Zhao, X.; Ran, K.; Wang, J.; Bao, S.; Shangguan, Y.; Huang, Z.; Liao, J.; Zhang, B.; Cheng, S.; Xu, H.; Wang, W.; Dong, Z.-Y.; Meng, S.; Lu, Z.; Yano, S.-I.; Yu, S.-L.; Li, J.-X.; Wen, J.: Neutron Spectroscopy Evidence for a Possible Magnetic-Field-Induced Gapless Quantum-Spin-Liquid Phase in a Kitaev Material α-RuCl3. Chinese Physics Letters 39 (2022), p. 057501/1-7
10.1088/0256-307X/39/5/057501
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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-spinwave 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.