Local structure and short-range correlation in pressure-induced charge glass state of BiNiO3

The order or disorder of electrons in condensed matter plays a crucial role in determining the physical properties of the materials. In many mixed-valence materials, a charge-ordered (CO) insulating state can be observed, which is analogues to a crystalline solid. Upon heating, this charge ordered state melts and transitions into a “charge-liquid” (metallic) phase, often accompanied by intriguing physical phenomena and functionalities, such as the Verwey transition in Fe3O4 and colossal magnetoresistance effects in manganites like perovskite manganite La0.5Ca0.5MnO3. BiNiO3 is a unique perovskite oxide that requires high pressure high temperature to prepare and exhibits a rich phase diagram due to melting of electronic orderings that drive a large negative thermal expansion. We have recently observed a novel pressure- and temperature induced intermediate "charge glassy" state that we propose to study here, leveraging our recent high pressure PDF developments on PEARL.