Coupling lattice instabilities across the interface in ultrathin oxide heterostructures*

The resistivity of ultrathin SrIrO3 films grown epitaxially on SrTiO3 displays an anomaly at the temperature corresponding to the cubic tetragonal transition of the substrate. We investigate its origin through synchrotron X-ray diffraction measurements, electronic transport and ab-initio calculations. The effect is ascribed to a redistribution of orthorhombic structural domains, driven by the cubic-tetragonal transition of SrTiO3. The compressive strain induced by the substrate is found to force the in-phase octahedral rotation axis of the film to lie in-plane, giving rise to a twofold degenerate domain structure that couples to SrTiO3 tetragonal domains. Transport measurements in van der Pauw devices reveal that a strong anisotropy of the longitudinal resistivity develops below the transition temperature. The strong structure-property relationships in the iridates makes these compounds particularly suitable for static and dynamic coupling at interfaces, providing a promising route towards realizing novel functionalities in oxide heterostructures.