Effective J=1/2 Insulating State in Ruddlesden-Popper Iridates: An LDA plus DMFT Study

Using ab initio methods for correlated electrons in solids, we investigate the metal-insulator transition across the Ruddlesden-Popper (RP) series of iridates and explore the robustness of the J(eff) = 1/2 state against band effects due to itineracy, tetragonal distortion, octahedral rotation, and Coulomb interaction. We predict the effects of epitaxial strain on the optical conductivity, magnetic moments, and J(eff) = 1/2 ground-state wave functions in the RP series. To describe the solution of the many-body problem in an intuitive picture, we introduce a concept of energy-dependent atomic states, which strongly resemble the atomic J(eff) = 1/2 states but with coefficients that are energy or time dependent. We demonstrate that the deviation from the ideal J(eff) = 1/2 state is negligible at short time scales for both single-and double-layer iridates, while it becomes quite significant for Sr3Ir2O7 at long times and low energy. Interestingly, Sr2IrO4 is positioned very close to the SU(2) limit, with only similar to 3% deviation from the ideal J(eff) = 1/2 situation.