Phonon Density of States of LaFeAsO1-xFx

Abstract

We have studied the phonon density of states (PDOS) in LaFeAsO1�xFx with inelastic neutron scattering methods. The PDOS of the parent compound (x=0) is very similar to the PDOS of samples optimally doped with �uorine to achieve the maximum Tc (x� 0:1). Good agreement is found between the experimental PDOS and first-principle calculations with the exception of a small di�erence in Fe mode frequencies. The PDOS reported here is not consistent with conventional electron-phonon mediated superconductivity.