Absence of spin-orbit coupling induced effects on the lattice dynamics inCePt3Si

Abstract

Motivated by model calculations, for the heavy fermion superconductor $\mathrm{CeP}{\mathrm{t}}_{3}\mathrm{Si}$ predicting phonon anomalies because of antisymmetric spin-orbit coupling, we performed a detailed experimental study of the lattice dynamical properties of $\mathrm{CeP}{\mathrm{t}}_{3}\mathrm{Si}$. 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 $\mathrm{CeP}{\mathrm{t}}_{3}\mathrm{Si}$. 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 $\mathrm{CeP}{\mathrm{t}}_{3}\mathrm{Si}$ 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.