New Universality Class of Quantum Criticality in Ce- and Yb-based Heavy Fermions

TL;DR

This paper introduces a new universality class of quantum criticality in heavy fermion systems caused by local valence fluctuations, unifying explanations for various unconventional behaviors observed in Ce- and Yb-based compounds.

Contribution

It proposes a novel quantum criticality class driven by valence fluctuations, expanding understanding of heavy fermion quantum phase transitions.

Findings

Unifies criticality in YbRh2Si2, AlB4, and other heavy fermions.

Highlights the role of local valence fluctuations near the critical end point.

Suggests new experimental directions to explore this criticality.

Abstract

A new universality class of quantum criticality emerging in itinerant electron systems with strong local electron correlations is discussed. The quantum criticality of a Ce- or Yb-valence transition gives us a unified explanation for unconventional criticality commonly observed in heavy fermion metals such as YbRh2Si2 and \beta-YbAlB4, YbCu5-xAlx, and CeIrIn5. The key origin is due to the locality of the critical valence fluctuation mode emerging near the quantum critical end point of the first-order valence transition, which is caused by strong electron correlations for f electrons. Wider relevance of this new criticality and important future measurements to uncover its origin are also discussed.