Strain-engineering of the charge and spin-orbital interactions in Sr2IrO4

Abstract

In the high spin-orbit coupled Sr2IrO4, the high sensitivity of the ground state to the details of the local lattice structure shows a large potential for the manipulation of the functional properties by inducing local lattice distortions. We use epitaxial strain to modify the Ir-O bond geometry in Sr2IrO4 and perform momentum-dependent Resonant Inelastic X-ray Scattering (RIXS) at the metal and at the ligand sites to unveil the response of the low energy elementary excitations. We observe that the pseudospin-wave dispersion for tensile-strained Sr2IrO4 films displays large softening along the [h,0] direction, while along the [h,h] direction it shows hardening. This evolution reveals a renormalization of the magnetic interactions caused by a strain-driven crossover from anisotropic to isotropic interactions between the magnetic moments. Moreover, we detect dispersive electron-hole pair excitations which shift to lower (higher) energies upon compressive (tensile) strain, manifesting a reduction (increase) in the size of the charge gap. This behavior shows an intimate coupling between charge excitations and lattice distortions in Sr2IrO4, originating from the modified hopping elements between the t2g orbitals. Our work highlights the central role played by the lattice degrees of freedom in determining both the pseudospin and charge excitations of Sr2IrO4 and provides valuable information towards the control of the ground state of complex oxides in the presence of high spin-orbit coupling.

arXiv commentPublished in Proceedings of the National Academy of Sciences, September 2020

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• Controllable emergent spatial spin modulation in Sr2IrO4 by in situ shear strain
• Strain tuned magnetotransport of Jeff=1/2 antiferromagnetic Sr2IrO4 thin films
• Probing magnetic orbitals and Berry curvature with circular dichroism in resonant inelastic X-ray scattering
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• Charge ordering in Ir dimers in the ground state of Ba${}_5$AlIr${}_2$O${}_{11}$
• Modeling multiorbital effects in Sr2IrO4 under strain and a Zeeman field
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• Orbital inversion and emergent lattice dynamics in infinite layer CaCoO${}_2$
• Strain tunable electronic ground states in two-dimensional iridate thin films
• Anisotropy of Antiferromagnetic Domains in a Spin-orbit Mott Insulator
• Coexistence of insulator-like paramagnon and metallic spin-orbit exciton modes in SrIrO${}_3$
• Orbital-Selective Spin-Orbit Mott Insulator in Fractional Valence Iridate La${}_3$Ir${}_3$O${}_{11}$