Evidence of quantum dimer excitations in Sr${}_3$Ir${}_2$O${}_7$

Abstract

The magnetic excitation spectrum in the bilayer iridate Sr${}_3$Ir${}_2$O${}_7$ has been investigated using high-resolution resonant inelastic x-ray scattering (RIXS) performed at the iridium L${}_3$ edge and theoretical techniques. A study of the systematic dependence of the RIXS spectrum on the orientation of the wavevector transfer, $\mathbf{Q}$, with respect to the iridium-oxide bilayer has revealed that the magnon dispersion is comprised of two branches well separated in energy and gapped across the entire Brillouin zone. Our results contrast with those of an earlier study which reported the existence of a single dominant branch. While these earlier results were interpreted as two overlapping modes within a spin-wave model of weakly coupled iridium-oxide planes, our results are more reminiscent of those expected for a system of weakly coupled dimers. In this latter approach the lower and higher energy modes find a natural explanation as those corresponding to transverse and longitudinal fluctuations, respectively. We have therefore developed a bond-operator theory which describes the magnetic dispersion in Sr${}_3$Ir${}_2$O${}_7$ in terms of quantum dimer excitations. In our model dimerisation is produced by the leading Heisenberg exchange, $J_c$, which couples iridium ions in adjacent planes of the bilayer. The Hamiltonian also includes in plane exchange, $J$, as well as further neighbour couplings and relevant anisotropies. The bond-operator theory provides an excellent account of the dispersion of both modes, while the measured $\mathbf{Q}$ dependence of the RIXS intensities is in reasonable qualitative accord with the spin-spin correlation function calculated from the theory. We discuss our results in the context of the quantum criticality of bilayer dimer systems in the presence of anisotropic interactions derived from strong spin-orbit coupling.

arXiv comment9 pages, 6 figures

References in corpus (31)

• 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
• Resonant Inelastic X-ray Scattering Studies of Elementary Excitations
• Correlated quantum phenomena in the strong spin-orbit regime
• Mott physics and band topology in materials with strong spin-orbit interaction
• Isospin Dynamics in Sr2IrO4 : Forging Links to Cuprate Superconductivity
• Spin-ladders with spin gaps: A description of a class of cuprates
• Spin Gaps and Spin Dynamics in La_{2-x}Sr_xCuO_4 and YBa_2Cu_3O7_δ
• Order-Disorder Transition in a Two-Layer Quantum Antiferromagnet
• Lattice-Driven Magnetoresistivity and Metal-Insulator Transition in Single-Layered Iridates
• Giant Magnon Gap in Bilayer Iridate Sr3Ir2O7: Enhanced Pseudo-dipolar Interactions Near the Mott Transition
• Statics and dynamics of weakly coupled antiferromagnetic spin-1/2 ladders in a magnetic field
• Dimensionality Driven Spin-Flop Transition in Layered Iridates
• Measurement of magnetic excitations in the two-dimensional antiferromagnetic Sr2CuO2Cl2 insulator using resonant x-ray scattering:Evidence for extended interactions
• Robustness of basal-plane antiferromagnetic order and the $J_{eff}=1/2$ state in single-layer iridate spin-orbit Mott insulators
• Testing the validity of the strong spin-orbit-coupling limit for octahedrally coordinated iridates in a model system Sr${}_3$CuIrO${}_6$
• Slaving of the magnetic moment canting to the correlated oxygen rotation in Sr2IrO4 revealed by X-ray resonant scattering
• Bound states of magnons in the S=1/2 quantum spin ladder
• Imaging the evolution of metallic states in a spin-orbit interaction driven correlated iridate
• Magnetic properties and spin waves of bilayer magnets in a uniform field
• CaIrO3: a Spin-Orbit Mott Insulator Beyond the jeff = 1/2 Ground State
• Antiferromagnetic order and domains in Sr3Ir2O7 probed by x-ray resonant scattering
• Resonant X-ray scattering and the $j_{\mathrm{eff}}=1/2$ electronic ground state in iridate perovskites
• Unified quantitative model for magnetic and electronic spectra of the undoped cuprates
• Spin Gaps and Bilayer Coupling in YBa${}_2$Cu${}_3$O${}_{7-\delta }$ and YBa${}_2$Cu${}_4$O${}_8$
• Spin ordering and electronic texture in the bilayer iridate Sr${}_3$Ir${}_2$O${}_7$
• Non-linear bond-operator theory and 1/d expansion for coupled-dimer magnets I: Paramagnetic phase
• Crystal field splitting in Sr${}_{n+1}$Ir${}_n$O${}_{3n+1}$ ($n$ = 1, 2) iridates probed by x-ray Raman spectroscopy
• Direct observation of the Mott gap in strontium iridate with a scanning tunneling microscope
• Non-linear bond-operator theory and 1/d expansion for coupled-dimer magnets II: Antiferromagnetic phase and quantum phase transition
• Bi-layer Heisenberg model studied by the Schwinger-boson Gutzwiller-projection method

