Single Spin Localization and Manipulation in Graphene Open-Shell Nanostructures

TL;DR

This study demonstrates the detection, manipulation, and theoretical understanding of localized magnetic moments in graphene nanostructures, confirming predictions of graphene magnetism and enabling control of individual spins.

Contribution

It provides the first experimental observation and manipulation of single spins in graphene nanostructures, supported by theoretical simulations of electron correlations.

Findings

Single electron spins localized at zigzag sites detected via Kondo effect

Coupled spins form a singlet ground state with measurable exchange interaction

Magnetic moments can be switched by hydrogen atom binding and STM tip manipulation

Abstract

Predictions state that graphene can spontaneously develop magnetism from the Coulomb repulsion of its $\pi$-electrons, but its experimental verification has been a challenge. Here, we report on the observation and manipulation of individual magnetic moments localized in graphene nanostructures on a Au(111) surface. Using scanning tunneling spectroscopy, we detected the presence of single electron spins localized around certain zigzag sites of the carbon backbone via the Kondo effect. Two near-by spins were found coupled into a singlet ground state, and the strength of their exchange interaction was measured via singlet-triplet inelastic tunnel electron excitations. Theoretical simulations demonstrate that electron correlations result in spin-polarized radical states with the experimentally observed spatial distributions. Hydrogen atoms bound to these radical sites quench their magnetic moment, permitting us to switch the spin of the nanostructure using the tip of the microscope.