Magnetism between magnetic adatoms on monolayer NbSe$_2$

TL;DR

This study uses ab-initio calculations to explore how transition metal adatoms interact magnetically on monolayer NbSe2, revealing oscillatory RKKY-type interactions and robustness of magnetic coupling, with implications for superconductivity.

Contribution

It provides the first detailed ab-initio analysis of magnetic adatom interactions on monolayer NbSe2, linking magnetic coupling features to Fermi surface properties and external perturbations.

Findings

Exchange interactions are oscillatory and decay exponentially, consistent with RKKY theory.

Magnetic coupling features are tied to Fermi surface nesting vectors.

Magnetism remains stable despite changes in impurity height.

Abstract

In this work, we report on an $ab-initio$ computational study of the electronic and magnetic properties of transition metal adatoms on a monolayer of NbSe$_2$. We demonstrate that Cr, Mn, Fe and Co prefer all to sit above the Nb atom, where the $d$ states experience a substantial hybridization. The inter-atomic exchange coupling is shown to have an oscillatory nature accompanied by an exponential decay, in accordance with what theory predicts for a damped Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction. Our results indicate that the qualitative features of the magnetic coupling for the four investigated adatoms can be connected to the fine details of their Fermi surface. In particular, the oscillations of the exchange in Fe and Co are found to be related to a single nesting vector, connecting large electrons and hole pockets. Most interestingly, this behavior is found to be unaffected by changes induced on the height of the impurity, which makes the magnetism robust to external perturbations. Considering that NbSe$_2$ is a superconductor down to a single layer, our research might open the path for further research into the interplay between magnetic and superconducting characteristics, which could lead to novel superconductivity engineering.