Spin-orbit effects in pentavalent Iridates: Models and materials

Abstract

Spin-orbit effects in heavy 5$d$ transition metal oxides, in particular, iridates, have received enormous current interest due to the prediction as well as the realization of a plethora of exotic and unconventional magnetic properties. While a bulk of these works are based on tetravalent iridates ($d^5$), where the counter-intuitive insulating state of the rather extended 5$d$ orbitals are explained by invoking strong spin-orbit coupling, the recent quest in iridate research has shifted to the other valencies of Ir, of which pentavalent iridates constitute a notable representative. In contrast to the tetravalent iridates, spin-orbit entangled electrons in $d^4$ systems are expected to be confined to the $J=0$ singlet state without any resultant moment or magnetic response. However, it has been recently predicted that, magnetism in $d^4$ systems may occur via magnetic condensation of excitations across spin-orbit-coupled states. In reality, the magnetism in Ir${}^{5+}$ systems are often quite debatable both from theoretical as well as experimental point of view. Here we provide a comprehensive overview of the spin-orbit coupled $d^4$ model systems and its implications in the studied pentavalent iridates. In particular, we review here the current experimental and theoretical understanding of the double perovskite ($A_{2}B$YIrO${}_6$, $A=$ Sr, Ba, $B=$Y, Sc, Gd), 6H-perovskite (Ba${}_{3}M$Ir${}_2$O${}_9$, $M=$ Zn, Mg, Sr, Ca), post-perovskite (NaIrO${}_3$), and Hexagonal (Sr${}_3$MIrO${}_6$) iridates, along with a number of open questions that require future investigation.

References in corpus (99)

