Moir\'e tuning of spin excitations: Individual Fe atoms on MoS$_2$/Au(111)

TL;DR

This study investigates how the moiré pattern influences the spin excitations of individual Fe atoms on MoS$_2$/Au(111), revealing site-dependent magnetic behaviors and Kondo effects modulated by the surface structure.

Contribution

It demonstrates the moiré pattern's role in tuning spin excitations and Kondo correlations of Fe adatoms on MoS$_2$/Au(111), providing insights into surface-induced magnetic phenomena.

Findings

Fe adatoms at moiré minima show pure inelastic spin excitations.

Off-minimum sites develop Kondo resonances, especially at moiré maxima.

Kondo correlations increase while single-ion anisotropy decreases.

Abstract

Magnetic adatoms on surfaces are exchange coupled to their environment, inducing fast relaxation of excited spin states and decoherence. These interactions can be suppressed by inserting decoupling layers between the magnetic adsorbate and the metallic substrate. Using low-temperature scanning tunneling microscopy and spectroscopy, we investigate the magnetic properties of single Fe atoms on Au(111) covered by a monolayer of MoS$_2$ and explore the influence of the moir\'e structure on the spin excitation spectra. Fe adatoms absorbed at minima of the moir\'e structure exhibit almost pure inelastic spin excitations. Kondo correlations develop for adsorption sites off the moir\'e minimum, culminating in fully developed Kondo resonances on moir\'e maxima. The increase in Kondo correlations is accompanied by a decrease in the single-ion anisotropy, which we rationalize by poor-person's scaling. Local variations in the tunneling spectra indicate pronounced interference between tunneling paths involving the spin-carrying orbitals and a hybrid Fe-S orbital, which forms despite the nominally inert nature of the terminating S layer.