.7592,
title = {Wave vector dependent electron-phonon coupling drives charge-density-wave formation in TbTe3},
author = {M. Maschek and S. Rosenkranz and R. Heid and A. H. Said and P. Giraldo-Gallo and I. R. Fisher and F. Weber},
journal= {arXiv preprint arXiv:1410.7592},
year = {2015}
}