• Topological Insulators
• Topological insulators and superconductors
• $Z_2$ Topological Order and the Quantum Spin Hall Effect
• Superconducting proximity effect and Majorana fermions at the surface of a topological insulator
• Electronic Structure of Pyrochlore Iridates: From Topological Dirac Metal to Mott Insulator
• Mott Insulators in the Strong Spin-Orbit Coupling Limit: From Heisenberg to a Quantum Compass and Kitaev Models
• New Perspectives for Rashba Spin-Orbit Coupling
• Topological Insulator Materials
• Novel Jeff = 1/2 Mott State Induced by Relativistic Spin-Orbit Coupling in Sr2IrO4
• Correlated quantum phenomena in the strong spin-orbit regime
• Mott physics and band topology in materials with strong spin-orbit interaction
• 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
• Generic spin model for the honeycomb iridates beyond the Kitaev limit
• Models and Materials for Generalized Kitaev Magnetism
• Spin-Liquid State in the S = 1/2 Hyperkagome Antiferromagnet Na4Ir3O8
• Direct evidence of a zigzag spin chain structure in the honeycomb lattice: A neutron and x-ray diffraction investigation on single crystal $\mathrm{N}{\mathrm{a}}_2\mathrm{Ir}{\mathrm{O}}_3$
• Quantum Criticality
• Hyper-honeycomb iridate $\beta$-Li2IrO3 as a platform for Kitaev magnetism
• Long range magnetic ordering in Na${}_2$IrO${}_3$
• Observation of a $d$-wave gap in electron-doped Sr${}_2$IrO${}_4$
• Semimetal and Topological Insulator in Perovskite Iridates
• Excitonic Magnetism in Van Vleck-type d^4 Mott Insulators
• Evidence of an odd-parity hidden order in a spin-orbit coupled correlated iridate
• Optical evidence for a Weyl semimetal state in pyrochlore Eu2Ir2O7
• The Challenge of Spin-Orbit-Tuned Ground States in Iridates
• Higgs mode and its decay in a two dimensional antiferromagnet
• Recent progress on correlated electron systems with strong spin-orbit coupling
• Non-coplanar and counter-rotating incommensurate magnetic order stabilized by Kitaev interactions in $\gamma$-Li2IrO3
• Dirac nodal lines and induced spin Hall effect in metallic rutile oxides
• Unconventional magnetic order on the hyperhoneycomb Kitaev lattice in $\beta$-Li2IrO3: full solution via magnetic resonant x-ray diffraction
• Kitaev-Heisenberg models for iridates on the triangular, hyperkagome, kagome, fcc, and pyrochlore lattices
• Spin-orbit coupling in $d^2$ ordered double perovskites
• Novel magnetism of Ir5+ ions in the double perovskite Sr2YIrO6
• Effective J=1/2 insulating state in Ruddlesden-Popper iridates: An LDA+DMFT study
• Transport in two-dimensional topological materials: recent developments in experiment and theory
• Valence bond glass on an fcc lattice in the double perovskite Ba2YMoO6
• Importance of anisotropic exchange interactions in honeycomb iridates. Minimal model for zigzag antiferromagnetic order in Na${}_2$IrO${}_3$
• Spin-orbit semimetal SrIrO${}_3$ in the two-dimensional limit
• Coulomb-Enhanced Spin-Orbit Splitting: The Missing Piece in the Sr2RhO4 Puzzle
• Nature of the magnetism of iridium in the double perovskite Sr2CoIrO6
• Spectroscopic signatures of a bandwidth-controlled Mott transition at the surface of 1T-TaSe${}_2$
• Spin-orbit physics of j=1/2 Mott insulators on the triangular lattice
• Dimensionality-driven metal-insulator-transition in spin-orbit coupled SrIrO${}_3$
• Ba2YIrO6: A cubic double perovskite material with Ir5+ ions
• Metal-insulator transition and topological properties of pyrochlore iridates
• Novel magnetic state in $d^4$ Mott insulators
• Square Lattice Iridates
• Spin liquid behaviour in Jeff=1/2 triangular lattice Ba3IrTi2O9
• Quantum behavior of Orbitals in Ferromagnetic Titanates: Novel Orderings and Excitations
• Mixing of $t_{2g}$-$e_g$ orbitals in 4d and 5d transition metal oxides
• Cubic spin-orbit coupling and anomalous Josephson effect in planar junctions
• NaIrO3 - A pentavalent post-perovskite
• Spin-orbital liquid state assisted by singlet-triplet excitation in $J=0$ ground state of Ba${}_3$ZnIr${}_2$O${}_9$
• Effects of Strain on Orbital Ordering and Magnetism at the Perovskite Oxide Interfaces: LaMnO${}_3$/SrMnO${}_3$
• Coulomb Correlations in 4d and 5d Oxides from First Principles - or How Spin-Orbit Materials choose their Effective Orbital Degeneracies
