Breakdown of the Fermi liquid theory in heavy fermion compounds

TL;DR

This paper reviews the breakdown of Fermi liquid theory in heavy fermion compounds near quantum critical points, highlighting anomalous properties and recent experimental insights into their non-Fermi liquid behavior.

Contribution

It discusses the fundamental breakdown of Fermi liquid theory in heavy fermion systems and explores the potential role of spin-charge separation at quantum critical points.

Findings

Anomalous resistivity, specific heat, and magnetic properties near quantum critical points.

Experimental evidence of non-Fermi liquid behavior in compounds like YbRh₂Si₂.

Possible link between spin-charge separation and the underscreened Kondo model.

Abstract

We review the anomalous properties of heavy fermion compounds like CeCu$_{6-x}$Au$_x$ or CeMIn$_5$ close to a zero temperature phase transition called a quantum critical point. Anomalous behavior of the resistivity, specific heat and magnetic properties observed in various compounds suggests a fundamental breakdown of the Fermi liquid theory. Recent measurements on YbRh$_2$Si$_2$, field-tuned through the quantum critical point, provide interesting insights on the evolution of the Fermi liquid close to criticality. We discuss the possibility of a kind of spin-charge separation at the quantum critical point and make some remarks about its possible link with the underscreened Kondo model.