Tuning electronic correlations in transition metal pnictides: chemistry beyond the valence count

TL;DR

This study investigates how electronic correlations in iron-based pnictide superconductors depend on orbital filling rather than valence count, revealing a key factor influencing their electronic structure and superconductivity.

Contribution

It demonstrates that electronic correlations are governed by orbital filling, not valence count, supported by SX-ARPES experiments and DFT+DMFT calculations.

Findings

Correlations relate to effective orbital filling, not valence count.

Experimental and theoretical results show correlation strength varies with orbital occupation.

Supports link between cuprate and pnictide phase diagrams.

Abstract

The effects of electron-electron correlations on the low-energy electronic structure and their relationship with unconventional superconductivity are central aspects in the research on the iron-based pnictide superconductors. Here we use soft X-ray angle-resolved photoemission spectroscopy (SX-ARPES) to study how electronic correlations evolve in different chemically substituted iron pnictides. We find that correlations are intrinsically related to the effective filling of the correlated orbitals, rather than to the filling obtained by valence counting. Combined density functional theory (DFT) and dynamical mean-field theory (DMFT) calculations capture these effects, reproducing the experimentally observed trend in the correlation strength. The occupation-driven trend in the electronic correlation reported in our work supports the recently proposed connection between cuprate and pnictides phase diagrams.