Heavy Fermion Quantum Criticality and Destruction of the Kondo Effect in a Nickel Oxypnictide

TL;DR

This study demonstrates a quantum critical point in a nickel oxypnictide, CeNiAsO, revealing a destruction of the Kondo effect and non-Fermi liquid behavior, expanding understanding of quantum criticality beyond traditional intermetallic compounds.

Contribution

It provides evidence of a heavy-fermion quantum critical point in CeNiAsO, showing Kondo destruction and non-Fermi liquid behavior in an oxypnictide material.

Findings

Observation of a quantum critical point via pressure and P/As substitution

Detection of non-Fermi liquid behavior and divergent effective mass

Fermi surface jump indicated by Hall coefficient sign change

Abstract

A quantum critical point arises at a continuous transformation between distinct phases of matter at zero temperature. Studies in antiferromagnetic heavy fermion materials have revealed that quantum criticality has several classes, with an unconventional type that involves a critical destruction of the Kondo entanglement. In order to understand such varieties, it is important to extend the materials basis beyond the usual setting of intermetallic compounds. Here we show that a nickel oxypnictide, CeNiAsO, displays a heavy-fermion antiferromagnetic quantum critical point as a function of either pressure or P/As substitution. At the quantum critical point, non-Fermi liquid behavior appears, which is accompanied by a divergent effective carrier mass. Across the quantum critical point, the low-temperature Hall coefficient undergoes a rapid sign change, suggesting a sudden jump of the Fermi surface and a destruction of the Kondo effect. Our results imply that the enormous materials basis for the oxypnictides, which has been so crucial to the search for high temperature superconductivity, will also play a vital role in the effort to establish the universality classes of quantum criticality in strongly correlated electron systems.