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

Eugenio Paris, Yi Tseng, Ekaterina M. Pärschke, Wenliang Zhang, Mary H. Upton, Anna Efimenko, Katharina Rolfs, Daniel E. McNally, Laura Maurel, Muntaser Naamneh, Marco Caputo, Vladimir N. Strocov, Zhiming Wang, Diego Casa, Christof W. Schneider, Ekaterina Pomjakushina, Krzysztof Wohlfeld, Milan Radovic, Thorsten Schmitt

Research output: Contribution to journalArticlepeer-review

18 Scopus citations

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 Sr2 IrO4 and perform momentumdependent 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 Sr2IrO4films 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 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 Sr2IrO4and provides valuable information toward the control of the ground state of complex oxides in the presence of high spin-orbit coupling.

Original languageEnglish
Pages (from-to)24764-24770
Number of pages7
JournalProceedings of the National Academy of Sciences of the United States of America
Volume117
Issue number40
DOIs
StatePublished - 6 Oct 2020
Externally publishedYes

Keywords

  • Elementary excitations
  • Magnetoelastic coupling
  • Resonant inelastic X-ray scattering
  • Spin-orbit coupling
  • Strain engineering

ASJC Scopus subject areas

  • General

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