Determining the local low-energy excitations in the Kondo semimetal CeRu$_4$Sn$_6$ using resonant inelastic x-ray scattering

TL;DR

This study uses resonant inelastic x-ray scattering to analyze low-energy excitations in CeRu$_4$Sn$_6$, revealing crystal-electric field effects, magnetic anisotropy, and ground state properties relevant to strongly correlated Weyl semimetals.

Contribution

First application of Ce M5 RIXS to CeRu$_4$Sn$_6$, providing detailed insights into its crystal-electric field parameters and magnetic ground state.

Findings

Crystal-electric field parameters explain magnetic susceptibility behavior.

All CEF states are nearly rotationally symmetric.

Ground state magnetic moment is reduced due to multiplet mixing.

Abstract

We have investigated the local low-energy excitations in CeRu$_4$Sn$_6$, a material discussed recently in the framework of strongly correlated Weyl semimetals, by means of Ce $M_5$ resonant inelastic x-ray scattering (RIXS). The availability of both $^2$F$_\frac{5}{2}$ and $^2$F$_\frac{7}{2}$ excitations of the Ce $4f^1$ configuration in the spectra allows for the determination of the crystal-electric field parameters that explain quantitatively the temperature dependence and anisotropy of the magnetic susceptibility. The absence of an azimuthal dependence in the spectra indicates that all crystal-electric field states are close to being rotational symmetric. We show further that the non-negligible impact of the $\check A_6^0$ parameter on the ground state of CeRu$_4$Sn$_6$ leads to a reduction of the magnetic moment due to multiplet intermixing. The RIXS results are consistent with inelastic neutron scattering (INS) data and are compared to the predictions from \textsl{ab-initio} based electronic structure calculations.