The classical and quantum dynamics of molecular spins on graphene

The interaction between graphene and the spins of molecular magnets grown on it has been studied. The coupling between graphene phonons, spins and Dirac fermions modifies—and may be used for controlling—the quantum spin dynamics. Controlling the dynamics of spins on surfaces is pivotal to the design of spintronic1 and quantum computing2 devices. Proposed schemes involve the interaction of spins with graphene to enable surface-state spintronics3,4 and electrical spin manipulation4,5,6,7,8,9,10,11. However, the influence of the graphene environment on the spin systems has yet to be unravelled12. Here we explore the spin–graphene interaction by studying the classical and quantum dynamics of molecular magnets13 on graphene. Whereas the static spin response remains unaltered, the quantum spin dynamics and associated selection rules are profoundly modulated. The couplings to graphene phonons, to other spins, and to Dirac fermions are quantified using a newly developed model. Coupling to Dirac electrons introduces a dominant quantum relaxation channel that, by driving the spins over Villain’s threshold, gives rise to fully coherent, resonant spin tunnelling. Our findings provide fundamental insight into the interaction between spins and graphene, establishing the basis for electrical spin manipulation in graphene nanodevices.