Pairing Mechanism in Hunds Metal Superconductors and the Universality of the Superconducting Gap to Critical Temperature Ratio

TL;DR

This paper investigates a model of Hund's metal superconductors, showing that despite parameter changes, the ratio of the maximum gap to critical temperature remains near the BCS value, aligning with experimental data.

Contribution

It introduces a simple model capturing Hund's metal physics and demonstrates the universality of the gap to Tc ratio in these materials.

Findings

The gap to Tc ratio stays close to twice the BCS value across parameter variations.

Critical temperature and gap vary significantly with parameters.

Model aligns with experimental observations in iron-based superconductors.

Abstract

We analyze a simple model containing the physical ingredients of a Hund's metal, the local spin fluctuations with power-law correlators, $(\Omega_0/|\Omega|)^\gamma$, with $\gamma$ greater than one, interacting with electronic quasiparticles. While the critical temperature and the gap change significantly with varying parameters, the $2\Delta_{max}/k_BT_c$ remains close to twice the BCS value in agreement with experimental observations in the iron-based superconductors (FeSC).