An Odd-Parity Hidden Order in a Perovskite Iridate Revealed Using Nonlinear Optics
Abstract: Iridium oxides are electronic systems that combine two central threads of modern quantum materials research - correlated electron physics that underlies phenomena such as high-Tc superconductors, and spin-orbit physics that describes systems such as topological insulators. The perovskite iridate Sr2IrO4 is of particular interest owing to its remarkable analogy to high-Tc cuprates, including its striking structural and electronic similarities to the curpate parent compound La2CuO4 and recent observations of pseudogap and d-wave gap behaviors upon doping. In this talk, I will describe the nonlinear optical spectroscopy and microscopy techniques that we developed recently to identify unconventional multipolar ordered phases. I will show the experimental evidences for an odd-parity non-dipolar ordered phase in both undoped and hole-doped Sr2IrO4, and discuss the potential relevance of this novel phase to pseudogap and superconductivity in both Sr2IrO4 and high-Tc cuprate YBa2Cu3Oy.