Inelastic X-ray Scattering Study of superconducting SmFeAs(O$_{1-x}$F$_{y}$) Single Crystals: Evidence for Strong Momentum-Dependent Doping-Induced Renormalizations of Optical Phonons

TL;DR

This study uses inelastic x-ray scattering to explore how fluorine doping affects lattice vibrations in SmFeAsO superconductors, revealing strong momentum-dependent phonon renormalizations linked to electron-lattice interactions.

Contribution

It provides new evidence of momentum-dependent doping-induced phonon renormalizations in SmFeAsO superconductors, highlighting the role of spin-phonon coupling.

Findings

Strong phonon renormalizations upon fluorine doping

Momentum-dependent lattice dynamics changes

Insights into electron-phonon and spin-phonon interactions

Abstract

We report inelastic x-ray scattering experiments on the lattice dynamics in SmFeAsO and superconducting SmFeAsO$_{0.6}$F$_{0.35}$ single crystals. Particular attention was paid to the dispersions along the [100] direction of three optical modes close to 23 meV, polarized out of the FeAs planes. Remarkably, two of these modes are strongly renormalized upon fluorine doping. These results provide significant insight into the energy and momentum dependence of the coupling of the lattice to the electron system and underline the importance of spin-phonon coupling in the superconducting iron-pnictides.