Quantum phase transitions in heavy fermion metals and Kondo insulators

TL;DR

This paper reviews recent advances in understanding quantum phase transitions in heavy fermion metals and Kondo insulators, highlighting the role of Kondo destruction, global phase diagrams, and potential topological states.

Contribution

It synthesizes theoretical and experimental developments on quantum criticality, Kondo destruction, and extends the phase diagram concepts to Kondo insulators and other f-electron systems.

Findings

Kondo destruction is key to beyond-Landau quantum critical points

Global phase diagram framework unifies various heavy fermion behaviors

Potential for topological states in Kondo insulators

Abstract

Strongly correlated electron systems at the border of magnetism are of active current interest, particularly because the accompanying quantum criticality provides a route towards both strange-metal non-Fermi liquid behavior and unconventional superconductivity. Among the many important questions is whether the magnetism acts simply as a source of fluctuations in the textbook Landau framework, or instead serves as a proxy for some unexpected new physics. We put into this general context the recent developments on quantum phase transitions in antiferromagnetic heavy fermion metals. Among these are the extensive recent theoretical and experimental studies on the physics of Kondo destruction in a class of beyond-Landau quantum critical points. Also discussed are the theoretical basis for a global phase diagram of antiferromagnetic heavy fermion metals, and the recent surge of materials suitable for studying this phase diagram. Furthermore, we address the generalization of this global phase diagram to the case of Kondo insulators, and consider the future prospect to study the interplay among Kondo coherence, magnetism and topological states. Finally, we touch upon related issues beyond the antiferromagnetic settings, arising in mixed valent, ferromagnetic, quadrupolar, or spin glass f-electron systems, as well as some general issues on emergent phases near quantum critical points.