Role of correlations in Ruddlesden-Popper bilayer nickelates under compressive strain

It has been discovered that thin films of the bilayer Ruddlesden-Popper (RP) nickelate La3Ni2O7 (La327) are superconducting under compressive strain. In order to better understand the many-body normal state (which superconductivity arises from), it is necessary to understand the role that correlations play in its electronic structure. We use a fully charge self-consistent DFT+eDMFT approach to study La327 at three compressive strain levels. In contrast with DFT and DFT+U studies, at the compressive strain where superconductivity has been experimentally observed (-2%), we find a γ-pocket, consistent with recent ARPES results, when dynamical correlations are included. Its associated band (mainly of dz2 character) displays “flat band” like features where it crosses the Fermi level. Larger strain levels suppress the γ-pocket, which may have implications for superconductivity or its pairing symmetry.