Non-Fermi liquid transport and "universal" ratios in quantum Griffiths phases

TL;DR

This paper investigates how disordered metals near an antiferromagnetic quantum phase transition exhibit non-Fermi liquid transport behaviors due to spin-fluctuations in Griffiths phases, revealing singular temperature dependencies and Griffiths-controlled power-laws.

Contribution

It introduces a semi-classical Boltzmann approach to analyze transport in Griffiths phases, linking transport singularities to the Griffiths exponent and exploring universal ratios in non-Fermi liquids.

Findings

Transport properties follow Griffiths-controlled power-laws.

Singular temperature dependencies occur throughout the Griffiths phase.

Universal ratios deviate from Fermi-liquid behavior.

Abstract

We use the semi-classical Boltzmann equation to investigate transport properties such as electrical resistivity, thermal resistivity, thermopower, and the Peltier coefficient of disordered metals close to an antiferromagnetic quantum phase transition. In the quantum Griffiths phase, the electrons are scattered by spin-fluctuations in the rare regions. This leads to singular temperature dependencies not just at the quantum critical point, but in the entire Griffiths phase. We show that the resulting non-universal power-laws in transport properties are controlled by the same Griffiths exponent $\lambda$ which governs the thermodynamics. $\lambda$ takes the value zero at the quantum critical point and increases throughout the Griffiths phase. We also study some of the "universal" ratios commonly used to characterize Fermi-liquid behavior.