Observation of Current-Induced Lattice Distortion in Spin–Orbit Coupled Iridium Oxide Ca₅Ir₃O₁₂

We report current-induced lattice distortion in iridium oxide Ca₅Ir₃O₁₂ with a hexagonal structure that exhibits nonlinear conductivity along the c-axis. Using the synchrotron radiation X-ray diffraction experiments on the single crystal, the change in the lattice constant due to thermal expansion at temperatures above room temperature and the change in the lattice constant due to the application of current along the c-axis were investigated. We found that the current application along the c-axis caused anisotropic lattice distortion that expanded within the c-plane direction. These results show that the change in the lattice constant ratio a/c due to the application of current is greater than the change in thermal expansion caused by self-heating. In spin–orbit coupled oxides, this result reveals the possibility of significant current-induced distortion based on a mechanism different from the conventional piezoelectric effect.