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

## TL;DR

This paper provides experimental evidence for the single-site quadrupolar Kondo effect in a dilute non-Kramers system, using acoustic measurements that reveal characteristic temperature dependencies and elastic constant divergences.

## Contribution

It demonstrates the direct acoustic evidence of the quadrupolar Kondo effect in Y$_{1-x}$Pr$_x$Ir$_2$Zn$_{20}$, confirming previous indirect observations.

## Key findings

- Logarithmic temperature dependence of elastic constant below 0.3 K
- Curie-type divergence of elastic constant down to 1 K
- Pr ions have a non-Kramers ground-state doublet

## 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.