Cited by in corpus (42)

• The Challenge of Spin-Orbit-Tuned Ground States in Iridates
• Spin-orbit-entangled electronic phases in 4$d$ and 5$d$ transition-metal compounds
• Mixing of $t_{2g}$-$e_g$ orbitals in 4d and 5d transition metal oxides
• Fingerprints of Kitaev physics in the magnetic excitations of honeycomb iridates
• Two-magnon Raman scattering and pseudospin-lattice interactions in Sr2IrO4 and Sr3Ir2O7
• Using RIXS to uncover elementary charge and spin excitations in correlated materials
• Dynamical structure factors and excitation modes of the bilayer Heisenberg model
• Pseudospin-lattice coupling in the spin-orbit Mott insulator Sr2IrO4
• A charge density wave-like instability in a doped spin-orbit-assisted weak Mott insulator
• Resonant inelastic x-ray incarnation of Young's double-slit experiment
• Pressure-Induced Confined Metal from the Mott Insulator Sr3Ir2O7
• Strain-engineering of the charge and spin-orbital interactions in Sr2IrO4
• Structural investigation of the bilayer iridate Sr3Ir2O7
• Laser-Induced Transient Magnons in Sr3Ir2O7 Throughout the Brillouin Zone
• Dispersive Magnetic and Electronic Excitations in Iridate Perovskites Probed with Oxygen $K$-Edge Resonant Inelastic X-ray Scattering
• Doping Evolution of Magnetic Order and Magnetic Excitations in (Sr${}_{1-x}$La${}_x$)${}_3$Ir${}_2$O${}_7$
• Antiferromagnetic Excitonic Insulator State in Sr3Ir2O7
• Lattice frustration in spin-orbit Mott insulator Sr3Ir2O7 at high pressure
• Magnetic excitations in a three-orbital model for the strongly spin-orbit coupled iridates: Effect of mixing between the J=1/2 and 3/2 sectors
• Disordered dimer state in electron-doped Sr${}_3$Ir${}_2$O${}_7$
• Quasimolecular electronic structure of the spin-liquid candidate Ba${}_3$InIr${}_2$O${}_9$
• Symmetry-resolved two-magnon excitations in a strong spin-orbit-coupled bilayer antiferromagnet
• Resonant inelastic x-ray scattering of magnetic excitations under pressure
• Octahedral tilting induced isospin reorientation transition in iridate heterostructures
• Stable Higgs mode in anisotropic quantum magnets
• Exciton condensation in bilayer spin-orbit insulator
• Overdamped antiferromagnetic strange metal state in Sr${}_3$IrRuO${}_7$
• Doping driven structural distortion in the bilayer iridate (Sr${}_{1-x}$La${}_x$)${}_3$Ir${}_2$O${}_7$
• Spin-orbital-lattice entanglement in the ideal j=1/2 compound K${}_2$IrCl${}_6$
• Reconciling monolayer and bilayer $J_{\mathrm{eff}}=1/2$ square lattices in hybrid oxide superlattice
• Observation of excitons bound by antiferromagnetic correlations
• Critical fluctuations in the spin-orbit Mott insulator Sr${}_3$Ir${}_2$O${}_7$
• Sr${}_3$Ir${}_2$O${}_7$F${}_2$: Topochemical conversion of a relativistic Mott state into a spin-orbit driven band insulator
• Carrier dynamics in doped bilayer iridates near magnetic quantum criticality
• A $j_{\mathrm{eff}}=1/2$ pseudospinon continuum in CaIrO${}_3$
• Spin dynamics in the square-lattice cupola system Ba(TiO)Cu${}_4$(PO${}_4$)${}_4$
• Putative magnetic quantum criticality in (Sr${}_{\text{1-x}}$La${}_{\text{x}}$)${}_{\text{3}}$Ir${}_{\text{2}}$O${}_{\text{7}}$
• Coexistence of insulator-like paramagnon and metallic spin-orbit exciton modes in SrIrO${}_3$
• Magnetism in artificial Ruddlesden-Popper iridates leveraged by structural distortions
• Mixed-pairing superconductivity in 5d Mott insulators with antisymmetric exchange
• BCS-BEC Crossover of Triplet Exciton Condensation in Bilayer Systems
• Possibility of an unconventional spin state of Ir${}^{4+}$ in Ba${}_{21}$Ir${}_9$O${}_{43}$ single crystal