Wide Quantum Critical Region of Valence Fluctuations: Origin of Robust Quantum Criticality in Quasicrystal Yb15Al34Au51 under Pressure

TL;DR

This paper explains the robust quantum criticality in the quasicrystal Yb15Al34Au51 under pressure by showing overlapping valence transition critical points create a wide quantum critical region, with predictions for similar behavior in its crystalline approximant.

Contribution

The study introduces a minimal model demonstrating how overlapping valence transition critical points lead to a wide quantum critical region in quasicrystals and approximants.

Findings

Overlapping critical points create a wide quantum critical region.

Robust criticality explained by valence transition critical spots.

Predicted critical behavior in crystalline approximant under pressure.

Abstract

The mechanism of the emergence of robust quantum criticality in the heavy-electron quasicrystal Yb15Al34Au51 is analyzed theoretically. By constructing a minimal model for the quasicrystal and its crystalline approximant, which contain concentric shell structures with Yb and Al-Au clusters, we show that a set of quantum critical points of the first-order valence transition of Yb appears as spots in the ground-state phase diagram. Their critical regions overlap each other, giving rise to a wide quantum critical region. This well explains the robust criticality observed in Yb15Al34Au51 under pressure, and predicts the emergence of the common criticality in the crystalline approximant under pressure. The wider critical region in the quasicrystal than that in the crystalline approximant in the T-P phase diagram and the field-induced valence-crossover "region" in the T-H phase diagram are predicted to appear.