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

Abstract

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.

Citation

Ran, K., Wang, J., Song, B., Cai, Z., Shangguan, Y., Ma, Z., Wang, W., Dong, Z.-Y., Cermák, P., Schneidewind, A., Meng, S., Lu, Z., Yu, S.-L., Li, J.-X., & Wen, J. (2022). Evidence for Magnetic Fractional Excitations in a Kitaev Quantum-Spin-Liquid Candidate α-RuCl3. Chinese Physics Letters, 39(2), Article 027501. https://doi.org/10.1088/0256-307X/39/2/027501

• 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
• DOI: https://doi.org/10.1088/0256-307X/39/2/027501
• Public URL: http://researchrepository.napier.ac.uk/Output/2831958