Spin Fluctuations and Non-Fermi-Liquid Behavior of CeNi_2Ge_2

TL;DR

This study reveals that low-energy spin fluctuations are responsible for the non-Fermi-liquid behavior in CeNi_2Ge_2, highlighting complex spin dynamics involving multiple energy scales and wave vectors.

Contribution

It provides detailed neutron scattering evidence of spin fluctuation development at different energy scales and wave vectors in CeNi_2Ge_2, linking these to non-Fermi-liquid behavior.

Findings

Low-energy spin fluctuations (~0.6 meV) develop around specific antiferromagnetic wave vectors.

High-energy spin fluctuations (~4 meV) coexist with low-energy ones.

Unusual energy-dependent structure of spin susceptibility suggests importance of quasiparticle bands.

Abstract

Neutron scattering shows that non-Fermi-liquid behavior of the heavy-fermion compound CeNi_2Ge_2 is brought about by the development of low-energy spin fluctuations with an energy scale of 0.6 meV. They appear around the antiferromagnetic wave vectors $({1/2} {1/2} 0)$ and $(0 0 {3/4})$ at low temperatures, and coexist with high-energy spin fluctuations with an energy scale of 4 meV and a modulation vector $(0.23, 0.23, {1/2})$. This unusual energy dependent structure of $\text{Im} \chi (\bm{Q}, E)$ in $\bm{Q}$ space suggests that quasiparticle bands are important.