Abstract
We present a high-energy-resolution inelastic x-ray scattering investigation of the soft phonon mode in the charge-density-wave (CDW) system . 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 linewidths over a large part in reciprocal space adjacent to the CDW ordering vector . Further, is clearly offset from the wave vector of (weak) Fermi surface nesting , and our detailed analysis indicates that electron-phonon coupling is responsible for this shift. Hence, we can add , 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.
- Received 5 November 2014
- Revised 10 June 2015
DOI:https://doi.org/10.1103/PhysRevB.91.235146
©2015 American Physical Society