From High-T_c to Low-T_c: Multi-orbital Effects in Transition Metal Oxides

Despite the structural resemblance of certain cuprate and nickelate parent compounds there is a striking spread of T_c among such transition metal oxide superconductors. We adopt a minimal two-orbital e_g model which covers cuprates and nickelate heterostructures in different parametric limits, and analyse its superconducting instabilities. The joint consideration of interactions, doping, Fermiology, and in particular the e_g orbital splitting allows us to explain the strongly differing pairing propensities in cuprate and nickelate superconductors.