The Stability, Energetics, and Magnetic States of Cobalt Adatoms on Graphene

TL;DR

This study uses advanced many-body calculations to analyze the stability, energetics, and magnetic states of cobalt adatoms on graphene, revealing preferred adsorption sites and states consistent with recent experiments.

Contribution

It introduces a combined frozen-orbital embedding and auxiliary-field quantum Monte Carlo approach to accurately study Co on graphene, identifying stable configurations and magnetic states.

Findings

Co prefers the top site at 2.2 Å with a high-spin 3d8 4s1 state

At 3.3 Å, Co adopts a van der Waals region with a high-spin 3d7 4s2 state

Results align with recent experimental observations of Co on graphene

Abstract

We investigate the stability and electronic properties of single Co atoms on graphene with near-exact many-body calculations. A frozen-orbital embedding scheme was combined with auxiliary-field quantum Monte Carlo to increase the reach in system sizes. Several energy minima are found as a function of the distance $h$ between Co and graphene. Energetics only permit the Co atom to occupy the top site at $h = 2.2$ \AA\ in a high-spin $3d^{8}4s^{1}$ state, and the van der Waals region at $h = 3.3$ \AA\ in a high-spin $3d^{7}4s^{2}$ state. The findings provide an explanation for recent experimental results with Co on free-standing graphene.