Metastable honeycomb SrTiO₃/SrIrO₃ heterostructures

Recent theory predictions of exotic band topologies in (111) honeycomb perovskite SrIrO₃ layers sandwiched between SrTiO₃ have garnered much attention in the condensed matter physics and materials communities. However, perovskite SrIrO₃ film growth in the (111) direction remains unreported, as efforts to synthesize pure SrIrO₃ on (111) perovskite substrates have yielded films with monoclinic symmetry rather than the perovskite structure required by theory predictions. In this study, we report the synthesis of ultra-thin metastable perovskite SrIrO₃ films capped with SrTiO₃ grown on (111) SrTiO₃ substrates by pulsed laser deposition. The atomic structure of the ultra-thin films was examined with scanning transmission electron microscopy (STEM), which suggests a perovskite layering distinct from the bulk SrIrO₃ monoclinic phase. In-plane 3-fold symmetry for the entire heterostructure was confirmed using synchrotron surface X-ray diffraction to measure symmetry equivalent crystal truncation rods. Our findings demonstrate the ability to stabilize (111) honeycomb perovskite SrIrO₃, which provides an experimental avenue to probe the phenomena predicted for this material system.