Imaging the Real Space Structure of the Spin Fluctuations in an Iron-based superconductor

TL;DR

This paper demonstrates how low-temperature scanning tunnelling microscopy can be used to image and analyze the real space structure of spin fluctuations in an iron-based superconductor, providing new insights beyond neutron scattering methods.

Contribution

It introduces a novel STM-based approach to characterize spin resonance in real space, revealing non-local properties of spin susceptibility in high-temperature superconductors.

Findings

Inelastic tunnelling produces a dip-hump feature linked to spin excitations.

Spatial mapping near defects reveals the non-local structure of spin fluctuations.

The method offers a new way to study spin dynamics in superconductors.

Abstract

Spin fluctuations are a leading candidate for the pairing mechanism in high temperature superconductors, supported by the common appearance of a distinct resonance in the spin susceptibility across the cuprates, iron-based superconductors and many heavy fermion materials. The information we have about the spin resonance comes almost exclusively from neutron scattering. Here we demonstrate that by using low-temperature scanning tunnelling microscopy and spectroscopy we can characterize the spin resonance in real space. We show that inelastic tunnelling leads to the characteristic dip-hump feature seen in tunnelling spectra in high temperature superconductors and that this feature arises from excitations of the spin fluctuations. Spatial mapping of this feature near defects allows us to probe non-local properties of the spin susceptibility and to image its real space structure.