Symmetry breaking of in-plane anisotropic magnetoresistance with temperature in La-doped Sr₂IrO₄ film

Electron-doped Sr₂IrO₄ has been the subject of recent attention because of its similarities with hole-doped La₂CuO₄. However, direct evidence of its superconductivity has not yet been observed, which has led to various unresolved issues related to this material. In this study, a 14-nm thick La-doped Sr₂IrO₄ film was grown on a (001) SrTiO₃ substrate. We found that the fourfold component of the in-plane anisotropic magnetoresistance disappears and is replaced by a twofold symmetry as the temperature increases. Variable-temperature x-ray diffraction and spatially resolved optical second-harmonic generation experiments eliminate the possibility of crystal structural distortion. The temperature dependence of direct current magnetization measurements indicates that a change in the spin structure may account for the symmetry breaking, similar to the nematic ordering of iron-based and other superconductors. These provide a perspective on these materials that helps elucidate the nature of magnetic interactions and explores the expected superconductivity of iridates.