The Hund's Superconductor Li(Fe,Co)As

TL;DR

This study investigates how Hund's coupling influences low-energy electronic properties and superconductivity in Li(Fe,Co)As, revealing universal behavior of the superconducting gap across doping levels.

Contribution

It provides a comprehensive analysis combining multiple spectroscopic techniques to elucidate Hund's coupling effects and the universal nature of the superconducting gap in this material.

Findings

Doping dependence of the coherent-incoherent crossover temperature

Effective mass enhancement varies with doping

Superconducting gap-to-Tc ratio is doping-independent

Abstract

We combine transport, angle-resolved photoemission spectroscopy and scanning tunneling spectroscopy to investigate several low energy manifestations of the Hund coupling in a canonical FeSC family Li(Fe,Co)As. We determine the doping dependence of the coherent-incoherent crossover temperature and the quasi-particle effective mass enhancement in the normal state. Our tunneling spectroscopy result in the superconducting state supports the idea that superconductivity emerging from Hund's metal state displays a universal maximal superconducting gap vs transition temperature (2$\Delta_{max}/k_{B}T_{c}$) value, which is independent of doping level and $T_{c}$.