In Fe-As based superconductors magnetism and superconductivity show strong sensitivity to the lattice, suggesting a possibility of unconventional electron-phonon coupling. We investigated c-axis polarized phonons in doped and undoped BaFe2As2 by inelastic X-ray scattering. Phonon peak positions and linewidths did not vary significantly as a function of doping either by Co or by K. The linewidth of the Fe vibration shows unusual wavevector-dependence, which may be due to hybridization with in-plane modes. Comparison with the density functional theory shows significant difference for the energy of the As-As vibrations (Raman active at the zone center) but not for the Fe-As vibrations (infrared-active at the zone center). This behavior cannot be explained by a 10% softening of Fe-As interaction strength as proposed previously for in-plane polarized vibrations.
@article{arxiv.0810.4941,
title = {C-axis Phonons in Fe-As Based Superconductors Investigated by Inelastic X-ray Scattering},
author = {D. Reznik and K. Lokshin and D. C. Mitchell and D. Parshall and W. Dmowski and D. Lamago and R. Heid and K. -P. Bohnen and A. S. Sefat and M. A. McGuire and B. C. Sales and D. G. Mandrus and A. Asubedi and D. J. Singh and A. Alatas and M. H. Upton and A. H. Said and Yu. Shvyd'ko and T. Egami},
journal= {arXiv preprint arXiv:0810.4941},
year = {2010}
}