Orbital selectivity in electron correlations and superconducting pairing of iron-based superconductors

TL;DR

This paper reviews recent advances in understanding how orbital-selective electron correlations influence the normal and superconducting states of iron-based superconductors, highlighting the role of orbital physics in their complex behaviors.

Contribution

It provides a comprehensive survey of orbital-selective correlations, Mott physics, nematicity, and pairing mechanisms in iron-based superconductors, including emerging topics like topology.

Findings

Orbital-selective Mott physics is prominent in iron chalcogenides.

Interplay between orbital selectivity and nematicity affects electronic properties.

Orbital-selective pairing is a key concept in superconductivity of these materials.

Abstract

Electron correlations play a central role in iron-based superconductors. In these systems, multiple Fe $3d$-orbitals are active in the low-energy physics, and they are not all degenerate. For these reasons, the role of orbital-selective correlations has been an active topic in the study of the iron-based systems. In this paper, we survey the recent developments on the subject. For the normal state, we emphasize the orbital-selective Mott physics that has been extensively studied, especially in the iron chalcogenides, in the case of electron filling $n \sim 6$. In addition, the interplay between orbital selectivity and electronic nematicity is addressed. For the superconducting state, we summarize the initial ideas for orbital-selective pairing, and discuss the recent explosive activities along this direction. We close with some perspectives on several emerging topics. These include the evolution of the orbital-selective correlations, magnetic and nematic orders and superconductivity as the electron filling factor is reduced from $6$ to $5$, as well as the interplay between electron correlations and topological bandstructure in iron-based superconductors.