Absence of Kondo effect in CeNiGe3 revealed by coherent phonon dynamics

Cerium-based intermetallic CeNiGe3 has been generally believed to be a heavy-fermion material with Kondo behavior at low temperatures. Using femtosecond-resolved coherent phonon spectroscopy, we present a temperature-dependent dynamic investigation of the bosonic quasiparticles in CeNiGe3. Our data do not agree with the heavy-fermion expectation and instead show that the phonon stiffening from room temperature down to 5 K can be well explained by the anharmonic effect in the absence of a Kondo mechanism. Furthermore, the coherent lattice vibration located at similar to 7.9 THz exhibits a mode splitting at T+ approximate to 105 K, which is close to the energy scale of the first excited crystal field splitting of the Ce 4 f level. We argue that an orbital crossover may account for this intriguing observation.

Automated summary

Experimental study revealed that the phonon stiffening phenomenon in CeNiGe3 is not caused by the Kondo effect, but by the anharmonic effect in the absence of the Kondo mechanism. Additionally, a mode splitting in lattice vibration was observed at around 105K in CeNiGe3, possibly due to the excited crystal field splitting of the Ce 4f level.