Effective Exchange Interactions for Bad Metals and Implications for Iron-based Superconductors

TL;DR

This paper investigates the nature of exchange interactions in bad metals, specifically iron-based superconductors, revealing their enhancement near the Mott transition and discussing implications for superconductivity.

Contribution

It introduces a microscopic slave rotor approach to analyze exchange interactions in bad metals and explores their behavior near the Mott transition in multi-orbital systems.

Findings

Exchange interactions are maximized near the Mott transition.

Magnetic excitations mainly originate from incoherent electronic states.

Implications for superconducting pairing strength are discussed.

Abstract

The experimentally observed bad metal behavior in parent iron pnictides and chalcogenides suggests that these systems contain strong electronic correlations and are on the verge of a metal-to-insulator transition. The magnetic excitations in this bad-metal regime mainly derive from the incoherent part of the electronic spectrum away from the Fermi energy. We present a microscopic study of the exchange interactions in such a regime within a slave rotor approach. We find that the exchange interaction is maximized near the Mott transition. Generalizations to the multi-orbital case are discussed, as are the implications for the strength of superconducting pairing amplitude in the iron-based superconductors.