Giant Magnon Gap in Bilayer Iridate Sr3Ir2O7: Enhanced Pseudo-dipolar Interactions Near the Mott Transition

Abstract

Using resonant inelastic x-ray scattering, we observe in the bilayer iridate Sr3Ir2O7, a spin-orbit coupling driven magnetic insulator with a small charge gap, a magnon gap of ~92 meV for both acoustic and optical branches. This exceptionally large magnon gap exceeds the total magnon bandwidth of ~70 meV and implies a marked departure from the Heisenberg model, in stark contrast to the case of the single-layer iridate Sr2IrO4. Analyzing the origin of these observations, we find that the giant magnon gap results from bond-directional pseudo-dipolar interactions that are strongly enhanced near the metal-insulator transition boundary. This suggests that novel magnetism, such as that inspired by the Kitaev model built on the pseudo-dipolar interactions, may emerge in small charge-gap iridates.

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• Surface States of Perovskite Iridates AIrO${}_3$; Signatures of Topological Crystalline Metal with Nontrivial ${\mathbb{Z}}_2$ Index
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• Non-collinear antiferromagnetism of coupled spins and pseudospins in the double perovskite La2CuIrO6
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• Strain-engineering of the charge and spin-orbital interactions in Sr2IrO4
• 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${}_7$
• $J_{eff}=1/2$ Mott Insulating State in Rh and Ir Fluorides
• Lattice frustration in spin-orbit Mott insulator Sr3Ir2O7 at high pressure
• Magnetic properties of bilayer Sr${}_3$Ir${}_2$O${}_7$: role of epitaxial strain and oxygen vacancies
• Disordered dimer state in electron-doped Sr${}_3$Ir${}_2$O${}_7$
• Probing single magnon excitations in Sr${}_2$IrO${}_4$ using O $K$-edge resonant inelastic X-ray scattering
• Anomalous Magnetoresistance due to Longitudinal Spin Fluctuations in a Jeff = 1/2 Mott Semiconductor
• Symmetry-resolved two-magnon excitations in a strong spin-orbit-coupled bilayer antiferromagnet
• Strong anisotropy within a Heisenberg model in the J=1/2 insulating state of Sr2Ir0.8Ru0.2O4
• Overdamped antiferromagnetic strange metal state in Sr${}_3$IrRuO${}_7$
• Effect of broken symmetry on resonant inelastic x-ray scattering from undoped cuprates
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