Direct Observation of Quadrupolar Excitons in the Heavy-Fermion Superconductor PrOs$_{4}$Sb$_{12}$

TL;DR

This study uses inelastic neutron scattering to observe quadrupolar excitons in PrOs$_{4}$Sb$_{12}$, revealing their connection to superconductivity and quadrupolar interactions in this heavy-fermion superconductor.

Contribution

First direct observation of quadrupolar excitons in PrOs$_{4}$Sb$_{12}$, linking excitonic behavior to superconductivity and nonmagnetic quadrupolar interactions.

Findings

Exciton softening at wave vector Q = (1,0,0)

Exciton linewidth narrows below superconducting transition

Excitonic behavior mainly from quadrupolar interactions

Abstract

We report inelastic neutron scattering experiments performed to investigate the low energy magnetic excitations on single crystals of the heavy-fermion superconductor PrOs$_{4}$Sb$_{12}$. The observed excitation clearly softens at a wave vector Q = (1,0,0), which is the same as the modulation vector of the field-induced antiferro-quadrupolar ordering, and its intensity at Q = (1,0,0) is smaller than that around the zone center. This result directly evidences that this excitonic behavior is derived mainly from nonmagnetic quadrupolar interactions. Furthermore, the narrowing of the linewidths of the excitations below the superconducting transition temperature indicates the close connection between the superconductivity and the excitons.