Structural evolution and negative thermal expansion of Sr2IrO4

Sr2IrO4 is an important material in condensed matter physics, displaying a novel Jeff=½ Mott insulating state and being a rare comparative system for understanding the high temperature cuprate superconductors. We have already discovered a high temperature phase transition in this material along with negative thermal expansion over a wide temperature range. We plan further detailed studies across the entire thermal phase diagram to elucidate the details of the octahedral distortions which are critical to the electronic structure and magnetism in this material. In addition our study will provide rare details of negative thermal expansion in a Ruddlesden-Popper perovskite.