Elastic Response in the Dilute non-Kramers System Y${}_{1-x}$Pr${}_x$Ir${}_2$Zn${}_{20}$

Abstract

Ultrasonic investigations of the single-site quadrupolar Kondo effect in diluted Pr system Y${}_{0.966}$Pr${}_{0.034}$Ir${}_2$Zn${}_{20}$ are reported. The elastic constant $(C_{11}-C_{12})/2$ is measured down to ~40 mK using ultrasound for the dilute system Y${}_{0.966}$Pr${}_{0.034}$Ir${}_2$Zn${}_{20}$ and the pure compound YIr${}_2$Zn${}_{20}$. We found that the elastic constant $(C_{11}-C_{12})/2$ of the Pr-dilute system exhibits a logarithmic temperature dependence below $T_0$ ~0.3 K, where non-Fermi-liquid (NFL) behavior in the specific heat and electrical resistivity is observed. This logarithmic temperature variation manifested in the ${\Gamma }_3$-symmetry quadrupolar susceptibility is consistent with the theoretical prediction of the quadrupolar Kondo effect by D. L. Cox. On the other hand, the pure compound YIr${}_2$Zn${}_{20}$ without $4f$-electron contributions shows nearly no change in its elastic constants evidencing negligible phonon contributions. In addition, clear acoustic de Haas-van Alphen (dHvA) oscillations in the elastic constant were detected for both compounds on applying magnetic field. This is mainly interpreted as contribution from the Fermi surface of YIr${}_2$Zn${}_{20}$.

9 pages, 4 figures, Proceedings of J-Physics 2019 International Conference