Low-energy spin fluctuations of the heavy-Fermion compound CeNi_2Ge_2: origin of non-Fermi liquid behavior

TL;DR

This study reveals that non-Fermi-liquid behavior in CeNi_2Ge_2 arises from low-energy spin fluctuations around specific wave vectors, highlighting the role of low-energy quasiparticle structures in heavy-Fermion physics.

Contribution

It demonstrates the coexistence of low- and high-energy spin fluctuations and links low-energy fluctuations to non-Fermi-liquid behavior in CeNi_2Ge_2.

Findings

Low-energy spin fluctuations appear at 0.6 meV near specific wave vectors.

High-energy spin fluctuations coexist at 4 meV with different modulation vectors.

The energy dependence of spin fluctuations is unique compared to typical heavy-Fermion compounds.

Abstract

Neutron scattering shows that non-Fermi-liquid behavior of the heavy-Fermion compound CeNi_2Ge_2 is brought about by development of low-energy spin fluctuations with an energy scale of 0.6 meV. They appear around 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 $(0.23, 0.23, {1/2})$. The energy dependence of the spin fluctuations is a peculiar character of CeNi_2Ge_2 which differs from typical heavy-Fermion compounds, and suggests importance of low-energy structures of quasiparticle bands.