Evidence for the Single-Site Quadrupolar Kondo Effect in the Dilute non-Kramers System Y${}_{1-x}$Pr${}_x$Ir${}_2$Zn${}_{20}$

Abstract

Acoustic signatures of the single-site quadrupolar Kondo effect in Y${}_{0.966}$Pr${}_{0.034}$Ir${}_2$Zn${}_{20}$ are presented. The elastic constant ($C_{11}-C_{12}$)/2, corresponding to the ${\Gamma }_3$(E)-symmetry electric-quadrupolar response, reveals a logarithmic temperature dependence of the quadrupolar susceptibility in the low-magnetic-field region below $\sim$0.3 K. Furthermore, the Curie-type divergence of the elastic constant down to $\sim$1 K indicates that the Pr ions in this diluted system have a non-Kramers ground-state doublet. These observations evidence the single-site quadrupolar Kondo effect, as previously suggested based on specific-heat and electrical resistivity data.

5 pages, 4 figures (+ Supplemental Material: 5 pages, 4 figures)