Ab initio Evidence for Strong Correlation Associated with Mott Proximity in Iron-based Superconductors

We predict that iron-based superconductors discovered near d6 configuration (5 Fe 3d orbitals filled by 6 electrons) is located on the foot of an unexpectedly large dome of correlated electron matter centered at the Mott insulator at d5 (namely, half filling). This is based on the many-variable variational Monte-Carlo results for ab initio low-energy models derived by the downfolding. The d5 Mott proximity extends to subsequent emergence of incoherent metals, orbital differentiations due to the Mott physics and Hund's-rule coupling, followed by antiferromagnetic quantum criticality, in quantitative accordance with available experiments.