On quantum Griffiths effects in metallic systems

TL;DR

This paper uses extremal statistics to analyze quantum Griffiths effects in metallic systems, finding that overdamping suppresses quantum tunneling and results in superparamagnetic behavior instead of Griffiths effects.

Contribution

It provides a theoretical analysis showing overdamping in metallic systems suppresses quantum Griffiths effects, challenging previous expectations of their presence.

Findings

Overdamping suppresses quantum tunneling of rare regions.

Results indicate superparamagnetic behavior dominates over Griffiths effects.

Implications for non-Fermi-liquid behavior in heavy fermion materials are discussed.

Abstract

Elementary analytical extremal statistics arguments are used to analyse the possibility of quantum Griffiths effects in nearly critical systems with overdamped dynamics, such as arise in conventional theories of metallic quantum criticality. The overdamping is found to strongly suppress quantum tunnelling of rare regions, leading to superparamagnetic rather than quantum griffiths behavior. Implications for theories of non-fermi-liquid behavior in heavy fermion materials are discussed.