Absence Of Spin-Orbit Coupling Induced Effects On The Lattice Dynamics In Cept3si

Motivated by model calculations, for the heavy fermion superconductor CePt3Si predicting phonon anomalies because of antisymmetric spin-orbit coupling, we performed a detailed experimental study of the lattice dynamical properties of CePt3Si. In particular, we investigated the dispersion of transverse acoustic and low energy optic phonon branches along the [110] direction using inelastic neutron scattering. In these branches we found deviations from our ab initio lattice dynamical calculations, which overall give a good description of the phonon dispersion in CePt3Si. However, the agreement for the [110] transverse modes can be improved if we neglect the Ce 4f states, done in an additional calculation. We conclude that the lattice dynamics of CePt3Si are conventional and that the observed deviations are not related to effects of antisymmetric spin-orbit coupling. More likely, ab initio calculations overestimate the exchange between different phonon branches, particularly in the presence of 4f electron states. Our results imply that the ASOC plays less a role in noncentrosymmetric superconductors than commonly believed.