Fluctuation Induced Non-Fermi Liquid Behavior near a Quantum Phase Transition in Itinerant Electron Systems

TL;DR

This paper investigates non-Fermi liquid behavior near quantum phase transitions in itinerant electron systems, attributing it to low-lying spin fluctuations, and provides theoretical calculations aligned with experimental observations.

Contribution

It introduces a self-consistent spin fluctuation theory to explain non-Fermi liquid behavior near quantum critical points in itinerant magnets, including effects of disorder.

Findings

Non-Fermi liquid behavior arises from critically damped spin fluctuations.

The theory predicts low-temperature behaviors consistent with experiments.

Disorder effects are briefly discussed.

Abstract

The signature for a non-Fermi liquid behavior near a quantum phase transition has been observed in thermal and transport properties of many metallic systems at low temperatures. In the present work we consider specific examples of itinerant ferromagnet as well as antiferromagnet in the limit of vanishing transition temperature. The temperature variation of spin susceptibility, electrical resistivity, specific heat, and NMR relaxation rates at low temperatures is calculated in the limit of infinite exchange enhancement within the frame work of a self consistent spin fluctuation theory. The resulting non-Fermi liquid behavior is due to the presence of the low lying critically damped spin fluctuations in these systems. The theory presented here gives the leading low temperature behavior, as it turns out that the fluctuation correlation term is always smaller than the mean fluctuation field term in three as well as in two space dimensions. A comparison with illustrative experimental results of these properties in some typical systems has been done. Finally we make some remarks on the effect of disorder in these systems.