Single to multi quasiparticle excitations in the itinerant helical magnet CeRhIn$_{5}$

TL;DR

This study explores the spin excitations in CeRhIn$_{5}$, revealing a transition from sharp spin waves to a broad continuum due to the interplay of localized and itinerant electron behaviors, indicating a breakdown of the single quasiparticle model.

Contribution

It provides detailed experimental insights into the spin excitation spectrum of CeRhIn$_{5}$, highlighting the breakdown of quasiparticle descriptions at higher energies due to itinerant-localized electron interactions.

Findings

Sharp spin waves with a specific exchange parameter observed at low energies.

High-energy spin fluctuations become heavily damped and form a continuum.

Breakdown of the single quasiparticle picture in CeRhIn$_{5}$.

Abstract

CeRhIn$_{5}$ is an itinerant magnet where the Ce$^{3+}$ spins order in a simple helical phase. We investigate the spin excitations and observe sharp spin-waves parameterized by a nearest neighbor exchange $J_{RKKY}$=0.88 $\pm$ 0.05 meV. At higher energies, the spin fluctuations are heavily damped where single quasiparticle excitations are replaced by a momentum and energy broadened continuum constrained by kinematics of energy and momentum conservation. The delicate energy balance between localized and itinerant characters results in the breakdown of the single quasiparticle picture in CeRhIn$_{5}$.