Destabilization of magnetic order in a dilute Kitaev spin liquid candidate

TL;DR

This study shows that introducing Ir$^{3+}$ vacancies in RuCl$_{3}$ suppresses magnetic order and preserves fractionalized excitations, suggesting a spin-liquid-like state consistent with Kitaev physics in a dilute limit.

Contribution

It demonstrates that magnetic order in RuCl$_{3}$ can be destabilized by spin vacancies, revealing a persistent spin-liquid-like state with fractionalized excitations.

Findings

Magnetic order temperature decreases with Ir doping.

Fractionalized excitations remain across all doping levels.

Spin-liquid-like state emerges in the dilute limit.

Abstract

The insulating honeycomb magnet $\alpha$-RuCl$_{3}$ exhibits fractionalized excitiations that signal its proximity to a Kitaev quantum spin liquid (QSL) state, however, at $T=0$, fragile long-range magnetic order arises from non-Kitaev terms in the Hamiltonian. Spin vacancies in the form of Ir$^{3+}$ substituted for Ru are found to destabilize this long-range order. Neutron diffraction and bulk characterization of Ru$_{1-x}$Ir$_{x}$Cl$_{3}$ show that the magnetic ordering temperature is suppressed with increasing $x$ and evidence of zizag magnetic order is absent for $x>0.3$. Inelastic neutron scattering demonstrates that the signature of fractionalized excitations is maintained over the full range of $x$ investigated. The depleted lattice without magnetic order thus hosts a spin-liquid-like ground state that may indicate the relevance of Kitaev physics in the magnetically dilute limit of RuCl$_{3}$.