Dominant Kitaev interactions in the honeycomb materials Na${}_3$Co${}_2$SbO${}_6$ and Na${}_2$Co${}_2$TeO${}_6$

Abstract

Cobaltates with 3$d$ based layered honeycomb structure were recently proposed as Kitaev magnets and putative candidates to host the long-sought Kitaev spin liquid. Here we present inelastic neutron scattering results down to 50 mK for powder samples of Na${}_3$Co${}_2$SbO${}_6$ and Na${}_2$Co${}_2$TeO${}_6$, with high resolution in regions of low momentum and energy transfers. We compare the experimental data below the antiferromagnetic zigzag ordering temperature with dynamical structure factors obtained within spin wave theory. We search the wide parameter range of a $K$-$J_1$-$\Gamma$-${\Gamma }^{\prime }$-$J_3$ spin 1/2 model and identify the best fits to constant momentum cuts of the inelastic neutron data. The powder average limits the selection of a unique parameter set for each material, but we see clear trends towards ferromagnetic Kitaev exchange in both compounds, and ratios $|K/J_1|$ could be as large as $5\dots 25$; in contrast, antiferromagnetic Kitaev exchange cannot be ruled out, but requires a fine-tuning of all involved spin exchange couplings with only moderate ratio $|K/J_1|\sim 1$. Our experimental data are incompatible with a purely isotropic Heisenberg model.

13 pages, 9 figures

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• Beyond Kitaev physics in strong spin-orbit coupled magnets
• Magnetic ground state of the Kitaev Na${}_2$Co${}_2$TeO${}_6$ spin liquid candidate
• Experimental signatures of quantum and topological states in frustrated magnetism
• Giant magnetic in-plane anisotropy and competing instabilities in Na3Co2SbO6
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• Triple-q order in Na${}_2$Co${}_2$TeO${}_6$ from proximity to hidden-SU(2)-symmetric point
• Magnetic phase diagram and possible Kitaev-like behavior of honeycomb-lattice antimonate Na3Co2SbO6
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• Effect of ring-exchange interactions in the extended Kitaev honeycomb model
• Proximate Dirac spin liquid in honeycomb lattice $J_1$-$J_3$ XXZ model: Numerical study and application to cobaltates
• Field evolution of magnetic phases and spin dynamics in the honeycomb lattice magnet Na2Co2TeO6: 23Na NMR study
• Spin vestigial orders in extended Heisenberg-Kitaev models near hidden SU(2) points: Application to Na${}_2$Co${}_2$TeO${}_6$
• Honeycomb oxide heterostructure: a new platform for Kitaev quantum spin liquid
• Field-induced phase transitions and quantum criticality in a honeycomb antiferromagnet Na3Co2SbO6
• Field and Polarization Dependent Quantum Spin Dynamics in Honeycomb Magnet Na${}_2$Co${}_2$TeO${}_6$: Magnetic Excitations and Continuum
• Comparative Raman Scattering Study of Crystal Field Excitations in Co-based Quantum Magnets
• Suppression of Antiferromagnetic Order by Strain in Honeycomb Cobaltate: Implication for Quantum Spin Liquid
• Persistent spin dynamics in magnetically ordered honeycomb cobalt oxides
• Ferrimagnetism from triple-q order in Na${}_2$Co${}_2$TeO${}_6$
• Advances in honeycomb layered oxides: Part I -- Syntheses and Characterisations of Pnictogen- and Chalcogen-Based Honeycomb Layered Oxides
• Probing critical spin fluctuations with a composite magnetoelectric method: A case study on a Kitaev spin liquid candidate Na${}_3$Co${}_2$SbO${}_6$
• Cobalt-Based Pyroxenes: A New Playground for Kitaev Physics and Ising Model Realization
• Dynamic structure factor of the antiferromagnetic Kitaev model in large magnetic fields
• Polymorphism and Magnetism in a Kitaev Honeycomb Cobaltate KCoAsO${}_4$
• Spin waves in Na${}_2$Co${}_2$TeO${}_6$ studied by high-frequency/high-field ESR: Successes and failures of the triple-$\mathbf{q}$ model
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• Ferrimagnetism from quantum fluctuations in Kitaev materials
• Anisotropic in-plane heat transport of Kitaev magnet Na${}_2$Co${}_2$TeO${}_6$
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• Anisotropic magnetoelastic coupling in the honeycomb magnet Na${}_3$Co${}_2$SbO${}_6$
• Kitaev interaction and possible spin liquid state in CoI2 and Co2/3Mg1/3I2
• Relevance of on-site and intersite Coulomb interactions in the Kitaev-Heisenberg magnet Na${}_3$Co${}_2$SbO${}_6$
• Direct probe of magnetic field effects on phonons by ultrasound propagation in a quasi-two-dimensional honeycomb magnet Na${}_2$Co${}_2$TeO${}_6$
• Signatures of a Majorana-Fermi surface in the Kitaev magnet Ag${}_3$LiIr${}_2$O${}_6$
• Susceptibility anisotropy and absence of ferroelectric order in the Kitaev spin liquid candidate Na${}_2$Co${}_2$TeO${}_6$
• Crystalline water intercalation into the Kitaev honeycomb cobaltate Na${}_2$Co${}_2$TeO${}_6$
• Dynamical Response of the Kitaev Spin Liquid under Third-Nearest-Neighbor Heisenberg Interaction