More bridging ligands activate direct exchange: the case of anisotropic Kitaev effective magnetic interactions

Abstract

A magnet is a collection of magnetic moments. How those interact is determined by what lies in between. In transition-metal and rare-earth magnetic compounds, the configuration of the ligands around each magnetic center and the connectivity of the ligand cages are therefore pivotal -- for example, the mutual interaction of magnetic species connected through one single ligand is qualitatively different from the case of two bridging anions. Two bridging ligands are encountered in Kitaev magnets. The latter represent one of the revelations of the 21st century in magnetism research: they feature highly anisotropic intersite couplings with seemingly counterintuitive directional dependence for adjacent pairs of magnetic sites and unique quantum spin-liquid ground states that can be described analytically. Current scenarios for the occurrence of pair-dependent magnetic interactions as proposed by Kitaev rely on $indirect$ exchange mechanisms based on intersite electron hopping. Analyzing the wavefunctions of Kitaev magnetic bonds at both single- and multi-configuration levels, we find however that $direct$, Coulomb exchange may be at least as important, in 5$d$ and 4$d$ $t_{2g}^5$, 3$d$ $t_{2g}^5{e}_g^2$, and even rare-earth 4$f^1$ Kitaev-Heisenberg magnets. Our study provides concept clarification in Kitaev magnetism research and the essential reference points for reliable computational investigation of how novel magnetic ground states can be engineered in Kitaev, Kitaev-Heisenberg, and Heisenberg edge-sharing systems.

References in corpus (34)

• 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
• Kitaev quantum spin liquid - concept and materialization
• Models and Materials for Generalized Kitaev Magnetism
• Spin waves and revised crystal structure of honeycomb iridate Na2IrO3
• Orbital order and fluctuations in Mott insulators
• Low-temperature crystal and magnetic structure of $\alpha$-RuCl3
• Evidence for a spinon Fermi surface in a triangular lattice quantum spin liquid candidate
• Pseudospin exchange interactions in d^7 cobalt compounds: Possible realization of the Kitaev model
• Spin-orbit excitation energies, anisotropic exchange, and magnetic phases of honeycomb RuCl3
• Field-tunable quantum disordered ground state in the triangular lattice antiferromagnet NaYbO${}_2$
• Kitaev-Heisenberg Hamiltonian for High-Spin $d^7$ Mott Insulators
• NaYbS${}_2$ - a new planar spin-$\frac{1}{2}$ triangular-lattice magnet and putative spin liquid
• Quantum fluctuations in the effective pseudospin-1/2 model for magnetic pyrochlore oxides
• Microscopic mechanism for higher-spin Kitaev model
• Frustration and anisotropic exchange in ytterbium magnets with edge-shared octahedra
• Materials design of Kitaev spin liquids beyond the Jackeli-Khaliullin mechanism
• Honeycomb Layered Oxides: Structure, Energy Storage, Transport, Topology and Relevant Insights
• Heisenberg exchange enhancement by orbital relaxation in cuprate compounds
• Magnetization-polarization cross-control near room temperature in hexaferrite single crystals
• Orbital reconstruction in nonpolar tetravalent transition-metal oxide layers
• Magnetic Couplings in Edge-Sharing High-Spin $d^7$ Compounds
• Non-Kitaev vs. Kitaev Honeycomb Cobaltates
• Bond-dependent anisotropy and magnon decay in cobalt-based Kitaev triangular antiferromagnet
• Competing Antiferromagnetic-Ferromagnetic States in $d^7$ Kitaev Honeycomb Magnet
• Synthesis and Anisotropic Magnetism in Quantum Spin Liquid Candidates $A$YbSe${}_2$ ($A$ = K and Rb)
• Extraction of the interaction parameters for $\alpha -$RuCl${}_3$ from neutron data using machine learning
• Magnetization reversal through an antiferromagnetic state
• Nearly-Resonant Crystalline-Phononic Coupling in Quantum Spin Liquid Candidate CsYbSe${}_2$
• NaRuO${}_2$: Kitaev-Heisenberg exchange in triangular-lattice setting
• Electronic and structural properties of RbCeX${}_2$ (X${}_2$: O${}_2$, S${}_2$, SeS, Se${}_2$, TeSe, Te${}_2$)
• Resonating holes vs molecular spin-orbit coupled states in group-5 lacunar spinels
• Electron correlation effects in diamond: a wave-function quantum chemistry study of the quasiparticle band structure
• Quantum chemical insights into hexaboride electronic structures: correlations within the boron $p$-orbital subsystem