Bandwidth-Controlled Insulator-Metal Transition and Correlated Metallic State in 5\(d\) Transition Metal Oxides Sr\(_{n+1}\)Ir\(_{n}\)O\(_{3n+1}\) (\(n\)=1, 2, and \(\infty\))

Abstract

We investigated the electronic structures of the 5\(d\) Ruddlesden-Popper series Sr\(_{n+1}\)Ir\(_{n}\)O\(_{3n+1}\) (\(n\)=1, 2, and \(\infty\)) using optical spectroscopy and first-principles calculations. As 5\(d\) orbitals are spatially more extended than 3\(d\) or 4\(d\) orbitals, it has been widely accepted that correlation effects are minimal in 5\(d\) compounds. However, we observed a bandwidth-controlled transition from a Mott insulator to a metal as we increased \(n\). In addition, the artificially synthesized perovskite SrIrO\(_{3}\) showed a very large mass enhancement of about 6, indicating that it was in a correlated metallic state.