Absence of spin-orbit-coupling-induced effects on lattice dynamics in CePt3Si

TL;DR

This study experimentally investigates the lattice dynamics of CePt3Si and finds no evidence of spin-orbit coupling effects on phonons, suggesting conventional lattice behavior contrary to some theoretical predictions.

Contribution

The paper provides the first detailed experimental phonon dispersion measurements in CePt3Si, challenging prior models that predicted spin-orbit coupling-induced anomalies.

Findings

Lattice dynamics of CePt3Si are conventional with no spin-orbit coupling effects.

Ab-initio calculations overestimate phonon branch interactions, especially with 4f electrons.

Experimental results show better agreement when Ce 4f states are neglected in calculations.

Abstract

Motivated by model calculations for the heavy fermion superconductor CePt3Si predicting phonon anomalies because of anti-symmetric 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 anti-symmetric 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 non-centrosymmetric superconductors than commonly believed.