(p,T,H) phase diagram of Heavy Fermion systems : Some systematics and some surprises from ytterbium

TL;DR

This paper reviews how pressure tuning affects heavy fermion systems, especially ytterbium, highlighting valence changes and unexpected behaviors observed with advanced synchrotron techniques.

Contribution

It provides a systematic analysis of the (p,T,H) phase diagram for heavy fermion systems, emphasizing valence changes and experimental insights from synchrotron methods.

Findings

Pressure induces valence changes in ytterbium systems.

Unexpected behaviors observed under pressure.

Synchrotron techniques accurately measure valence at low temperatures.

Abstract

Pressure is the cleanest way to tune heavy fermion systems to a quantum phase transition in order to study the rich physics and competing phases, and the comparison between ytterbium and cerium systems is particularly fruitful. We briefly review the mechanisms in play and show some examples of expected and unexpected behaviour. We emphasize the importance of the valence changes under pressure and show how modern synchrotron techniques can accurately determine this, including at low temperature.