Selective Mottness as a key to iron superconductors

TL;DR

This paper proposes that selective Mottness, driven by Hund's coupling, explains the doping-dependent electronic behavior in iron superconductors, linking their phase diagram to Mott physics similar to cuprates.

Contribution

It introduces a model where orbital-dependent correlations due to Hund's coupling account for the phase diagram and electronic properties of iron superconductors.

Findings

Weak and strong correlations coexist in the phase diagram.

Orbital selectivity increases with hole doping.

Hund's coupling decouples orbitals, leading to orbital-dependent Mott behavior.

Abstract

The phase diagram of the high-Tc cuprates is dominated by the Mott insulating phase of the parent compounds. As we approach it from large doping, a standard Fermi-liquid gradually turns into a bad non-Fermi liquid metal, a process which culminates in the pseudogap regime, in which the antinodal region in momentum space acquires a gap before reaching a fully gapped Mott state. Here we show that experiments for electron- and hole-doped BaFe2As2 support an analogous scenario. The doping evolution is dominated by the influence of a Mott insulator that would be realized for half-filled conduction bands, while the stoichiometric compound does not play a special role. Weakly and strongly correlated conduction electrons coexist in much of the phase diagram, a differentiation which increases with hole doping. We identify the reason for this selective Mottness in a strong Hund's coupling, which decouples the different orbitals. Each orbital then behaves as a single band Hubbard model, where the correlation degree only depends on how doped is each orbital from half-filling. Our scenario reconciles contrasting evidences on the electronic correlation strength and establishes a deep connection with the cuprates.