• Determination of Hund's coupling in 5d Oxides using Resonant Inelastic X-ray Scattering
• Magnetism and spin-orbit coupling in Ir-based double perovskites La${}_{(}2-x$Sr${}_x$CoIrO${}_6$
• New Evidence for a Low-Temperature Magnetic Ground State in Double-Perovskite Iridates with Ir5+(5d4) Ions
• The iridium double perovskite Sr2YIrO6 revisited: A combined structural and specific heat study
• Effective magnetic interactions in spin-orbit coupled $d^4$ Mott insulators
• Effect of Spin-Orbit Interaction on (4d)^3- and (5d)^3 -Based Transition-Metal Oxides
• Magnetic Orders Proximal to the Kitaev Limit in Frustrated Triangular Systems: Application to Ba${}_3$IrTi${}_2$O${}_9$
• Effect of spin orbit coupling and Hubbard $U$ on the electronic structure of IrO${}_2$
• Unraveling the nature of magnetism of the 5${\mathbf{d}}^4$ double perovskite Ba${}_2$YIrO${}_6$
• J-freezing and Hund's rules in spin-orbit-coupled multiorbital Hubbard models
• Long-Range Spin-Triplet Correlations and Edge Spin Currents in Diffusive Spin-Orbit Coupled SNS Hybrids with a Single Spin-Active Interface
• Critical supercurrent and ${\varphi }_0$ state for probing a persistent spin helix
• On the possibility of excitonic magnetism in Ir double perovskites
• Origin of magnetic moments and presence of a resonating valence bond state in Ba${}_2$YIrO${}_6$
• Spin-orbit coupled systems in the "atomic" limit: rhenates, osmates, iridates
• Revisiting the Kitaev material candidacy of Ir4+ double perovskite iridates
• From a quasimolecular band insulator to a relativistic Mott insulator in $t_{2g}^5$ systems with a honeycomb lattice structure
• Magnetism out of disorder in a J=0 compound Ba2YIrO6
• Possible spin-orbit driven spin-liquid ground state in the double perovskite phase of Ba3YIr2O9
• Influence of structural distortions on the Ir magnetism in Ba2-xSrxYIrO6 double perovskites
• Nonmagnetic $J=0$ State and Spin-Orbit Excitations in K${}_2$RuCl${}_6$
• Hopping induced ground-state magnetism in 6H perovskite iridates
• Strange semimetal dynamics in SrIrO${}_3$
• Putative spin liquid in the triangle-based iridate Ba${}_3$IrTi${}_2$O${}_9$
• Diluted paramagnetic impurities in nonmagnetic Ba${}_2$YIrO${}_6$
• Metal-insulator transition in three-band Hubbard model with strong spin-orbit interaction
• Complex Orbital State Stabilized by Strong Spin-Orbit Coupling in a Metallic Iridium Oxide IrO${}_2$
• The electronic structure of NaIrO${}_3$, Mott insulator or band insulator?
• Superconducting monolayer deposited on substrate: effects of the spin-orbit coupling induced by proximity effects
• Unconventional magnetism in the 4d${}^4$ based ($S=1$) honeycomb system Ag${}_3$LiRu${}_2$O${}_6$
• Current-induced spin-orbit field in permalloy interfaced with ultrathin Ti and Cu
• Lone octupole and bulk magnetism in osmate 5d2 double perovskites
• Spin-orbit coupling driven insulating state in hexagonal iridates Sr3MIrO6 (M = Sr, Na and Li)
• BCS-BEC crossover in a $(t_{2g}{)}^4$ Excitonic Magnet
• Spin-orbital excitons and their potential condensation in pentavalent iridates
• Magnetization Reversal by Tuning Rashba Spin-Orbit Interaction and Josephson Phase in a Ferromagnetic Josephson Junction
• A Poor Man's Derivation of Quantum Compass-Heisenberg Interaction: Superexchange Interaction in J-J Coupling Scheme
• Nature of the Magnetic Interactions in Sr${}_3$NiIrO${}_6$
• Study of Nontrivial Magnetism in 3$d$-5$d$ Transition Metal based Double Perovskites
• Magnetic phase transitions in quantum spin-orbital liquids
• Transport in two dimensional Rashba electron systems doped with interacting magnetic impurities
• Probing the magnetoelectric effect in noncentrosymmetric superconductors by equal-spin Andreev tunneling
• Failure to achieve the $J_{eff}$~=~0 state even in nearly isolated Ir${}^{5+}$ in Sr${}_3$NaIrO${}_6$: are iridates enough for realizing true $j$-$j$ coupling?

Cited by in corpus (4)

• Magnetization dynamics fingerprints of an excitonic condensate $t_{2g}^4$ magnet
• $J_{eff}$ states in a quasi one dimensional antiferromagnetic spin chain hexagonal Iridates Sr${}_3$MIrO${}_6$ (M=Mg, Zn, Cd): an $ab-initio$ comparative perspective
• On the electronic ground state of two non-magnetic pentavalent honeycomb iridates
• Jahn-Teller states mixed by spin-orbit coupling in an electromagnetic field