Itinerant spin fluctuations in iron-based superconductors

TL;DR

This paper explores how itinerant spin fluctuations influence electronic properties and induce unconventional superconductivity in multiband iron-based superconductors, highlighting the role of spin resonance and spin-orbit coupling.

Contribution

It develops a theoretical framework for spin fluctuation-induced superconductivity and analyzes the spin response, including the spin resonance feature, in multiband systems.

Findings

Unconventional superconductivity driven by spin fluctuations.

Presence of a spin resonance feature in the spin response.

Significant influence of spin-orbit coupling on magnetic properties.

Abstract

Multiband systems, which possess a wide parameter space, allow to explore a variety of competing ground states. Bright examples are the Fe-based pnictides and chalcogenides, which demonstrate metallic, superconducting, and various magnetic phases. Here I discuss only one of the many interesting topics, namely, spin fluctuations in metallic multiband systems. I show how to calculate the effect of itinerant spin excitations on the electronic properties and formulate a theory of spin fluctuation-induced superconductivity. The superconducting state is unconventional and thus the system demonstrates unusual spin response with the spin resonance feature. I discuss its origin, consequences, and relation to experimental observations. Role of the spin-orbit coupling is specifically emphasized.