Neutron scattering measurements of the phonon density of states of FeSe1-x superconductors

Inelastic neutron-scattering experiments have been carried out on polycrystalline samples of the FeSe1-x superconductors. We report the phonon density of states for FeSe1-x with T-c approximate to 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 , Phys. Rev. B 78, 134514 (2008)].