Orbital-dependent self-energy effects and consequences for the superconducting gap structure in multi-orbital correlated electron systems

TL;DR

This paper investigates how electronic correlations influence the superconducting gap structure in multi-orbital systems, revealing that self-energy effects can invert orbital hierarchies and significantly alter gap variations.

Contribution

It introduces a comparison between RPA and FLEX formalisms to show how self-energy feedback affects the pairing mechanism in multi-orbital superconductors.

Findings

Self-energy effects can invert orbital susceptibility hierarchy.

Orbital inversion impacts the superconducting gap structure.

Feedback effects are relevant for strongly correlated systems.

Abstract

We perform a theoretical study of the effects of electronic correlations on the superconducting gap structure of multi-band superconductors. In particular, by comparing standard RPA-based spin-fluctuation mediated gap structures to those obtained within the FLEX formalism for an iron-based superconductor, we obtain directly the feedback effects from electron-electron interactions on the momentum-space gap structure. We show how self-energy effects can lead to an orbital inversion of the orbital-resolved spin susceptibility, and thereby invert the hierarchy of the most important orbitals channels for superconducting pairing. This effect has important consequences for the detailed gap variations on the Fermi surface. We expect such self-energy feedback on the pairing gap to be generally relevant for superconductivity in strongly correlated multi-orbital systems.