Magnetic excitations in the Kitaev material Na${}_2$IrO${}_3$ studied by neutron scattering

Abstract

Inelastic neutron scattering experiments with a large set of comounted Na${}_2$IrO${}_3$ crystals reveal the low-energy magnon dispersion in this candidate material for Kitaev physics. The magnon gap amounts to 1.7(1) meV and can be interpreted similarly to the sister compound $\alpha$-RuCl${}_3$ to stem from the zone boundaries in the antiferromagnetic zigzag structure. The neutron experiments find no evidence for low-energy excitations with ferromagnetic character, which contrasts to the findings in $\alpha$-RuCl${}_3$. Our results are consistent with a recently proposed microscopic model that involves an antiferromagnetic Heisenberg nearest-neighbor exchange in Na${}_2$IrO${}_3$ in contrast to the ferromagnetic one considered for $\alpha$-RuCl${}_3$. Although the magnetic response shows the signatures of bond-directional anisotropy in both materials the different relative signs of Kitaev and Heisenberg interaction result in different deviations from the initial Kitaev model. Low-energy ferromagnetic fluctuations cannot be considered as a fingerprint of ferromagnetic Kitaev interaction.

arXiv comment11 pages, 6 figures

References in corpus (52)

• Non-Abelian Anyons and Topological Quantum Computation
• Anyons in an exactly solved model and beyond
• Mott Insulators in the Strong Spin-Orbit Coupling Limit: From Heisenberg to a Quantum Compass and Kitaev Models
• Novel Jeff = 1/2 Mott State Induced by Relativistic Spin-Orbit Coupling in Sr2IrO4
• Correlated quantum phenomena in the strong spin-orbit regime
• Kitaev-Heisenberg Model on Honeycomb Lattice: Possible Exotic Phases in Iridium Oxides $A_2$IrO${}_3$
• Kitaev quantum spin liquid - concept and materialization
• $\alpha$-RuCl3: a Spin-Orbit Assisted Mott Insulator on a Honeycomb Lattice
• Relevance of the Heisenberg-Kitaev model for the honeycomb lattice iridates A_2IrO_3
• Spin-Orbit Physics Giving Rise to Novel Phases in Correlated Systems: Iridates and Related Materials
• Neutron tomography of magnetic Majorana fermions in a proximate quantum spin liquid
• Generic spin model for the honeycomb iridates beyond the Kitaev limit
• Models and Materials for Generalized Kitaev Magnetism
• Spin waves and revised crystal structure of honeycomb iridate Na2IrO3
• Linear spin wave theory for single-Q incommensurate magnetic structures
• On the Origin of Zigzag Magnetic Order in Iridium Oxide Na2IrO3
• Challenges in Design of Kitaev Materials: Magnetic Interactions from Competing Energy Scales
• Quantum spin Hall effect in a transition metal oxide Na2IrO3
• Direct evidence of a zigzag spin chain structure in the honeycomb lattice: A neutron and x-ray diffraction investigation on single crystal $\mathrm{N}{\mathrm{a}}_2\mathrm{Ir}{\mathrm{O}}_3$
• Excitations in the field-induced quantum spin liquid state of alpha-RuCl3
• Long range magnetic ordering in Na${}_2$IrO${}_3$
• Crystal field splitting and correlation effect on the electronic structure of A2IrO3
• Kitaev interactions between j=1/2 moments in honeycomb Na2IrO3 are large and ferromagnetic: insights from ab initio quantum chemistry calculations
• Spin-wave excitations evidencing the Kitaev interaction in single crystalline $\alpha$-RuCl${}_3$
• Na2IrO3 as a spin-orbit-assisted antiferromagnetic insulator with a 340 meV gap
• First-Principles Study of the Honeycomb-Lattice Iridates Na2IrO3 in the Presence of Strong Spin-Orbit Interaction and Electron Correlations
• Kitaev Spin Liquid in 3d Transition Metal Compounds
• Finite-temperature phase diagram of the Heisenberg-Kitaev model
• Hidden symmetries of the extended Kitaev-Heisenberg model: Implications for honeycomb lattice iridates A2IrO3
• Ab initio analysis of the tight-binding parameters and magnetic interactions in Na2IrO3
• Kitaev-Heisenberg-J2-J3 model for the iridates A2IrO3
• The Challenge of Spin-Orbit-Tuned Ground States in Iridates
• Recent progress on correlated electron systems with strong spin-orbit coupling
• Magnetic anisotropy in the Kitaev model systems Na2IrO3 and RuCl3
• Importance of anisotropic exchange interactions in honeycomb iridates. Minimal model for zigzag antiferromagnetic order in Na${}_2$IrO${}_3$
• Finite field regime for a quantum spin liquid in $\alpha$-RuCl${}_3$
• Materials design of Kitaev spin liquids beyond the Jackeli-Khaliullin mechanism
• Clues and criteria for designing Kitaev spin liquid revealed by thermal and spin excitations of honeycomb iridates Na${}_2$IrO${}_3$
• Phase Diagram and Quantum Order by Disorder in the Kitaev $K_1$-$K_2$ Honeycomb Magnet
• Magnetic excitation spectrum of Na2IrO3 probed with resonant inelastic x-ray scattering
• Fingerprints of Kitaev physics in the magnetic excitations of honeycomb iridates
• Phase diagram and spin correlations of the Kitaev-Heisenberg model: Importance of quantum effects
• Beyond Kitaev physics in strong spin-orbit coupled magnets
• Probing the stability of the spin liquid phases in the Kitaev-Heisenberg model using tensor network algorithms
• Heat capacity evidence for proximity to the Kitaev QSL in A${}_2$IrO${}_3$ ($A=$ Na, Li)
• Selection of direction of the ordered moments in Na${}_2$IrO${}_3$ and $\alpha -$RuCl${}_3$
• Exchange interactions in $d^5$ Kitaev materials: From Na${}_2$IrO${}_3$ to $\alpha$-RuCl${}_3$
• Evidence for magnetic fractional excitations in a Kitaev quantum-spin-liquid candidate $\alpha$-RuCl${}_3$
• First-principles Study on the Magnetic Interactions in Honeycomb Na2IrO3
• The Saga of $\alpha$-RuCl${}_3$: Parameters, Models, and Phase Diagrams
• Exchange Interactions in Rare-earth Magnets $A_2$PrO${}_3$ ($A$= alkali metals): Revisited
• Direct evidence for anisotropic magnetic interaction in $\alpha$-RuCl${}_3$ from polarized inelastic neutron scattering