Correlated Phases in Thin Film Nickelates

Nickel oxides have long been of interest due to their strong electron interactions, dating back to the question of why NiO is an insulator, not a metal. In perovskite and infinite-layer structures (as well as related derivatives), the Ni oxidation state can range from 3+ to 1+ via structural and chemical doping - although all are commonly referred to as nickelates. This family of compounds exhibit a wide range of correlated phenomena, such as metal-insulator transitions, magnetism, density-wave/stripe instabilities, and recently superconductivity. We will present recent progress on using topochemical processes and strain to synthesize and probe some of these phase transitions and ground states.