High-temperature signatures of quantum criticality in heavy fermion systems

TL;DR

This paper introduces a new spectroscopic criterion to distinguish between two quantum criticality mechanisms in heavy fermion systems, demonstrating its application to CeCu$_{6-x}$Au$_{x}$ and supporting the local quantum critical scenario.

Contribution

The paper proposes a novel spectroscopic criterion based on spin screening suppression to differentiate quantum criticality mechanisms in heavy fermion systems.

Findings

The criterion can detect spin screening suppression above magnetic ordering temperature.

Application to CeCu$_{6-x}$Au$_{x}$ supports the local quantum critical scenario.

Spectroscopic signatures distinguish between Hertz-Millis and local quantum criticality.

Abstract

We propose a new criterion for distinguishing the Hertz-Millis (HM) and the local quantum critical (LQC) mechanism in heavy fermion systems with a magnetic quantum phase transition (QPT). The criterion is based on our finding that the spin screening of Kondo ions can be completely suppressed by the RKKY coupling to the surrounding magnetic ions even without magnetic ordering and that, consequently, the signature of this suppression can be observed in spectroscopic measurements above the magnetic ordering temperature. We apply the criterion to high-resolution photoemission (UPS) measurements on CeCu$_{6-x}$Au$_{x}$ and conclude that the QPT in this system is dominated by the LQC scenario.