Identification of the low-energy excitations in a quantum critical system

TL;DR

This study uses polarized neutron scattering to identify low-energy magnetic excitations in a doped quantum critical system, revealing their role in dynamical scaling without traditional critical behavior.

Contribution

It provides direct experimental evidence of superspin reorientations in magnetic clusters, advancing understanding of quantum criticality in disordered systems.

Findings

Identification of low-energy magnetic excitations via neutron scattering

Evidence of superspin reorientations in magnetic clusters

Observation of both frozen and dynamic clusters as predicted by theory

Abstract

We have identified low-energy magnetic excitations in a doped quantum critical system by means of polarized neutron scattering experiments. The presence of these excitations could explain why Ce(Fe$_{0.76}$Ru$_{0.24}$)$_2$Ge$_2$ displays dynamical scaling in the absence of local critical behavior or long-range spin-density wave criticality. The low-energy excitations are associated with the reorientations of the superspins of fully ordered, isolated magnetic clusters that form spontaneously upon lowering the temperature. The system houses both frozen clusters and dynamic clusters, as predicted by Hoyos and Vojta [Phys. Rev. B 74, 140401 (R) (2006)].