Abstract
Spin excitations are one of the top candidates for mediating electron pairing in unconventional superconductors. Their coupling to superconductivity is evident in a large number of systems, by the observation of an abrupt redistribution of magnetic spectral weight at the superconducting transition temperature, , for energies comparable to the superconducting gap. Here we report inelastic neutron scattering measurements on Fe-based superconductors, , that emphasize an additional signature. The overall shape of the low energy magnetic dispersion changes from two incommensurate vertical columns at to a distinctly different -shaped dispersion at low temperature. Importantly, this spectral reconstruction is apparent for temperatures up to . If the magnetic excitations are involved in the pairing mechanism, their surprising modification on the approach to demonstrates that strong interactions are involved.
- Received 20 January 2012
DOI:https://doi.org/10.1103/PhysRevLett.109.227002
© 2012 American Physical Society