Decoupled Pairing Amplitude and Electronic Coherence in Iron-Based Superconductors

TL;DR

This study reveals that in iron-based superconductors, the superconducting pairing amplitude is independent of electronic coherence, suggesting a universal strong coupling mechanism across different phases.

Contribution

It demonstrates that the superconducting pairing amplitude is decoupled from electronic coherence, challenging traditional BCS and BEC pairing scenarios in FeSCs.

Findings

Electronic coherence reshapes spectral function in superconducting state.

Superconducting pairing amplitude shows universal scaling across FeSCs.

Decoupling of pairing amplitude from electronic coherence.

Abstract

Here we use angle-resolved photoemission spectroscopy to study superconductivity that emerges in two extreme cases, from a Fermi liquid phase (LiFeAs) and an incoherent bad-metal phase (FeTe0.55Se0.45). We find that although the electronic coherence can strongly reshape the single-particle spectral function in the superconducting state, it is decoupled from the maximum superconducting pairing amplitude, which shows a universal scaling that is valid for all FeSCs. Our observation excludes pairing scenarios in the BCS and the BEC limit for FeSCs and calls for a universal strong coupling pairing mechanism for the FeSCs.