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Kitaev interactions underlying a quantum spin liquid have long been sought, but experimental data from which their strengths can be determined directly, are still lacking. Here, by carrying out inelastic neutron scattering measurements on high-quality single crystals of α-RuCl_{3}, we observe spin-wave spectra with a gap of ∼2  meV around the M point of the two-dimensional Brillouin zone. We derive an effective-spin model in the strong-coupling limit based on energy bands obtained from first-principles calculations, and find that the anisotropic Kitaev interaction K term and the isotropic antiferromagnetic off-diagonal exchange interaction Γ term are significantly larger than the Heisenberg exchange coupling J term. Our experimental data can be well fit using an effective-spin model with K=-6.8  meV and Γ=9.5  meV. These results demonstrate explicitly that Kitaev physics is realized in real materials.

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Summary Microstructural evolution is a key aspect of understanding and exploiting the processing-structure-property relationship of materials. Modeling microstructure evolution usually relies on coarse-grained simulations with evolution principles described by partial differential equations (PDEs). Here we demonstrate that convolutional recurrent neural networks can learn the underlying physical rules and replace PDE-based simulations in the prediction of microstructure phenomena. Neural nets are trained by self-supervised learning with image sequences from simulations of several common processes, including plane-wave propagation, grain growth, spinodal decomposition, and dendritic crystal growth. The trained networks can accurately predict both short-term local dynamics and long-term statistical properties of microstructures assessed herein and are capable of extrapolating beyond the training datasets in spatiotemporal domains and configurational and parametric spaces. Such a data-driven approach offers significant advantages over PDE-based simulations in time-stepping efficiency and offers a useful alternative, especially when the material parameters or governing PDEs are not well determined.

is a robust model anode for Li-insertion in batteries. The influence of nanocrystal size on the equilibrium potential and kinetics of Li-insertion is investigated with in operando spectroelectrochemistry of thin film electrodes. Distinct visible and infrared responses correlate with Li-insertion and electron accumulation, respectively, and these optical signals are used to deconvolute Li-insertion from other electrochemical responses, such as double-layer capacitance and electrolyte leakage.Electrochemical titration and phase-field simulations reveal that a difference in surface energies between anatase and lithiated phases of TiO 2 systematically tunes Li-insertion potentials with particle size. However, particle size does not affect the kinetics of Li-insertion in ensemble electrodes. Rather, Li-insertion rates depend on applied overpotential, electrolyte concentration, and initial state-of-charge. We conclude that Li diffusivity and phase propagation are not rate-limiting during Li-insertion in TiO 2 nanocrystals. Both of these processes occur rapidly once the transformation between the low-Li anatase and high-Li orthorhombic phases begins in a particle. Instead, discontinuous kinetics of Li accumulation in TiO 2 particles prior to the phase transformations limits (dis)charging rates. We demonstrate a practical means to deconvolute non-equilibrium charging behavior in nanocrystalline electrodes through a combination of colloidal synthesis, phase field simulations and spectroelectrochemistry. File list (2)download file view on ChemRxiv Manuscript_DynamicsofLithiumInsertion.pdf (2.46 MiB) download file view on ChemRxiv SupportingInfo_DynamicsofLithiumInsertion.pdf (3.34 MiB)

Superconductivity mediated by phonons is typically conventional, exhibiting a momentum-independent s -wave pairing function, due to the isotropic interactions between electrons and phonons along different crystalline directions. Here, by performing inelastic neutron scattering measurements on a superconducting single crystal of Sr 0.1 Bi 2 Se 3 , a prime candidate for realizing topological superconductivity by doping the topological insulator Bi 2 Se 3 , we find that there exist highly anisotropic phonons, with the linewidths of the acoustic phonons increasing substantially at long wavelengths, but only for those along the [001] direction. This observation indicates a large and singular electron-phonon coupling at small momenta, which we propose to give rise to the exotic p -wave nematic superconducting pairing in the M x Bi 2 Se 3 (M = Cu, Sr, Nb) superconductor family. Therefore, we show these superconductors to be example systems where electron-phonon interaction can induce more exotic superconducting pairing than the s -wave, consistent with the topological superconductivity.

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The relationship between the tourism economy and the ecological environment is under pressure, and balancing this relationship is crucial for promoting regional sustainability. In this study, the Yangtze River basin, the first largest river in Asia and third largest in the world, was selected as the focus area. The spatial and temporal characteristics of tourism economic development and ecological environmental pressure from 2000 to 2019 were analyzed using the tourism economic development index, ecological environmental pressure index and dynamic change index, and the decoupling process of tourism and the economic system was studied dynamically using the decoupling analysis model. The results show that (1) spatially, the tourism economy in the Yangtze River basin exhibits a pattern of high development in the east and low development in the west, and high in the south and low in the north. Ecological environmental pressures varied greatly, with less pressure in the upstream provinces and more pressure in the middle and downstream provinces. (2) Temporally, the tourism economies of Qinghai and Tibet started with a lower but faster growth rate, while Hunan and Hubei have a higher starting point but limited change. The ecological environmental pressure changes do not show a clear spatial distribution pattern. (3) The decoupling relationship between tourism economy and ecological environment in the Yangtze River basin is moving toward a harmonious development. Achieving a harmonious balance between the two systems is crucial for maintaining ecological balance and regional sustainability.