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The classical and quantum dynamics of molecular spins on graphene

Abstract

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.

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Figure 1: The graphene–spin hybrids.
Figure 2: Static magnetic properties of the hybrids.
Figure 3: Classical and quantum magnetization dynamics.
Figure 4: Contributions to the zero-field spin dynamics.

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Acknowledgements

We thank J. Wrachtrup and E. Rastelli for discussions; M. Konuma, U. Stützel, J. Sesé, A. L. Barra, D. Drung, Th. Schurig and L. Sebeke for assistance with the measurements; and financial support from Italian MIUR, Spanish MINECO (MAT2012-38318-C03-01), BW-Stiftung (Kompetenznetz Funktionelle Nanostrukturen), ERC-StG-338258 ‘OptoQMol’, the Royal Society (URF fellowship and grant) and the AvH Stiftung (Sofja Kovalevskaja award).

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Contributions

C.C. performed the functionalization and most measurements. A.C. synthetized the molecules. C.C. and S.R. acquired the MALDI-TOF spectra. A.Repollés and F.L. performed the ultralow-temperature magnetic measurements. A.Rettori, M.G.P. and L.B. performed the theoretical analysis. L.B. and M.B. conceived the experiments. L.B. wrote the draft and all authors contributed to discussions and the final manuscript.

Corresponding authors

Correspondence to Christian Cervetti or Lapo Bogani.

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The authors declare no competing financial interests.

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Cervetti, C., Rettori, A., Pini, M. et al. The classical and quantum dynamics of molecular spins on graphene. Nature Mater 15, 164–168 (2016). https://doi.org/10.1038/nmat4490

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