The role of orbital nesting in the superconductivity of Iron-based Superconductors

TL;DR

This paper investigates how orbital nesting influences the superconducting gap structure in iron-based superconductors, revealing that orbital matching, rather than Fermi surface nesting, is crucial for understanding their superconductivity.

Contribution

It introduces a low-energy model that emphasizes orbital selectivity, simplifying analysis while capturing key features of spin excitations and gap functions in multiorbital systems.

Findings

Orbital matching between hole and electron pockets determines gap hierarchy.

Orbital selectivity simplifies the analysis of spin excitations and superconductivity.

Fermi surface nesting is less critical than orbital matching for superconductivity.

Abstract

We analyze the magnetic excitations and the spin-mediated superconductivity in iron-based superconductors within a low-energy model that operates in the band basis but fully incorporates the orbital character of the spin excitations. We show how the orbital selectivity, encoded in our low-energy description, simplifies substantially the analysis and allows for analytical treatments, while retaining all the main features of both spin-excitations and gap functions computed using multiorbital models. Importantly, our analysis unveils the orbital matching between the hole and electron pockets as the key parameter to determine the momentum-dependence and the hierarchy of the superconducting gaps, instead of the Fermi surface matching as in the common nesting scenario.