Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

Ultrasonic investigations of the single-site quadrupolar Kondo effect in diluted Pr system Y_0.966Pr_0.034Ir₂Zn₂₀ are reported. The elastic constant (C₁₁C₁₂)/2 is measured down to ~40 mK using ultrasound for the dilute system Y_0.966Pr_0.034Ir₂Zn₂₀ and the pure compound Yir₂Zn₂₀. We found that the elastic constant (C₁₁C₁₂)/2 of the Pr-dilute system exhibits a logarithmic temperature dependence below T₀ ∼ 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 Γ3-symmetry quadrupolar susceptibility is consistent with the theoretical prediction of the quadrupolar Kondo effect by D. L. Cox [1]. On the other hand, the pure compound Yir₂Zn₂₀ 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 Yir₂Zn₂₀.