Local quasiparticle density of states of superconducting SmFeAsO$1-x$F$x$ single crystals: Evidence for spin-mediated pairing

TL;DR

This study uses scanning tunnelling spectroscopy to analyze the local quasiparticle density of states in SmFeAsO$_{1-x}$F$_{x}$ single crystals, revealing features indicative of spin-fluctuation-mediated pairing similar to cuprates.

Contribution

It provides direct spectroscopic evidence supporting spin-mediated pairing mechanisms in iron-based superconductors.

Findings

Spectral features resemble cuprates, including a dip-hump structure.

The collective mode energy decreases with increasing pairing strength.

Results support spin-fluctuation-mediated pairing in pnictides.

Abstract

We probe the local quasiparticles density-of-states in micron-sized SmFeAsO$_{1-x}$F$_{x}$ single-crystals by means of Scanning Tunnelling Spectroscopy. Spectral features resemble those of cuprates, particularly a dip-hump-like structure developed at energies larger than the gap that can be ascribed to the coupling of quasiparticles to a collective mode, quite likely a resonant spin mode. The energy of the collective mode revealed in our study decreases when the pairing strength increases. Our findings support spin-fluctuation-mediated pairing in pnictides.