Two-Fluid Description for Iron-Based Superconductors

TL;DR

This paper proposes a two-fluid model combining itinerant electrons and local moments to explain collective behaviors and phases in iron-based superconductors, aligning with experimental observations.

Contribution

It introduces a novel two-fluid framework coupling electrons and local moments via Hund's rule, explaining superconductivity and spin-density-wave phases.

Findings

Emergence of an electron-spinon composite mode in intermediate coupling

Explanation of hump-dip features in tunneling spectroscopy

Unified description of superconductivity and spin-density-wave phases

Abstract

We present a two-fluid description for iron-based superconductors, which contains an itinerant electron Fermi-liquid and a local moment spin-liquid, coupled together via an effective Hund's rule interaction. We examine the low-energy collective behavior of such a system. We find that an electron-spinon composite mode emerges in the intermediate coupling regime, which may account for the hump-dip behavior observed in the resent scanning tunneling spectroscopy experiments. The superconductivity and spin-density-wave phases are consistently described within the same framework. Possible experimental test is also proposed.