Neutron scattering Measurements of the phonon density of states of FeSe\(_{1-x}\) superconductors

Inelastic neutron-scattering experiments have been carried out on polycrystalline samples of the FeSe\(_{1-x}\) superconductors. We report the phonon density of states for FeSe\(_{1-x}\) with Tc\(\approx\)8 K. The phonon cutoff frequency is observed around 40 meV. No significant change is observed across the superconducting transition. The measurements support the published first-principles calculations [A. Subedi et al., Phys. Rev. B \textbf{78}, 134514 (2008)].