Effective model with strong Kitaev interactions for $\alpha$-$\mathrm{RuC}{\mathrm{l}}_3$

Abstract

We use an exact numerical diagonalization method to calculate the dynamical spin structure factors (DSFs) of three ab-initio models and one ab-initio-guided model for a honeycomb-lattice magnet $\alpha$-RuCl${}_3$. We also use thermal pure quantum states to calculate the temperature dependence of the heat capacity, the nearest-neighbor (NN) spin-spin correlation function, and the static spin structure factor. From the results obtained from these four effective models, we find that, even when the magnetic order is stabilized at low temperature, the intensity at the $\Gamma$ point in the DSFs increases with increasing NN spin correlation. In addition, we find that the four models fail to explain heat-capacity measurements whereas two of the four models succeed in explaining inelastic-neutron-scattering (INS) experiments. In the four models, when temperature decreases, the heat capacity shows a prominent peak at a high temperature where the NN spin-spin correlation function increases. However, the peak temperature in heat capacity is too low in comparison with that observed experimentally. To address these discrepancies, we propose an effective model that includes strong ferromagnetic Kitaev coupling, and we show that this model quantitatively reproduces both INS experiments and heat-capacity measurements. To further examine the adequacy of the proposed model, we calculate the field dependence of the polarized terahertz spectra, which reproduces the experimental results: the spin-gapped excitation survives up to an onset field where the magnetic order disappears and the response in the high-field region is almost linear. Based on these numerical results, we argue that the low-energy magnetic excitation in $\alpha$-RuCl${}_3$ is mainly characterized by interactions such as off-diagonal interactions and weak Heisenberg interactions between NN pairs, rather than by the strong Kitaev interactions.

12 pages and 9 figures. v2 : published version. Discussions for Raman spectra have been added. The numerical results for model 2 have been corrected by using the adequate parameters

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Cited by in corpus (31)

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• Magnon bound states vs. anyonic Majorana excitations in the Kitaev honeycomb magnet $\alpha$-RuCl${}_3$
• Anisotropic susceptibilities in the honeycomb Kitaev system $\alpha$-RuCl${}_3$
• Fingerprints of Kitaev physics in the magnetic excitations of honeycomb iridates
• Thermodynamic evidence of fractionalized excitations in α-RuCl3
• Dynamical and thermal magnetic properties of the Kitaev spin liquid candidate $\alpha$-RuCl${}_3$
• Field-induced intermediate ordered phase and anisotropic interlayer interactions in $\alpha$-RuCl${}_3$
• Identification of Magnetic Interactions and High-field Quantum Spin Liquid in $\alpha$-RuCl${}_3$
• Field evolution of magnons in $\alpha$-RuCl${}_3$ by high-resolution polarized terahertz spectroscopy
• Deriving models for the Kitaev spin-liquid candidate material $\alpha$-RuCl${}_3$ from first principles
• Magnetic field-dependent low-energy magnon dynamics in $\alpha$-RuCl3
• Kitaev Quantum Spin Liquids
• THz excitations in α-RuCl3: Majorana fermions, rigid-plane shear and compression modes
• Extraction of the interaction parameters for $\alpha -$RuCl${}_3$ from neutron data using machine learning
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• Scattering Signatures of Bond-Dependent Magnetic Interactions
• Thermal Hall Effect in the Kitaev-Heisenberg System with Spin-Phonon Coupling
• The Saga of $\alpha$-RuCl${}_3$: Parameters, Models, and Phase Diagrams
• Ground-state properties of the $K-\Gamma$ model on a honeycomb lattice
• Topological phase diagrams of in-plane field polarized Kitaev magnets
• Thermal Pure States for Systems with Antiunitary Symmetries and Their Tensor Network Representations
• Ground-state properties for bilayer Kitaev model: dimer expansion study
• Effective Model for Rare-earth Kitaev Materials and its Classical Monte Carlo Simulation
• Ground-state phase diagram of anisotropically interacting Heisenberg-$\Gamma$ models on a honeycomb lattice
• Coupled spin-1/2 antiferromagnetic chain Cs${}_2$LiRuCl${}_6$ with partially disordered crystal lattice
• Scale-invariant magnetic anisotropy in $\alpha$-RuCl${}_3$: A quantum Monte Carlo study
• First-principles study of bulk stacking, $J_{\mathrm{eff}}$ picture, magnetic Hamiltonian, $g$ factors, and structural distortions of $\alpha$-RuCl${}_3$
• Magnetotropic Response in Ruthenium Chloride