Multiple Spin-Orbit Excitons and the Electronic Structure of $\alpha$-RuCl${}_3$

Abstract

The honeycomb compound $\alpha$-RuCl${}_3$ is widely discussed as a proximate Kitaev spin-liquid material. This scenario builds on spin-orbit entangled $j=1/2$ moments arising for a $t_{2g}^5$ electron configuration with strong spin-orbit coupling $\lambda$ and a large cubic crystal field. The low-energy electronic structure of $\alpha$-RuCl${}_3$, however, is still puzzling. In particular infrared absorption features at 0.30 eV, 0.53 eV, and 0.75 eV seem to be at odds with theory. Also the energy of the spin-orbit exciton, the excitation from $j=1/2$ to 3/2, and thus the value of $\lambda$ are controversial. Combining infrared and Raman data, we show that the infrared features can be attributed to single, double, and triple spin-orbit excitons. We find $\lambda$ = 0.16 eV and $\Delta$ =42(4) meV for the observed non-cubic crystal-field splitting, supporting the validity of the $j=1/2$ picture for $\alpha$-RuCl${}_3$. The unusual strength of the double excitation is related to the underlying hopping interactions which form the basis for dominant Kitaev exchange.

arXiv comment7 pages, 4 figures

References in corpus (48)

• 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
• Correlated quantum phenomena in the strong spin-orbit regime
• Majorana quantization and half-integer thermal quantum Hall effect in a Kitaev spin liquid
• Kitaev quantum spin liquid - concept and materialization
• $\alpha$-RuCl3: a Spin-Orbit Assisted Mott Insulator on a Honeycomb Lattice
• 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
• Models and Materials for Generalized Kitaev Magnetism
• Challenges in Design of Kitaev Materials: Magnetic Interactions from Competing Energy Scales
• The monoclinic crystal structure of $\alpha$-RuCl${}_3$ and the zigzag antiferromagnetic ground state
• Scattering Continuum and Possible Fractionalized Excitations in $\alpha$-RuCl${}_3$
• Physics of the Kitaev model: fractionalization, dynamical correlations, and material connections
• Isospin Dynamics in Sr2IrO4 : Forging Links to Cuprate Superconductivity
• Kitaev magnetism in honeycomb RuCl3 with intermediate spin-orbit coupling
• Fermionic response from fractionalization in an insulating two-dimensional magnet
• Spin-orbit excitation energies, anisotropic exchange, and magnetic phases of honeycomb RuCl3
• Breakdown of Magnons in a Strongly Spin-Orbital Coupled Magnet
• Crystal field splitting and correlation effect on the electronic structure of A2IrO3
• Anisotropic Ru3+ 4d5 magnetism in the alpha-RuCl3 honeycomb system: susceptibility, specific heat and Zero field NMR
• Hidden symmetries of the extended Kitaev-Heisenberg model: Implications for honeycomb lattice iridates A2IrO3
• Magnetic Excitations and Continuum of a Field-Induced Quantum Spin Liquid in $\alpha$-RuCl${}_3$
• Spin-orbit excitations and electronic structure of the putative Kitaev magnet $\alpha$-RuCl${}_3$
• Classification of gapless Z2 spin liquids in three-dimensional Kitaev models
• Phonon Assisted Multimagnon Optical Absorption and Long Lived Two-Magnon States in Undoped Lamellar Copper Oxides
• Excitonic quasiparticles in a spin-orbit Mott insulator
• Relation between Kitaev magnetism and structure in $\alpha$-RuCl${}_3$
• Theoretical investigation of the magnetic dynamics in $\alpha$-RuCl${}_3$
• Importance of anisotropic exchange interactions in honeycomb iridates. Minimal model for zigzag antiferromagnetic order in Na${}_2$IrO${}_3$
• J${}_{eff}$ description of the honeycomb Mott insulator $\alpha$-RuCl${}_3$
• Antiferromagnetic resonance and terahertz continuum in $\alpha -$RuCl${}_3$
• Observation of two-magnon bound states in the two-leg ladders of (Ca,La)14Cu24O41
• Theory of Phonon-Assisted Multimagnon Optical Absorption and Bimagnon States in Quantum Antiferromagnets
• Electronic Structure of the Kitaev Material $\alpha$-${\text{RuCl}}_3$ Probed by Photoemission and Inverse Photoemission Spectroscopies
• The range of non-Kitaev terms and fractional particles in RuCl${}_3$
• Optical study of orbital excitations in transition-metal oxides
• Spin-orbit entangled j=1/2 moments in Ba${}_2$CeIrO${}_6$ -- a frustrated fcc quantum magnet
• Observation of spin-orbit excitations and Hund's multiplets in Ca${}_2$RuO${}_4$
• Detuning the Honeycomb of $\alpha$-RuCl${}_3$: Pressure-Dependent Optical Studies Reveal Broken Symmetry
• Electronically highly cubic conditions for Ru in alpha-RuCl3
• Electronic and phonon excitations in α-RuCl${}_3$
• Jahn-Teller effect in systems with strong on-site spin-orbit coupling
• From a quasimolecular band insulator to a relativistic Mott insulator in $t_{2g}^5$ systems with a honeycomb lattice structure
• Resonant inelastic x-ray scattering study of $\alpha$-RuCl${}_3$: a progress report
• Collective orbital excitations in orbitally ordered YVO3 and HoVO3
• Possibility to realize spin-orbit-induced correlated physics in iridium fluorides
• High-energy electronic excitations in Sr${}_2$IrO${}_4$ observed by Raman scattering
• Low temperature enhancement of ferromagnetic Kitaev correlations in α-RuCl3

Cited by in corpus (14)

• Exciton-driven antiferromagnetic metal in a correlated van der Waals insulator
• Experimental signatures of quantum and topological states in frustrated magnetism
• Modified Curie-Weiss Law for $j_{\mathrm{eff}}$ Magnets
• Light-induced magnetization driven by interorbital charge motion in a spin-orbit assisted Mott insulator alpha-RuCl3
• Energy scales in 4f1 delafossite magnets: crystal-field splittings larger than the strength of spin-orbit coupling in KCeO2
• Electronic excitations in $5d^4$ J=0 Os${}^{4+}$ halides studied by RIXS and optical spectroscopy
• Spin-orbit coupling in a half-filled $t_{2g}$ shell: the case of $5d^3$ K${}_2$ReCl${}_6$
• Spin-orbital-lattice entanglement in the ideal j=1/2 compound K${}_2$IrCl${}_6$
• Non-local features of the spin-orbit exciton in Kitaev materials
• Spin-orbit excitons in a correlated metal: Raman scattering study of Sr2RhO4
• Sweet spot in the RuCl${}_3$ magnetic system: nearly ideal $j_{\mathrm{eff}}=1/2$ moments and maximized $K/J$ ratio under pressure
• Understanding the magnetic interactions of the zig-zag honeycomb lattice: Application to $\alpha$-RuCl${}_3$
• Nature of the Topological Transition of the Kitaev Model in [111] Magnetic Field
• Photoinduced Pseudospin Polarization in a Three-Orbital Hubbard Model