Robustness of Quantum Criticality of Valence Fluctuations

TL;DR

This paper presents a theoretical analysis of how robust quantum criticality emerges in Yb- and Ce-based heavy electron systems under pressure, explaining experimental observations of wide critical regimes.

Contribution

It introduces a minimal model for quasicrystal Yb15Al34Au51 that demonstrates the emergence of overlapping quantum critical points of valence transition, explaining the robustness of quantum criticality.

Findings

Quantum critical points of valence transition appear in the phase diagram.

Critical regimes overlap, forming a wide quantum critical region.

The mechanism applies to other Yb- and Ce-based systems like beta-YbAlB4.

Abstract

The mechanism of emergence of robust quantum criticality in Yb- and Ce-based heavy electron systems under pressure is analyzed theoretically. By constructing a minimal model for quasicrystal Yb15Al34Au51 and its approximant, we show that quantum critical points of the first-order valence transition of Yb appear in the ground-state phase diagram with their critical regimes being overlapped to be unified, giving rise to a wide quantum critical regime. This well explains the robust unconventional criticality observed in Yb15Al34Au51 under pressure. We also discuss broader applicability of this mechanism to other Yb- and Ce-based systems such as beta-YbAlB4 showing unconventional quantum criticality.