# Ubiquity of Unconventional Phenomena Associated with Critical Valence Fluctuations in Heavy Fermion Metals

## TL;DR

This paper discusses the widespread unconventional phenomena in heavy fermion metals linked to critical valence fluctuations, proposing that sharp valence crossover phenomena occur in several compounds under pressure and magnetic field.

## Contribution

It introduces the idea that critical valence fluctuations are a unifying explanation for unconventional behaviors in heavy fermion metals, supported by experimental and theoretical analysis.

## Key findings

- Unconventional phenomena are common in heavy fermion metals.
- Sharp valence crossover phenomena are predicted in specific compounds.
- Pressure and magnetic field tuning induce valence changes.

## Abstract

Ubiquity of unconventional phenomena observed in a series of heavy fermion metals is discussed on the basis of an idea of critical valence fluctuations. After surveying experimental aspects of these unconventional behaviors in prototypical compounds, CeCu_2(Si,Ge)_2, under pressure, we propose that sharp valence crossover phenomena are realized in CeCu_6, CeRhIn_5, and Ce(Ir,Rh)Si_3 by tuning the pressure and the magnetic field simultaneously, on the basis of previous results for an extended Anderson lattice model with the Coulomb repulsion U_fc between localized f-electron and itinerant conduction electrons.