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Strain engineering of the charge and spin-orbital interactions in Sr 2 IrO 4

Type of publication Peer-reviewed
Publikationsform Original article (peer-reviewed)
Author Paris Eugenio, Tseng Yi, Pärschke Ekaterina M., Zhang Wenliang, Upton Mary H., Efimenko Anna, Rolfs Katharina, McNally Daniel E., Maurel Laura, Naamneh Muntaser, Caputo Marco, Strocov Vladimir N., Wang Zhiming, Casa Diego, Schneider Christof W., Pomjakushina Ekaterina, Wohlfeld Krzysztof, Radovic Milan, Schmitt Thorsten,
Project Electron-Phonon Interactions in Rare-Earth Nickelates and Superconducting Cuprates
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Original article (peer-reviewed)

Journal Proceedings of the National Academy of Sciences
Volume (Issue) 117(40)
Page(s) 24764 - 24770
Title of proceedings Proceedings of the National Academy of Sciences
DOI 10.1073/pnas.2012043117

Open Access

Type of Open Access Publisher (Gold Open Access)


In the high spin–orbit-coupled Sr 2 IrO 4 , 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 Sr 2 IrO 4 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 Sr 2 IrO 4 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 cross-over 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 Sr 2 IrO 4 , originating from the modified hopping elements between the t 2g orbitals. Our work highlights the central role played by the lattice degrees of freedom in determining both the pseudospin and charge excitations of Sr 2 IrO 4 and provides valuable information toward the control of the ground state of complex oxides in the presence of high spin–orbit coupling.