Pressure-Driven Quantum Criticality and T/H Scaling in the Icosahedral Au-Al-Yb Approximant

TL;DR

This study investigates pressure-induced quantum criticality in the Au-Al-Yb approximant, revealing a pressure-tuned quantum phase transition linked to valence fluctuations and contrasting behavior with the quasicrystal.

Contribution

It demonstrates pressure-driven quantum criticality in the approximant and discusses the applicability of T/H scaling, highlighting differences from the quasicrystal.

Findings

Quantum criticality emerges at P_c ≈ 2 GPa.

Susceptibility diverges as pressure approaches P_c.

Magnetic transition occurs below P_c at ~100 mK.

Abstract

We report on ac magnetic susceptibility measurements under pressure of the Au-Al-Yb alloy, a crystalline approximant to the icosahedral quasicrystal that shows unconventional quantum criticality. In describing the susceptibility as $\chi(T)^{-1} - \chi(0)^{-1} \propto T^{\gamma}$, we find that $\chi(0)^{-1}$ decreases with increasing pressure and vanishes to zero at the critical pressure $P_{\rm c} \simeq 2$ GPa, with $\gamma~ (\simeq 0.5)$ unchanged. We suggest that this quantum criticality emerges owing to critical valence fluctuations. Above $P_{\rm c}$, the approximant undergoes a magnetic transition at $T \simeq 100$ mK. These results are contrasted with the fact that, in the quasicrystal, the quantum criticality is robust against the application of pressure. The applicability of the so-called $T/H$ scaling to the approximant is also discussed.