Ir-pyrochlore epitaxial films for discovery of new topological phases

The A2B2O7 pyrochlore oxides have been predicted to exhibit potential novel topological phases, such as topological insulators and Weyl semimetals. The most promising materials for these new phenomena are pyrochlores with rare earth elements on the A site and 5d transition metals, such as iridium, on the B site. In particular, it is predicted that epitaxial strain is critically important in stabilizing the topological phases. Based on our sputtering deposition technique and experience in epitaxial growth of various complex oxides, we grow epitaxial Nd2Ir2O7 and Eu2Ir2O7 films. X-ray diffraction (XRD) and scanning transmission electron microscopy (STEM) results demonstrate the single crystalline structure and pyrochlore ordering in Nd2Ir2O7 films. We are currently characterizing the electronic and magnetic properties with the goal of observing the predicted topological phases.