Random Field effects in field-driven quantum critical points

TL;DR

This paper explores how disorder, especially random magnetic fields induced by impurities and external fields, influences quantum critical points in metallic antiferromagnets, with implications for heavy fermion systems and experimental observations.

Contribution

It introduces a perturbative renormalization group analysis of disorder effects on field-driven quantum phase transitions in metallic antiferromagnets, highlighting the significance of random field effects.

Findings

Disorder can significantly alter critical behavior near quantum phase transitions.

Random field effects are especially strong in heavy fermion systems with weak disorder.

Experimental neutron scattering results in CeCu_5.8Au_0.2 show possible manifestations of these effects.

Abstract

We investigate the role of disorder for field-driven quantum phase transitions of metallic antiferromagnets. For systems with sufficiently low symmetry, the combination of a uniform external field and non-magnetic impurities leads effectively to a random magnetic field which strongly modifies the behavior close to the critical point. Using perturbative renormalization group, we investigate in which regime of the phase diagram the disorder affects critical properties. In heavy fermion systems where even weak disorder can lead to strong fluctuations of the local Kondo temperature, the random field effects are especially pronounced. We study possible manifestation of random field effects in experiments and discuss in this light neutron scattering results for the field riven quantum phase transition in CeCu_5.8Au_0.2.