We used polarization-resolved Raman scattering to study the magneto-elastic coupling in the parent compounds of several families of Fe-based superconductors (BaFe2As2, EuFe2As2, NaFeAs, LiFeAs, FeSe and LaFeAsO). We observe an emergent Ag-symmetry As phonon mode in the XY scattering geometry whose intensity is significantly enhanced below the magneto-structural transition only for compounds showing magnetic ordering. We conclude that the small lattice anisotropy is insufficient to induce the in-plane electronic polarizability anisotropy necessary for the observed phonon intensity enhancement, and interpret this enhancement below the Neel temperature in terms of the anisotropy of the magnetic moment and magneto-elastic coupling. We evidence a Fano line- shape in the XY scattering geometry resulting from a strong coupling between the Ag (As) phonon mode and the B2g symmetry-like electronic continuum. Strong electron-phonon coupling may be relevant to superconductivity.
@article{arxiv.1712.01896,
title = {Magneto-elastic coupling in Fe-based superconductors},
author = {S. -F. Wu and W. -L. Zhang and V. K. Thorsmølle and G. F. Chen and G. T. Tan and P. C. Dai and Y. G. Shi and C. Q. Jin and T. Shibauchi and S. Kasahara and Y. Matsuda and A. S. Sefat and H. Ding and P. Richard and G. Blumberg},
journal= {arXiv preprint arXiv:1712.01896},
year = {2020}
}