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Evidence for Magnetic Fractional Excitations in a Kitaev Quantum-Spin-Liquid Candidate α-RuCl3

Ran, Kejing; Wang, Jinghui; Song, Bao; Cai, Zhengwei; Shangguan, Yanyan; Ma, Zhen; Wang, Wei; Dong, Zhao-Yang; Cermák, P.; Schneidewind, A.; Meng, Siqin; Lu, Zhilun; Yu, Shun-Li; Li, Jian-Xin; Wen, Jinsheng


Kejing Ran

Jinghui Wang

Bao Song

Zhengwei Cai

Yanyan Shangguan

Zhen Ma

Wei Wang

Zhao-Yang Dong

P. Cermák

A. Schneidewind

Siqin Meng

Zhilun Lu

Shun-Li Yu

Jian-Xin Li

Jinsheng Wen


It is known that α-RuCl3 has been studied extensively because of its proximity to the Kitaev quantum-spin-liquid (QSL) phase and the possibility of approaching it by tuning the competing interactions. Here we present the first polarized inelastic neutron scattering study on α-RuCl3 single crystals to explore the scattering continuum around the Γ point at the Brillouin zone center, which was hypothesized to be resulting from the Kitaev QSL state but without concrete evidence. With polarization analyses, we find that, while the spin-wave excitations around the M point vanish above the transition temperature TN, the pure magnetic continuous excitations around the Γ point are robust against temperature. Furthermore, by calculating the dynamical spin-spin correlation function using the cluster perturbation theory, we derive magnetic dispersion spectra based on the K–Γ model, which involves with a ferromagnetic Kitaev interaction of −7.2 meV and an off-diagonal interaction of 5.6 meV. We find this model can reproduce not only the spin-wave excitation spectra around the M point, but also the non-spin-wave continuous magnetic excitations around the Γ point. These results provide evidence for the existence of fractional excitations around the Γ point originating from the Kitaev QSL state, and further support the validity of the K–Γ model as the effective minimal spin model to describe α-RuCl3.

Journal Article Type Article
Acceptance Date Dec 24, 2021
Online Publication Date Dec 27, 2021
Publication Date 2022
Deposit Date Dec 29, 2021
Print ISSN 0256-307X
Electronic ISSN 1741-3540
Publisher IOP Publishing
Peer Reviewed Peer Reviewed
Volume 39
Issue 2
Article Number 027501
Public URL